Abstract
We establish a dimension-free improvement of Talagrand’s Gaussian transport-entropy inequality, under the assumption that the measures satisfy a Poincaré inequality. We also study stability of the inequality, in terms of relative entropy, when restricted to measures whose covariance matrix trace is smaller than the ambient dimension. In case the covariance matrix is strictly smaller than the identity, we give dimension-free estimates which depend on its eigenvalues. To complement our results, we show that our conditions cannot be relaxed, and that there exist measures with covariance larger than the identity, for which the inequality is not stable, in relative entropy. To deal with these examples, we show that, without any assumptions, one can always get quantitative stability estimates in terms of relative entropy to Gaussian mixtures. Our approach gives rise to a new point of view which sheds light on the hierarchy between Fisher information, entropy and transportation distance, and may be of independent interest. In particular, it implies that the described results apply verbatim to the log-Sobolev inequality and improve upon some known estimates in the literature.
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References
M. Barchiesi, A. Brancolini and V. Julin, Sharp dimension free quantitative estimates for the Gaussian isoperimetric inequality, Annals of Probability 45 (2017), 668–697.
S. G. Bobkov, N. Gozlan, C. Roberto and P.-M. Samson, Bounds on the deficit in the logarithmic Sobolev inequality, Journal of Functional Analysis 267 (2014), 4110–4138.
C. Borell, The Ehrhard inequality, Comptes Rendus Mathématique. Académie des Sciences. Paris 337 (2003), 663–666.
A. A. Borovkov and S. A. Utev, An inequality and a characterization of the normal distribution connected with it, Teoriya Veroyatnosteĭ i ee Primeneniya 28 (1983), 209–218.
H. J. Brascamp and E. H. Lieb, On extensions of the Brunn—Minkowski and Prékopa—Leindler theorems, including inequalities for log concave functions, and with an application to the diffusion equation, Journal of Functional Analysis 22 (1976), 366–389.
E. A. Carlen, M. C. Carvalho, J. Le Roux, M. Loss and C. Villani, Entropy and chaos in the Kac model, Kinetic and Related Models 3 (2010), 85–122.
A. Cianchi, N. Fusco, F. Maggi and A. Pratelli, On the isoperimetric deficit in Gauss space, American Journal of Mathematics 133 (2011), 131–186.
D. Cordero-Erausquin, Transport inequalities for log-concave measures, quantitative forms, and applications, Canadian Journal of Mathematics 69 (2017), 481–501.
T. A. Courtade, M. Fathi and A. Pananjady, Quantitative stability of the entropy power inequality, Institute of Electrical and Electronics Engineers. Transactions on Information Theory 64 (2018), 5691–5703.
T. M. Cover and J. A. Thomas, Elements of Information Theory, Wiley-Interscience, Hoboken, NJ, 2006.
R. Eldan and J. R. Lee, Regularization under diffusion and anticoncentration of the information content, Duke Mathematical Journal 167 (2018), 969–993.
R. Eldan, J. Lehec and Y. Shenfeld, Stability of the logarithmic Sobolev inequality via the Föllmer process, Annales de l’Institut Henri Poincaré Probabilités et Statistiques 56 (2020), 2253–2269.
R. Eldan and D. Mikulincer, Stability of the Shannon—Stam inequality via the Föllmer process, Probability Theory and Related Fields 177 (2020), 891–922.
R. Eldan, D. Mikulincer and A. Zhai, The CLT in high dimensions: quantitative bounds via martingale embedding, Annals of Probability 48 (2020), 2494–2524.
M. Fathi, E. Indrei and M. Ledoux, Quantitative logarithmic Sobolev inequalities and stability estimates, Discrete and Continuous Dynamical Systems 36 (2016), 6835–6853.
F. Feo, E. Indrei, M. R. Posteraro and C. Roberto, Some remarks on the stability of the log-Sobolev inequality for the Gaussian measure, Potential Analysis 47 (2017), 37–52.
H. Föllmer, An entropy approach to the time reversal of diffusion processes, in Stochastic Differential Systems (Marseille-Luminy 1984), Lecture Notes in Control and Information Sciences, Vol. 69, Springer, Berlin, 1985, pp. 156–163.
H. Föllmer, Time reversal on Wiener space, in Stochastic Processes—Mathematics and Physics (Bielefeld, 1984), Lecture Notes in Mathematics, Vol. 1158, Springer, Berlin, 1986, pp. 119–129.
I. Gentil, C. Léonard and L. Ripani, About the analogy between optimal transport and minimal entropy, Annales de la Faculté des Sciences de Toulouse. Mathématiques 26 (2017), 569–601.
N. Gozlan and C. Léonard, Transport inequalities. A survey, Markov Process and Related Fields 16 (2010), 635–736.
L. Gross, Logarithmic Sobolev inequalities, American Journal of Mathematics 97 (1975), 1061–1083.
A. V. Kolesnikov and E. D. Kosov, Moment measures and stability for Gaussian inequalities, Theory of Stochastic Processes 22 (2017), 47–61.
M. Ledoux, The Concentration of Measure Phenomenon, Mathematical Surveys and Monographs, Vol. 89, American Mathematical Society, Providence, RI, 2001.
M. Ledoux, I. Nourdin and G. Peccati, A Stein deficit for the logarithmic Sobolev inequality, Science China. Mathematics 60 (2017), 1163–1180.
J. Lehec, Representation formula for the entropy and functional inequalities, Annales de l’Institut Henri Poincaré Probabilités et Statistiques 49 (2013), 885–899.
E. Mossel and J. Neeman, Robust dimension free isoperimetry in Gaussian space, Annals of Probability 43 (2015), 971–991.
B. Øksendal, Stochastic Differential Equations, Universitext, Springer, Berlin, 2003.
G. Paouris and P. Valettas, A Gaussian small deviation inequality for convex functions, Annals of Probability 46 (2018), 1441–1454.
P.-M. Samson, Concentration of measure inequalities for Markov chains and Φ-mixing processes, Annals of Probability 28 (2000), 416–461.
M. Talagrand, Transportation cost for Gaussian and other product measures, Geometric and Functional Analysis 6 (1996), 587–600.
C. Villani, Optimal Transport, Grundlehren der Mathematischen Wissenschaften, Vol. 338, Springer, Berlin, 2009.
Acknowledgments
We wish to thank Ronen Eldan, Max Fathi, Renan Gross, Emanuel Indrei and Yair Shenfeld for useful discussions and for their comments concerning a preliminary draft of this work. We are also grateful to the anonymous referee for carefully reading this paper and providing thoughtful comments.
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Supported by an Azrieli foundation fellowship.
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Mikulincer, D. Stability of Talagrand’s Gaussian transport-entropy inequality via the Föllmer process. Isr. J. Math. 242, 215–241 (2021). https://doi.org/10.1007/s11856-021-2129-x
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DOI: https://doi.org/10.1007/s11856-021-2129-x