3,101 research outputs found
The Gauge Fields and Ghosts in Rindler Space
We consider 2d Maxwell system defined on the Rindler space with metric
ds^2=\exp(2a\xi)\cdot(d\eta^2-d\xi^2) with the goal to study the dynamics of
the ghosts. We find an extra contribution to the vacuum energy in comparison
with Minkowski space time with metric ds^2= dt^2-dx^2. This extra contribution
can be traced to the unphysical degrees of freedom (in Minkowski space). The
technical reason for this effect to occur is the property of Bogolubov's
coefficients which mix the positive and negative frequencies modes. The
corresponding mixture can not be avoided because the projections to positive
-frequency modes with respect to Minkowski time t and positive -frequency modes
with respect to the Rindler observer's proper time \eta are not equivalent. The
exact cancellation of unphysical degrees of freedom which is maintained in
Minkowski space can not hold in the Rindler space. In BRST approach this effect
manifests itself as the presence of BRST charge density in L and R parts. An
inertial observer in Minkowski vacuum |0> observes a universe with no net BRST
charge only as a result of cancellation between the two. However, the Rindler
observers who do not ever have access to the entire space time would see a net
BRST charge. In this respect the effect resembles the Unruh effect. The effect
is infrared (IR) in nature, and sensitive to the horizon and/or boundaries. We
interpret the extra energy as the formation of the "ghost condensate" when the
ghost degrees of freedom can not propagate, but nevertheless do contribute to
the vacuum energy. Exact computations in this simple 2d model support the claim
made in [1] that the ghost contribution might be responsible for the observed
dark energy in 4d FLRW universe.Comment: Final version to appear in Phys. Rev. D. Comments on relation with
energy momentum computations and few new refs are adde
Quasigroups, Asymptotic Symmetries and Conservation Laws in General Relativity
A new quasigroup approach to conservation laws in general relativity is
applied to study asymptotically flat at future null infinity spacetime. The
infinite-parametric Newman-Unti group of asymptotic symmetries is reduced to
the Poincar\'e quasigroup and the Noether charge associated with any element of
the Poincar\'e quasialgebra is defined. The integral conserved quantities of
energy-momentum and angular momentum are linear on generators of Poincar\'e
quasigroup, free of the supertranslation ambiguity, posess the flux and
identically equal to zero in Minkowski spacetime.Comment: RevTeX4, 5 page
Lagrangian for the Majorana-Ahluwalia Construct
The equations describing self/anti-self charge conjugate states, recently
proposed by Ahluwalia, are re-written to covariant form. The corresponding
Lagrangian for the neutral particle theory is proposed. From a
group-theoretical viewpoint the construct is an example of the
Nigam-Foldy-Bargmann-Wightman-Wigner-type quantum field theory based on the
doubled representations of the extended Lorentz group. Relations with the
Sachs-Schwebel and Ziino-Barut concepts of relativistic quantum theory are
discussed.Comment: 10pp., REVTeX 3.0 fil
Towards gravitationally assisted negative refraction of light by vacuum
Propagation of electromagnetic plane waves in some directions in
gravitationally affected vacuum over limited ranges of spacetime can be such
that the phase velocity vector casts a negative projection on the time-averaged
Poynting vector. This conclusion suggests, inter alia, gravitationally assisted
negative refraction by vacuum.Comment: 6 page
Conformal Field Theory Interpretation of Black Hole Quasi-normal Modes
We obtain exact expressions for the quasi-normal modes of various spin for
the BTZ black hole. These modes determine the relaxation time of black hole
perturbations. Exact agreement is found between the quasi-normal frequencies
and the location of the poles of the retarded correlation function of the
corresponding perturbations in the dual conformal field theory. This then
provides a new quantitative test of the AdS/CFT correspondence.Comment: 4 pages, RevTeX, references adde
Entropy, Contact Interaction with Horizon and Dark Energy
We present some arguments suggesting that the mismatch between Bekenstein-
Hawking entropy and the entropy of entanglement for vector fields is due to the
same gauge configurations which saturate the contact term in topological
susceptibility in QCD. In both cases the extra term with a "wrong sign" is due
to distinct topological sectors in gauge theories. This extra term has
non-dispersive nature, can not be restored from conventional spectral function
through dispersion relations, and can not be associated with any physical
propagating degrees of freedom. We make few comments on some profound
consequences of our findings. In particular, we speculate that the source of
the observed dark energy may also be related to the same type of gauge
configurations which are responsible for the mismatch between black hole
entropy and the entropy of entanglement in the presence of causal horizon.Comment: final version to appear in Phys. Rev. D (2011
QSSC re-examined for the newly discovered SNe Ia
We examine the possible consistency of the quasi-steady state model with the
newly discovered SNe Ia. The model assumes the existence of metallic dust
ejected from the SNe explosions, which extinguishes light travelling over long
distances. We find that the model shows a reasonable fit to the data, which
improves if one takes account of the weak gravitational lensing effect of the
SNe which have been observed on the brighter side.Comment: 13 pages including 2 figures; accepted in Int. J. Mod. Phys.
Generalized observers and velocity measurements in General Relativity
To resolve some unphysical interpretations related to velocity measurements
by static observers, we discuss the use of generalized observer sets, give a
prescription for defining the speed of test particles relative to those
observers and show that, for any locally inertial frame, the speed of a freely
falling material particle is always less than the speed of light at the
Schwarzschild black hole surface.Comment: 20 pages, 1 figure, submitted to General Relativity and Gravitatio
Asymptotic Behaviour of Inhomogeneous String Cosmologies
The asymptotic behaviour at late times of inhomogeneous axion-dilaton
cosmologies is investigated. The space-times considered here admit two abelian
space-like Killing vectors. These space-times evolve towards an anisotropic
universe containing gravitational radiation. Furthermore, a peeling-off
behaviour of the Weyl tensor and the antisymmetric tensor field strength is
found. The relation to the pre-big-bang scenario is briefly discussed.Comment: 15 pages, Late
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