194 research outputs found
Thermodynamics of black holes with an infinite effective area of a horizon
In some kinds of classical dilaton theory there exist black holes with (i)
infinite horizon area or infinite (the coefficient at curvature in
Lagrangian) and (ii) zero Hawking temperature . For a generic static
black hole, without an assumption about spherical symmetry, we show that
infinite is compatible with a regularity of geometry in the case
only. We also point out that infinite is incompatible with the
regularity of a horizon of a generic static black hole, both for finite or
infinite . Direct application of the standard Euclidean approach in the case
of an infinite ''effective'' area of the horizon leads to
inconsistencies in the variational principle and gives for a black hole entropy
an indefinite expression, formally proportional to . We show
that treating a horizon as an additional boundary (that is, adding to the
action some terms calculated on the horizon) may restore self-consistency of
the variational procedure, if near the horizon grows not too rapidly. We
apply this approach to Brans-Dicke black holes and obtain the same answer S=0
as for ''usual'' (for example, Reissner-Nordstr\"{o}m) extreme classical black
holes. We also consider the exact solution for a conformal coupling, when
is finite but diverges and find that in the latter case both the standard
and modified approach give rise to an infinite action. Thus, this solution
represents a rare exception of a black hole without nontrivial thermal
properties.Comment: 24 pages. Accepted for publication in Class. Quant. Gra
Charged C-metric with conformally coupled scalar field
We present a generalisation of the charged C-metric conformally coupled with
a scalar field in the presence of a cosmological constant. The solution is
asymptotically flat or a constant curvature spacetime. The spacetime metric has
the geometry of a usual charged C-metric with cosmological constant, where the
mass and charge are equal. When the cosmological constant is absent it is found
that the scalar field only blows up at the angular pole of the event horizon.
The presence of the cosmological constant can generically render the scalar
field regular where the metric is regular, pushing the singularity beyond the
event horizon. For certain cases of enhanced acceleration with a negative
cosmological constant, the conical singularity disappears all together and the
scalar field is everywhere regular. The black hole is then rather a black
string with its event horizon extending all the way to asymptotic infinity and
providing itself the necessary acceleration.Comment: regular article, no figures, typos corrected, to appear in Classical
and Quantum Gravit
"No-Scalar-Hair" Theorems for Nonminimally Coupled Fields with Quartic Self-Interaction
Self-gravitating scalar fields with nonminimal coupling to gravity and having
a quartic self-interaction are considered in the domain of outer communications
of a static black hole. It is shown that there is no value of the nonminimal
coupling parameter for which nontrivial static black hole solutions
exist. This result establishes the correctness of Bekenstein ``no-scalar-hair''
conjecture for quartic self-interactions.Comment: 8 pages, RevTeX
A simple theorem to generate exact black hole solutions
Under certain conditions imposed on the energy-momentum tensor, a theorem
that characterizes a two-parameter family of static and spherically symmetric
solutions to Einstein's field equations (black holes), is proved. A discussion
on the asymptotics, regularity, and the energy conditions is provided. Examples
that include the best known exact solutions within these symmetries are
considered. A trivial extension of the theorem includes the cosmological
constant {\it ab-initio}, providing then a three-parameter family of solutions.Comment: 14 pages; RevTex; no figures; typos corrected; references adde
Large-Angle Electron Diffraction Structure in Laser-Induced Rescattering from Rare Gases
We have measured full momentum images of electrons rescattered from Xe, Kr, and Ar following the liberation of the electrons from these atoms by short, intense laser pulses. At high momenta the spectra show angular structure (diffraction) which is very target dependent and in good agreement with calculated differential cross sections for the scattering of free electrons from the corresponding ionic cores
Conformally dressed black hole in 2+1 dimensions
A three dimensional black hole solution of Einstein equations with negative
cosmological constant coupled to a conformal scalar field is given. The
solution is static, circularly symmetric, asymptotically anti-de Sitter and
nonperturbative in the conformal field. The curvature tensor is singular at the
origin while the scalar field is regular everywhere. The condition that the
Euclidean geometry be regular at the horizon fixes the temperature to be
. Using the Hamiltonian formulation including
boundary terms of the Euclidean action, the entropy is found to be
of the standard value (), and in agreement with
the first law of thermodynamics.Comment: LaTeX ,RevTeX, 13pages, no figure
Computational psychiatry approach to stigma subtyping in patients with mental disorders: explicit and implicit internalized stigma
BACKGROUND: Psychiatric stigma has potentially controversial effects on patients health-related behaviors. It appears that both stigmatization and motivation in psychiatric patients are heterogeneous and multi-dimensional, and that the relationship between stigma and treatment motivation may be more complex than previously believed.
AIM: To determine psychiatric stigma subtypes as they relate to treatment motivation among inpatients with various mental disorders.
METHODS: Sixy-three psychiatric inpatients were examined by the Treatment Motivation Assessment Questionnaire (TMAQ) and the Russian version of Internalized Stigma of Mental Illness scale (ISMI). K-Means cluster and dispersion analysis were conducted.
RESULTS: Cluster 3 (25 subjects) was the least stigmatized. Cluster 1 (18 subjects) showed an explicit stigma. Cluster 2 (20 subjects) showed an implicit stigma that took the form of the lowest treatment motivation compared to other clusters. Implicitly stigmatized patients, in contrast to explicitly stigmatized individuals, showed a decline in 3 out of 4 TMAQ factors (Mean dif.=1.051.67).
CONCLUSION: Cooperation with doctors, together with reliance on ones own knowledge and skills to cope with the disorder, might be the way to overcome an internalized stigma for patients with mental disorders
Black hole polarization and new entropy bounds
Zaslavskii has suggested how to tighten Bekenstein's bound on entropy when
the object is electrically charged. Recently Hod has provided a second tighter
version of the bound applicable when the object is rotating. Here we derive
Zaslavskii's optimized bound by considering the accretion of an ordinary
charged object by a black hole. The force originating from the polarization of
the black hole by a nearby charge is central to the derivation of the bound
from the generalized second law. We also conjecture an entropy bound for
charged rotating objects, a synthesis of Zaslavskii's and Hod's. On the basis
of the no hair principle for black holes, we show that this last bound cannot
be tightened further in a generic way by knowledge of ``global'' conserved
charges, e.g., baryon number, which may be borne by the object.Comment: 21 pages, RevTex, Regularization of potential made clearer. Error in
energy of the particle corrected with no consequence for final conclusions.
New references adde
Field-free orientation of CO molecules by femtosecond two-color laser fields
We report the first experimental observation of non-adiabatic field-free
orientation of a heteronuclear diatomic molecule (CO) induced by an intense
two-color (800 and 400 nm) femtosecond laser field. We monitor orientation by
measuring fragment ion angular distributions after Coulomb explosion with an
800 nm pulse. The orientation of the molecules is controlled by the relative
phase of the two-color field. The results are compared to quantum mechanical
rigid rotor calculations. The demonstrated method can be applied to study
molecular frame dynamics under field-free conditions in conjunction with a
variety of spectroscopy methods, such as high-harmonic generation, electron
diffraction and molecular frame photoemission
Genes of the Glutamatergic System and Tardive Dyskinesia in Patients with Schizophrenia
Background: Tardive dyskinesia (TD) is an extrapyramidal side effect of the long-term use of antipsychotics. In the present study, the role of glutamatergic system genes in the pathogenesis of total TD, as well as two phenotypic forms, orofacial TD and limb-truncal TD, was studied. Methods: A set of 46 SNPs of the glutamatergic system genes (GRIN2A, GRIN2B, GRIK4, GRM3, GRM7, GRM8, SLC1A2, SLC1A3, SLC17A7) was studied in a population of 704 Caucasian patients with schizophrenia. Genotyping was performed using the MassARRAY Analyzer 4 (Agena Bioscience™). Logistic regression analysis was performed to test for the association of TD with the SNPs while adjusting for confounders. Results: No statistically significant associations between the SNPs and TD were found after adjusting for multiple testing. Since three SNPs of the SLC1A2 gene demonstrated nominally significant associations, we carried out a haplotype analysis for these SNPs. This analysis identified a risk haplotype for TD comprising CAT alleles of the SLC1A2 gene SNPs rs1042113, rs10768121, and rs12361171. Nominally significant associations were identified for SLC1A3 rs2229894 and orofacial TD, as well as for GRIN2A rs7192557 and limb-truncal TD. Conclusions: Genes encoding for mGlu3, EAAT2, and EAAT1 may be involved in the development of TD in schizophrenia patients
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