1,621 research outputs found
Hamiltonian thermodynamics of three-dimensional dilatonic black holes
The action for a class of three-dimensional dilaton-gravity theories with a
cosmological constant can be recast in a Brans-Dicke type action, with its free
parameter. These theories have static spherically symmetric black
holes. Those with well formulated asymptotics are studied through a Hamiltonian
formalism, and their thermodynamical properties are found out. The theories
studied are general relativity (), a dimensionally reduced
cylindrical four-dimensional general relativity theory (), and a
theory representing a class of theories (). The Hamiltonian
formalism is setup in three dimensions through foliations on the right region
of the Carter-Penrose diagram, with the bifurcation 1-sphere as the left
boundary, and anti-de Sitter infinity as the right boundary. The metric
functions on the foliated hypersurfaces are the canonical coordinates. The
Hamiltonian action is written, the Hamiltonian being a sum of constraints. One
finds a new action which yields an unconstrained theory with one pair of
canonical coordinates , being the mass parameter and its
conjugate momenta The resulting Hamiltonian is a sum of boundary terms only. A
quantization of the theory is performed. The Schr\"odinger evolution operator
is constructed, the trace is taken, and the partition function of the canonical
ensemble is obtained. The black hole entropies differ, in general, from the
usual quarter of the horizon area due to the dilaton.Comment: 34 pages, 3 figures, references added, minor changes in the revised
versio
Charged shells in Lovelock gravity: Hamiltonian treatment and physical implications
Using a Hamiltonian treatment, charged thin shells in spherically symmetric
spacetimes in d dimensional Lovelock-Maxwell theory are studied. The
coefficients of the theory are chosen to obtain a sensible theory, with a
negative cosmological constant appearing naturally. After writing the action
and the Lagrangian for a spacetime comprised of an interior and an exterior
regions, with a thin shell as a boundary in between, one finds the Hamiltonian
using an ADM description. For spherically symmetric spacetimes, one reduces the
relevant constraints. The dynamic and constraint equations are obtained. The
vacuum solutions yield a division of the theory into two branches, d-2k-1>0
(which includes general relativity, Born-Infeld type theories) and d-2k-1=0
(which includes Chern-Simons type theories), where k gives the highest power of
the curvature in the Lagrangian. An additional parameter, chi, gives the
character of the vacuum solutions. For chi=1 the solutions have a black hole
character. For chi=-1 the solutions have a totally naked singularity character.
The integration through the thin shell takes care of the smooth junction. The
subsequent analysis is divided into two cases: static charged thin shell
configurations, and gravitationally collapsing charged dust shells. Physical
implications are drawn: if such a large extra dimension scenario is correct,
one can extract enough information from the outcome of those collapses as to
know, not only the actual dimension of spacetime, but also which particular
Lovelock gravity, is the correct one.Comment: 25 pages, 9 figure
Hamiltonian thermodynamics of charged three-dimensional dilatonic black holes
The action for a class of three-dimensional dilaton-gravity theories, with an
electromagnetic Maxwell field and a cosmological constant, can be recast in a
Brans-Dicke-Maxwell type action, with its free parameter. For a
negative cosmological constant, these theories have static, electrically
charged, and spherically symmetric black hole solutions. Those theories with
well formulated asymptotics are studied through a Hamiltonian formalism, and
their thermodynamical properties are found. The theories studied are general
relativity, a dimensionally reduced cylindrical four-dimensional general
relativity theory, and a theory representing a class of theories, all with a
Maxwell term. The Hamiltonian formalism is setup in three dimensions through
foliations on the right region of the Carter-Penrose diagram, with the
bifurcation 1-sphere as the left boundary, and anti-de Sitter infinity as the
right one. The metric functions on the hypersurfaces and the radial component
of the vector potential one-form are the canonical coordinates. The Hamiltonian
action is written, the Hamiltonian being a sum of constraints. One finds a new
action which yields an unconstrained theory with two pairs of canonical
coordinates , where is the mass parameter, which needs
renormalization, its conjugate momenta, is the charge parameter, and
its conjugate momentum. The resulting Hamiltonian is a sum of boundary
terms only. A quantization of the theory is performed. The Schr\"odinger
evolution operator is constructed, the trace is taken, and the partition
function of the grand canonical ensemble is obtained, the chemical potential
being the electric potential. The charged black hole entropies differ, in
general, from the usual quarter of the horizon area due to the dilaton.Comment: 38 pages, 3 figure
Thin-shell wormholes in d-dimensional general relativity: Solutions, properties, and stability
We construct thin-shell electrically charged wormholes in d-dimensional
general relativity with a cosmological constant. The wormholes constructed can
have different throat geometries, namely, spherical, planar and hyperbolic.
Unlike the spherical geometry, the planar and hyperbolic geometries allow for
different topologies and in addition can be interpreted as higher-dimensional
domain walls or branes connecting two universes. In the construction we use the
cut-and-paste procedure by joining together two identical vacuum spacetime
solutions. Properties such as the null energy condition and geodesics are
studied. A linear stability analysis around the static solutions is carried
out. A general result for stability is obtained from which previous results are
recovered.Comment: 16 pages, 1 figur
Conformal entropy from horizon states: Solodukhin's method for spherical, toroidal, and hyperbolic black holes in D-dimensional anti-de Sitter spacetimes
A calculation of the entropy of static, electrically charged, black holes
with spherical, toroidal, and hyperbolic compact and oriented horizons, in D
spacetime dimensions, is performed. These black holes live in an anti-de Sitter
spacetime, i.e., a spacetime with negative cosmological constant. To find the
entropy, the approach developed by Solodukhin is followed. The method consists
in a redefinition of the variables in the metric, by considering the radial
coordinate as a scalar field. Then one performs a 2+(D-2) dimensional
reduction, where the (D-2) dimensions are in the angular coordinates, obtaining
a 2-dimensional effective scalar field theory. This theory is a conformal
theory in an infinitesimally small vicinity of the horizon. The corresponding
conformal symmetry will then have conserved charges, associated with its
infinitesimal conformal generators, which will generate a classical Poisson
algebra of the Virasoro type. Shifting the charges and replacing Poisson
brackets by commutators, one recovers the usual form of the Virasoro algebra,
obtaining thus the level zero conserved charge eigenvalue L_0, and a nonzero
central charge c. The entropy is then obtained via the Cardy formula.Comment: 21 page
Hamiltonian thermodynamics of d-dimensional (d=4 and d>4) Reissner-Nordstr\"om anti-de Sitter black holes with spherical, planar, and hyperbolic topology
The Hamiltonian thermodynamics formalism is applied to the general
-dimensional Reissner-Nordstr\"om-anti-de Sitter black hole with spherical,
planar, and hyperbolic horizon topology. After writing its action and
performing a Legendre transformation, surface terms are added in order to
guarantee a well defined variational principle with which to obtain sensible
equations of motion, and also to allow later on the thermodynamical analysis.
Then a Kucha\v{r} canonical transformation is done, which changes from the
metric canonical coordinates to the physical parameters coordinates. Again a
well defined variational principle is guaranteed through boundary terms. These
terms influence the fall-off conditions of the variables and at the same time
the form of the new Lagrange multipliers. Reduction to the true degrees of
freedom is performed, which are the conserved mass and charge of the black
hole. Upon quantization a Lorentzian partition function is written for the
grand canonical ensemble, where the temperature and the electric
potential are fixed at infinity. After imposing Euclidean boundary
conditions on the partition function, the respective effective action ,
and thus the thermodynamical partition function, is determined for any
dimension and topology . This is a quite general action. Several
previous results can be then condensed in our single general formula for the
effective action . Phase transitions are studied for the spherical case,
and it is shown that all the other topologies have no phase transitions. A
parallel with the Bose-Einstein condensation can be established. Finally, the
expected values of energy, charge, and entropy are determined for the black
hole solution.Comment: 24 pages, 3 figures, published versio
Conservation status of a recently described endemic land snail, Candidula coudensis, from the Iberian Peninsula
Research ArticleWe assessed the distribution, population size and conservation status of Candidula coudensis,
a recently described endemic land snail from Portugal. From March 2013 to April
2014, surveys were carried out in the region where the species was described. We found an
extent of occurrence larger than originally described, but still quite small (13.5 km2). The
species was found mainly in olive groves, although it occurred in a variety of other habitats
with limestone soils, including grasslands, scrublands and stone walls. Minimum population
estimate ranged from 110,000–311,000 individuals. The main identified potential threats to
the species include wildfires, pesticides and quarrying. Following the application of IUCN
criteria, we advise a conservation status of either “Least Concern” or “Near-threatened”
under criterion D (restricted population)info:eu-repo/semantics/publishedVersio
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector
The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30
Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector
Results of a search for H → τ τ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ → `νν¯ with ` = e, µ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of µ = 1.43 +0.43 −0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model
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