675 research outputs found
Universal criterion for black hole stability
It is shown that a non-rotating macroscopic black hole with very large
horizon area can remain in stable thermal equilibrium with Hawking radiation
provided {\it its mass, as a function of horizon area, exceeds its
microcanonical entropy, i.e., its entropy when isolated, without thermal
radiation or accretion, and having a constant horizon area} (in appropriate
units). The analysis does not use properties of specific classical spacetimes,
but depends only on the plausible assumption that the mass is a function of the
horizon area for large areas.Comment: 6 pages Latex, no figures; an equation adde
Universal canonical black hole entropy
Non-rotating black holes in three and four dimensions are shown to possess a
canonical entropy obeying the Bekenstein-Hawking area law together with a
leading correction (for large horizon areas) given by the logarithm of the area
with a {\it universal} finite negative coefficient, provided one assumes that
the quantum black hole mass spectrum has a power law relation with the quantum
area spectrum found in Non-perturbative Canonical Quantum General Relativity.
The thermal instability associated with asymptotically flat black holes appears
in the appropriate domain for the index characterising this power law relation,
where the canonical entropy (free energy) is seen to turn complex.Comment: Revtex, 5 pages, no figures. Typos corrected and a footnote and some
references adde
Mass and charge fluctuations and black hole entropy
The effects of thermal fluctuations of the mass (horizon area) and electric
charge, on the entropy of non-rotating charged {\it macroscopic} black holes,
are analyzed using a grand canonical ensemble. Restricting to Gaussian
fluctuations around equilibrium, and assuming a power law type of relation
between the black hole mass, charge and horizon area, characterized by two real
positive indices, the grand canonical entropy is shown to acquire a logarithmic
correction with a positive coefficient proportional to the sum of the indices.
However, the root mean squared fluctuations of mass and charge relative to the
mean values of these quantities turn out to be independent of the details of
the assumed mass-area relation. We also comment on possible cancellation
between log (area) corrections arising due to {\it fixed area} quantum
spacetime fluctuations and that due to thermal fluctuations of the area and
other quantities.Comment: 8 pages revtex, no figure
Cosmic optical activity from an inhomogeneous Kalb-Ramond field
The effects of introducing a harmonic spatial inhomogeneity into the
Kalb-Ramond field, interacting with the Maxwell field according to a
`string-inspired' proposal made in earlier work are investigated. We examine in
particular the effects on the polarization of synchrotron radiation from
cosmologically distant (i.e. of redshift greater than 2) galaxies, as well as
the relation between the electric and magnetic components of the radiation
field. The rotation of the polarization plane of linearly polarized radiation
is seen to acquire an additional contribution proportional to the square of the
frequency of the dual Kalb-Ramond axion wave, assuming that it is far smaller
compared to the frequency of the radiation field.Comment: 9 pages, Revtex, no figure
Reflection coefficient for superresonant scattering
We investigate superresonant scattering of acoustic disturbances from a
rotating acoustic black hole in the low frequency range. We derive an
expression for the reflection coefficient, exhibiting its frequency dependence
in this regime.Comment: 7 page
Multiple stab incision technique to prevent postoperative acute compartment syndrome of leg in proximal and segmental fracture tibia and fibula: a prospective study
The objective is to study the effectiveness of Multiple stab incision technique in preventing acute compartment syndrome (ACS) in proximal and segmental fractures of both bones (Tibia and fibula) in leg. This study is prospective done at K. S. Hospital Koppal, Karnataka spanning for a period of one year (April 2020 to April 2021). A total of 20 patients of both genders aged 20-60 years were included in the study. Multiple stab incision technique was performed in patients after fixation of Tibia by either closed nailing or MIPPO plating. This procedure was done under spinal anesthesia. Multiple stab incision technique significantly decreased the chances of post-op ACS in proximal and segmental fractures of both bones (tibia and fibula) in leg. Multiple stab incision technique is help full in preventing developing compartment syndrome.Â
Design and Development of Sports Intimate Apparel - A Review
It is necessary to evaluate and analyze the brassiere design problems to alleviate theproblems in terms of fit, support, elastics and fastening. With an aim to achieve a perfectbrassiere, designers have a strong drive to develop a super quality brassiere with highperformance and proper usage of components and materials. The encapsulation brassiere wasmore effective than compression brassiere in controlling breast displacement. The mainproblems were shoulder straps digging into the shoulder and shoulder straps slipping off theshoulder. There are several design flaws associated with these sports brassiere which lead todiscomfort, pain and swelling of the breasts. Tightness around the chest may also cause beastsoreness. The straps are often very thin and cut into the shoulders of women. The mosteffective brassiere had a unique inverted-u shape bounded seam over the upper and sideboundaries of the cups with a wide cross-back design. Wicking materials are used in this typeof brassieres to give comfort and breast supporting pads having pad components to giveadequate support. The inner layer consists of silicone material which can increase theadherence capacity due to its high coefficient of friction. This review paper contains detailsabout the design and development of sports brassiere
Current-driven orbital order-disorder transition in LaMnO3
We report significant influence of electric current on the orbital
order-disorder transition in LaMnO3. The transition temperature T_OO, thermal
hysteresis in the resistivity (rho) versus temperature (T) plot around T_OO,
and latent heat L associated with the transition decrease with the increase in
current density. Eventually, at a critical current density, L reaches zero. The
transition zone, on the other hand, broadens with the increase in current
density. The states at ordered, disordered, and transition zone are all found
to be stable within the time window from ~10^-3 to ~10^4 seconds.Comment: 7 pages including 5 figures; resolution of Fig.1 is better here than
the published versio
Generalized Hawking-Page Phase Transition
The issue of radiant spherical black holes being in stable thermal
equilibrium with their radiation bath is reconsidered. Using a simple
equilibrium statistical mechanical analysis incorporating Gaussian thermal
fluctuations in a canonical ensemble of isolated horizons, the heat capacity is
shown to diverge at a critical value of the classical mass of the isolated
horizon, given (in Planckian units) by the {\it microcanonical} entropy
calculated using Loop Quantum Gravity. The analysis reproduces the Hawking-Page
phase transition discerned for anti-de Sitter black holes and generalizes it in
the sense that nowhere is any classical metric made use of.Comment: 9 Pages, Latex with 2 eps figure
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