2,643 research outputs found
Applications of hidden symmetries to black hole physics
This work is a brief review of applications of hidden symmetries to black
hole physics. Symmetry is one of the most important concepts of the science. In
physics and mathematics the symmetry allows one to simplify a problem, and
often to make it solvable. According to the Noether theorem symmetries are
responsible for conservation laws. Besides evident (explicit) spacetime
symmetries, responsible for conservation of energy, momentum, and angular
momentum of a system, there also exist what is called hidden symmetries, which
are connected with higher order in momentum integrals of motion. A remarkable
fact is that black holes in four and higher dimensions always possess a set
(`tower') of explicit and hidden symmetries which make the equations of motion
of particles and light completely integrable. The paper gives a general review
of the recently obtained results. The main focus is on understanding why at all
black holes have something (symmetry) to hide.Comment: This is an extended version of the talks at NEB-14 conference
(June,Ioannina,Greece) and JGRG20 meeting (September, Kyoto, Japan
Statistical Origin of Black Hole Entropy in Matrix Theory
The statistical entropy of black holes in M-theory is considered. Assuming
Matrix theory is the discretized light-cone quantization of a theory with
eleven-dimensional Lorentz invariance, we map the counting problem onto the
original Gibbons-Hawking calculation of the thermodynamic entropy.Comment: 9 pages, harvmac, (v2 References added, typo fixed), (v3 Some
clarifying comments added.
Photon rockets and the Robinson-Trautman geometries
We point out the relation between the photon rocket spacetimes and the
Robinson Trautman geometries. This allows a discussion of the issues related to
the distinction between the gravitational and matter energy radiation that
appear in these metrics in a more geometrical way, taking full advantage of
their asymptotic properties at null infinity to separate the Weyl and Ricci
radiations, and to clearly establish their gravitational energy content. We
also give the exact solution for the generalized photon rockets.Comment: 7 pages, no figures, LaTeX2
Asymptotic symmetries on Kerr--Newman horizon without anomaly of diffeomorphism invariance
We analyze asymptotic symmetries on the Killing horizon of the
four-dimensional Kerr--Newman black hole. We first derive the asymptotic
Killing vectors on the Killing horizon, which describe the asymptotic
symmetries, and find that the general form of these asymptotic Killing vectors
is the universal one possessed by arbitrary Killing horizons. We then construct
the phase space associated with the asymptotic symmetries. It is shown that the
phase space of an extreme black hole either has the size comparable with a
non-extreme black hole, or is small enough to exclude degeneracy, depending on
whether or not the global structure of a Killing horizon particular to an
extreme black hole is respected. We also show that the central charge in the
Poisson brackets algebra of these asymptotic symmetries vanishes, which implies
that there is not an anomaly of diffeomorphism invariance. By taking into
account other results in the literature, we argue that the vanishing central
charge on a black hole horizon, in an effective theory, looks consistent with
the thermal feature of a black hole. We furthermore argue that the vanishing
central charge implies that there are infinitely many classical configurations
that are associated with the same macroscopic state, while these configurations
are distinguished physically.Comment: 14 pages, v2: references added, minor corrections, v3: new pars and
refs. added and corresponding correction
Energy, Hamiltonian, Noether Charge, and Black Holes
It is shown that in general the energy and the Hamiltonian of matter fields on the black hole exterior play different roles. is a generator of the time evolution along the Killing time while enters the first law of black hole thermodynamics. For non-minimally
coupled fields the difference is not zero and is a Noether
charge analogous to that introduced by Wald to define the black hole
entropy. If fields vanish at the spatial boundary, is reduced to an
integral over the horizon. The analysis is carried out and an explicit
expression for is found for general diffeomorphism invariant theories. As
an extension of the results by Wald et al, the first law of black hole
thermodynamics is derived for arbitrary weak matter fields.Comment: 20 pages, latex, no figure
Anomalous variations in the thermohaline structure of the Arctic Ocean (Aus dem Russ. übersetzt)
Introduction:
In the last two decades, significant changes have occurred in the Arctic Ocean as well as in the entire Arctic region. The ice cover of Arctic seas, which was gradually (linearly) decreasing from the beginning of the 20th century to the end of it [1], began to shrink rapidly in the 1990s and in the 21st century [2]. Salinity variations in the upper layer changed sign in different regions [3]. The temperature of Atlantic waters in the Arctic basin started to increase. At the end of the 1990s, stabilization of Atlantic water transport to the Arctic Basin was observed [4], but starting from 2004, the temperature of Atlantic waters in the Eurasian sub-basin increased even more and reached values that had not been observed here previously [5]. In 2007, extreme summer processes in the Arctic that followed this increase and anomalous state of the ice cover and upper layer of the ocean that were formed by the beginning of autumn put forward a pressing problem to evaluate the variation in the thermohaline structure of the Arctic Ocean as a whole
The Value of Singularities
We point out that spacetime singularities play a useful role in gravitational
theories by eliminating unphysical solutions. In particular, we argue that any
modification of general relativity which is completely nonsingular cannot have
a stable ground state. This argument applies both to classical extensions of
general relativity, and to candidate quantum theories of gravity.Comment: 5 pages, no figures; a few clarifying comments adde
A note on the universality of the Hagedorn behavior of pp-wave strings
Following on from recent studies of string theory on a one-parameter family
of integrable deformations of proposed by Lunin and
Maldacena, we carry out a systematic analysis of the high temperature
properties of type IIB strings on the associated pp-wave geometries. In
particular, through the computation of the thermal partition function and free
energy we find that not only does the theory exhibit a Hagedorn transition in
both the and class of pp-waves, but that the Hagedorn
temperature is insensitive to the deformation suggesting an interesting
universality in the high temperature behaviour of the pp-wave string theory. We
comment also on the implications of this universality on the
confinement/deconfinement transition in the dual
Leigh-Strassler deformation of Yang-Mills theory.Comment: 25 pages; fixed minor typo; added reference
Gravitational Effects of Quantum Fields in the Interior of a Cylindrical Black Hole
The gravitational back-reaction is calculated for the conformally invariant
scalar field within a black cosmic string interior with cosmological constant.
Using the perturbed metric, the gravitational effects of the quantum field are
calculated. It is found that the perturbations initially strengthen the
singularity. This effect is similar to the case of spherical symmetry (without
cosmological constant). This indicates that the behaviour of quantum effects
may be universal and not dependent on the geometry of the spacetime nor the
presence of a non-zero cosmological constant.Comment: 13 pages, 1 figure, uses AMS package. D.E. solution corrected. Some
qualitative results are change
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