2,209 research outputs found
Lukewarm black holes in quadratic gravity
Perturbative solutions to the fourth-order gravity describing
spherically-symmetric, static and electrically charged black hole in an
asymptotically de Sitter universe is constructed and discussed. Special
emphasis is put on the lukewarm configurations, in which the temperature of the
event horizon equals the temperature of the cosmological horizon
The Hawking temperature of expanding cosmological black holes
In the context of a debate on the correct expression of the Hawking
temperature of an expanding cosmological black hole, we show that the correct
expression in terms of the Hawking-Hayward quasi-local energy m of the hole is
T=1/(8\pi m(t)). This expression holds for comoving black holes and agrees with
a recent proposal by Saida, Harada, and Maeda.Comment: 5 latex pages, to appear in Phys. Rev. D. Some references adde
Implication of Compensator Field and Local Scale Invariance in the Standard Model
We introduce Weyl's scale symmetry into the standard model (SM) as a local
symmetry. This necessarily introduces gravitational interactions in addition to
the local scale invariance group \tilde U(1) and the SM groups SU(3) X SU(2) X
U(1). The only other new ingredients are a new scalar field \sigma and the
gauge field for \tilde U(1) we call the Weylon. A noteworthy feature is that
the system admits the St\" uckelberg-type compensator. The \sigma couples to
the scalar curvature as (-\zeta/2) \sigma^2 R, and is in turn related to a St\"
uckelberg-type compensator \varphi by \sigma \equiv M_P e^{-\varphi/M_P} with
the Planck mass M_P. The particular gauge \varphi = 0 in the St\" uckelberg
formalism corresponds to \sigma = M_P, and the Hilbert action is induced
automatically. In this sense, our model presents yet another mechanism for
breaking scale invariance at the classical level. We show that our model
naturally accommodates the chaotic inflation scenario with no extra field.Comment: This work is to be read in conjunction with our recent comments
hep-th/0702080, arXiv:0704.1836 [hep-ph] and arXiv:0712.2487 [hep-ph]. The
necessary ingredients for describing chaotic inflation in the SM as
entertained by Bezrukov and Shaposhnikov [17] have been provided by our
original model [8]. We regret their omission in citing our original model [8
Particle phenomenology on noncommutative spacetime
We introduce particle phenomenology on the noncommutative spacetime called
the Groenewold-Moyal plane. The length scale of spcetime noncommutativity is
constrained from the CPT violation measurements in system
and difference of . The system
provides an upper bound on the length scale of spacetime noncommutativity of
the order of , corresponding to a lower energy bound
of the order of . The difference of constrains the noncommutativity length scale to be of the order of
, corresponding to a lower energy bound of the order
of .
We also present the phenomenology of the electromagnetic interaction of
electrons and nucleons at the tree level in the noncommutative spacetime. We
show that the distributions of charge and magnetization of nucleons are
affected by spacetime noncommutativity. The analytic properties of
electromagnetic form factors are also changed and it may give rise to
interesting experimental signals.Comment: 10 pages, 3 figures. Published versio
Conformal Invariance in Einstein-Cartan-Weyl space
We consider conformally invariant form of the actions in Einstein, Weyl,
Einstein-Cartan and Einstein-Cartan-Weyl space in general dimensions() and
investigate the relations among them. In Weyl space, the observational
consistency condition for the vector field determining non-metricity of the
connection can be obtained from the equation of motion. In Einstein-Cartan
space a similar role is played by the vector part of the torsion tensor. We
consider the case where the trace part of the torsion is the Kalb-Ramond type
of field. In this case, we express conformally invariant action in terms of two
scalar fields of conformal weight -1, which can be cast into some interesting
form. We discuss some applications of the result.Comment: 10 pages, version to appear MPL
Gravitational charges of transverse asymptotically AdS spacetimes
Using Killing-Yano symmetries, we construct conserved charges of spacetimes
that asymptotically approach to the flat or Anti-de Sitter spaces only in
certain directions. In D dimensions, this allows one to define gravitational
charges (such as mass and angular momenta densities) of p-dimensional
branes/solitons or any other extended objects that curve the transverse space
into an asymptotically flat or AdS one. Our construction answers the question
of what kind of charges the antisymmetric Killing-Yano tensors lead to.Comment: 11 pages, no figures, REVTeX 4; version 2: important corrections
made; version 3: one new paragraph and 2 references added, accepted for
publication in PR
Weyl Geometry as Characterization of Space-Time
Motivated by an axiomatic approach to characterize space-time it is
investigated a reformulation of Einstein's gravity where the pseudo-riemannian
geometry is substituted by a Weyl one. It is presented the main properties of
the Weyl geometry and it is shown that it gives extra contributions to the
trajectories of test particles, serving as one more motivation to study general
relativity in Weyl geometry. It is introduced its variational formalism and it
is established the coupling with other physical fields in such a way that the
theory acquires a gauge symmetry for the geometrical fields. It is shown that
this symmetry is still present for the red-shift and it is concluded that for
cosmological models it opens the possibility that observations can be fully
described by the new geometrical scalar field. It is concluded then that this
reformulation, although representing a theoretical advance, still needs a
complete description of their objects.Comment: 12 page
Universal entanglement concentration
We propose a new protocol of \textit{universal} entanglement concentration,
which converts many copies of an \textit{unknown} pure state to an \textit{%
exact} maximally entangled state. The yield of the protocol, which is outputted
as a classical information, is probabilistic, and achives the entropy rate with
high probability, just as non-universal entanglement concentration protocols
do.
Our protocol is optimal among all similar protocols in terms of wide
varieties of measures either up to higher orders or non-asymptotically,
depending on the choice of the measure. The key of the proof of optimality is
the following fact, which is a consequence of the symmetry-based construction
of the protocol: For any invariant measures, optimal protocols are found out in
modifications of the protocol only in its classical output, or the claim on the
product.
We also observe that the classical part of the output of the protocol gives a
natural estimate of the entropy of entanglement, and prove that that estimate
achieves the better asymptotic performance than any other (potentially global)
measurements.Comment: Revised a lot, especially proofs, though no change in theorems,
lemmas itself. Very long, but essential part is from Sec.I to Sec IV-C. Some
of the appendces are almost independent of the main bod
Possible way out of the Hawking paradox: Erasing the information at the horizon
We show that small deviations from spherical symmetry, described by means of
exact solutions to Einstein equations, provide a mechanism to "bleach" the
information about the collapsing body as it falls through the aparent horizon,
thereby resolving the information loss paradox. The resulting picture and its
implication related to the Landauer's principle in the presence of a
gravitational field, is discussed.Comment: 11 pages, Latex. Some comments added to answer to some raised
questions. Typos corected. Final version, to appear in Int. J. Modern. Phys.
Accelerated black holes in an anti-de Sitter universe
The C-metric is one of few known exact solutions of Einstein's field
equations which describes the gravitational field of moving sources. For a
vanishing or positive cosmological constant, the C-metric represents two
accelerated black holes in asymptotically flat or de Sitter spacetime. For a
negative cosmological constant the structure of the spacetime is more
complicated. Depending on the value of the acceleration, it can represent one
black hole or a sequence of pairs of accelerated black holes in the spacetime
with an anti-de Sitter-like infinity. The global structure of this spacetime is
analyzed and compared with an empty anti-de Sitter universe. It is illustrated
by 3D conformal-like diagrams.Comment: 14 pages, 17 figures [see
http://utf.mff.cuni.cz/~krtous/physics/CADS/ for the version with the high
quality figures and for related animations and interactive 3D diagrams
- …