26 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
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
Continuous Family of Einstein-Yang-Mills Wormholes
It is shown that for some particular value of the cosmological constant
depending on the gauge coupling constant a continuous one-parameter family of
Einstein-Yang-Mills wormholes exists which interpolates between the instanton
and the gravitating meron solutions. In contradistinction with the previously
known solutions the topological charge of these wormholes is not quantized. For
all of them the contribution of gravity to the action exactly cancels that of
the gauge field.Comment: 15 page
Radiation Problem in Transplanckian Scattering
We investigate hard radiation emission in small-angle transplanckian
scattering. We show how to reduce this problem to a quantum field theory
computation in a classical background (gravitational shock wave). In momentum
space, the formalism is similar to the flat-space light cone perturbation
theory, with shock wave crossing vertices added. In the impact parameter
representation, the radiating particle splits into a multi-particle virtual
state, whose wavefunction is then multiplied by individual eikonal factors. As
a phenomenological application, we study QCD radiation in transplanckian
collisions of TeV-scale gravity models. We derive the distribution of initial
state radiation gluons, and find a suppression at large transverse momenta with
respect to the standard QCD result. This is due to rescattering events, in
which the quark and the emitted gluon scatter coherently. Interestingly, the
suppression factor depends on the number of extra dimensions and provides a new
experimental handle to measure this number. We evaluate the leading-log
corrections to partonic cross-sections due to the initial state radiation, and
prove that they can be absorbed into the hadronic PDF. The factorization scale
should then be chosen in agreement with an earlier proposal of Emparan, Masip,
and Rattazzi. In the future, our methods can be applied to the gravitational
radiation in transplanckian scattering, where they can go beyond the existing
approaches limited to the soft radiation case.Comment: 41 pp, v2: minor changes and added refs, conforms with published
versio
Rotating Dilaton Black Holes
We consider the axially symmetric coupled system of gravitation,
electromagnetism and a dilaton field. Reducing from four to three dimensions,
the system is described by gravity coupled to a non-linear -model. We
find the target space isometries and use them to generate new solutions. It
seems that it is only possible to generate rotating solutions from non-rotating
ones for the special cases when the dilaton coupling parameter . For those particular values, the target space symmetry is enlarged.Comment: 11 pages, RevTex, one figure include
Sphaleron glueballs in NBI theory with symmetrized trace
We derive a closed expression for the SU(2) Born-Infeld action with the
symmetrized trace for static spherically symmetric purely magnetic
configurations. The lagrangian is obtained in terms of elementary functions.
Using it, we investigate glueball solutions to the flat space NBI theory and
their self-gravitating counterparts. Such solutions, found previously in the
NBI model with the 'square root - ordinary trace' lagrangian, are shown to
persist in the theory with the symmetrized trace lagrangian as well. Although
the symmetrized trace NBI equations differ substantially from those of the
theory with the ordinary trace, a qualitative picture of glueballs remains
essentially the same. Gravity further reduces the difference between solutions
in these two models, and, for sufficiently large values of the effective
gravitational coupling, solutions tends to the same limiting form. The black
holes in the NBI theory with the symmetrized trace are also discussed.Comment: 19 pages,6 eps figures, late
Saddle point solutions in Yang-Mills-dilaton theory
The coupling of a dilaton to the -Yang-Mills field leads to
interesting non-perturbative static spherically symmetric solutions which are
studied by mixed analitical and numerical methods. In the abelian sector of the
theory there are finite-energy magnetic and electric monopole solutions which
saturate the Bogomol'nyi bound. In the nonabelian sector there exist a
countable family of globally regular solutions which are purely magnetic but
have zero Yang-Mills magnetic charge. Their discrete spectrum of energies is
bounded from above by the energy of the abelian magnetic monopole with unit
magnetic charge. The stability analysis demonstrates that the solutions are
saddle points of the energy functional with increasing number of unstable
modes. The existence and instability of these solutions are "explained" by the
Morse-theory argument recently proposed by Sudarsky and Wald.Comment: 11 page
All the Four Dimensional Static, Spherically Symmetric Solutions of Abelian Kaluza-Klein Theory
We present the explicit form for all the four dimensional, static,
spherically symmetric solutions in -d Abelian Kaluza-Klein theory by
performing a subset of transformations corresponding to four
boosts on the Schwarzschild solution, supplemented by
transformations. The solutions are parameterized by the mass , Taub-Nut
charge , electric and magnetic
charges. Non-extreme black holes (with zero Taub-NUT charge) have either the
Reissner-Nordstr\" om or Schwarzschild global space-time. Supersymmetric
extreme black holes have a null or naked singularity, while non-supersymmetric
extreme ones have a global space-time of extreme Reissner-Nordstr\" om black
holes.Comment: 8 pages, uses RevTex, improved version to appear in Phys. Rev. Let