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 $E^2\gg eH$, the maximum in the spectrum is shown to be at $\hbar \omega=E/3$, and the average photon energy is $4E/9$. The normalized spectrum is universal, depending neither on $E$ nor on $H$. 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

Non-Abelian brane cosmology

We discuss isotropic and homogeneous D-brane-world cosmology with non-Abelian Born-Infeld (NBI) matter on the brane. In the usual Friedmann-Robertson-Walker (FRW) model the scale non-invariant NBI matter gives rise to an equation of state which asymptotes to the string gas equation $p=-\epsilon/3$ and ensures a start-up of the cosmological expansion with zero acceleration. We show that the same state equation in the brane-world setup leads to the Tolman type evolution as if the conformal symmetry was effectively restored. This is not precisely so in the NBI model with symmetrized trace, but the leading term in the expansion law is still the same. A cosmological sphaleron solution on the D-brane is presented.Comment: 6 pages, latex, 1 figure. Submitted to the Proceedings of the VFC workshop at JENAM2002, Portu, Portugal, 1-6 september 200