7,411 research outputs found
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
The effect of peculiar velocities on the epoch of reionization (EoR) 21-cm signal
We have used semi-numerical simulations of reionization to study the
behaviour of the power spectrum of the EoR 21-cm signal in redshift space. We
have considered two models of reionization, one which has homogeneous
recombination (HR) and the other incorporating inhomogeneous recombination
(IR). We have estimated the observable quantities --- quadrupole and monopole
moments of HI power spectrum at redshift space from our simulated data. We find
that the magnitude and nature of the ratio between the quadrupole and monopole
moments of the power spectrum () can be a possible probe for the
epoch of reionization. We observe that this ratio becomes negative at large
scales for irrespective of the reionization model, which is a
direct signature of an inside-out reionization at large scales. It is possible
to qualitatively interpret the results of the simulations in terms of the
fluctuations in the matter distribution and the fluctuations in the neutral
fraction which have power spectra and cross-correlation ,
and respectively. We find that at large scales
the fluctuations in matter density and neutral fraction is exactly
anti-correlated through all stages of reionization. This provides a simple
picture where we are able to qualitatively interpret the behaviour of the
redshift space power spectra at large scales with varying entirely in
terms of a just two quantities, namely and the ratio . The nature of becomes different for HR and IR
scenarios at intermediate and small scales. We further find that it is possible
to distinguish between an inside-out and an outside-in reionization scenario
from the nature of the ratio at intermediate length scales.Comment: 11 pages, 6 figures. Accepted for publication in MNRAS. Replaced to
match the accepted version. Added one appendix to quantify the possible
uncertainties in the estimation of the multipole moments of redshift space
power spectru
Inhomogeneous Ferromagnetism and Unconventional Charge Dynamics in Disordered Double Exchange Magnets
We solve the double exchange model in the presence of arbitrary
substitutional disorder by using a self consistently generated effective
Hamiltonian for the spin degrees of freedom. The magnetic properties are
studied through classical Monte Carlo while the effective exchange, ,
are calculated by solving the disordered fermion problem, and renormalised
self-consistently with increasing temperature. We present exact results on the
conductivity, magnetoresistance, optical response and `real space' structure of
the inhomogeneous ferromagnetic state, and compare our results with charge
dynamics in disordered La_{1-x}Sr_xMnO_3. The large sizes, ,
accessible within our method allows a complete, controlled calculation on the
disordered strongly interacting problem.Comment: 4 pages, 2 column revtex, 5 embedded figure
Two Cases of Primary Ectopic Ovarian Pregnancy
Primary ovarian pregnancy is one of the rarest varieties of ectopic pregnancies. Patients frequently present with abdominal pain and menstrual irregularities. Intrauterine devices have evolved as probable risk factors. Preoperative diagnosis is challenging but transvaginal sonography has often been helpful. A diagnostic delay may lead to rupture, secondary implantation or operative difficulties. Therefore, awareness of this rare condition is important in reducing the associated risks. Here, we report two cases of primary ovarian pregnancies presenting with acute abdominal pain. Transabdominal ultrasonography failed to hint at ovarian pregnancy in one, while transvaginal sonography aided in the correct diagnosis of the other. Both cases were confirmed by histopathological examinations and were successfully managed by surgery
Detecting mixedness of qutrit systems using the uncertainty relation
We show that the uncertainty relation as expressed in the
Robertson-Schrodinger generalized form can be used to detect the mixedness of
three-level quantum systems in terms of measureable expectation values of
suitably chosen observables when prior knowledge about the basis of the given
state is known. In particular, we demonstrate the existence of observables for
which the generalized uncertainty relation is satisfied as an equality for pure
states and a strict inequality for mixed states corresponding to single as well
as bipartite sytems of qutrits. Examples of such observables are found for
which the magnitude of uncertainty is proportional to the linear entropy of the
system, thereby providing a method for measuring mixedness.Comment: 7 pages, 2 figure, Eqs.(10) and (14) are corrected, and results and
conclusions are unchange
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