Generalized principal eigenvalues for parabolic operators in bounded domains
Résumé
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 := R, R + or 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 [3, 5]. 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.
Mots clés
- generalized principal eigenvalues linear parabolic operator principal Floquet bundles semilinear parabolic equation parabolic maximum principle AMS classification. 35B40 35B50 35K10 35K57 35P05 47A75
- generalized principal eigenvalues
- linear parabolic operator
- principal Floquet bundles
- semilinear parabolic equation
- parabolic maximum principle
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