ABP maximum principles for fully nonlinear integro-differential equations with unbounded inhomogeneous terms

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ORIGINAL PAPER

ABP maximum principles for fully nonlinear integrodifferential equations with unbounded inhomogeneous terms Shuhei Kitano1 Ó Springer Nature Switzerland AG 2020

Abstract Aleksandrov–Bakelman–Pucci maximum principles are studied for a class of fully nonlinear integro-differential equations of order r 2 ½2  e0 ; 2Þ, where e0 is a small constant depending only on given parameters. The goal of this paper is to improve an estimate of Guillen and Schwab (Arch Ration Mech Anal 206(1):111–157, 2012) in order to avoid the dependence on L1 norm of the inhomogeneous term. Mathematics Subject Classification 35R09  47G20

1 Introduction In this paper, we study the fully nonlinear nonlocal equation of the form:   M uðxÞ  f ðxÞ in B1 ;

ð1Þ

in Rn n B1 ;

uðxÞ  0 where by setting

dðu; x; yÞ :¼ uðx þ yÞ þ uðx  yÞ  2uðxÞ; we define the minimal fractional Pucci operator: ( 

M uðxÞ :¼

inf

k  TrðAÞ and O  A  KId

ð2  rÞ

Z dðu; x; yÞ Rn

yT Ay jyjnþrþ2

) dy :

This article is part of the topical collection ‘‘Viscosity solutions – Dedicated to Hitoshi Ishii on the award of the 1st Kodaira Kunihiko Prize’’ edited by Kazuhiro Ishige, Shigeaki Koike, Tohru Ozawa and Senjo Shimizu. & Shuhei Kitano [email protected] 1

Department of Applied Physics, Waseda University, Tokyo 169-8555, Japan SN Partial Differential Equations and Applications

16 Page 2 of 11

SN Partial Differ. Equ. Appl. (2020)1:16

Throughout this paper, we suppose that n  2;

0\k  nK;

n

and define Br :¼ fy 2 R : jyj\rg. Furthermore, Qr  Rn denotes the open cube with its center at 0 and its side-length r. We also set Br ðxÞ :¼ x þ Br and Qr ðxÞ :¼ x þ Qr . We will also use the maximal Pucci operator defined by ( ) Z yT Ay þ M uðxÞ :¼ sup ð2  rÞ dðu; x; yÞ nþrþ2 dy : jyj Rn k  TrðAÞ and O  A  KId The main purpose of this paper is to show the Aleksandrov–Bakelman–Pucci (ABP for short) maximum principle depending only on Ln norm of f þ :¼ maxff ; 0g. Theorem 1.1 There exist constants C^ [ 0 and e0 2 ð0; 1Þ depending only on n; k and K such that if u 2 L1 ðRn Þ \ LSCðRn Þ is a viscosity supersolution of (1) with r 2 ½2  e0 ; 2Þ and f 2 CðB1 Þ; then it follows that ^ þk n  inf u  Ckf L ðfu  0gÞ : B1

ð2Þ

The ABP maximum principle plays a fundamental role in the regularity theory of fully nonlinear equations (see [1, 2] for instance). The ABP maximum principle for the second order equation presents a bound for the infimum of supersolutions by Ln norm of inhomogeneous terms. In the case of nonlocal equations, the ABP maximum principle is investigated in [3, 5, 7] and references therein. More precisely, for viscosity solutions, Caffarelli and Silvestre prove that the maximum is estimated from above by Riemann sums of f instead of their Ln norms in [3]. A more quantitative version of the ABP maximum principle is established by Guillen and Schwab in [5]. For an application of results in [5], W r;e -estimate is obtained by Yu [8], which was inspired by earlier works by [4, 6]. The ABP