2,447 research outputs found
Continuous Self-Similarity Breaking in Critical Collapse
This paper studies near-critical evolution of the spherically symmetric
scalar field configurations close to the continuously self-similar solution.
Using analytic perturbative methods, it is shown that a generic growing
perturbation departs from the critical Roberts solution in a universal way. We
argue that in the course of its evolution, initial continuous self-similarity
of the background is broken into discrete self-similarity with echoing period
, reproducing the symmetries of the critical
Choptuik solution.Comment: RevTeX 3.1, 28 pages, 5 figures; discussion rewritten to clarify
several issue
SL(2) spin chain and spinning strings on AdS_5xS^5
We derive the coherent state representation of the integrable spin chain
Hamiltonian with symmetry group SL(2,R). By passing to the continuum limit, we
find a spin chain sigma model describing a string moving on the hyperboloid
SL(2,R)/U(1). The same sigma model is found by considering strings rotating
with large angular momentum in AdS_5xS^5. The spinning strings are identified
with semiclassical coherent states built out of SL(2,R) spin chain states.Comment: 18 pages, 1 fig, References added. Earlier results in [38] are
pointed ou
Physics of the interior of a spherical, charged black hole with a scalar field
We analyse the physics of nonlinear gravitational processes inside a
spherical charged black hole perturbed by a self-gravitating massless scalar
field. For this purpose we created an appropriate numerical code. Throughout
the paper, in addition to investigation of the properties of the mathematical
singularities where some curvature scalars are equal to infinity, we analyse
the properties of the physical singularities where the Kretschmann curvature
scalar is equal to the planckian value. Using a homogeneous approximation we
analyse the properties of the spacetime near a spacelike singularity in
spacetimes influenced by different matter contents namely a scalar field,
pressureless dust and matter with ultrarelativistic isotropic pressure. We also
carry out full nonlinear analyses of the scalar field and geometry of spacetime
inside black holes by means of an appropriate numerical code with adaptive mesh
refinement capabilities. We use this code to investigate the nonlinear effects
of gravitational focusing, mass inflation, matter squeeze, and these effects
dependence on the initial boundary conditions. It is demonstrated that the
position of the physical singularity inside a black hole is quite different
from the positions of the mathematical singularities. In the case of the
existence of a strong outgoing flux of the scalar field inside a black hole it
is possible to have the existence of two null singularities and one central
singularity simultaneously
Self-Similar Collapse of Scalar Field in Higher Dimensions
This paper constructs continuously self-similar solution of a spherically
symmetric gravitational collapse of a scalar field in n dimensions. The
qualitative behavior of these solutions is explained, and closed-form answers
are provided where possible. Equivalence of scalar field couplings is used to
show a way to generalize minimally coupled scalar field solutions to the model
with general coupling.Comment: RevTex 3.1, 15 pages, 3 figures; references adde
Non-abelian magnetic black strings versus black holes
We present dimensional pure magnetic Yang-Mills (YM) black strings (or
branes) induced by the dimensional Einstein-Yang-Mills-Dilaton black
holes. Born-Infeld version of the YM field makes our starting point which goes
to the standard YM field through a limiting procedure. The lifting from black
holes to black strings, (with less number of fields) is by adding an extra,
compact coordinate. This amounts to the change of horizon topology from
to a product structure. Our black string in dimensions is a
rather special one, with uniform Hawking temperature and non-asymptotically
flat structure. As the YM charge becomes large the string gets thinner to tend
into a breaking point and transform into a % dimensional black hole.Comment: 5 pages no figure; Final version to appear in EPJ
Sigma model from SU(1,1|2) spin chain
We derive the coherent state representation of the integrable spin chain
Hamiltonian with supersymmetry group . By the use of a projected
Hamiltonian onto bosonic states, we give explicitly the action of the
Hamiltonian on coherent states. Passing to the continuous
limit, we find that the corresponding bosonic sigma model is the sum of the
known SU(2) and SL(2) ones, and thus it gives a string spinning fast on
in . The full sigma model on the supercoset is given.Comment: 20 pages, no figures, 4 tables, 1 appendix; typos corrected,
references adde
Gravitational Radiation from the radial infall of highly relativistic point particles into Kerr black holes
In this paper, we consider the gravitational radiation generated by the
collision of highly relativistic particles with rotating Kerr black holes. We
use the Sasaki-Nakamura formalism to compute the waveform, energy spectra and
total energy radiated during this process. We show that the gravitational
spectrum for high-energy collisions has definite characteristic universal
features, which are independent of the spin of the colliding objects. We also
discuss possible connections between these results and the black hole-black
hole collision at the speed of light process. With these results at hand, we
predict that during the high speed collision of a non-rotating hole with a
rotating one, about 35% of the total energy can get converted into
gravitational waves. Thus, if one is able to produce black holes at the Large
Hadron Collider, as much as 35% of the partons' energy should be emitted during
the so called balding phase. This energy will be missing, since we don't have
gravitational wave detectors able to measure such amplitudes. The collision at
the speed of light between one rotating black hole and a non-rotating one or
two rotating black holes turns out to be the most efficient gravitational wave
generator in the Universe.Comment: 15 pages, REVTEX4. Some comments and references adde
Simulation of Acoustic Black Hole in a Laval Nozzle
A numerical simulation of fluid flows in a Laval nozzle is performed to
observe formations of acoustic black holes and the classical counterpart to
Hawking radiation under a realistic setting of the laboratory experiment. We
determined the Hawking temperature of the acoustic black hole from obtained
numerical data. Some noteworthy points in analyzing the experimental data are
clarified through our numerical simulation.Comment: 26 pages, published versio
Giant Magnons under NS-NS and Melvin Fields
The giant magnon is a rotating spiky string configuration which has the same
dispersion relation between the energy and angular momentum as that of a spin
magnon. In this paper we investigate the effects of the NS-NS and Melvin fields
on the giant magnon. We first analyze the energy and angular momenta of the
two-spin spiky D-string moving on the with the NS-NS field.
Due to the infinite boundary of the AdS spacetime the D-string solution will
extend to infinity and it appears the divergences. After adding the counter
terms we obtain the dispersion relation of the corresponding giant magnon. The
result shows that there will appear a prefactor before the angular momentum, in
addition to some corrections in the sine function. We also see that the spiky
profile of a rotating D-string plays an important role in mapping it to a spin
magnon. We next investigate the energy and angular momentum of the one-spin
spiky fundamental string moving on the with the electric or
magnetic Melvin field. The dispersion relation of the corresponding deformed
giant magnon is also obtained. We discuss some properties of the correction
terms and their relations to the spin chain with deformations.Comment: Latex 20 pages, mention D-string and add reference
Spin bits at two loops
We consider the Super Yang--Mills/spin system map to construct the SU(2) spin
bit model at the level of two loops in Yang--Mills perturbation theory. The
model describes a spin system with chaining interaction. In the large limit
the model is shown to be reduced to the two loop planar integrable spin chain.Comment: 10 pages, 3 figures, References and Acknowledgements adde
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