Nonlocal double phase Neumann and Robin problem with variable $s(\cdot,\cdot)-$order

TL;DR

This paper investigates properties of variable order fractional operators and proves the existence of weak solutions for a nonlocal double phase Neumann and Robin problem using variational methods.

Contribution

It introduces new properties of variable order fractional derivatives and establishes existence results for complex nonlocal boundary value problems.

Findings

Developed properties of the $a_{x,y}(ullet)$-Neumann derivative.

Proved basic properties of fractional Musielak-Sobolev spaces with variable order.

Established existence of weak solutions for the nonlocal double phase problem.

Abstract

In this paper, we develop some properties of the $a_{x,y}(\cdot)$-Neumann derivative for the nonlocal $s(\cdot,\cdot)$-order operator in fractional Musielak-Sobolev spaces with variable $s(\cdot,\cdot)-$order. Therefore we prove the basic proprieties of the correspondent function spaces. In the second part of this paper, by means of Ekeland's variational principal and direct variational approach, we prove the existence of weak solutions to the following double phase Neumann and Robin problem with variable $s(\cdot,\cdot)-$order: $$\left\{\begin{array} (-\Delta)^{s_1(x,\cdot)}_{a^1_{(x,\cdot)}} u+(-\Delta)^{s_2(x,\cdot)}_{a^2_{(x,\cdot)}} u +\widehat{a}^1_x(|u|)u+\widehat{a}^2_x(|u|)u &= \lambda f(x,u) \quad {\rm in\ } \Omega, \\ \mathcal{N}^{s_1(x,\cdot)}_{a^1(x,\cdot)}u+\mathcal{N}^{s_2(x,\cdot)}_{a^2(x,\cdot)}u+\beta(x)\left( \widehat{a}^1_x(|u|)u+\widehat{a}^2_x(|u|)u \right) &= 0 \quad {\rm in\ } \mathbb{R}^N\setminus \Omega, \end{array} \right. $$ where $(-\Delta)^{s_i(x,\cdot)}_{a^i_{(x,\cdot)}}$ and $\mathcal{N}^{s_i(x,\cdot)}_{a^i(x,\cdot)}$ denote the variable $s_i(\cdot,\cdot)$-order fractional Laplace operator and the nonlocal normal $a_i(\cdot,\cdot)$-derivative of $s_i(\cdot,\cdot)$-order, respectively.