A note on stochastic semilinear dissipative evolution equations
Carlo Marinelli
TL;DR
This note addresses the well-posedness of stochastic semilinear dissipative evolution equations with additive noise, where the linear part $A$ generates a compact contraction semigroup and the nonlinearity $f$ is a monotone superposition operator. Existence and uniqueness of a probabilistically strong mild solution are established by approximating $f$ with Yosida regularizations, obtaining pathwise a priori estimates, and leveraging a novel compactness result for deterministic convolutions to pass to the limit. The approach avoids variational structure on $A$ and Aubin–Lions–Simon-type compactness, extending well-posedness to broader operator classes. The resulting solution $u$ decomposes into a deterministic part plus the stochastic convolution, with the remainder $v=u-S\diamond(B\cdot W)$ enjoying strong continuity in $L^1$ and weak continuity in $L^2$, and the framework accommodates quasi-monotone extensions of $A$ and $f$.
Abstract
Existence and uniqueness of mild solutions to a class of semilinear stochastic evolution equations with additive noise is proved. The linear part of the drift term is the generator of a compact semigroup of contractions, while the nonlinear part is only assumed to be the superposition operator associated to a decreasing function.
