Star-UBB Seminar Series:- Highly relativistic solutions of the Einstein-Vlasov system and a comparison to solutions of the Einstein-Dirac system
In the first part of this talk the speaker will review some results on highly compact stationary solutions of the Einstein-Vlasov(EV) system. A comparison to Wheeler’s idealized spherically symmetric geons will be made which indicates that solutions of the massless EV system have very similar properties. In the second part he will focus on a comparison between solutions of the Einstein-Dirac(ED) system and the EV system. In 1999 Finster et al. found for the first-time static solutions to the Einstein-Dirac system in the case of two fermions with opposite spins. Recently this study has been extended to a larger number of particles by Leith et al. In particular, they construct highly relativistic solutions. The structure of the solutions is strikingly similar to the structure of highly relativistic solutions of the EV system. Since solutions of the EV system are classical whereas solutions of the ED system have a quantum signature this study provides insights about the transition from quantum to classical behaviour for a small number of particles. A particular feature in this context is that the pressure may be negative in the case of a few particles for solutions of the ED system, but as the number of particles increase (above 16) it becomes non-negative, i.e. it behaves classically.
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講者：Prof. Håkan Andréasson (Department of Mathematical Sciences, Chalmers University of Technology, University of Gothenburg, Gothenburg, Sweden)
Scientific and Technological Advanced Research- Babeș-Bolyai University(Star-UBB) Seminar Series in Gravitation, Cosmology and Astrophysics
Presently a period of rapid and intense change are being witnessed in our understanding of the gravitational force, at a rate that is quickly increasing since the important observational discoveries of the late 1990s. With the advent of new observational techniques, the emergence of important cosmological and astrophysical paradigms can be seen that lead to a deep change in our understanding of the Universe. Astronomical observations strongly suggest that at large scales the force of gravity may not behave according to standard general relativity, and that a generalization of the gravitational action, either at the geometric level, or at the matter level, may be required for a full understanding of the gravitational interaction.
The goal of the present seminar is to bring Theoretical Gravitational Physics closer to the observations and experiments, and to discuss current topics in general relativity, high-energy physics, astrophysics and cosmology.