13,096 research outputs found
Thermodynamics of black holes in finite boxes
We analyze the thermodynamical behavior of black holes in closed finite
boxes. First the black hole mass evolution is analyzed in an initially empty
box. Using the conservation of the energy and the Hawking evaporation flux, we
deduce a minimal volume above which one black hole can loss all of its mass to
the box, a result which agrees with the previous analysis made by Page. We then
obtain analogous results using a box initially containing radiation, allowed to
be absorbed by the black hole. The equilibrium times and masses are evaluated
and their behavior discussed to highlight some interesting features arising.
These results are generalized to black holes + thermal radiation. Using
physically simple arguments, we prove that these black holes achieve the same
equilibrium masses (even that the initial masses were different). The entropy
of the system is used to obtain the dependence of the equilibrium mass on the
box volume, number of black holes and the initial radiation. The equilibrium
mass is shown to be proportional to a {\it positive} power law of the effective
volume (contrary to naive expectations), a result explained in terms of the
detailed features of the system. The effect of the reflection of the radiation
on the box walls which comes back into the black hole is explicitly considered.
All these results (some of them counter-intuitive) may be useful to formulate
alternative problems in thermodynamic courses for graduate and advanced
undergraduate students. A handful of them are suggested in the Appendix.Comment: RevTex file, 2 .ps figures. Submitted to AmJPhy
Phantom Accretion by Black Holes and the Generalized Second Law of Thermodynamics
The accretion of a phantom fluid with non-zero chemical potential by black
holes is discussed with basis on the Generalized Second Law of thermodynamics.
For phantom fluids with positive temperature and negative chemical potential we
demonstrate that the accretion process is possible, and that the condition
guaranteeing the positiveness of the phantom fluid entropy coincides with the
one required by Generalized Second Law. In particular, this result provides a
complementary confirmation that cosmological phantom fluids do not need to have
negative temperatures
Pion mass effects on axion emission from neutron stars through NN bremsstrahlung processes
The rates of axion emission by nucleon-nucleon bremsstrahlung are calculated
with the inclusion of the full momentum contribution from a nuclear one pion
exchange (OPE) potential. The contributions of the neutron-neutron (nn),
proton-proton (pp) and neutron-proton (np) processes in both the nondegenerate
and degenerate limits are explicitly given. We find that the finite momentum
corrections to the emissivities are quantitatively significant for the
non-degenerate regime and temperature-dependent, and should affect the existing
axion mass bounds. The trend of these nuclear effects is to diminish the
emissivities
Self-bound Interacting QCD Matter in Compact Stars
The quark gluon plasma (QGP) at zero temperature and high baryon number is a
system that may be present inside compact stars. It is quite possible that this
cold QGP shares some relevant features with the hot QGP observed in heavy ion
collisions, being also a strongly interacting system. In a previous work we
have derived from the QCD Lagrangian an equation of state (EOS) for the cold
QGP, which can be considered an improved version of the MIT bag model EOS.
Compared to the latter, our equation of state reaches higher values of the
pressure at comparable baryon densities. This feature is due to perturbative
corrections and also to non-perturbative effects. Here we apply this EOS to the
study of neutron stars, discussing the absolute stability of quark matter and
computing the mass-radius relation for self-bound (strange) stars. The maximum
masses of the sequences exceed two solar masses, in agreement with the recently
measured values of the mass of the pulsar PSR J1614-2230, and the corresponding
radii around 10-11 km
Pion Decay Constant, and Chiral Log from Overlap Fermions
We report our calculation of the pion decay constant , the axial
renormalization constant , and the quenched chiral logarithms from the
overlap fermions. The calculation is done on a quenched lattice at
fm using tree level tadpole improved gauge action. The smallest pion
mass we reach is about 280 MeV. The lattice size is about 4 times the Compton
wavelength of the lowest mass pion.Comment: Lattice2001(Hadronic Matrix Elements), 3pages, 5figure
Measurements of the structure and circulation of the stratosphere and mesosphere, 1971-2
Complete data from a total of 43 meteorological rocket soundings of the stratosphere and mesosphere conducted from Barrow, Alaska; Churchill, Canada; Wallops Island Va.; and Kourou, French Guiana are presented. These data consist of temperature, pressure, density, and wind profiles from 35 acoustic grenade soundings that cover the 30 to 90 km altitude range, and temperature, pressure, and density profiles from 8 pitot probe soundings that cover the 25 to 120 km altitude range. Errors for each of the 35 acoustic grenade soundings are also included
A preliminary look at AVE-SESAME 1 conducted on 10-11 April 1979
Preliminary information on the general weather conditions during the AVE-SESAME 1 period is presented together with a summary of severe weather reports
Sequence analysis of Hungarian LHON patients not carrying the common primary mutations
We describe sequence analysis of the mitochondrial DNA of five Hungarian patients diagnosed with probable LHON, who do not carry any of the three primary point mutations. We report three novel mutations, one of which might have a pathogenic rol
Chiral Properties of Pseudoscalar Mesons on a Quenched Lattice with Overlap Fermions
The chiral properties of the pseudoscalar mesons are studied numerically on a
quenched lattice with the overlap fermion. We elucidate the role of the
zero modes in the meson propagators, particularly that of the pseudoscalar
meson. The non-perturbative renormalization constant is determined from
the axial Ward identity and is found to be almost independent of the quark mass
for the range of quark masses we study; this implies that the error is
small. The pion decay constant, , is calculated from which we
determine the lattice spacing to be 0.148 fm. We look for quenched chiral log
in the pseudoscalar decay constants and the pseudoscalar masses and we find
clear evidence for its presence. The chiral log parameter is
determined to be in the range 0.15 -- 0.4 which is consistent with that
predicted from quenched chiral perturbation theory.Comment: Version accepted for publication by PRD. A few minor typographical
errors have been corrected. 24 pages, 11 figure
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