# Mathematical Sciences Research Institute

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# Seminar

Water waves and other interface problems (Part 2): The relativistic Euler equations with a physical vacuum boundary March 02, 2021 (09:30 AM PST - 10:30 AM PST)
Parent Program: Mathematical problems in fluid dynamics MSRI: Online/Virtual
Speaker(s) MARCELO DISCONZI (Vanderbilt University)
Description

To participate in this seminar, please register here: https://www.msri.org/seminars/25657

Video

#### The Relativistic Euler Equations with a Physical Vacuum Boundary

Abstract/Media

To participate in this seminar, please register here: https://www.msri.org/seminars/25657

Abstract:

We consider the relativistic Euler equations with a physical vacuum boundary and an equation of state $p(\varrho)=\varrho^\gamma$, $\gamma > 1$. We establish the following results. (i) local well-posedness in the Hadamard sense, i.e., local existence, uniqueness, and continuous dependence on the data; (ii) low regularity solutions: our uniqueness result holds at the level of Lipschitz velocity and density, while our rough solutions, obtained as unique limits of smooth solutions, have regularity only a half derivative above scaling; (iii) stability: our uniqueness in fact follows from a more general result, namely, we show that a certain nonlinear functional that tracks the distance between two solutions (in part by measuring the distance between their respective boundaries) is propagated by the flow; (iv) we establish sharp, essentially scale invariant energy estimates for solutions; (v) we establish a sharp continuation criterion, at the level of scaling, showing that solutions can be continued as long as the velocity is in $L^1_t Lip_x$ and a suitable weighted version of the density is at the same regularity level. This is joint work with Mihaela Ifrim and Daniel Tataru.

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