Global well-posedness and refined regularity criterion for the uni-directional Euler-alignment system

TL;DR

This paper proves global well-posedness and refines regularity criteria for the uni-directional Euler-alignment system with singular communication protocols, using novel methods based on propagating multiple moduli of continuity.

Contribution

It introduces a new approach employing multiple moduli of continuity to establish global regularity and improves regularity criteria in the supercritical regime.

Findings

Established global regularity for subcritical and critical regimes.

Developed a novel method propagating multiple moduli of continuity.

Improved regularity criteria in the supercritical regime.

Abstract

We investigate global solutions to the Euler-alignment system in $d$ dimensions with unidirectional flows and strongly singular communication protocols $\phi(x) = |x|^{-(d+\alpha)}$ for $\alpha \in (0,2)$. Our paper establishes global regularity results in both the subcritical regime $1<\alpha<2$ and the critical regime $\alpha=1$. Notably, when $\alpha=1$, the system exhibits a critical scaling similar to the critical quasi-geostrophic equation. To achieve global well-posedness, we employ a novel method based on propagating the modulus of continuity. Our approach introduces the concept of simultaneously propagating multiple moduli of continuity, which allows us to effectively handle the system of two equations with critical scaling. Additionally, we improve the regularity criteria for solutions to this system in the supercritical regime $0<\alpha<1$.