159 research outputs found
Quantization Near Violent Singularities in Einstein-Yang-Mills Black Holes
Classical singularities inside black holes in the Einstein-Yang-Mills theory
exhibit unusual features. Only for discrete values of the black hole mass one
encounters singularities of the Schwarzschild type (timelike) and the
Reissner-Nordstrom type (spacelike). For a generic mass the approach to
singularity is not smooth: the metric oscillates with an infinitely growing
amplitude and decreasing period. In spite of some similarity with the BKL
oscillations, here the behavior is not chaotic. However the oscillation
amplitude exceeds classical limits after few cycles, so the question arises how
this behavior gets modified by quantum effects. We discuss this issue both in
the framework of QFT and in the string theory.Comment: 2 pages, Contribution to the 9th Marcel Grossmann meeting (MG9),
Rome, July 200
Gravitating lumps
Recent progress in the study of solitons and black holes in non-Abelian field
theories coupled to gravity is reviewed. New topics include gravitational
binding of monopoles, black holes with non-trivial topology, Lue-Weinberg
bifurcation, asymptotically AdS lumps, solutions to the Freedman-Schwarz model
with applications to holography, non-Abelian Born-Infeld solutionsComment: A written version of the talk given at the 16th International
Conference on General Relativity and Gravitation, held on July 15-21, 2001,
in Durban, South Africa. Latex error on the title page corrected. New
references adde
Synchrotron radiation from massless charge
Classical radiation power from an accelerated massive charge diverges in the
zero-mass limit, while some general arguments suggest that strictly massless
charge does not not radiate at all. On the other hand, the regularized
classical radiation reaction force, though looking odd, is non-zero and finite.
To clarify this controversy, we consider radiation problem in massless scalar
quantum electrodynamics in the external magnetic field. In this framework,
synchrotron radiation is found to be non-zero, finite, and essentially quantum.
Its spectral distribution is calculated using Schwinger's proper time technique
for {\em ab initio} massless particle of zero spin. Provided , the
maximum in the spectrum is shown to be at , and the average
photon energy is . The normalized spectrum is universal, depending
neither on nor on . Quantum nature of radiation makes classical
radiation reaction equation meaningless for massless charge. Our results are
consistent with the view (supported by the renormalization group argument) that
the correct classical limit of massless quantum electrodynamics is free theory.Comment: 13 pages, 1 figur
HYM-flation: Yang-Mills cosmology with Horndeski coupling
We propose new mechanism for inflation using classical SU(2) Yang-Mills (YM)
homogeneous and isotropic field non-minimally coupled to gravity via Horndeski
prescription. This is the unique generally and gauge covariant ghost-free YM
theory with the curvature-dependent action leading to second-order gravity and
Yang-Mills field equations. We show that its solution space contains de Sitter
boundary to which the trajectories are attracted for some finite time, ensuring
the robust inflation with a graceful exit. The theory can be generalized to
include the Higgs field leading to two-steps inflationary scenario, in which
the Planck-scale YM-generated inflation naturally prepares the desired initial
conditions for the GUT-scale Higgs inflation.Comment: 13 pages, 3 figure
The near-horizon geometry of dilaton-axion black holes
Static black holes of dilaton-axion gravity become singular in the extreme
limit, which prevents a direct determination of their near-horizon geometry.
This is addressed by first taking the near-horizon limit of extreme rotating
NUT-less black holes, and then going to the static limit. The resulting
four-dimensional geometry may be lifted to a Bertotti-Robinson-like solution of
six-dimensional vacuum gravity, which also gives the near-horizon geometry of
extreme Kaluza-Klein black holes in five dimensions.Comment: 2 pages, "mprocl.sty" with Latex 2.09, contribution to the 9th Marcel
Grossmann meeting (MG9), Rome, July 200
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