# Sharp bounds for the resolvent of linearized Navier Stokes equations in the half space around a shear profile

## TL;DR

This paper establishes precise bounds on the behavior of solutions to linearized Navier-Stokes equations near shear layers in half-space domains, accounting for boundary layer effects and vorticity unboundedness in the inviscid limit.

## Contribution

It introduces boundary layer norms to accurately capture unbounded vorticity and derives sharp, uniform estimates in the inviscid limit for shear flows in half-space geometries.

## Key findings

- Sharp bounds on the semigroup of linearized Navier-Stokes equations.
- Boundary layer norms effectively capture unbounded vorticity.
- Uniform estimates in the inviscid limit are established.

## Abstract

In this paper, we derive sharp bounds on the semigroup of the linearized incompressible Navier-Stokes equations near a stationary shear layer in the half plane and in the half space ($\mathbb{R}_+^2$ or $\mathbb{R}_+^3$), with Dirichlet boundary conditions, assuming that this shear layer in spectrally unstable for Euler equations. In the inviscid limit, due to the prescribed no-slip boundary conditions, vorticity becomes unbounded near the boundary. The novelty of this paper is to introduce boundary layer norms that capture the unbounded vorticity and to derive sharp estimates on this vorticity that are uniform in the inviscid limit.