Ergodic attractors and almost-everywhere asymptotics of scalar semilinear parabolic differential equations

TL;DR

This paper investigates the ergodic properties of scalar semilinear parabolic equations, revealing that invariant measures' supports project uniquely onto a two-dimensional space, and demonstrates measure uniqueness in mass-conserving cases.

Contribution

It introduces a novel zero-number technique application to measure evolution, establishing a one-to-one correspondence of invariant measures' supports and proving measure uniqueness for mass-conserving equations.

Findings

Supports of invariant measures project injectively to .

Zero-number techniques applied to measure dynamics.

Uniqueness of invariant measure for mass-conserving equations.

Abstract

We consider dynamics of scalar semilinear parabolic equations on bounded intervals with periodic boundary conditions, and on the entire real line, with a general nonlinearity $g(t,x,u,u_x)$ either not depending on $t$, or periodic in $t$. While the topological and geometric structure of their attractors has been investigated in depth, we focus here on ergodic-theoretical properties. The main result is that the union of supports of all the invariant measures projects one-to-one to $\mathbb{R}^2$. We rely on a novel application of the zero-number techniques with respect to evolution of measures on the phase space, and on properties of the flux of zeroes, and the dissipation of zeroes. As an example of an application, we prove uniqueness of an invariant measure for a large family of considered equations which conserve a certain quantity ("mass"), thus generalizing the results by Sinai for the scalar viscous Burgers equation.