PDE and Applied Mathematics Seminar[ Edit ]
Moderator: Amy Novick-Cohen
The Euler--Poisson equations govern gas motion underself gravitational force. In this context the density is not strictly positive, it vanishes in the vacuum region, or falls off to zero at infinity. That causes a degeneration of the hyperbolic systems.The lecture will discuss local existence theorems under these circumstances and with a polytropic equation of state $p=K\rho^\gamma$, here $p$ is the pressure, $\rho $ the density and $\gamma>1$ is the adiabatic gas exponent. In particular, we shall discuss the question whether the initial data include the static spherical solutions for various values of the adiabatic constant $\gamma$. This is a joint work with U. Brauer, Universidad Complutense Madrid.
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Spectral theory for general classes of first order systems has been less popular since 1990's. In this talk, I would like to propose a new class of first order systems which generalize both Maxwell and Dirac equations. In this new class, we can treat these two equations in a unified manner, although their physical backgrounds are very different from each other. The main point of my talk is space-time estimates for the new class of first order systems. The essential part of the idea is to derive uniform boundedness of the spectral densities. This talk is based on joint work with Matania Ben-Artzi.