Generalized principal eigenvalues for parabolic operators in bounded domains

TL;DR

This paper introduces new generalized principal eigenvalues for parabolic operators with heterogeneous coefficients, providing insights into their large-time behavior, solutions, and relations to Floquet theory, with explicit computations for various coefficient classes.

Contribution

It extends the concept of principal eigenvalues to heterogeneous parabolic operators, linking them to maximum principles, Floquet bundles, and providing explicit calculations for diverse coefficient types.

Findings

Eigenvalues determine large-time behavior of solutions.

Relations established with Floquet bundles for characterization.

Explicit eigenvalues computed for various coefficient classes.

Abstract

We introduce here new generalized principal eigenvalues for linear parabolic operators with heterogeneous coefficients in space and time. We consider a bounded spatial domain and an unbounded time interval $I$ : $I=\mathbb{R},\ \mathbb{R}^+$ or $\mathbb{R}^-$, and operators with coefficients having a fairly general dependence on space and time. The notions we introduce rely on the parabolic maximum principle and extend some earlier definitions introduced for elliptic operators [BNV]. We first show that these eigenvalues hold the key to understanding the large time behavior and entire solutions of heterogeneous Fisher-KPP type equations. We then describe the relation of these quantities with principal Floquet bundles for parabolic operators which provides further characterizations of the principal eigenvalues. These allow us to derive monotonicity properties and comparisons between generalized principal eigenvalues, as well as perturbation results and further properties involving limit operators. We show that the sign of these eigenvalues encodes different versions of the maximum principle for parabolic operators. Lastly, we explicitly compute the generalized principal eigenvalues for several classes of operators such as spatial-independent, periodic, almost periodic, uniquely ergodic or random stationary ergodic coefficients.