Homogenization of the higher-order Schr\"odinger-type equations with periodic coefficients

TL;DR

This paper establishes the homogenization of higher-order Schrödinger-type equations with periodic coefficients, proving operator exponential convergence and providing sharp error estimates for the effective approximation.

Contribution

It introduces a homogenization result for higher-order elliptic operators with periodic coefficients, including explicit error bounds for the operator exponential convergence.

Findings

Operator exponential $e^{-i au A_ ext{ ext{ε}}}$ converges to $e^{-i au A^0}$ as ε→0.

Sharp-order error estimates for the homogenization process.

Application to Schrödinger-type Cauchy problems with effective operator approximation.

Abstract

In $L_2({\mathbb R}^d; {\mathbb C}^n)$, we consider a matrix strongly elliptic differential operator ${A}_\varepsilon$ of order $2p$, $p \geqslant 2$. The operator ${A}_\varepsilon$ is given by ${A}_\varepsilon = b(\mathbf{D})^* g(\mathbf{x}/\varepsilon) b(\mathbf{D})$, $\varepsilon >0$, where $g(\mathbf{x})$ is a periodic, bounded, and positive definite matrix-valued function, and $b(\mathbf{D})$ is a homogeneous differential operator of order $p$. We prove that, for fixed $\tau \in {\mathbb R}$ and $\varepsilon \to 0$, the operator exponential $e^{-i \tau {A}_\varepsilon}$ converges to $e^{-i \tau {A}^0}$ in the norm of operators acting from the Sobolev space $H^s({\mathbb R}^d; {\mathbb C}^n)$ (with a suitable $s$) into $L_2({\mathbb R}^d; {\mathbb C}^n)$. Here $A^0$ is the effective operator. Sharp-order error estimate is obtained. The results are applied to homogenization of the Cauchy problem for the Schr\"odinger-type equation $i \partial_\tau {\mathbf u}_\varepsilon = {A}_\varepsilon {\mathbf u}_\varepsilon + {\mathbf F}$, ${\mathbf u}_\varepsilon\vert_{\tau=0} = \boldsymbol{\phi}$.