Preprints, Working Papers, ...

Special modes and hypocoercivity for linear kinetic equations with several conservation laws and a confining potential
Kleber Carrapatoso, Jean Dolbeault, Frédéric Hérau, Stéphane Mischler, Clément Mouhot, Christian Schmeiser
2021

We study linear inhomogeneous kinetic equations with an external confining potential and a collision operator with several local conservation laws (local density, momentum and energy). We exhibit all equilibria and entropy-maximizing special modes, and we prove asymptotic exponential convergence of solutions to them with quantitative rate. This is the first complete picture of hypocoercivity and quantitative $H$-theorem for inhomogeneous kinetic equations in this setting.

Stability in Gagliardo-Nirenberg-Sobolev inequalities: flows, regularity and the entropy method
Matteo Bonforte, Jean Dolbeault, Bruno Nazaret, Nikita Simonov
2021

The purpose of this work is to establish a quantitative and constructive stability result for a class of subcritical Gagliardo-Nirenberg-Sobolev inequalities which interpolates between the logarithmic Sobolev inequality and the standard Sobolev inequality (in dimension larger than three), or Onofri's inequality in dimension two. We develop a new strategy, in which the flow of the fast diffusion equation is used as a tool: a stability result in the inequality is equivalent to an improved rate of convergence to equilibrium for the flow. The regularity properties of the parabolic flow allow us to connect an improved entropy - entropy production inequality during an initial time layer to spectral properties of a suitable linearized problem which is relevant for the asymptotic time layer. Altogether, the stability in the inequalities is measured by a deficit which controls in strong norms (a Fisher information which can be interpreted as a generalized Heisenberg uncertainty principle) the distance to the manifold of optimal functions. The method is constructive and, for the first time, quantitative estimates of the stability constant are obtained, including in the critical case of Sobolev's inequality. To build the estimates, we establish a quantitative global Harnack principle and perform a detailed analysis of large time asymptotics by entropy methods.

Explicit constants in Harnack inequalities and regularity estimates, with an application to the fast diffusion equation
Matteo Bonforte, Jean Dolbeault, Bruno Nazaret, Nikita Simonov
2020

This paper is devoted to the computation of various explicit constants in functional inequalities and regularity estimates for solutions of parabolic equations, which are not available from the literature. We provide new expressions and simplified proofs of the Harnack inequality and the corresponding Hölder continuity of the solution of a linear parabolic equation. We apply these results to the computation of a constructive estimate of a threshold time for the uniform convergence in relative error of the solution of the fast diffusion equation.

Existence and stability of infinite time blow-up in the Keller-Segel system
Juan Davila, Manuel del Pino, Jean Dolbeault, Monica Musso, Juncheng Wei
2020

The simplest version of the parabolic-elliptic Patlak-Keller-Segel system in the two-dimensional Euclidean space has an 8π critical mass which corresponds to the exact threshold between finite-time blow-up and self-similar diffusion towards zero. Among functions with mass 8π, we find a neighborhood of a radial function such that any solution with initial condition in this neighborhood is globally defined and blows-up in infinite time with an explicit scaling involving the square root of the logarithm of the time.

Fractional hypocoercivity
Emeric Bouin, Jean Dolbeault, Laurent Lafleche, Christian Schmeiser
2019

This research report is devoted to kinetic equations without confinement. We investigate the large time behaviour induced by collision operators with fat tailed local equilibria. Such operators have an anomalous diffusion limit. In the appropriate scaling, the macroscopic equation involves a fractional diffusion operator so that the optimal decay rate is determined by a fractional Nash inequality. At kinetic level we develop an L 2 hypocoercivity approach and establish a rate of decay compatible with the anomalous diffusion limit.

Reverse Hardy-Littlewood-Sobolev inequalities
Jean Dolbeault, Rupert Frank, Franca Hoffmann
2018

This paper is devoted to a new family of reverse Hardy-Littlewood-Sobolev inequalities which involve a power law kernel with positive exponent. We investigate the range of the admissible parameters and characterize the optimal functions. A striking open question is the possibility of concentration which is analyzed and related with nonlinear diffusion equations involving mean field drifts.

Symmetry of optimizers of the Caffarelli-Kohn-Nirenberg inequalities
Jean Dolbeault, Maria J. Esteban, Michael Loss
2016

In their simplest form, the Caffarelli-Kohn-Nirenberg inequalities are a two parameter family of inequalities. It has been known that there is a region in parameter space where the optimizers for the inequalities have broken symmetry. It has been shown recently that in the complement of this region the optimizers are radially symmetric. The ideas for the proof will be given.

Journal articles

Social heterogeneity and the COVID-19 lockdown in a multi-group SEIR model
Jean Dolbeault, Gabriel Turinici
Computational and Mathematical Biophysics, de Gruyter, 2021, 9, pp.14-21. ⟨10.1515/cmb-2020-0115⟩

The goal of the lockdown is to mitigate and if possible prevent the spread of an epidemic. It consists in reducing social interactions. This is taken into account by the introduction of a factor of reduction of social interactions q, and by decreasing the transmission coefficient of the disease accordingly. Evaluating q is a difficult question and one can ask if it makes sense to compute an average coefficient q for a given population, in order to make predictions on the basic reproduction rate R0, the dynamics of the epidemic or the fraction of the population that will have been infected by the end of the epidemic. On a very simple example, we show that the computation of R0 in a heterogeneous population is not reduced to the computation of an average q but rather to the direct computation of an average coefficient R0. Even more interesting is the fact that, in a range of data compatible with the Covid-19 outbreak, the size of the epidemic is deeply modified by social heterogeneity, as is the height of the epidemic peak, while the date at which it is reached mainly depends on the average R0 coefficient. This short note is an application and a summary of the technical results that can be found in J. Dolbeault and G. Turinici, Heterogeneous social interactions and the COVID-19 lockdown outcome in a multi-group SEIR model. Preprint hal-02559938, Apr. 2020.

Inequalities involving Aharonov-Bohm magnetic potentials in dimensions 2 and 3
Denis Bonheure, Jean Dolbeault, Maria J. Esteban, Ari Laptev, Michael Loss
Reviews in Mathematical Physics, World Scientific Publishing, 2021, 33 (3), pp.2150006-1-2150006-29. ⟨10.1142/S0129055X21500069⟩

This paper is devoted to a collection of results on nonlinear interpolation inequalities associated with Schrödinger operators involving Aharonov-Bohm magnetic potentials, and to some consequences. As symmetry plays an important role for establishing optimality results, we shall consider various cases corresponding to a circle, a two-dimensional sphere or a two-dimensional torus, and also the Euclidean spaces of dimensions two and three. Most of the results are new and we put the emphasis on the methods, as very little is known on symmetry, rigidity and optimality in presence of a magnetic field. The most spectacular applications are new magnetic Hardy inequalities in dimensions 2 and 3.

Weighted Korn and Poincaré-Korn inequalities in the Euclidean space and associated operators
Kleber Carrapatoso, Jean Dolbeault, Frédéric Hérau, Stéphane Mischler, Clément Mouhot
Archive for Rational Mechanics and Analysis, Springer Verlag, In press

We prove functional inequalities on vector fields on the Euclidean space when it is equipped with a bounded measure that satisfies a Poincaré inequality, and study associated self-adjoint operators. The weighted Korn inequality compares the differential matrix, once projected orthogonally to certain finite-dimensional spaces, with its symmetric part and, in an improved form of the inequality, an additional term. We also consider Poincaré-Korn inequalities for estimating a projection of the vector field by the symmetric part of the differential matrix and zeroth-order versions of these inequalities obtained using the Witten-Laplace operator. The constants depend on geometric properties of the potential and the estimates are quantitative and constructive. These inequalities are motivated by kinetic theory and related with the Korn inequality (1906) in mechanics, on a bounded domain.

L2-Hypocoercivity and large time asymptotics of the linearized Vlasov-Poisson-Fokker-Planck system
Lanoir Addala, Jean Dolbeault, Xingyu Li, M Lazhar Tayeb
Journal of Statistical Physics, Springer Verlag, 2021, 184 (1), pp.4. ⟨10.1007/s10955-021-02784-4⟩

This paper is devoted to the linearized Vlasov-Poisson-Fokker-Planck system in presence of an external potential of confinement. We investigate the large time behaviour of the solutions using hypocoercivity methods and a notion of scalar product adapted to the presence of a Poisson coupling. Our framework provides estimates which are uniform in the diffusion limit. As an application in a simple case, we study the one-dimensional case and prove the exponential convergence of the nonlinear Vlasov-Poisson-Fokker-Planck system without any small mass assumption.

Heterogeneous social interactions and the COVID-19 lockdown outcome in a multi-group SEIR model
Jean Dolbeault, Gabriel Turinici
Mathematical Modelling of Natural Phenomena, EDP Sciences, 2020, Coronavirus: Scientific insights and societal aspects, 15 (36), pp.1-18. ⟨10.1051/mmnp/2020025⟩

We study variants of the SEIR model for interpreting some qualitative features of the statistics of the Covid-19 epidemic in France. Standard SEIR models distinguish essentially two regimes: either the disease is controlled and the number of infected people rapidly decreases, or the disease spreads and contaminates a significant fraction of the population until herd immunity is achieved. After lockdown, at first sight it seems that social distancing is not enough to control the outbreak. We discuss here a possible explanation, namely that the lockdown is creating social heterogeneity: even if a large majority of the population complies with the lockdown rules, a small fraction of the population still has to maintain a normal or high level of social interactions, such as health workers, providers of essential services, etc. This results in an apparent high level of epidemic propagation as measured through re-estimations of the basic reproduction ratio. However, these measures are limited to averages, while variance inside the population plays an essential role on the peak and the size of the epidemic outbreak and tends to lower these two indicators. We provide theoretical and numerical results to sustain such a view.

Improved interpolation inequalities and stability
Jean Dolbeault, Maria J. Esteban
Advanced Nonlinear Studies, Walter de Gruyter GmbH, 2020, 20 (2), pp.277-291. ⟨10.1515/ans-2020-2080⟩

For exponents in the subcritical range, we revisit some optimal interpolation inequalities on the sphere with carré du champ methods and use the remainder terms to produce improved inequalities. The method provides us with lower estimates of the optimal constants in the symmetry breaking range and stability estimates for the optimal functions. Some of these results can be reformulated in the Euclidean space using the stereographic projection.

Hypocoercivity and sub-exponential local equilibria
Emeric Bouin, Jean Dolbeault, Laurent Lafleche, Christian Schmeiser
Monatshefte für Mathematik, Springer Verlag, In press, ⟨10.1007/s00605-020-01483-8⟩

Hypocoercivity methods are applied to linear kinetic equations without any space confinement, when local equilibria have a sub-exponential decay. By Nash type estimates, global rates of decay are obtained, which reflect the behavior of the heat equation obtained in the diffusion limit. The method applies to Fokker-Planck and scattering collision operators. The main tools are a weighted Poincar\'e inequality (in the Fokker-Planck case) and norms with various weights. The advantage of weighted Poincar\'e inequalities compared to the more classical weak Poincar\'e inequalities is that the description of the convergence rates to the local equilibrium does not require extra regularity assumptions to cover the transition from super-exponential and exponential local equilibria to sub-exponential local equilibria.

Interpolation inequalities in W1,p(S1) and carré du champ methods
Jean Dolbeault, Marta Garcia-Huidobro, Raul Manásevich
Discrete and Continuous Dynamical Systems - Series A, American Institute of Mathematical Sciences, 2020, 40 (1), pp.375-394. ⟨10.3934/dcds.2020014⟩

This paper is devoted to an extension of rigidity results for nonlinear differential equations, based on carré du champ methods, in the one-dimensional periodic case. The main result is an interpolation inequality with non-trivial explicit estimates of the constants in W1,p(S1) with p ≥ 2. Mostly for numerical reasons, we relate our estimates with issues concerning periodic dynamical systems. Our interpolation inequalities have a dual formulation in terms of generalized spectral estimates of Keller-Lieb-Thirring type, where the differential operator is now a p-Laplacian type operator. It is remarkable that the carré du champ method adapts to such a nonlinear framework, but significant changes have to be done and, for instance, the underlying parabolic equation has a nonlocal term whenever p≠2.

Diffusion and kinetic transport with very weak confinement
Emeric Bouin, Jean Dolbeault, Christian Schmeiser
Kinetic and Related Models , AIMS, 2020, 13 (2), pp.345-371. ⟨10.3934/krm.2020012⟩

This paper is devoted to Fokker-Planck and linear kinetic equations with very weak confinement corresponding to a potential with an at most logarithmic growth and no integrable stationary state. Our goal is to understand how to measure the decay rates when the diffusion wins over the confinement although the potential diverges at infinity.

A variational proof of Nash's inequality
Emeric Bouin, Jean Dolbeault, Christian Schmeiser
Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Serie IX. Rendiconti Lincei. Matematica e Applicazioni, European Mathematical Society, In press, 31, pp.211-223. ⟨10.4171/RLM/886⟩

This paper is intended to give a characterization of the optimality case in Nash's inequality, based on methods of nonlinear analysis for elliptic equations and techniques of the calculus of variations. By embedding the problem into a family of Gagliardo-Nirenberg inequalities, this approach reveals why optimal functions have compact support and also why optimal constants are determined by a simple spectral problem.

Hypocoercivity without confinement
Emeric Bouin, Jean Dolbeault, Stéphane Mischler, Clément Mouhot, Christian Schmeiser
Pure and Applied Analysis, Mathematical Sciences Publishers, 2020, 2 (2), pp.203-232. ⟨10.2140/paa.2020.2.203⟩

In this paper, hypocoercivity methods are applied to linear kinetic equations with mass conservation and without confinement, in order to prove that the solutions have an algebraic decay rate in the long-time range, which the same as the rate of the heat equation. Two alternative approaches are developed: an analysis based on decoupled Fourier modes and a direct approach where, instead of the Poincar\'e inequality for the Dirichlet form, Nash's inequality is employed. The first approach is also used to provide a simple proof of exponential decay to equilibrium on the flat torus. The results are obtained on a space with exponential weights and then extended to larger function spaces by a factorization method. The optimality of the rates is discussed. Algebraic rates of decay on the whole space are improved when the initial datum has moment cancellations.

Reverse Hardy-Littlewood-Sobolev inequalities
José Carrillo, Matías Delgadino, Jean Dolbeault, Rupert Frank, Franca Hoffmann
Journal de Mathématiques Pures et Appliquées, Elsevier, 2019, 132, pp.133-165. ⟨10.1016/j.matpur.2019.09.001⟩

This paper is devoted to a new family of reverse Hardy-Littlewood-Sobolev inequalities which involve a power law kernel with positive exponent. We investigate the range of the admissible parameters and the properties of the optimal functions. A striking open question is the possibility of concentration which is analyzed and related with free energy functionals and nonlinear diffusion equations involving mean field drifts.

Symmetry results in two-dimensional inequalities for Aharonov-Bohm magnetic fields
Denis Bonheure, Jean Dolbeault, Maria J. Esteban, Ari Laptev, Michael Loss
Communications in Mathematical Physics, Springer Verlag, 2019, 375 (3), pp.2071-2087. ⟨10.1007/s00220-019-03560-y⟩

This paper is devoted to the symmetry and symmetry breaking properties of a two-dimensional magnetic Schrödinger operator involving an Aharonov-Bohm magnetic vector potential. We investigate the symmetry properties of the optimal potential for the corresponding magnetic Keller-Lieb-Thir-ring inequality. We prove that this potential is radially symmetric if the intensity of the magnetic field is below an explicit threshold, while symmetry is broken above a second threshold corresponding to a higher magnetic field. The method relies on the study of the magnetic kinetic energy of the wave function and amounts to study the symmetry properties of the optimal functions in a magnetic Hardy-Sobolev interpolation inequality. We give a quantified range of symmetry by a non-perturbative method. To establish the symmetry breaking range, we exploit the coupling of the phase and of the modulus and also obtain a quantitative result.

Generalized logarithmic Hardy-Littlewood-Sobolev inequality
Jean Dolbeault, Xingyu Li
International Mathematics Research Notices, Oxford University Press (OUP), In press, ⟨10.1093/imrn/rnz324⟩

This paper is devoted to logarithmic Hardy-Littlewood-Sobolev inequalities in the two-dimensional Euclidean space, in presence of an external potential with logarithmic growth. The coupling with the potential introduces a new parameter, with two regimes. The attractive regime reflects the standard logarithmic Hardy-Littlewood-Sobolev inequality. The second regime corresponds to a reverse inequality, with the opposite sign in the convolution term, that allows us to bound the free energy of a drift-diffusion-Poisson system from below. Our method is based on an extension of an entropy method proposed by E. Carlen, J. Carrillo and M. Loss, and on a nonlinear diffusion equation.

Une cartographie de la communauté mathématique française
Maxime Chupin, Jean Dolbeault, Maria J. Esteban, Mathieu Lewin
Gazette des Mathématiciens, Société Mathématique de France, 2018, 156, pp.49-61

Cette étude tente de dresser une cartographie thématique des mathématiques universitaires en France, définies ici comme l'ensemble des électeurs des deux sections CNU 25 et 26. Basée sur les publications référencées dans MathSciNet et la classification MSC, elle met en évidence la répartition des forces entre les différents domaines de recherche, et compare ces résultats avec le découpage en deux sections CNU. L'approche retenue permet aussi de déterminer la part des chercheurs et enseignants-chercheurs travaillant sur les "applications des mathématiques" et de réaliser une cartographie similaire pour les recrutements des CR au CNRS pendant la période 2005-2016.

Phi-Entropies: convexity, coercivity and hypocoercivity for Fokker–Planck and kinetic Fokker–Planck equations
Jean Dolbeault, Xingyu Li
Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2018, 28 (13), pp.2637-2666. ⟨10.1142/S0218202518500574⟩

This paper is devoted to ϕ-entropies applied to Fokker-Planck and kinetic Fokker-Planck equations in the whole space, with confinement. The so-called ϕ-entropies are Lyapunov functionals which typically interpolate between Gibbs entropies and L2 estimates. We review some of their properties in the case of diffusion equations of Fokker-Planck type, give new and simplified proofs, and then adapt these methods to a kinetic Fokker-Planck equation acting on a phase space with positions and velocities. At kinetic level, since the diffusion only acts on the velocity variable, the transport operator plays an essential role in the relaxation process. Here we adopt the H1 point of view and establish a sharp decay rate. Rather than giving general but quantitatively vague estimates, our goal here is to consider simple cases, benchmark available methods and obtain sharp estimates on a key example. Some ϕ-entropies give rise to improved entropy – entropy production inequalities and, as a consequence, to faster decay rates for entropy estimates of solutions to non-degenerate diffusion equations. Our main result is to prove that faster entropy decay also holds at kinetic level and that optimal decay rates are achieved only in asymptotic regimes.

Magnetic rings
Jean Dolbeault, Maria J. Esteban, Ari Laptev, Michael Loss
Journal of Mathematical Physics, American Institute of Physics (AIP), 2018, 59 (5), pp.051504. ⟨10.1063/1.5022121⟩

We study functional and spectral properties of perturbations of the magnetic Laplace operator on the circle. This operator appears when considering the restriction to the unit circle of a two-dimensional Schrödinger operator with the Bohm-Aharonov vector potential. We prove a Hardy-type inequality on the two-dimensional Euclidean space and, on the circle, a sharp interpolation inequality and a sharp Keller-Lieb-Thirring inequality.

Interpolation inequalities and spectral estimates for magnetic operators
Jean Dolbeault, Maria J. Esteban, Ari Laptev, Michael Loss
Annales Henri Poincaré. A Journal of Theoretical and Mathematical Physics, 2018, 19 (5), pp.1439-1463. ⟨10.1007/s00023-018-0663-9⟩

We prove magnetic interpolation inequalities and Keller-Lieb-Thir-ring estimates for the principal eigenvalue of magnetic Schrödinger operators. We establish explicit upper and lower bounds for the best constants and show by numerical methods that our theoretical estimates are accurate.

Flows and functional inequalities for fractional operators
Jean Dolbeault, An Zhang
Applicable Analysis, Taylor & Francis, 2017, 96 (9), pp.1547-1560

This paper collects results concerning global rates and large time asymptotics of a fractional fast diffusion on the Euclidean space, which is deeply related with a family of fractional Gagliardo-Nirenberg-Sobolev inequalities. Generically, self-similar solutions are not optimal for the Gagliardo-Nirenberg-Sobolev inequalities, in strong contrast with usual standard fast diffusion equations based on non-fractional operators. Various aspects of the stability of the self-similar solutions and of the entropy methods like carré du champ and Rényi entropy powers methods are investigated and raise a number of open problems.

Weighted fast diffusion equations (Part I): Sharp asymptotic rates without symmetry and symmetry breaking in Caffarelli-Kohn-Nirenberg inequalities
Matteo Bonforte, Jean Dolbeault, Matteo Muratori, Bruno Nazaret
Kinetic and Related Models , AIMS, 2017, 10 (1), pp. 33-59

In this paper we consider a family of Caffarelli-Kohn-Nirenberg interpolation inequalities (CKN), with two radial power law weights and exponents in a subcritical range. We address the question of symmetry breaking: are the optimal functions radially symmetric, or not ? Our intuition comes from a weighted fast diffusion (WFD) flow: if symmetry holds, then an explicit entropy - entropy production inequality which governs the intermediate asymptotics is indeed equivalent to (CKN), and the self-similar profiles are optimal for (CKN). We establish an explicit symmetry breaking condition by proving the linear instability of the radial optimal functions for (CKN). Symmetry breaking in (CKN) also has consequences on entropy - entropy production inequalities and on the intermediate asymptotics for (WFD). Even when no symmetry holds in (CKN), asymptotic rates of convergence of the solutions to (WFD) are determined by a weighted Hardy-Poincaré inequality which is interpreted as a linearized entropy - entropy production inequality. All our results rely on the study of the bottom of the spectrum of the linearized diffusion operator around the self-similar profiles, which is equivalent to the linearization of (CKN) around the radial optimal functions, and on variational methods. Consequences for the (WFD) flow will be studied in Part II of this work.

Uniqueness and rigidity in nonlinear elliptic equations, interpolation inequalities and spectral estimates
Jean Dolbeault, Michal Kowalczyk
Annales de la Faculté des Sciences de Toulouse. Mathématiques., Université Paul Sabatier _ Cellule Mathdoc In press, 26 (4), pp.949-977. ⟨10.5802/afst.1557⟩

This paper is devoted to the Lin-Ni conjecture for a semi-linear elliptic equation with a super-linear, sub-critical nonlinearity and homogeneous Neumann boundary conditions. We establish a new rigidity result, that is, we prove that the unique positive solution is a constant if the parameter of the problem is below an explicit bound that we relate with an optimal constant for a Gagliardo-Nirenberg-Sobolev interpolation inequality and also with an optimal Keller-Lieb-Thirring inequality. Our results are valid in a sub-linear regime as well. The rigidity bound is obtained by nonlinear flow methods inspired by recent results on compact manifolds, which unify nonlinear elliptic techniques and the carré du champ method in semi-group theory. Our method requires the convexity of the domain. It relies on integral quantities, takes into account spectral estimates and provides improved functional inequalities.

Weighted fast diffusion equations (Part II): Sharp asymptotic rates of convergence in relative error by entropy methods
Matteo Bonforte, Jean Dolbeault, Matteo Muratori, Bruno Nazaret
Kinetic and Related Models , AIMS, 2017, 10 (1), pp.61-91

This paper is the second part of the study. In Part~I, self-similar solutions of a weighted fast diffusion equation (WFD) were related to optimal functions in a family of subcritical Caffarelli-Kohn-Nirenberg inequalities (CKN) applied to radially symmetric functions. For these inequalities, the linear instability (symmetry breaking) of the optimal radial solutions relies on the spectral properties of the linearized evolution operator. Symmetry breaking in (CKN) was also related to large-time asymptotics of (WFD), at formal level. A first purpose of Part~II is to give a rigorous justification of this point, that is, to determine the asymptotic rates of convergence of the solutions to (WFD) in the symmetry range of (CKN) as well as in the symmetry breaking range, and even in regimes beyond the supercritical exponent in (CKN). Global rates of convergence with respect to a free energy (or entropy) functional are also investigated, as well as uniform convergence to self-similar solutions in the strong sense of the relative error. Differences with large-time asymptotics of fast diffusion equations without weights will be emphasized.

Interpolation inequalities on the sphere: linear vs. nonlinear flows
Jean Dolbeault, Maria J. Esteban, Michael Loss
Annales de la Faculté des Sciences de Toulouse. Mathématiques., Université Paul Sabatier _ Cellule Mathdoc 2017, 26 (2), pp.351-379

This paper is devoted to sharp interpolation inequalities on the sphere and their proof using flows. The method explains some rigidity results and proves uniqueness in related semilinear elliptic equations. Nonlinear flows allow to cover the interval of exponents ranging from Poincaré to Sobolev inequality, while an intriguing limitation (an upper bound on the exponent) appears in the carré du champ method based on the heat flow. We investigate this limitation, describe a counter-example for exponents which are above the bound, and obtain improvements below.

Onofri inequalities and rigidity results
Jean Dolbeault, Maria J. Esteban, Gaspard Jankowiak
Discrete and Continuous Dynamical Systems, 2017, 37 (6), pp.3059-3078

This paper is devoted to the Moser-Trudinger-Onofri inequality on smooth compact connected Riemannian manifolds. We establish a rigidity result for the Euler-Lagrange equation and deduce an estimate of the optimal constant in the inequality on two-dimensional closed Riemannian manifolds. Compared to existing results, we provide a non-local criterion which is well adapted to variational methods, introduce a nonlinear flow along which the evolution of a functional related with the inequality is monotone and get an integral remainder term which allows us to discuss optimality issues. As an important application of our method, we also consider the non-compact case of the Moser-Trudinger-Onofri inequality on the two-dimensional Euclidean space, with weights. The standard weight is the one that is computed when projecting the two-dimensional sphere using the stereographic projection, but we also give more general results which are of interest, for instance, for the Keller-Segel model in chemotaxis.

Symmetry for extremal functions in subcritical Caffarelli-Kohn-Nirenberg inequalities
Jean Dolbeault, Maria J. Esteban, Michael Loss, Matteo Muratori
Comptes Rendus. Mathématique, Académie des sciences (Paris), 2017, 355 (2), pp.133-154

We use the formalism of the Rényi entropies to establish the symmetry range of extremal functions in a family of subcriti-cal Caffarelli-Kohn-Nirenberg inequalities. By extremal functions we mean functions which realize the equality case in the inequalities, written with optimal constants. The method extends recent results on critical Caffarelli-Kohn-Nirenberg inequalities. Using heuristics given by a nonlinear diffusion equation, we give a variational proof of a symmetry result, by establishing a rigidity theorem: in the symmetry region, all positive critical points have radial symmetry and are therefore equal to the unique positive, radial critical point, up to scalings and multiplications. This result is sharp. The condition on the parameters is indeed complementary of the condition which determines the region in which symmetry breaking holds as a consequence of the linear instability of radial optimal functions. Compared to the critical case, the subcritical range requires new tools. The Fisher information has to be replaced by Rényi entropy powers, and since some invariances are lost, the estimates based on the Emden-Fowler transformation have to be modified.

Rigidity versus symmetry breaking via nonlinear flows on cylinders and Euclidean spaces
Jean Dolbeault, Maria J. Esteban, Michael Loss
Inventiones Mathematicae, Springer Verlag, 2016, 206 (2), pp.397-440

This paper is motivated by the characterization of the optimal symmetry breaking region in Caffarelli-Kohn-Nirenberg inequalities. As a consequence, optimal functions and sharp constants are computed in the symmetry region. The result solves a longstanding conjecture on the optimal symmetry range. As a byproduct of our method we obtain sharp estimates for the principal eigenvalue of Schrödinger operators on some non-flat non-compact manifolds, which to the best of our knowledge are new. The method relies on generalized entropy functionals for nonlinear diffusion equations. It opens a new area of research for approaches related to carré du champ methods on non-compact manifolds. However key estimates depend as much on curvature properties as on purely nonlinear effects. The method is well adapted to functional inequalities involving simple weights and also applies to general cylinders. Beyond results on symmetry and symmetry breaking, and on optimal constants in functional inequalities, rigidity theorems for nonlinear elliptic equations can be deduced in rather general settings.

Weighted interpolation inequalities: a perturbation approach
Jean Dolbeault, Matteo Muratori, Bruno Nazaret
Mathematische Annalen, Springer Verlag, 2016, ⟨10.1007/s00208-016-1480-4⟩

We study optimal functions in a family of Caffarelli-Kohn-Nirenberg inequalities with a power-law weight, in a regime for which standard symmetrization techniques fail. We establish the existence of optimal functions, study their properties and prove that they are radial when the power in the weight is small enough. Radial symmetry up to translations is true for the limiting case where the weight vanishes, a case which corresponds to a well-known subfamily of Gagliardo-Nirenberg inequalities. Our approach is based on a concentration-compactness analysis and on a perturbation method which uses a spectral gap inequality. As a consequence, we prove that optimal functions are explicit and given by Barenblatt-type profiles in the perturbative regime.

Optimal functional inequalities for fractional operators on the sphere and applications
Jean Dolbeault, An Zhang
Advanced Nonlinear Studies, Walter de Gruyter GmbH, 2016, 16 (4), pp.863-880

This paper is devoted to optimal functional inequalities for fractional Laplace operators on the sphere. Based on spectral properties, subcritical inequalities are established. Their consequences for fractional heat flows are considered. These subcritical inequalities interpolate between fractional Sobolev and subcritical fractional logarithmic Sobolev inequalities. Their optimal constants are determined by a spectral gap. In the subcritical range, the method also provides us with remainder terms which can be considered as an improved version of the optimal inequalities. We also consider inequalities which interpolate between fractional logarithmic Sobolev and fractional Poincaré inequalities. Finally, weighted inequalities involving the fractional Laplacian are obtained in the Euclidean space, using a stereographic projection and scaling properties.

Interpolation inequalities, nonlinear flows, boundary terms, optimality and linearization
Jean Dolbeault, Maria J. Esteban, Michael Loss
Journal of Elliptic and Parabolic Equations, 2016, 2, pp.267-295

This paper is devoted to the computation of the asymptotic boundary terms in entropy methods applied to a fast diffusion equation with weights associated with Caffarelli-Kohn-Nirenberg interpolation inequalities. So far, only elliptic equations have been considered and our goal is to justify, at least partially, an extension of the carré du champ / Bakry-Emery / Rényi entropy methods to parabolic equations. This makes sense because evolution equations are at the core of the heuristics of the method even when only elliptic equations are considered, but this also raises difficult questions on the regularity and on the growth of the solutions in presence of weights. We also investigate the relations between the optimal constant in the entropy - entropy production inequality, the optimal constant in the information - information production inequality, the asymptotic growth rate of generalized Rényi entropy powers under the action of the evolution equation and the optimal range of parameters for symmetry breaking issues in Caffarelli-Kohn-Nirenberg inequalities, under the assumption that the weights do not introduce singular boundary terms at x=0. These considerations are new even in the case without weights. For instance, we establish the equivalence of carré du champ and Rényi entropy methods and explain why entropy methods produce optimal constants in entropy - entropy production and Gagliardo-Nirenberg inequalities in absence of weights, or optimal symmetry ranges when weights are present.

Nonlinear diffusions: extremal properties of Barenblatt profiles, best matching and delays
Jean Dolbeault, Giuseppe Toscani
Nonlinear Analysis: Theory, Methods and Applications, Elsevier, 2016, 138, pp.31-43

In this paper, we consider functionals based on moments and non-linear entropies which have a linear growth in time in case of source-type so-lutions to the fast diffusion or porous medium equations, that are also known as Barenblatt solutions. As functions of time, these functionals have convexity properties for generic solutions, so that their asymptotic slopes are extremal for Barenblatt profiles. The method relies on scaling properties of the evo-lution equations and provides a simple and direct proof of sharp Gagliardo-Nirenberg-Sobolev inequalities in scale invariant form. The method also gives refined estimates of the growth of the second moment and, as a consequence, establishes the monotonicity of the delay corresponding to the best matching Barenblatt solution compared to the Barenblatt solution with same initial sec-ond moment. Here the notion of best matching is defined in terms of a relative entropy.

Stability results for logarithmic Sobolev and Gagliardo-Nirenberg inequalities
Jean Dolbeault, Giuseppe Toscani
International Mathematics Research Notices, Oxford University Press (OUP), 2015, 2016 (2), pp.473-498

This paper is devoted to improvements of functional inequalities based on scalings and written in terms of relative entropies. When scales are taken into account and second moments fixed accordingly, deficit functionals provide explicit stability measurements, i.e., bound with explicit constants distances to the manifold of optimal functions. Various results are obtained for the Gaussian logarithmic Sobolev inequality and its Euclidean counterpart, for the Gaussian generalized Poincaré inequalities and for the Gagliardo-Nirenberg inequalities. As a consequence, faster convergence rates in diffusion equations (fast diffusion, Ornstein-Uhlenbeck and porous medium equations) are obtained.

Stationary solutions of Keller-Segel type crowd motion and herding models: multiplicity and dynamical stability
Jean Dolbeault, Peter Markowich, Gaspard Jankowiak
Mathematics and Mechanics of Complex Systems, International Research Center for Mathematics & Mechanics of Complex Systems (M&MoCS),University of L’Aquila in Italy, 2015, 3 (3), pp.211-241

In this paper we study two models for crowd motion and herding. Each of the models is of Keller-Segel type and involves two parabolic equations, one for the evolution of the density and one for the evolution of a mean field potential. We classify all radial stationary solutions, prove multiplicity results and establish some qualitative properties of these solutions, which are characterized as critical points of an energy functional. A notion of variational stability is associated to such solutions. The dynamical stability in a neighborhood of a stationary solution is also studied in terms of the spectral properties of the linearized evolution operator. For one of the two models, we exhibit a Lyapunov functional which allows to make the link between the two notions of stability. Even in that case, for certain values of the mass parameter and all other parameters taken in an appropriate range, we find that two dynamically stable stationary solutions exist. We further discuss qualitative properties of the solutions using theoretical methods and numerical computations.

Hypocoercivity for linear kinetic equations conserving mass
Jean Dolbeault, Clément Mouhot, Christian Schmeiser
Transactions of the American Mathematical Society, American Mathematical Society, 2015, 367, pp.3807-3828

We develop a new method for proving hypocoercivity for a large class of linear kinetic equations with only one conservation law. Local mass conservation is assumed at the level of the collision kernel, while transport involves a confining potential, so that the solution relaxes towards a unique equilibrium state. Our goal is to evaluate in an appropriately weighted $L^2$ norm the exponential rate of convergence to the equilibrium. The method covers various models, ranging from diffusive kinetic equations like Vlasov-Fokker-Planck equations, to scattering models like the linear Boltzmann equation or models with time relaxation collision kernels corresponding to polytropic Gibbs equilibria, including the case of the linear Boltzmann model. In this last case and in the case of Vlasov-Fokker-Planck equations, any linear or superlinear growth of the potential is allowed.

Best matching Barenblatt profiles are delayed
Jean Dolbeault, Giuseppe Toscani
Journal of Physics A General Physics (1968-1972), Institute of Physics (IOP), 2015, 48 (6), pp.065206, 14

The growth of the second moments of the solutions of fast diffusion equations is asymptotically governed by the behavior of self-similar solutions. However, at next order, there is a correction term which amounts to a delay depending on the nonlinearity and on a distance of the initial data to the set of self-similar Barenblatt solutions. This distance can be measured in terms of a relative entropy to the best matching Barenblatt profile. This best matching Barenblatt function determines a scale. In new variables based on this scale, which are given by a self-similar change of variables if and only if the initial datum is one of the Barenblatt profiles, the typical scale is monotone and has a li

The Moser-Trudinger-Onofri inequality
Jean Dolbeault, Maria J. Esteban, Gaspard Jankowiak
Chinese Annals of Mathematics - Series B, Springer Verlag, 2015, 36 (5), pp.777-802

This paper is devoted to results on the Moser-Trudinger-Onofri inequality, or Onofri inequality for brevity. In dimension two this inequality plays a role similar to the Sobolev inequality in higher dimensions. After justifying this statement by recovering the Onofri inequality through various limiting procedures and after reviewing some known results, we state several elementary remarks. We also prove various new results. We give a proof of the inequality using mass transportation methods (in the radial case), consistently with similar results for Sobolev's inequalities. We investigate how duality can be used to improve the Onofri inequality, in connection with the logarithmic Hardy-Littlewood-Sobolev inequality. In the framework of fast diffusion equations, we establish that the inequality is an entropy--entropy production inequality, which provides an integral remainder term. Finally we give a proof of the inequality based on rigidity methods and introduce a related nonlinear flow.

Bifurcation diagrams and multiplicity for nonlocal elliptic equations modeling gravitating systems based on Fermi-Dirac statistics
Jean Dolbeault, Robert Stanczy
Discrete and Continuous Dynamical Systems - Series A, American Institute of Mathematical Sciences, 2015, 35 (1), pp.139-154

This paper is devoted to multiplicity results of solutions to nonlocal elliptic equations modeling gravitating systems. By considering the case of Fermi-Dirac statistics as a singular perturbation of Maxwell-Boltzmann one, we are able to produce multiplicity results. Our method is based on cumulated mass densities and a logarithmic change of coordinates that allows us to describe the set of all solutions by a non-autonomous perturbation of an autonomous dynamical system. This has interesting consequences in terms of bifurcation diagrams, which are illustrated by a some numerical computations. More specifically, we study a model based on the Fermi function as well as a simplified one for which estimates are easier to establish. The main difficulty comes from the fact that the mass enters in the equation as a parameter which makes the whole problem non-local.

Rigidity results with applications to best constants and symmetry of Caffarelli-Kohn-Nirenberg and logarithmic Hardy inequalities
Jean Dolbeault, Maria J. Esteban, Stathis Filippas, Achiles Tertikas
Calculus of Variations and Partial Differential Equations, Springer Verlag, 2015, pp.10.1007/s00526-015-0871-9

We take advantage of a rigidity result for the equation satisfied by an extremal function associated with a special case of the Caffarelli-Kohn-Nirenberg inequalities to get a symmetry result for a larger set of inequali-ties. The main ingredient is a reparametrization of the solutions to the Euler-Lagrange equations and estimates based on the rigidity result. The symmetry results cover a range of parameters which go well beyond the one that can be achieved by symmetrization methods or comparison techniques so far.

Keller-Lieb-Thirring inequalities for Schrödinger operators on cylinders
Jean Dolbeault, Maria J. Esteban, Michael Loss
Comptes Rendus. Mathématique, Académie des sciences (Paris), 2015, 353 (9), pp.813-818

This note is devoted to Keller-Lieb-Thirring spectral estimates for Schrödinger operators on infinite cylinders: the absolute value of the ground state level is bounded by a function of a norm of the potential. Optimal potentials with small norms are shown to depend on a single variable. The proof is a perturbation argument based on recent rigidity results for nonlinear elliptic equations on cylinders. Conversely, optimal single variable potentials with large norms must be unstable. The optimal threshold between the two regimes is established in the case of the product of a sphere by a line. Résumé. Cette note est consacréè a des estimations spectrales de Keller-Lieb-Thirring pour des opérateurs de Schrödinger sur des cylindres infinis : la valeur absolue de l'´ etat fondamental est bornée par une fonction d'une norme du potentiel. Il est montré que les potentiels optimaux de petite norme ne dépendent que d'une seule variable. La preuve provient d'un argument de perturbation qui repose sur des résultats de rigidité récents pour des equations elliptiques non-linéaires sur des cylindres. A l'inverse, les potentiels optimaux de grande norme qui ne dépendent que d'une seule variable sont instables. La valeur optimale qui sépare les deux régimes est etablie dans le cas du produit d'une sphère et d'une droite.

Improved interpolation inequalities on the sphere
Jean Dolbeault, Maria J. Esteban, Michal Kowalczyk, Michael Loss
Discrete and Continuous Dynamical Systems - Series S, American Institute of Mathematical Sciences, 2014, 7 (4), pp.695-724

This paper contains a review of available methods for establishing improved interpolation inequalities on the sphere for subcritical exponents. Pushing further these techniques we also establish some new results, clarify the range of applicability of the various existing methods and state several explicit estimates.

Existence of sign changing solutions for an equation with a weighted p-Laplace operator
Carmen Cortázar, Jean Dolbeault, Marta Garcia-Huidobro, Raul Manásevich
Nonlinear Analysis: Theory, Methods and Applications, Elsevier, 2014, 110, pp.1-22

We consider radial solutions of a general elliptic equation involving a weighted $p$-Laplace operator with a subcritical nonlinearity. By a shooting method we prove the existence of solutions with any prescribed number of nodes. The method is based on a change of variables in the phase plane, a very general computation of an angular velocity and new estimates for the decay of an energy associated with an asymptotic Hamiltonian problem. Estimating the rate of decay for the energy requires a sub-criticality condition. The method covers the case of solutions which are not compactly supported or which have compact support. In the last case, we show that the size of the support increases with the number of nodes.

Spectral estimates on the sphere
Jean Dolbeault, Maria J. Esteban, Ari Laptev
Analysis & PDE, Mathematical Sciences Publishers, 2014, 7 (2), pp.435-460

In this article we establish optimal estimates for the first eigenvalue of Schrödinger operators on the d-dimensional unit sphere. These estimates depend on Lebsgue's norms of the potential, or of its inverse, and are equivalent to interpolation inequalities on the sphere. We also characterize a semi-classical asymptotic regime and discuss how our estimates on the sphere differ from those on the Euclidean space.

Sobolev and Hardy-Littlewood-Sobolev inequalities
Jean Dolbeault, Gaspard Jankowiak
Journal of Differential Equations, Elsevier, 2014, 257 (6), pp.1689-1720

This paper is devoted to improvements of Sobolev and Onofri inequalities. The additional terms involve the dual counterparts, i.e. Hardy-Littlewood-Sobolev type inequalities. The Onofri inequality is achieved as a limit case of Sobolev type inequalities. Then we focus our attention on the constants in our improved Sobolev inequalities, that can be estimated by completion of the square methods. Our estimates rely on nonlinear flows and spectral problems based on a linearization around optimal Aubin-Talenti functions.

Asymptotic estimates for the parabolic-elliptic Keller-Segel model in the plane
Juan Campos Serrano, Jean Dolbeault
Communications in Partial Differential Equations, Taylor & Francis, 2014, 39 (5), pp.806-841

We investigate the large-time behavior of the solutions of the two-dimensional Keller-Segel system in self-similar variables, when the total mass is subcritical, that is less than 8π after a proper adimensionalization. It was known from previous works that all solutions converge to stationary solutions, with exponential rate when the mass is small. Here we remove this restriction and show that the rate of convergence measured in relative entropy is exponential for any mass in the subcritical range, and independent of the mass. The proof relies on symmetrization techniques, which are adapted from a paper of J.I. Diaz, T. Nagai, and J.-M. Rakotoson, and allow us to establish uniform estimates for Lp norms of the solution. Exponential convergence is obtained by the mean of a linearization in a space which is defined consistently with relative entropy estimates and in which the linearized evolution operator is self-adjoint. The core of proof relies on several new spectral gap estimates which are of independent interest.

Branches of non-symmetric critical points and symmetry breaking in nonlinear elliptic partial differential equations
Jean Dolbeault, Maria J. Esteban
Nonlinearity, IOP Publishing, 2014, 27, p. 435-465

In this paper we study the bifurcation of branches of non-symmetric solutions from the symmetric branch of solutions to the Euler-Lagrange equations satisfied by optimal functions in functional inequalities of Caffarelli-Kohn-Nirenberg type. We establish the asymptotic behavior of the branches for large values of the bifurcation parameter. We also perform an expansion in a neighborhood of the first bifurcation point on the branch of symmetric solutions, that characterizes the local behavior of the non-symmetric branch. These results are compatible with earlier numerical and theoretical observations. Further numerical results allow us to distinguish two global scenarios. This sheds a new light on the symmetry breaking phenomenon.

Nonlinear flows and rigidity results on compact manifolds
Jean Dolbeault, Maria J. Esteban, Michael Loss
Journal of Functional Analysis, Elsevier, 2014, 267 (5), pp.1338-1363

This paper is devoted to rigidity results for some elliptic PDEs and related interpolation inequalities of Sobolev type on smooth compact connected Riemannian manifolds without boundaries. Rigidity means that the PDE has no other solution than the constant one at least when a parameter is in a certain range. This parameter can be used as an estimate for the best constant in the corresponding interpolation inequality. Our approach relies in a nonlinear flow of porous medium / fast diffusion type which gives a clear-cut interpretation of technical choices of exponents done in earlier works. We also establish two integral criteria for rigidity that improve upon known, pointwise conditions, and hold for general manifolds without positivity conditions on the curvature. Using the flow, we are also able to discuss the optimality of the corresponding constant in the interpolation inequalities.

One-dimensional Gagliardo-Nirenberg-Sobolev inequalities: Remarks on duality and flows
Jean Dolbeault, Maria J. Esteban, Ari Laptev, Michael Loss
Journal of the London Mathematical Society, London Mathematical Society, 2014, 90 (2), pp.525-550

This paper is devoted to one-dimensional interpolation Gagliardo-Nirenberg-Sobolev inequalities. We study how various notions of duality, transport and monotonicity of functionals along flows defined by some nonlinear diffusion equations apply. We start by reducing the inequality to a much simpler dual variational problem using mass transportation theory. Our second main result is devoted to the construction of a Lyapunov functional associated with a nonlinear diffusion equation, that provides an alternative proof of the inequality. The key observation is that the inequality on the line is equivalent to Sobolev's inequality on the sphere, at least when the dimension is an integer, or to the critical interpolation inequality for the ultraspherical operator in the general case. The time derivative of the functional along the flow is itself very interesting. It explains the machinery of some rigidity estimates for nonlinear elliptic equations and shows how eigenvalues of a linearized problem enter in the computations. Notions of gradient flows are then discussed for various notions of distances. Throughout this paper we shall deal with two classes of inequalities corresponding either to p>2 or to p

Improved interpolation inequalities, relative entropy and fast diffusion equations
Jean Dolbeault, Giuseppe Toscani
Annales de l'Institut Henri Poincaré (C) Non Linear Analysis, Elsevier, 2013, 30 (5), pp.917-934

We consider a family of Gagliardo-Nirenberg-Sobolev interpolation inequalities which interpolate between Sobolev's inequality and the logarithmic Sobolev inequality, with optimal constants. The difference of the two terms in the interpolation inequalities (written with optimal constant) measures a distance to the manifold of the optimal functions. We give an explicit estimate of the remainder term and establish an improved inequality, with explicit norms and fully detailed constants. Our approach is based on nonlinear evolution equations and improved entropy - entropy production estimates along the associated flow. Optimizing a relative entropy functional with respect to a scaling parameter, or handling properly second moment estimates, turns out to be the central technical issue. This is a new method in the theory of nonlinear evolution equations, which can be interpreted as the best fit of the solution in the asymptotic regime among all asymptotic profiles.

Existence of steady states for the Maxwell-Schrödinger-Poisson system: exploring the applicability of the concentration-compactness principle
Isabelle Catto, Jean Dolbeault, Óscar Sánchez, Juan Soler
Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2013, 23 (10), pp.1915-1938

This paper is intended to review recent results and open problems concerning the existence of steady states to the Maxwell-Schrödinger system. A combination of tools, proofs and results are presented in the framework of the concentration--compactness method.

A scenario for symmetry breaking in Caffarelli-Kohn-Nirenberg inequalities
Jean Dolbeault, Maria J. Esteban
Journal of Numerical Mathematics, De Gruyter, 2013, 30 (3-4), pp.233-249

The purpose of this paper is to explain the phenomenon of symmetry breaking for optimal functions in functional inequalities by the numerical computations of some well chosen solutions of the corresponding Euler-Lagrange equations. For many of those inequalities it was believed that the only source of symmetry breaking would be the instability of the symmetric optimizer in the class of all admissible functions. But recently, it was shown by an indirect argument that for some Caffarelli-Kohn-Nirenberg inequalities this conjecture was not true. In order to understand this new symmetry breaking mechanism we have computed the branch of minimal solutions for a simple problem. A reparametrization of this branch allows us to build a scenario for the new phenomenon of symmetry breaking. The computations have been performed using Freefem++.

The Euclidean Onofri inequality in higher dimensions
Manuel del Pino, Jean Dolbeault
International Mathematics Research Notices, Oxford University Press (OUP), 2013, 15, pp.3600-3611

The classical Onofri inequality in the two-dimensional sphere assumes a natural form in the plane when transformed via stereographic projection. We establish an optimal version of a generalization of this inequality in the d-dimensional Euclidean space for any d≥2, by considering the endpoint of a family of optimal Gagliardo-Nirenberg interpolation inequalities. Unlike the two-dimensional case, this extension involves a rather unexpected Sobolev-Orlicz norm, as well as a probability measure no longer related to stereographic projection.

Exponential rate of convergence to equilibrium for a model describing fiber lay-down processes
Jean Dolbeault, Axel Klar, Clément Mouhot, Christian Schmeiser
Applied Mathematics Research eXpress, Oxford University Press (OUP): Policy H - Oxford Open Option A, 2013, 2013, pp.165-175. ⟨10.1093/amrx/abs015⟩

This paper is devoted to the adaptation of the method developed in [4,3] to a Fokker-Planck equation for fiber lay-down which has been studied in [1,5]. Exponential convergence towards a unique stationary state is proved in a norm which is equivalent to a weighted $L^2$ norm. The method is based on a micro / macro decomposition which is well adapted to the diffusion limit regime.

Qualitative properties and existence of sign changing solutions with compact support for an equation with a p-Laplace operator
Jean Dolbeault, Marta Garcia-Huidobro, Raul Manásevich
Avanced Nonlinear Studies, 2013

We consider radial solutions of an elliptic equation involving the p-Laplace operator and prove by a shooting method the existence of compactly supported solutions with any prescribed number of nodes. The method is based on a change of variables in the phase plane corresponding to an asymptotic Hamiltonian system and provides qualitative properties of the solutions.

Sharp interpolation inequalities on the sphere : new methods and consequences
Jean Dolbeault, Maria J. Esteban, Michal Kowalczyk, Michael Loss
Chinese Annals of Mathematics - Series B, Springer Verlag, 2013, 34 (1), pp.99-112. ⟨10.1007/s11401-012-0756-6⟩

These notes are devoted to various considerations on a family of sharp interpolation inequalities on the sphere, which in dimension two and higher interpolate between Poincaré, logarithmic Sobolev and critical Sobolev (Onofri in dimension two) inequalities. We emphasize the connexion between optimal constants and spectral properties of the Laplace-Beltrami operator on the sphere. We shall address a series of related observations and give proofs based on symmetrization and the ultraspherical setting.

Spectral properties of Schrödinger operators on compact manifolds: rigidity, flows, interpolation and spectral estimates
Jean Dolbeault, Maria J. Esteban, Ari Laptev, Michael Loss
Comptes rendus de l'Académie des sciences. Série I, Mathématique, Elsevier, 2013, 351 (11-12), pp.437-440

This note is devoted to optimal spectral estimates for Schrödinger operators on compact connected Riemannian manifolds without boundary. These estimates are based on the use of appropriate interpolation inequalities and on some recent rigidity results for nonlinear elliptic equations on those manifolds.

Improved Poincaré inequalities
Jean Dolbeault, Bruno Volzone
Nonlinear Analysis: Theory, Methods and Applications, Elsevier, 2012, 75 (16), pp.5985 - 6001

Although the Hardy inequality corresponding to one quadratic singularity, with optimal constant, does not admit any extremal function, it is well known that such a potential can be improved, in the sense that a positive term can be added to the quadratic singularity without violating the inequality, and even a whole asymptotic expansion can be build, with optimal constants for each term. This phenomenon has not been much studied for other inequalities. Our purpose is to prove that it also holds for the gaussian Poincaré inequality. The method is based on a recursion formula, which allows to identify the optimal constants in the asymptotic expansion, order by order. We also apply the same strategy to a family of Hardy-Poincaré inequalities which interpolate between Hardy and gaussian Poincaré inequalities.

Symmetry of extremals of functional inequalities via spectral estimates for linear operators
Jean Dolbeault, Maria J. Esteban, Michael Loss
Journal of Mathematical Physics, American Institute of Physics (AIP), 2012, 53(P), pp.095204

We prove new symmetry results for the extremals of the Caffarelli-Kohn-Nirenberg inequalities in any dimension larger or equal than 2, in a range of parameters for which no explicit results of symmetry were previously known.

Extremal functions for Caffarelli-Kohn-Nirenberg and logarithmic Hardy inequalities
Jean Dolbeault, Maria J. Esteban
Proceedings of the Royal Society of Edinburgh: Section A Mathematics, Cambridge University Press (CUP), 2012, 142A, pp.745-767

We consider a family of Caffarelli-Kohn-Nirenberg interpolation inequalities and weighted logarithmic Hardy inequalities which have been obtained recently as a limit case of the first ones. We discuss the ranges of the parameters for which the optimal constants are achieved by extremal functions. The comparison of these optimal constants with the optimal constants of Gagliardo-Nirenberg interpolation inequalities and Gross' logarithmic Sobolev inequality, both without weights, gives a general criterion for such an existence result in some particular cases.

From Poincaré to logarithmic Sobolev inequalities: a gradient flow approach
Jean Dolbeault, Bruno Nazaret, Giuseppe Savaré
SIAM Journal on Mathematical Analysis, Society for Industrial and Applied Mathematics, 2012, 44 (5), pp.3186-3216

We use the distances introduced in a previous joint paper to exhibit the gradient flow structure of some drift-diffusion equations for a wide class of entropy functionals. Functional inequalities obtained by the comparison of the entropy with the entropy production functional reflect the contraction properties of the flow. Our approach provides a unified framework for the study of the Kolmogorov-Fokker-Planck (KFP) equation.

A functional framework for the Keller-Segel system: logarithmic Hardy-Littlewood-Sobolev and related spectral gap inequalities
Jean Dolbeault, Juan Campos Serrano
Comptes Rendus. Mathématique, Académie des sciences (Paris), 2012, 350 (21-22), pp.949-954

This note is devoted to several inequalities deduced from a special form of the logarithmic Hardy-Littlewood-Sobolev, which is well adapted to the characterization of stationary solutions of a Keller-Segel system written in self-similar variables, in case of a subcritical mass. For the corresponding evolution problem, such functional inequalities play an important role for identifying the rate of convergence of the solutions towards the stationary solution with same mass.

Large mass self-similar solutions of the parabolic-parabolic Keller--Segel model of chemotaxis
Piotr Biler, Lucilla Corrias, Jean Dolbeault
Journal of Mathematical Biology, Springer Verlag (Germany), 2011, 63, pp.1-32. ⟨10.1007/s00285-010-0357-5⟩

In two space dimensions, the parabolic-parabolic Keller--Segel system shares many properties with the parabolic-elliptic Keller--Segel system. In particular, solutions globally exist in both cases as long as their mass is less than 8π. However, this threshold is not as clear in the parabolic-parabolic case as it is in the parabolic-elliptic case, in which solutions with mass above 8π always blow up. Here we study forward self-similar solutions of the parabolic-parabolic Keller--Segel system and prove that, in some cases, such solutions globally exist even if their total mass is above 8π, which is forbidden in the parabolic-elliptic case.

Improved intermediate asymptotics for the heat equation
Jean-Philippe Bartier, Adrien Blanchet, Jean Dolbeault, Miguel Escobedo
Applied Mathematics Letters, Elsevier, 2011, 24 (1), pp.76 - 81. ⟨10.1016/j.aml.2010.08.020⟩

This letter is devoted to results on intermediate asymptotics for the heat equation. We study the convergence towards a stationary solution in self-similar variables. By assuming the equality of some moments of the initial data and of the stationary solution, we get improved convergence rates using entropy / entropy-production methods. We establish the equivalence of the exponential decay of the entropies with new, improved functional inequalities in restricted classes of functions. This letter is the counterpart in a linear framework of a recent work on fast diffusion equations, see [Bonforte-Dolbeault-Grillo-Vazquez]. Results extend to the case of a Fokker-Planck equation with a general confining potential.

Sobolev and Hardy-Littlewood-Sobolev inequalities: duality and fast diffusion
Jean Dolbeault
Math. Res. Lett., 2011, 18 (6), pp.1037-1050

In the euclidean space, Sobolev and Hardy-Littlewood-Sobolev inequalities can be related by duality. In this paper, we investigate how to relate these inequalities using the flow of a fast diffusion equation in dimension $d\ge3$. The main consequence is an improvement of Sobolev's inequality when $d\ge5$, which involves the various terms of the dual Hardy-Littlewood-Sobolev inequality. In dimension $d=2$, Onofri's inequality plays the role of Sobolev's inequality and can also be related to its dual inequality, the logarithmic Hardy-Littlewood-Sobolev inequality, by a super-fast diffusion equation.

Thermal effects in gravitational Hartree systems
Gonca Aki, Jean Dolbeault, Christof Sparber
Annales Henri Poincaré, Springer Verlag, 2011, 12, pp.1055-1079

We consider the non-relativistic Hartree model in the gravitational case, i.e. with attractive Coulomb-Newton interaction. For a given mass, we construct stationary states with non-zero temperature by minimizing the corresponding free energy functional. It is proved that minimizers exist if and only if the temperature of the system is below a certain threshold(possibly infinite), which itself depends on the specific choice of the entropy functional. We also investigate whether the corresponding minimizers are mixed or pure quantum states and characterize a positive critical temperature above which mixed states appear.

Fast diffusion equations: matching large time asymptotics by relative entropy methods
Jean Dolbeault, Giuseppe Toscani
Kinetic and Related Models , AIMS, 2011, 4 (3), pp.701-716

A non self-similar change of coordinates provides improved matching asymptotics of the solutions of the fast diffusion equation for large times, compared to already known results, in the range for which Barenblatt solutions have a finite second moment. The method is based on relative entropy estimates and a time-dependent change of variables which is determined by second moments, and not by the scaling corresponding to the self-similar Barenblatt solutions, as it is usually done.

Radial symmetry and symmetry breaking for some interpolation inequalities
Jean Dolbeault, Maria J. Esteban, Gabriella Tarantello, Achiles Tertikas
Calculus of Variations and Partial Differential Equations, Springer Verlag, 2011, 42, pp.461-485

We analyze the radial symmetry of extremals for a class of interpolation inequalities known as Caffarelli-Kohn-Nirenberg inequalities, and for a class of weighted logarithmic Hardy inequalities which appear as limiting cases of the first ones. In both classes we show that there exists a continuous surface that splits the set of admissible parameters into a region where extremals are symmetric and a region where symmetry breaking occurs. In previous results, the symmetry breaking region was identified by showing the linear instability of the radial extremals. Here we prove that symmetry can be broken even within the set of parameters where radial extremals correspond to local minima for the variational problem associated with the inequality. For interpolation inequalities, such a symmetry breaking phenomenon is entirely new.

Sharp rates of decay of solutions to the nonlinear fast diffusion equation via functional inequalities
Matteo Bonforte, Jean Dolbeault, Gabriele Grillo, Juan-Luis Vázquez
Proceedings of the National Academy of Sciences of the United States of America , National Academy of Sciences, 2010, 107 (38), pp.16459-16464. ⟨10.1073/pnas.1003972107⟩

The goal of this note is to state the optimal decay rate for solutions of the nonlinear fast diffusion equation and, in self-similar variables, the optimal convergence rates to Barenblatt self-similar profiles and their generalizations. It relies on the identification of the optimal constants in some related Hardy-Poincaré inequalities and concludes a long series of papers devoted to generalized entropies, functional inequalities and rates for nonlinear diffusion equations.

Relative equilibria in continuous stellar dynamics
Juan Campos Serrano, Manuel del Pino, Jean Dolbeault
Communications in Mathematical Physics, Springer Verlag, 2010, 300, pp.765-788. ⟨10.1007/s00220-010-1128-2⟩

We study a three dimensional continuous model of gravitating matter rotating at constant angular velocity. In the rotating reference frame, by a finite dimensional reduction, we prove the existence of non radial stationary solutions whose supports are made of an arbitrarily large number of disjoint compact sets, in the low angular velocity and large scale limit. At first order, the solutions behave like point particles, thus making the link with the relative equilibria} in N-body dynamics.

A logarithmic Hardy inequality
Manuel del Pino, Jean Dolbeault, Stathis Filippas, Achiles Tertikas
Journal of Functional Analysis, Elsevier, 2010, 259 (8), pp.2045-2072. ⟨10.1016/j.jfa.2010.06.005⟩

We prove a new inequality which improves on the classical Hardy inequality in the sense that a nonlinear integral quantity with super-quadratic growth, which is computed with respect to an inverse square weight, is controlled by the energy. This inequality differs from standard logarithmic Sobolev inequalities in the sense that the measure is neither Lebesgue's measure nor a probability measure. All terms are scale invariant. After an Emden-Fowler transformation, the inequality can be rewritten as an optimal inequality of logarithmic Sobolev type on the cylinder. Explicit expressions of the sharp constant, as well as minimizers, are established in the radial case. However, when no symmetry is imposed, the sharp constants are not achieved among radial functions, in some range of the parameters.

On the symmetry of extremals for the Caffarelli-Kohn-Nirenberg inequalities
Jean Dolbeault, Maria J. Esteban, Michael Loss, Gabriella Tarantello
Advanced Nonlinear Studies, Walter de Gruyter GmbH, 2009, 9, pp.713-727

In this paper we prove some new symmetry results for the extremals of the Caffarelli-Kohn-Nirenberg inequalities, in any dimension larger or equal than two.

Non-existence and uniqueness results for supercritical semilinear elliptic equations
Jean Dolbeault, Robert Stanczy
Annales Henri Poincaré, Springer Verlag, 2009, 10 (7), pp.1311-1333

Non-existence and uniqueness results are proved for several local and non-local supercritical bifurcation problems involving a semilinear elliptic equation depending on a parameter. The domain is star-shaped but no other symmetry assumption is required. Uniqueness holds when the bifurcation parameter is in a certain range. Our approach can be seen, in some cases, as an extension of non-existence results for non-trivial solutions. It is based on Rellich-Pohozaev type estimates. Semilinear elliptic equations naturally arise in many applications, for instance in astrophysics, hydrodynamics or thermodynamics. We simplify the proof of earlier results by K. Schmitt and R. Schaaf in the so-called local multiplicative case, extend them to the case of a non-local dependence on the bifurcation parameter and to the additive case, both in local and non-local settings.

Orbitally stable states in generalized Hartree-Fock theory
Jean Dolbeault, Patricio Felmer, Mathieu Lewin
Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2009, 19 (3), pp.347-367

This paper is devoted to the Hartree-Fock model with temperature in the euclidean space. For large classes of free energy functionals, minimizers are obtained as long as the total charge of the system does not exceed a threshold which depends on the temperature. The usual Hartree-Fock model is recovered in the zero temperature limit. An orbital stability result for the Cauchy problem is deduced from the variational approach.

Multiplicity results for the assigned Gauss curvature problem in R2
Jean Dolbeault, Maria J. Esteban, Gabriella Tarantello
Nonlinear Analysis: Theory, Methods and Applications, Elsevier, 2009, 70 (8), pp.2870-2881

To study the problem of the assigned Gauss curvature with conical singularities on Riemanian manifolds, we consider the Liouville equation with a single Dirac measure on the two-dimensional sphere. By a stereographic projection, we reduce the problem to a Liouville equation on the euclidean plane. We prove new multiplicity results for bounded radial solutions, which improve on earlier results of C.-S. Lin and his collaborators. Based on numerical computations, we also present various conjectures on the number of unbounded solutions. Using symmetries, some multiplicity results for non radial solutions are also stated.

The two-dimensional Keller-Segel model after blow-up
Jean Dolbeault, Christian Schmeiser
Discrete and Continuous Dynamical Systems - Series B, American Institute of Mathematical Sciences, 2009, 25, pp.109-121

In the two-dimensional Keller-Segel model for chemotaxis of biological cells, blow-up of solutions in finite time occurs if the total mass is above a critical value. Blow-up is a concentration event, where point aggregates are created. In this work global existence of generalized solutions is proven, allowing for measure valued densities. This extends the solution concept after blow-up. The existence result is an application of a theory developed by Poupaud, where the cell distribution is characterized by an additional defect measure, which vanishes for smooth cell densities. The global solutions are constructed as limits of solutions of a regularized problem. A strong formulation is derived under the assumption that the generalized solution consists of a smooth part and a number of smoothly varying point aggregates. Comparison with earlier formal asymptotic results shows that the choice of a solution concept after blow-up is not unique and depends on the type of regularization. This work is also concerned with local density profiles close to point aggregates. An equation for these profiles is derived by passing to the limit in a rescaled version of the regularized model. Solvability of the profile equation can also be obtained by minimizing a free energy functional.

Stochastic Stokes' drift, homogenized functional inequalities, and large time behavior of Brownian ratchets
Adrien Blanchet, Jean Dolbeault, Michal Kowalczyk
SIAM Journal on Mathematical Analysis, Society for Industrial and Applied Mathematics, 2009, 41, pp.46-76

A periodic perturbation of a Gaussian measure modifies the sharp constants in Poincaré and logarithmic Sobolev inequalities in the homogenization limit, that is, when the period of a periodic perturbation converges to zero. We use variational techniques to determine the homogenized constants and get optimal convergence rates towards equilibrium of the solutions of the perturbed diffusion equations. The study of these sharp constants is motivated by the study of the stochastic Stokes' drift. It also applies to Brownian ratchets and molecular motors in biology. We first establish a transport phenomenon. Asymptotically, the center of mass of the solution moves with a constant velocity, which is determined by a doubly periodic problem. In the reference frame attached to the center of mass, the behaviour of the solution is governed at large scale by a diffusion with a modified diffusion coefficient. Using the homogenized logarithmic Sobolev inequality, we prove that the solution converges in self-similar variables attached to the center of mass to a stationary solution of a Fokker-Planck equation modulated by a periodic perturbation with fast oscillations, with an explicit rate. We also give an asymptotic expansion of the traveling diffusion front corresponding to the stochastic Stokes' drift with given potential flow.

Asymptotics of the fast diffusion equation via entropy estimates
Adrien Blanchet, Matteo Bonforte, Jean Dolbeault, Gabriele Grillo, Juan-Luis Vázquez
Archive for Rational Mechanics and Analysis, Springer Verlag, 2009, 191, pp.347-385

We consider non-negative solutions of the fast diffusion equation u_t=\Delta u^m with m\in(0,1), in the Euclidean space R^d, d \ge 3, and study the asymptotic behavior of a natural class of solutions, in the limit corresponding to t\to\infty for m \ge mc=(d-2)/d, or as t approaches the extinction time when m

A new class of transport distances between measures
Jean Dolbeault, Bruno Nazaret, Giuseppe Savaré
Calc. Var. Partial Differential Equations, 2009, 34 (2), pp.193-231

We introduce a new class of distances between nonnegative Radon measures on the euclidean space. They are modeled on the dynamical characterization of the Kantorovich-Rubinstein-Wasserstein distances proposed by Benamou and Brenier and provide a wide family interpolating between Wasserstein and homogeneous Sobolev distances. From the point of view of optimal transport theory, these distances minimize a dynamical cost to move a given initial distribution of mass to a final configuration. An important difference with the classical setting in mass transport theory is that the cost not only depends on the velocity of the moving particles but also on the densities of the intermediate configurations with respect to a given reference measure. We study the topological and geometric properties of these new distances, comparing them with the notion of weak convergence of measures and the well established Kantorovich-Rubinstein-Wasserstein theory. An example of possible applications to the geometric theory of gradient flows is also given.

Harnack inequalities and discrete - continuum error estimates for a chain of atoms with two - body interactions
Rafael Benguria, Jean Dolbeault, Régis Monneau
Journal of Statistical Physics, Springer Verlag, 2009, 134, pp.27-51

In the three-dimensional euclidean space, we consider deformations of an infinite linear chain of atoms where each atom interacts with all others through a two-body potential. We compute the effect of an external force applied to the chain. At equilibrium, the positions of the particles satisfy an Euler-Lagrange equation. For large classes of potentials, we prove that every solution is well approximated by the solution of a continuous model. We establish an error estimate between the discrete and the continuous solution based on a Harnack lemma of independent interest. Finally we apply our results to some Lennard-Jones potentials.

Hypocoercivity for kinetic equations with linear relaxation terms
Jean Dolbeault, Clément Mouhot, Christian Schmeiser
Comptes Rendus. Mathématique, Académie des sciences (Paris), 2009, 347 (9-10), pp.511-516

This note is devoted to a simple method for proving hypocoercivity of the solutions of a kinetic equation involving a linear time relaxation operator, i.e. the construction of an adapted Lyapunov functional satisfying a Gronwall-type inequality. The method clearly distinguishes the coercivity at microscopic level, which directly arises from the properties of the relaxation operator, and a spectral gap inequality at the macroscopic level for the spatial density, which is connected to the diffusion limit. It improves on previously known results. Our approach is illustrated by the linear BGK model and a relaxation operator which corresponds at macroscopic level to the linearized fast diffusion.

Asymptotic behaviour for small mass in the two-dimensional parabolic-elliptic Keller-Segel model
Adrien Blanchet, Jean Dolbeault, Miguel Escobedo, Javier Fernández
Journal of Mathematical Analysis and Applications, Elsevier, 2008, 361 (2), pp.533-542. ⟨10.1016/j.jmaa.2009.07.034⟩

The Keller-Segel system describes the collective motion of cells that are attracted by a chemical substance and are able to emit it. In its simplest form, it is a conservative drift-diffusion equation for the cell density coupled to an elliptic equation for the chemo-attractant concentration. This paper deals with the rate of convergence towards a unique stationary state in self-similar variables, which describes the intermediate asymptotics of the solutions in the original variables. Although it is known that solutions globally exist for any mass less $8\pi\,$, a smaller mass condition is needed in our approach for proving an exponential rate of convergence in self-similar~variables.

Travelling fronts in stochastic Stokes' drifts
Adrien Blanchet, Jean Dolbeault, Michal Kowalczyk
Physica A: Statistical Mechanics and its Applications, Elsevier, 2008, 387 (23), pp.5741-5751. ⟨10.1016/j.physa.2008.06.011⟩

By analytical methods we study the large time properties of the solution of a simple one-dimensional model of stochastic Stokes' drift. Semi-explicit formulae allow us to characterize the behaviour of the solutions and compute global quantities such as the asymptotic speed of the center of mass or the effective diffusion coefficient. Using an equivalent tilted ratchet model, we observe that the speed of the center of mass converges exponentially to its limiting value. A diffuse, oscillating front attached to the center of mass appears. The description of the front is given using an asymptotic expansion. The asymptotic solution attracts all solutions at an algebraic rate which is determined by the effective diffusion coefficient. The proof relies on an entropy estimate based on homogenized logarithmic Sobolev inequalities. In the traveling frame, the macroscopic profile obeys to an isotropic diffusion. Compared with the original diffusion, diffusion is enhanced or reduced, depending on the regime. At least in the limit cases, the rate of convergence to the effective profile is always decreased. All these considerations allow us to define a notion of efficiency for coherent transport, characterized by a dimensionless number, which is illustrated on two simple examples of traveling potentials with a sinusoidal shape in the first case, and a sawtooth shape in the second case.

Localized minimizers of flat rotating gravitational systems
Jean Dolbeault, Javier Fernández
Annales de l'Institut Henri Poincaré (C) Non Linear Analysis, Elsevier, 2008, 25, pp.1043-1071

We study a two dimensional system in solid rotation at constant angular velocity driven by a self-consistent three dimensional gravitational field. We prove the existence of non symmetric stationary solutions of such a flat system in the rotating frame as long as the angular velocity does not exceed some critical value which depends on the mass. The solutions can be seen as stationary solutions of a kinetic equation with a relaxation-time collision kernel forcing the convergence to the polytropic gas solutions, or as stationary solutions of an extremely simplified drift-diffusion model, which is derived from the kinetic equation by formally taking a diffusion limit. In both cases, the solutions are critical points of a free energy functional, and can be seen as localized minimizers in an appropriate sense. Symmetry breaking occurs for small angular velocities.

Lq-functional inequalities and weighted porous media equations
Jean Dolbeault, Ivan Gentil, Arnaud Guillin, Feng-Yu Wang
Potential Analysis, Springer Verlag, 2008, 28, pp.35-59

Using measure-capacity inequalities we study new functional inequalities, namely L^q-Poincaré inequalities and L^q-logarithmic Sobolev inequalities. As a consequence, we establish the asymptotic behavior of the solutions to the so-called weighted porous media equation for m?1, in terms of L^2-norms and entropies.

Estimates for the optimal constants in multipolar Hardy inequalities for Schrödinger and Dirac operators
Roberta Bosi, Jean Dolbeault, Maria J. Esteban
Communications on Pure and Applied Mathematics, Wiley, 2008, 7, pp.533-562

By expanding squares, we prove several Hardy inequalities with two critical singularities and constants which explicitly depend upon the distance between the two singularities. These inequalities involve the L2 norm. Such results are generalized to an arbitrary number of singularities and compared with standard results given by the IMS method. The generalized version of Hardy inequalities with several singularities is equivalent to some spectral information on a Schrödinger operator involving a potential with several inverse square singularities. We also give a generalized Hardy inequality for Dirac operators in the case of a potential having several singularities of Coulomb type, which are critical for Dirac operators.

The role of Onofri type inequalities in the symmetry properties of extremals for Caffarelli-Kohn-Nirenberg inequalities, in two space dimensions
Jean Dolbeault, Maria J. Esteban, Gabriella Tarantello
Annali della Scuola Normale Superiore di Pisa, 2008, 7, pp.313-341

We first prove a weighted inequality of Moser-Trudinger type depending on a parameter, in the two-dimensional Euclidean space. The inequality holds for radial functions if the parameter is larger than -1. Without symmetry assumption, it holds if and only if the parameter is in the interval (-1,0]. The inequality gives us some insight on the symmetry breaking phenomenon for the extremal functions of the Hardy-Sobolev inequality, as established by Caffarelli-Kohn-Nirenberg, in two space dimensions. In fact, for suitable sets of parameters (asymptotically sharp) we prove symmetry or symmetry breaking by means of a blow-up method. In this way, the weighted Moser-Trudinger inequality appears as a limit case of the Hardy-Sobolev inequality.

On the Bakry-Emery criterion for linear diffusions and weighted porous media equations
Jean Dolbeault, Bruno Nazaret, Giuseppe Savaré
Communications in Mathematical Sciences, International Press, 2008, 6, pp.477-494

The goal of this paper is to give a non-local sufficient condition for generalized Poincaré inequalities, which extends the well-known Bakry-Emery condition. Such generalized Poincaré inequalities have been introduced by W. Beckner in the gaussian case and provide, along the Ornstein-Uhlenbeck flow, the exponential decay of some generalized entropies which interpolate between the $L^2$ norm and the usual entropy. Our criterion improves on results which, for instance, can be deduced from the Bakry-Emery criterion and Holley-Stroock type perturbation results. In a second step, we apply the same strategy to non-linear equations of porous media type. This provides new interpolation inequalities and decay estimates for the solutions of the evolution problem. The criterion is again a non-local condition based on the positivity of the lowest eigenvalue of a Schrödinger operator. In both cases, we relate the Fisher information with its time derivative. Since the resulting criterion is non-local, it is better adapted to potentials with, for instance, a non-quadratic growth at infinity, or to unbounded perturbations of the potential.

Lieb-Thirring inequalities with improved constants
Jean Dolbeault, Ari Laptev, Michael Loss
Journal of the European Mathematical Society, European Mathematical Society, 2008, 10, pp.1121-1126

Following Eden and Foias we obtain a matrix version of a generalised Sobolev inequality in one-dimension. This allow us to improve on the known estimates of best constants in Lieb-Thirring inequalities for the sum of the negative eigenvalues for multi-dimensional Schroedinger operators.

Compactness properties for trace-class operators and applications to quantum mechanics
Jean Dolbeault, Patricio Felmer, Juan Mayorga-Zambrano
Monatshefte für Mathematik, Springer Verlag, 2008, 155 (1), pp.43-66

Interpolation inequalities of Gagliardo-Nirenberg type and compactness results for self-adjoint trace-class operators with finite kinetic energy are established. Applying these results to the minimization of various free energy functionals, we determine for instance stationary states of the Hartree problem with temperature corresponding to various statistics.

Characterization of the critical magnetic field in the Dirac-Coulomb equation
Jean Dolbeault, Maria J. Esteban, Michael Loss
Journal of Physics A General Physics (1968-1972), Institute of Physics (IOP), 2008, 41, pp.185303

We consider a relativistic hydrogenic atom in a strong magnetic field. The ground state level depends on the strength of the magnetic field and reaches the lower end of the spectral gap of the Dirac-Coulomb operator for a certain critical value, the critical magnetic field. We also define a critical magnetic field in a Landau level ansatz. In both cases, when the charge Z of the nucleus is not too small, these critical magnetic fields are huge when measured in Tesla, but not so big when the equation is written in dimensionless form. When computed in the Landau level ansatz, orders of magnitude of the critical field are correct, as well as the dependence in Z. The computed value is however significantly too big for a large Z, and the wave function is not well approximated. Hence, accurate numerical computations involving the Dirac equation cannot systematically rely on the Landau level ansatz. Our approach is based on a scaling property. The critical magnetic field is characterized in terms of an equivalent eigenvalue problem. This is our main analytical result, and also the starting point of our numerical scheme.

Interpolation between logarithmic Sobolev and Poincaré inequalities
Anton Arnold, Jean-Philippe Bartier, Jean Dolbeault
Communications in Mathematical Sciences, International Press, 2007, 5 (4), pp.971-979

This note is concerned with intermediate inequalities which interpolate between the logarithmic Sobolev and the Poincaré inequalities. For such generalized Poincaré inequalities we improve upon the known constants from the literature. Cette note est consacrée à des inégalités intermédiaires qui interpolent entre les inégalités de Sobolev logarithmiques et les inégalités de Poincaré. Pour de telles inégalités de Poincaré généralisées, nous améliorons les constantes données dans la littérature.

Hardy-type estimates for Dirac operators
Jean Dolbeault, Javier Duoandikoetxea, Maria J. Esteban, Luis Vega
Annales Scientifiques de l'École Normale Supérieure, Société mathématique de France, 2007, 40 (6), pp.885-900

We prove some Hardy type inequalities related to the Dirac operator by elementary methods, for a large class of potentials, which even includes measure valued potentials. Optimality is achieved by the Coulomb potential. When potentials are smooth enough, our estimates provide some spectral information on the operator.

Nonlinear diffusions as limit of kinetic equations with relaxation collision kernels
Jean Dolbeault, Peter Markowich, Dietmar Oelz, Christian Schmeiser
Archive for Rational Mechanics and Analysis, Springer Verlag, 2007, 186 (1), pp.133-158

Kinetic transport equations with a given confining potential and non-linear relaxation type collision operators are considered. General (monotone) energy dependent equilibrium distributions are allowed with a chemical potential ensuring mass conservation. Existence and uniqueness of solutions is proven for initial data bounded by equilibrium distributions. The diffusive macroscopic limit is carried out using compensated compactness theory. The result are drift-diffusion equations with nonlinear diffusion. The most notable examples are of porous medium or fast diffusion type, with exponent ranging from 0 to 5/3, in dimension 3.

A qualitative study of linear drift-diffusion equations with time-dependent or degenerate coefficients
Jean-Philippe Bartier, Jean Dolbeault, Reinhard Illner, Michal Kowalczyk
Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2007, 17 (3), pp.327-362

This paper is concerned with entropy methods for linear drift-diffusion equations with explicitly time-dependent or degenerate coefficients. Our goal is to establish a list of various qualitative properties of the solutions. The motivation for this study comes from a model for molecular motors, the so-called Brownian ratchet, and from a nonlinear equation arising in traffic flow models, for which complex long time dynamics occurs. General results are out of the scope of this paper, but we deal with several examples corresponding to most of the expected behaviors of the solutions. We first prove a contraction property for general entropies which is a useful tool for uniqueness and for the convergence to some eventually time-dependent large time asymptotic solutions. Then we focus on power law and logarithmic relative entropies. When the diffusion term is of the type $\nabla(|x|^\alpha\,\nabla\cdot)$, we prove that the inequality relating the entropy with the entropy production term is a Hardy-Poincaré type inequality, that we establish. Here we assume that $\alpha\in (0,2]$ and the limit case $\alpha=2$ appears as a threshold for the method. As a consequence, we obtain an exponential decay of the relative entropies. In the case of time-periodic coefficients, we prove the existence of a unique time-periodic solution which attracts all other solutions. The case of a degenerate diffusion coefficient taking the form $|x|^\alpha$ with $\alpha>2$ is also studied. The Gibbs state exhibits a non integrable singularity. In this case concentration phenomena may occur, but we conjecture that an additional time-dependence restores the smoothness of the asymptotic solution.

Relativistic hydrogenic atoms in strong magnetic fields
Jean Dolbeault, Maria J. Esteban, Michael Loss
Annales Henri Poincaré, Springer Verlag, 2007, 8 (4), pp.749-779

In the Dirac operator framework we characterize and estimate the ground state energy of relativistic hydrogenic atoms in a constant magnetic field and describe the asymptotic regime corresponding to a large field strength using relativistic Landau levels. We also define and estimate a critical magnetic field beyond which stability is lost.

Hardy-Poincaré inequalities and applications to nonlinear diffusions
Adrien Blanchet, Matteo Bonforte, Jean Dolbeault, Gabriele Grillo, Juan-Luis Vázquez
Comptes rendus de l'Académie des sciences. Série I, Mathématique, Elsevier, 2007, 344 (7), pp.431-436

We systematically study weighted Poincaré type inequalities which are closely connected with Hardy type inequalities and establish the form of the optimal constants in some cases. Such inequalities are then used to relate entropy with entropy production and get intermediate asymptotics results for fast diffusion equations.

Stability for the gravitational Vlasov-Poisson system in dimension two
Jean Dolbeault, Javier Fernández, Óscar Sánchez
Communications in Partial Differential Equations, Taylor & Francis, 2006, 31, pp.1425-1449

Nous considérons en dimension deux le système de Vlasov-Poisson gravitationnel. Par des méthodes variationnelles, nous prouvons l'existence de solutions stationnaires d'énergie minimale sous une contrainte de type Casimir. La méthode donne aussi un résultat de stabilité de ces solutions pour le problème d'évolution. We consider the two dimensional gravitational Vlasov-Poisson system. Using variational methods, we prove the existence of stationary solutions of minimal energy under a Casimir type constraint. The method also provides a stability criterion of these solutions for the evolution problem.

Entropy-Energy inequalities and improved convergence rates for nonlinear parabolic equations
José Carrillo, Jean Dolbeault, Ivan Gentil, Ansgar Juengel
Discrete and Continuous Dynamical Systems - Series B, American Institute of Mathematical Sciences, 2006, 6 (5), pp.1027-1050

In this paper, we prove new functional inequalities of Poincaré type on the one-dimensional torus $S^1$ and explore their implications for the long-time asymptotics of periodic solutions of nonlinear singular or degenerate parabolic equations of second and fourth order. We generically prove a global algebraic decay of an entropy functional, faster than exponential for short times, and an asymptotically exponential convergence of positive solutions towards their average. The asymptotically exponential regime is valid for a larger range of parameters for all relevant cases of application: porous medium/fast diffusion, thin film and logarithmic fourth order nonlinear diffusion equations. The techniques are inspired by direct entropy-entropy production methods and based on appropriate Poincaré type inequalities.

Two-dimensional Keller-Segel model: optimal critical mass and qualitative properties of the solutions
Adrien Blanchet, Jean Dolbeault, Benoît Perthame
Electronic Journal of Differential Equations, Texas State University, Department of Mathematics, 2006, 44, pp.32
Two-dimensional Keller-Segel model: Optimal critical mass and qualitative properties of the solutions
Adrien Blanchet, Jean Dolbeault, Benoît Perthame
Electronic Journal of Differential Equations, Texas State University, Department of Mathematics, 2006, 44, 32 pp

The Keller-Segel system describes the collective motion of cells which are attracted by a chemical substance and are able to emit it. In its simplest form it is a conservative drift-diffusion equation for the cell density coupled to an elliptic equation for the chemo-attractant concentration. It is known that, in two space dimensions, for small initial mass, there is global existence of solutions and for large initial mass blow-up occurs. In this paper we complete this picture and give a detailed proof of the existence of weak solutions below the critical mass, above which any solution blows-up in finite time in the whole euclidean space. Using hypercontractivity methods, we establish regularity results which allow us to prove an inequality relating the free energy and its time derivative. For a solution with sub-critical mass, this allows us to give for large times an intermediate asymptotics'' description of the vanishing. In self-similar coordinates, we actually prove a convergence result to a limiting self-similar solution which is not a simple reflect of the diffusion.

Lieb-Thirring type inequalities and Gagliardo-Nirenberg inequalities for systems
Jean Dolbeault, Patricio Felmer, Michael Loss, Eric Paturel
Journal of Functional Analysis, Elsevier, 2006, 238 (1), pp.193-220

We prove a Lieb-Thirring type inequality for potentials such that the associated Schrödinger operator has a pure discrete spectrum made of an unbounded sequence of eigenvalues. This inequality is equivalent to a generalized Gagliardo-Nirenberg inequality for systems. As a special case, we prove a logarithmic Sobolev inequality for infinite systems of mixed states. Optimal constants are determined and free energy estimates in connection with mixed states representations are also investigated.

General results on the eigenvalues of operators with gaps, arising from both ends of the gaps. Application to Dirac operators.
Jean Dolbeault, Maria J. Esteban, Eric Séré
Journal of the European Mathematical Society, European Mathematical Society, 2006, 8 (2), pp.243-251

This paper is concerned with an extension and reinterpretation of previous results on the variational characterization of eigenvalues in gaps of the essential spectrum of self-adjoint operators. We state two general abstract results on the existence of eigenvalues in the gap and a continuation principle. Then, these results are applied to Dirac operators in order to characterize simultaneously eigenvalues corresponding to electronic and positronic bound states.

On the continuity of the time derivative of the solution to the parabolic obstacle problem with variable coefficients
Adrien Blanchet, Jean Dolbeault, Régis Monneau
Journal de Mathématiques Pures et Appliquées, Elsevier, 2006, 85 (3), pp.371-414

This paper is devoted to continuity results of the time derivative of the solution to the one-dimensional parabolic obstacle problem with variable coefficients. Under regularity assumptions on the obstacle and on the coefficients, we prove that the time derivative of the solution is continuous for almost every time. When the solution is nondecreasing in time this result holds for every time. We also give an energy criterion which characterizes the continuity of the time derivative of the solution at a point of the free boundary. Such a problem arises in the pricing of american options in generalized Black-Scholes models of finance. Our results apply in financial mathematics.

Convex Sobolev inequalities and spectral gap
Jean Dolbeault, Jean-Philippe Bartier
Comptes Rendus. Mathématique, Académie des sciences (Paris), 2006, 342 (5), pp.307-312

This note is devoted to the proof of convex Sobolev (or generalized Poincaré) inequalities which interpolate between spectral gap (or Poincaré) inequalities and logarithmic Sobolev inequalities. We extend to the whole family of convex Sobolev inequalities results which have recently been obtained by Cattiaux and Carlen and Loss for logarithmic Sobolev inequalities. Under local conditions on the density of the measure with respect to a reference measure, we prove that spectral gap inequalities imply all convex Sobolev inequalities with constants which are uniformly bounded in the limit approaching the logarithmic Sobolev inequalities. We recover the case of the logarithmic Sobolev inequalities as a special case.

Oscillating minimizers of a fourth order problem invariant under scaling
Isabelle Catto, Jean Dolbeault, Rafael Benguria, Régis Monneau
Journal of Differential Equations, Elsevier, 2004, 205 (1), pp.253-269. ⟨10.1016/j.jde.2004.03.024⟩

By variational methods, we prove the inequality $$\int_\R u''{}^2\,dx-\int_\R u''\,u^2\,dx\geq I\,\int_\R u^4\,dx\quad \forall\; u\in L^4(\R)\;\mbox{such that}\; u''\in L^2(\R)$$ for some constant $I\in (-9/64,-1/4)$. This inequality is connected to Lieb-Thirring type problems and has interesting scaling properties. The best constant is achieved by sign changing minimizers of a problem on periodic functions, but does not depend on the period. Moreover, we completely characterize the minimizers of the periodic problem.

A variational method for relativistic computations in atomic and molecular physics
Jean Dolbeault, Maria J. Esteban, Eric Séré
International Journal of Quantum Chemistry, Wiley, 2003, pp.149-155
Minimization methods for the one-particle Dirac equation
Jean Dolbeault, Maria J. Esteban, Eric Séré, Michel Vanbreugel
Physical Review Letters, American Physical Society, 2000, 85 (19), pp.4020-4023. ⟨10.1103/PhysRevLett.85.4020⟩

Taking into account relativistic effects in quantum chemistry is crucial for accurate computations involving heavy atoms. Standard numerical methods can deal with the problem of variational collapse and the appearance of spurious roots only in special cases. The goal of this Letter is to provide a general and robust method to compute particle bound states of the Dirac equation.

On the eigenvalues of operators with gaps. Application to Dirac operators.
Jean Dolbeault, Maria J. Esteban, Eric Séré
Journal of Functional Analysis, Elsevier, 2000, 174, pp.208-226. ⟨10.1006/jfan.1999.3542⟩

This paper is devoted to a general min-max characterization of the eigenvalues in a gap of the essential spectrum of a self-adjoint unbounded operator. We prove an abstract theorem, then we apply it to the case of Dirac operators with a Coulomb-like potential. The result is optimal for the Coulomb potential.

Conference papers

Symmetry and symmetry breaking: rigidity and flows in elliptic PDEs
Jean Dolbeault, Maria J. Esteban, Michael Loss
International Congress of Mathematicians, IMU, 2018, Rio de Janeiro, Brazil. pp.2279-2304, ⟨10.1142/9789813272880_0138⟩

The issue of symmetry and symmetry breaking is fundamental in all areas of science. Symmetry is often assimilated to order and beauty while symmetry breaking is the source of many interesting phenomena such as phase transitions, instabilities, segregation, self-organization, etc. In this contribution we review a series of sharp results of symmetry of nonnegative solutions of nonlinear elliptic differential equation associated with minimization problems on Euclidean spaces or manifolds. Nonnegative solutions of those equations are unique, a property that can also be interpreted as a rigidity result. The method relies on linear and nonlinear flows which reveal deep and robust properties of a large class of variational problems. Local results on linear instability leading to symmetry breaking and the bifurcation of non-symmetric branches of solutions are reinterpreted in a larger, global, variational picture in which our flows characterize directions of descent.

Extremal functions and symmetry breaking in Caffarelli-Kohn-Nirenberg inequalities
Jean Dolbeault
Optimal Constants in the Theory of Sobolev Spaces and PDEs, Feb 2010, Germany. pp.330-334

Results on extremal functions of some interpolation inequalities introduced by Caffarelli, Kohn and Nirenberg and of weighted logarithmic Hardy inequalities are briefly reviewed. Some results of radial symmetry or of symmetry breaking are sketched, which result in the statement of an open question. These notes are based on a collaboration with M. Esteban, M. Loss, G. Tarantello and A. Tertikas.

Extremal functions in some interpolation inequalities: Symmetry, symmetry breaking and estimates of the best constants
Jean Dolbeault, Maria J. Esteban
QMath11 Conference Mathematical Results in Quantum Physics, 2010, Czech Republic. pp.178-182

This contribution is devoted to a review of some recent results on existence, symmetry and symmetry breaking of optimal functions for Caffarelli-Kohn-Nirenberg and weighted logarithmic Hardy inequalities. These results have been obtained in a series of papers in collaboration with M. del Pino, S. Filippas, M. Loss, G. Tarantello and A. Tertikas and are presented from a new viewpoint.

About existence, symmetry and symmetry breaking for extremal functions of some interpolation functional inequalities
Jean Dolbeault, Maria J. Esteban
The Abel Symposium 2010, 2010, Norway. pp.117-130

This article is devoted to a review of some recent results on existence, symmetry and symmetry breaking of optimal functions for Caffarelli-Kohn-Nirenberg (CKN) and weighted logarithmic Hardy (WLH) inequalities. These results have been obtained in a series of papers in collaboration with M. del Pino, S. Filippas, M. Loss, G. Tarantello and A. Tertikas. Here we put the highlights on a symmetry breaking result: extremals of some inequalities are not radially symmetric in regions where the symmetric extremals are linearly stable. Special attention is paid to the study of the critical cases for (CKN) and (WLH).

On the one-dimensional parabolic obstacle problem with variable coefficients
Adrien Blanchet, Jean Dolbeault, Régis Monneau
Elliptic and parabolic problems, 2005, France. pp.5-66

Cette note est consacrée à la continuité de la dérivée en temps de la solution du problème de l'obstacle parabolique à coefficients variables. Les résultats s'appliquent au principe du "smooth fit" en analyse numérique et en mathématiques financières. Ce travail repose sur divers outils qui permettent d'étudier les problème à frontière libre : méthode de blow-up, formules de monotonie, résultats du type Liouville. ––––– This note is devoted to continuity results of the time derivative of the solution to the one-dimensional parabolic obstacle problem with variable coefficients. It applies to the smooth fit principle in numerical analysis and in financial mathematics. It relies on various tools for the study of free boundary problems: blow-up method, monotonicity formulae, Liouville's results.

Book sections

Critical magnetic field for 2d magnetic Dirac-Coulomb operators and Hardy inequalities
Jean Dolbeault, Maria J. Esteban, Michael Loss
Partial Differential Equations, Spectral Theory, and Mathematical Physics. The Ari Laptev Anniversary Volume, 18, EMS Press, pp.41-63, 2021, Partial Differential Equations, Spectral Theory, and Mathematical Physics. The Ari Laptev Anniversary Volume. EMS Series of Congress Reports

This paper is devoted to the study of the two-dimensional Dirac-Coulomb operator in presence of an Aharonov-Bohm external magnetic potential. We characterize the highest intensity of the magnetic field for which a two-dimensional magnetic Hardy inequality holds. Up to this critical magnetic field, the operator admits a distinguished self-adjoint extension and there is a notion of ground state energy, defined as the lowest eigenvalue in the gap of the continuous spectrum.

Sharpening of decay rates in Fourier based hypocoercivity methods
Anton Arnold, Jean Dolbeault, Christian Schmeiser, Tobias Wöhrer
F. Salvarani. Recent Advances in Kinetic Equations and Applications, 48, Springer INdAM Series, In press, ⟨10.1007/978-3-030-82946-9_1⟩

This paper is dealing with two L2 hypocoercivity methods based on Fourier decomposition and mode-by-mode estimates, with applications to rates of convergence or decay in kinetic equations on the torus and on the whole Euclidean space. The main idea is to perturb the standard L2 norm by a twist obtained either by a nonlocal perturbation build upon diffusive macroscopic dynamics, or by a change of the scalar product based on Lyapunov matrix inequalities. We explore various estimates for equations involving a Fokker-Planck and a linear relaxation operator. We review existing results in simple cases and focus on the accuracy of the estimates of the rates. The two methods are compared in the case of the Goldstein-Taylor model in one-dimension.

Entropies and Equilibria of Many-Particle Systems: An Essay on Recent Research
Anton Arnold, José Antonio Carrillo, Laurent Desvillettes, Jean Dolbeault, Ansgar Jüngel, Lederman Claudia, Peter A. Markowich, Giuseppe Toscani, Cédric Villani
Nonlinear Differential Equation Models, pp.35-43, 2004, ⟨10.1007/978-3-7091-0609-9_5⟩

.This essay is intended to present a fruitful collaboration which has developed among a group of people whose names are listed above: entropy methods have proved over the last years to be an efficient tool for the understanding of the qualitative properties of physically sound models, for accurate numerics and for a more mathematical understanding of nonlinear PDEs. The goal of this essay is to sketch the historical development of the concept of entropy in connection with PDEs of continuum mechanics, to present recent results which have been obtained by the members of the group and to emphasize the most striking achievements of this research. The presentation is by no way an exhaustive review of the methods and results involving the entropy, not even in the field of PDEs. Many other researchers in and outside Europe have contributed to the development of this field, including – but not only – in collaboration with some of the people of the group. However, it can be claimed that this group had a leading role over the recent years and this essay is intended to explain how this occurred.

Computational approaches of relativistic models in quantum chemistry
Jean-Paul Desclaux, Jean Dolbeault, Maria J. Esteban, Paul Indelicato, Eric Séré
P.G. Ciarlet (series editor), C. Le Bris (guest editor). Handbook of numerical analysis, Vol. X. Special volume: computational chemistry., North-Holland, Amsterdam, pp.453-483, 2003, Handbook of numerical analysis

This chapter is a review of some methods used for the computation of relativistic atomic and molecular models based on the Dirac equation. In the linear case, we briefly describe finite basis set approaches, including ones that are generated numerically, perturbation theory and effective Hamiltonians procedures, direct variational methods based on nonlinear transformations, min-max formulations and constrained minimizations. In the atomic case, we describe the MCDF method and some ways to solve numerically the homogeneous and inhomogeneous Dirac-Fock equations. Finally, we describe also some numerical methods relevant to the case of molecules.