# Non-autonomous rough semilinear PDEs and the multiplicative Sewing Lemma

## TL;DR

This paper develops a framework for solving non-autonomous rough semilinear PDEs with subcritical noise, introducing a multiplicative sewing lemma to handle infinite-dimensional product integrals and unbounded operators.

## Contribution

It introduces a novel multiplicative sewing lemma for infinite dimensions, enabling the analysis of rough PDEs with unbounded operators and non-autonomous evolution.

## Key findings

- Established existence and uniqueness of solutions for rough parabolic equations.
- Developed a product integral construction in infinite dimensions.
- Extended sewing lemma techniques to non-autonomous PDE settings.

## Abstract

We investigate existence, uniqueness and regularity for local solutions of rough parabolic equations with subcritical noise of the form $du_t- L_tu_tdt= N(u_t)dt + \sum_{i = 1}^dF_i(u_t)d\mathbf X^i_t$ where $(L_t)_{t\in[0,T]}$ is a time-dependent family of unbounded operators acting on some scale of Banach spaces, while $\mathbf X\equiv(X,\mathbb X)$ is a two-step (non-necessarily geometric) rough path of H\"older regularity $\gamma >1/3.$ Besides dealing with non-autonomous evolution equations, our results also allow for unbounded operations in the noise term (up to some critical loss of regularity depending on that of the rough path $\mathbf X$). As a technical tool, we introduce a version of the multiplicative sewing lemma, which allows to construct the so-called product integrals in infinite dimensions. We later use it to construct a semigroup analogue for the non-autonomous linear PDEs as well as show how to deduce the semigroup version of the usual sewing lemma from it.