Communications in Mathematical Sciences

Volume 21 (2023)

Number 6

Uniqueness of weak solutions to the Boussinesq equations with fractional dissipation

Pages: 1531 – 1548

DOI: https://dx.doi.org/10.4310/CMS.2023.v21.n6.a4

Authors

Ruihong Ji (Geomathematics Key Laboratory of Sichuan Province, Chengdu University of Technology, Chengdu, China)

Dan Li (Department of Mathematics, Sichuan University, Chengdu, China)

Jiahong Wu (Department of Mathematics, Oklahoma State University, Stillwater, Ok., U.S.A.)

Abstract

This paper examines the existence and uniqueness of weak solutions to the ddimensional Boussinesq equations with fractional dissipation $(-\Delta)^{\alpha}u$ and fractional thermal diffusion $(-\Delta)^{\beta}\theta$. The aim is at the uniqueness of weak solutions in the weakest possible inhomogeneous Besov spaces. We establish the local existence and uniqueness in the functional setting $u\in L^{\infty}(0,T;B_{2,1}^{{d/2}-2\alpha+1}(\mathbb{R}^d))$ and $\theta\in L^{\infty}(0,T;B_{2,1}^{d/2}(\mathbb{R}^{d}))$ when $\alpha>{1/4}$, $\beta\geq 0$ and $\alpha+2\beta\geq 1$. By decomposing the bilinear term into different frequencies, we are able to obtain a suitable upper bound on the bilinear term, which allows us to close the estimates in the aforementioned Besov spaces.

Keywords

Boussinesq equations, Littlewood–Paley, weak solution, uniqueness

2010 Mathematics Subject Classification

35Axx, 35Q35, 76Dxx

Received 16 November 2019

Received revised 30 October 2022

Accepted 18 November 2022

Published 22 September 2023