2,898 research outputs found
Exact Collapse Solutions in D=4, N=4 Gauged Supergravity and Their Generalizations
We construct an exact time-dependent solution in , gauged
supergravity, where the gauge fields of the subgroup of the
carry independent conserved charges. The solution describes a decaying
white hole that settles down to the final state as a static charged black hole.
We analyze the global structure and lift the solution back to
supergravity. We further extend the theory by adding an extra term in the
scalar potential and obtain a more general class of collapse solutions. The
result constitutes a charged generalization of the Roberts solution and the
dynamical scalar-hairy black hole solutions that have been very recently found
by us. The generalized Roberts solutions demonstrate that a scalar coupled to
gravity can be unstable even when it is confined by a scalar potential with a
fixed point.Comment: 15 page
Exact Black Hole Formation in Asymptotically (A)dS and Flat Spacetimes
We consider four-dimensional Einstein gravity minimally coupled to a dilaton
scalar field with a supergravity-inspired scalar potential. We obtain an exact
time-dependent spherically symmetric solution describing gravitational collapse
to a static scalar-hairy black hole. The solution can be asymptotically AdS,
flat or dS depending on the value of the cosmological constant parameter
in the potential. As the advanced time increases, the spacetime
reaches equilibrium in an exponential fashion, i.e., with
, where is the mass of the final black
hole and is the second parameter in the potential. Similar to the
Vaidya solution, at , the spacetime can be matched to an (A)dS or flat
vacuum except that at the origin a naked singularity may occur. Moreover, a
limiting case of our solution with gives rise to an (A)dS
generalization of the Roberts solution, thereby making it relevant to critical
phenomena. Our results provide a new model for investigating formation of real
life black holes with . For , it can be instead used
to study non-equilibrium thermalization of certain strongly-coupled field
theory.Comment: Latex, 8 pages, typos corrected and references adde
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