Singular hypersurfaces in quadratic gravity

by Dr. Inna Ivanova

BGU

at Particles and Fields Seminar

Mon, 07 Apr 2025, 14:00
Sacta-Rashi Building for Physics (54), room 207

Abstract

It is shown that the equations of motion for singular hypersurfaces in quadratic gravity can be derived using the least action principle for any type of hypersurface, including lightlike ones. It turns out that for the Gauss-Bonnet model, neither double layers nor thin shells exist when the Lichnerowicz junction conditions are satisfied. For all types of hypersurfaces, criteria are established to determine whether a singular hypersurface represents a double layer or a thin shell. Our study reveals that Lichnerowicz conditions can be relaxed for lightlike hypersurfaces, and that "external pressure" vanishes for this type of hypersurfaces. Spherically symmetric singular hypersurfaces of all types are investigated that separate two spherically symmetric solutions of conformal gravity, such as various vacuums and Vaidya-type solutions. Using the matching of corresponding solutions, analogues of physical models like "vacuum burning", cosmological phase transition and thin shell collapse are analyzed in the context of conformal gravity. To clarify the physical meaning of "external pressure" and "external flow" (which are zero in general relativity), these components of the surface energy-momentum tensor are derived directly from the matter Lagrangian. Specifically, the surface energy-momentum tensor is obtained from the action of perfect fluid with a variable number of particles in the Eulerian picture.

Created on 02-04-2025 by Palti, Eran (palti)
Updaded on 02-04-2025 by Palti, Eran (palti)