368 research outputs found
Killing tensors and a new geometric duality
We present a theorem describing a dual relation between the local geometry of
a space admitting a symmetric second-rank Killing tensor, and the local
geometry of a space with a metric specified by this Killing tensor. The
relation can be generalized to spinning spaces, but only at the expense of
introducing torsion. This introduces new supersymmetries in their geometry.
Interesting examples in four dimensions include the Kerr-Newman metric of
spinning black-holes and self-dual Taub-NUT.Comment: 20 pages (a4), standard LaTeX, no figure
Supersymmetry and the Geometry of Taub-NUT
The supersymmetric extension of Taub-NUT space admits 4 standard
supersymmetries plus several additional non-standard ones. The geometrical
origin of these symmetries is traced. The result has applications to fermion
modes in gravitational instantons as well as in long-range monopole dynamics.Comment: 9 pages, NIKHEF-H/94-2
On the Obstructions to non-Cliffordian Pin Structures
We derive the topological obstructions to the existence of non-Cliffordian
pin structures on four-dimensional spacetimes. We apply these obstructions to
the study of non-Cliffordian pin-Lorentz cobordism. We note that our method of
derivation applies equally well in any dimension and in any signature, and we
present a general format for calculating obstructions in these situations.
Finally, we interpret the breakdown of pin structure and discuss the relevance
of this to aspects of physics.Comment: 31 pages, latex, published in Comm. Math. Phys. 164, No. 1, pages
65-87 (1994
Dilaton black holes in grand canonical ensemble near the extreme state
Dilaton black holes with a pure electric charge are considered in a framework
of a grand canonical ensemble near the extreme state. It is shown that there
exists such a subset of boundary data that the Hawking temperature smoothly
goes to zero to an infinite value of a horizon radius but the horizon area and
entropy are finite and differ from zero. In string theory the existence of a
horizon in the extreme limit is due to the finiteness of a system only.Comment: 8 pages, RevTex 3.0. Presentation improved, discussion on metrics in
string theory simplified. To be published in Phys.Rev.
Spinning particles in Taub-NUT space
The geodesic motion of pseudo-classical spinning particles in Euclidean
Taub-NUT space is analysed. The constants of motion are expressed in terms of
Killing-Yano tensors. Some previous results from the literature are corrected.Comment: LaTeX, 8 page
Action of Singular Instantons of Hawking-Turok Type
Using Kaluza-Klein technique we show that the singularity of Hawking-Turok
type has a fixed point (bolt) contribution to the action in addition to the
usual boundary contribution. Interestingly by adding this contribution we can
obtain a simple expression for the total action which is feasible for both
regular and singular instantons. Our result casts doubt on the constraint
proposed by Turok in the recent calculation in which Vilenkin's instantons are
regarded as a limit of certain constrained instantons.Comment: 14 pages, LaTe
Thermodynamics of a Kerr Newman de Sitter Black Hole
We compute the conserved quantities of the four-dimensional Kerr-Newman-dS
(KNdS) black hole through the use of the counterterm renormalization method,
and obtain a generalized Smarr formula for the mass as a function of the
entropy, the angular momentum and the electric charge. The first law of
thermodynamics associated to the cosmological horizon of KNdS is also
investigated. Using the minimal number of intrinsic boundary counterterms, we
consider the quasilocal thermodynamics of asymptotic de Sitter
Reissner-Nordstrom black hole, and find that the temperature is equal to the
product of the surface gravity (divided by ) and the Tolman redshift
factor. We also perform a quasilocal stability analysis by computing the
determinant of Hessian matrix of the energy with respect to its thermodynamic
variables in both the canonical and the grand-canonical ensembles and obtain a
complete set of phase diagrams. We then turn to the quasilocal thermodynamics
of four-dimensional Kerr-Newman-de Sitter black hole for virtually all possible
values of the mass, the rotation and the charge parameters that leave the
quasilocal boundary inside the cosmological event horizon, and perform a
quasilocal stability analysis of KNdS black hole.Comment: REVTEX4, 12 pages, 12 figures, references added and some points in
Sec II have been clarified, version to appear in Can. J. Phy
Are Causality Violations Undesirable?
Causality violations are typically seen as unrealistic and undesirable
features of a physical model. The following points out three reasons why
causality violations, which Bonnor and Steadman identified even in solutions to
the Einstein equation referring to ordinary laboratory situations, are not
necessarily undesirable. First, a space-time in which every causal curve can be
extended into a closed causal curve is singularity free--a necessary property
of a globally applicable physical theory. Second, a causality-violating
space-time exhibits a nontrivial topology--no closed timelike curve (CTC) can
be homotopic among CTCs to a point, or that point would not be causally well
behaved--and nontrivial topology has been explored as a model of particles.
Finally, if every causal curve in a given space-time passes through an event
horizon, a property which can be called "causal censorship", then that
space-time with event horizons excised would still be causally well behaved.Comment: Accepted in October 2008 by Foundations of Physics. Latex2e, 6 pages,
no figures. Presented at a seminar at the Universidad Nacional Autonoma de
Mexico. Version 2 was co-winner of the QMUL CTC Essay Priz
SUSY in the sky
Spinning particles in curved space-time can have fermionic symmetries
generated by the square root of bosonic constants of motion other than the
Hamiltonian. We present a general analysis of the conditions under which such
new supersymmetries appear, and discuss the Poisson-Dirac algebra of the
resulting set of charges, including the conditions of closure of the new
algebra. An example of a new non-trivial supersymmetry is found in black-hole
solutions of the Kerr-Newman type and corresponds to the Killing-Yano tensor,
which plays an important role in solving the Dirac equation in these black-hole
metrics.Comment: 28, NIKHEF-H/93-04 and DAMTP R92/4
On "Non-Geometric" Contribution To The Entropy Of Black Hole Due To Quantum Corrections
The quantum corrections to the entropy of charged black holes are calculated.
The Reissner-Nordstrem and dilaton black holes are considered. The appearance
of logarithmically divergent terms not proportional to the horizon area is
demonstrated. It is shown that the complete entropy which is sum of classical
Bekenstein-Hawking entropy and the quantum correction is proportional to the
area of quantum-corrected horizon.Comment: Latex, 9 page
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