# The Fujita-Kato Theorem for some Oldroyd-B model

## TL;DR

This paper extends classical results on Navier-Stokes equations to Oldroyd-B models, proving global existence and uniqueness of solutions in two and higher dimensions under specific initial data conditions.

## Contribution

It establishes the existence, uniqueness, and Lipschitz regularity of solutions for Oldroyd-B models, including non-corotational cases, using techniques similar to those for Navier-Stokes.

## Key findings

- Global-in-time classical solutions in 2D for large data.
- Propagation of Lipschitz regularity in higher dimensions.
- Conditions on initial data ensuring well-posedness.

## Abstract

In this paper, we investigate the Cauchy problem associated to a system of PDE's of Oldroyd type. The considered model describes the evolution of certain viscoelastic fluids within a corotational framework. The non-corotational setting is also addressed in dimension two. We show that some widespread results concerning the incompressible Navier-Stokes equations can be extended to the considered systems. In particular we show the existence and uniqueness of global-in-time classical solutions for large data in dimension two. This result is supported by suitable condition on the initial data to provide a global-in-time Lipschitz regularity for the flow, which allows to overcome specific challenging due to the non time decay of the main forcing terms. Secondly, we address the global-in-time well posedness in dimension larger or equal to three. We prove the propagation of Lipschitz regularities for the flow. For this result, we just assume the initial data to be sufficiently small in a critical Lorentz space.