289 research outputs found
Matrix Ernst potentials for EMDA with multiple vector fields
We show that the Einstein-Maxwell-Dilaton-Axion system with multiple vector
fields (bosonic sector of the D=4, N=4 supergravity) restricted to spacetimes
possessing a non-null Killing vector field admits a concise representation in
terms of the Ernst-type matrix valued potentials. A constructive derivation of
the SWIP solutions is given and a colliding waves counterpart of the DARN-NUT
solution is obtained. SU(m,m) chiral representation of the two-dimensionally
reduced system is derived and the corresponding Kramer-Neugebauer-type map is
presented.Comment: Latex file, no figure
Stringy Sphalerons and Non-Abelian Black Holes
Static spherically symmetric asymptotically flat particle-like and black hole
solutions are constructed within the SU(2) sector of 4-dimensional heterotic
string effective action. They separate topologically distinct Yang-Mills vacua
and are qualitatively similar to the Einstein-Yang-Mills spha- lerons and
non-abelian black holes discussed recently. New solutions possess quantized
values of the dilaton charge.Comment: 12 pages, LATEX, (8 figures upon request
Charged Stringy Black Holes With Non-Abelian Hair
Static spherically symmetric asymptotically flat charged black hole solutions
are constructed within the magnetic SU(3) sector of the 4-dimensional heterotic
string effective action. They possess non-abelian hair in addition to the
Coulomb magnetic field and are qualitatively similar to the Einstein-Yang-Mills
colored SU(3) black holes except for the extremal case. In the extremality
limit the horizon shrinks and the resulting geometry around the origin
coincides with that of an extremal abelian dilatonic black hole with magnetic
charge. Non-abelian hair exibits then typical sphaleron structure.Comment: 11 pages, LaTex, (7 figures upon request
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
Solitons and black holes in non-Abelian Einstein-Born-Infeld theory
Recently it was shown that the Born-Infeld-type modification of the quadratic
Yang-Mills action gives rise to classical particle-like solutions in the flat
space which have a striking similarity with the Bartnik-McKinnon solutions
known in the gravity coupled Yang-Mills theory. We show that both families are
continuously related within the framework of the Einstein-Born-Infeld theory
through interpolating sequences of parameters. We also investigate an internal
structure of the associated black holes. It is found that the Born-Infeld
non-linearity leads to a drastic modification of the black hole interior
typical for the usual Yang-Mills theory. In the latter case a generic solution
exhibits violent metric oscillations near the singularity. In the Born-Infeld
case a generic interior solution is smooth, the metric has the standard
Schwarzschild type singularity, and we did not observe internal horizons. Such
smoothing of the 'violent' EYM singularity may be interpreted as a result of
quantum effects.Comment: Latex, 9 pages, 9 eps figure
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