Abstract
We prove a nonsmooth implicit function theorem applicable to the zero set of the difference of convex functions. This theorem is explicit and global: it gives a formula representing this zero set as a difference of convex functions which holds throughout the entire domain of the original functions. As applications, we prove results on the stability of singularities of envelopes of semi-convex functions, and solutions to optimal transport problems under appropriate perturbations, along with global structure theorems on certain discontinuities arising in optimal transport maps for the bilinear cost \({c(x, \bar{x}):=-\langle {x}, {\bar{x}}\rangle}\) for \({x,\bar{x} \in {\bf R}^n}\). For targets whose components satisfy additional convexity, separation, multiplicity, and affine independence assumptions, we show that these discontinuities occur on submanifolds of the appropriate codimension which are parameterized locally as differences of convex functions (DC, hence \({C^2}\) rectifiable), and—depending on the precise assumptions—\({C^{1,\alpha}}\) smooth. Under these hypotheses, any \({n+1}\) affinely independent components of the target measure select at most one point from the source measure where the transport divides between all \({n+1}\) specified target components.
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References
Alberti, G.: On the structure of singular sets of convex functions. Calc. Var. Part. Differ. Equ. 2(1), 17–27 (1994)
Ambrosio, L., Bertrand, J.: DC calculus. Math. Z. 288(3–4), 1037–1080 (2018)
Brenier, Y.: Polar factorization and monotone rearrangement of vector-valued functions. Commun. Pure Appl. Math. 44(4), 375–417 (1991)
Butler, G.J., Timourian, J.G., Viger, C.: The rank theorem for locally Lipschitz continuous functions. Can. Math. Bull. 31(2), 217–226 (1988)
Caffarelli, L.A.: The regularity of mappings with a convex potential. J. Am. Math. Soc. 5(1), 99–104 (1992)
Caffarelli, L.A., McCann, R.J.: Free boundaries in optimal transport and Monge–Ampère obstacle problems. Ann. Math. (2) 171(2), 673–730 (2010)
Chen, S.: Regularity of free boundary in optimal transportation. (Preprint)
Chodosh, O., Jain, V., Lindsey, M., Panchev, L., Rubinstein, Y.A.: On discontinuity of planar optimal transport maps. J. Topol. Anal. 7(2), 239–260 (2015)
Clarke, F.H.: On the inverse function theorem. Pac. J. Math. 64(1), 97–102 (1976)
Clarke, F.H.: Optimization and Nonsmooth Analysis, Volume 5 of Classics in Applied Mathematics, 2nd edn. Society for Industrial and Applied Mathematics (SIAM), Philadelphia, PA (1990)
De Philippis, G., Figalli, A.: Partial regularity for optimal transport maps. Publ. Math. Inst. Hautes Études Sci. 121, 81–112 (2015)
Figalli, A.: Regularity properties of optimal maps between nonconvex domains in the plane. Commun. Part. Differ. Equ. 35(3), 465–479 (2010)
Figalli, A., Kim, Y.-H.: Partial regularity of Brenier solutions of the Monge-Ampère equation. Discrete Contin. Dyn. Syst. 28(2), 559–565 (2010)
Gigli, N.: On the inverse implication of Brenier-McCann theorems and the structure of \(({\cal{P}}_2(M), W_2)\). Methods Appl. Anal. 18(2), 127–158 (2011)
Goldman, M., Otto, F.: A variational proof for partial regularity of optimal transportation maps. Preprint at arXiv:1704.05339v1
Jian, H.-Y., Wang, X.-J.: Continuity estimates for the Monge-Ampère equation. SIAM J. Math. Anal. 39(2), 608–626 (2007)
Liu, J., Trudinger, N.S., Wang, X.-J.: Interior \(C^{2,\alpha }\) regularity for potential functions in optimal transportation. Commun. Part. Differ. Equ. 35(1), 165–184 (2010)
Loeper, G.: On the regularity of solutions of optimal transportation problems. Acta Math. 202(2), 241–283 (2009)
Ma, X.-N., Trudinger, N.S., Wang, X.-J.: Regularity of potential functions of the optimal transportation problem. Arch. Ration. Mech. Anal. 177(2), 151–183 (2005)
McCann, R.J.: Existence and uniqueness of monotone measure-preserving maps. Duke Math. J. 80(2), 309–323 (1995)
Perelman, G.: DC structure on Alexandrov space (preliminary version). https://www.math.psu.edu/petrunin/papers/akp-papers/perelman-DC.pdf
Rockafellar, R.T.: Convex Analysis. Princeton University Press, Princeton (1970)
Trudinger, N.S.: Recent developments in elliptic partial differential equations of Monge–Ampère type. In: International Congress of Mathematicians, vol. III, pp. 291–301. European Mathematical Society, Zürich (2006)
Trudinger, N.S., Wang, X.-J.: On the second boundary value problem for Monge–Ampère type equations and optimal transportation. Ann. Sci. Norm. Super. Pisa Class. Sci. 8(1), 143–174 (2009)
Veselý, L., Zajíček, L.: Delta-convex mappings between Banach spaces and applications. Diss. Math. (Rozprawy Mat.) 289, 52 (1989)
Villani, C.: Topics in Optimal Transportation, Volume 58 of Graduate Studies in Mathematics. American Mathematical Society, Providence, RI (2003)
Villani, C.: Optimal Transport: Old and New, Volume 338 of Grundlehren der Mathematischen Wissenschaften [Fundamental Principles of Mathematical Sciences]. Springer, Berlin (2009)
Wang, X.-J.: Remarks on the Regularity of Monge–Ampère, pp. 257–263. Academic Press, Beijing (1992)
Warga, J.: An implicit function theorem without differentiability. Proc. Am. Math. Soc. 69(1), 65–69 (1978)
Zajíček, L.: On the differentiation of convex functions in finite and infinite dimensional spaces. Czechoslov. Math. J. 29(104)(3), 340–348 (1979)
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Communicated by A. Figalli
JK’s research was supported in part by a AMS-SimonsTravel Grant and National Science Foundation grant DMS-1700094. RM’s research was supported in part by NSERC grants 217006-08 and -15 and by a Simons Foundation Fellowship. Parts of this project were carried out while both authors were in residence at the Mathematical Sciences Reseach Institute in Berkeley CA during the Fall 2013 program supported by National Science Foundation Grant No. 0932078 000, and later at the Fields Insititute for the Mathematical Sciences in Toronto during Fall 2014.
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Kitagawa, J., McCann, R. Free Discontinuities in Optimal Transport. Arch Rational Mech Anal 232, 1505–1541 (2019). https://doi.org/10.1007/s00205-018-01348-3
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DOI: https://doi.org/10.1007/s00205-018-01348-3