15,469 research outputs found
Proof of the Generalized Second Law for Quasistationary Semiclassical Black Holes
A simple direct explicit proof of the generalized second law of black hole
thermodynamics is given for a quasistationary semiclassical black hole.Comment: 12 pages, LaTeX, report Alberta-Thy-10-93 (revision of paper in
response to Phys. Rev. Lett. referees' comments, which suffered a series of
long delays
Evaporation of a Kerr black hole by emission of scalar and higher spin particles
We study the evolution of an evaporating rotating black hole, described by
the Kerr metric, which is emitting either solely massless scalar particles or a
mixture of massless scalar and nonzero spin particles. Allowing the hole to
radiate scalar particles increases the mass loss rate and decreases the angular
momentum loss rate relative to a black hole which is radiating nonzero spin
particles. The presence of scalar radiation can cause the evaporating hole to
asymptotically approach a state which is described by a nonzero value of . This is contrary to the conventional view of black hole
evaporation, wherein all black holes spin down more rapidly than they lose
mass. A hole emitting solely scalar radiation will approach a final asymptotic
state described by . A black hole that is emitting scalar
particles and a canonical set of nonzero spin particles (3 species of
neutrinos, a single photon species, and a single graviton species) will
asymptotically approach a nonzero value of only if there are at least 32
massless scalar fields. We also calculate the lifetime of a primordial black
hole that formed with a value of the rotation parameter , the minimum
initial mass of a primordial black hole that is seen today with a rotation
parameter , and the entropy of a black hole that is emitting scalar or
higher spin particles.Comment: 22 pages, 13 figures, RevTeX format; added clearer descriptions for
variables, added journal referenc
Information Flow in Entangled Quantum Systems
All information in quantum systems is, notwithstanding Bell's theorem,
localised. Measuring or otherwise interacting with a quantum system S has no
effect on distant systems from which S is dynamically isolated, even if they
are entangled with S. Using the Heisenberg picture to analyse quantum
information processing makes this locality explicit, and reveals that under
some circumstances (in particular, in Einstein-Podolski-Rosen experiments and
in quantum teleportation) quantum information is transmitted through
'classical' (i.e. decoherent) information channels.Comment: PostScript version now available:
http://www.qubit.org/people/patrickh/Papers/InformationFlow.p
Opaque or transparent? A link between neutrino optical depths and the characteristic duration of short gamma-ray bursts
Cosmological gamma ray bursts (GRBs) are thought to occur from violent
hypercritical accretion onto stellar mass black holes, either following core
collapse in massive stars or compact binary mergers. This dichotomy may be
reflected in the two classes of bursts having different durations. Dynamical
calculations of the evolution of these systems are essential if one is to
establish characteristic, relevant timescales. We show here for the first time
the result of dynamical simulations, lasting approximately one second, of
post--merger accretion disks around black holes, using a realistic equation of
state and considering neutrino emission processes. We find that the inclusion
of neutrino optical depth effects produces important qualitative temporal and
spatial transitions in the evolution and structure of the disk, which may
directly reflect upon the duration and variability of short GRBs.Comment: Accepted for publication in ApJ Letter
Speculative Antitrust Damages
The most important antitrust penalties are treble damage awards based on the individual harms that violations cause. For these penalties to function as an economically rational deterrent, there must be a practical mechanism for proving individual harm, and for distinguishing such harm from speculation. In this article, the authors present an account of that mechanism. First, they argue that the law\u27s measure of antitrust damages is based on a standard of net individual harm that is qualified in certain cases by a principle of net social harm. Net harm is measured by the difference between the plaintiff\u27s actual condition (given that the violation has occurred) and its but-for condition (assuming that the violation did not occur). Second, the authors show that law\u27s mechanism for proof of damages requires a projection of the but-for condition from a reasonably comparable base experience. The projection must use both the evidentiary foundation and a theoretical model to isolate the defendant\u27s illegal conduct as the difference between the actual and but-for conditions. Proof is speculative if the projection fails to account for actual or theoretical factors other than the violation that may have caused the asserted harm
Controlling the Competitor Plaintiff in Antitrust Litigation
In Misuse of the Antitrust Laws: The Competitor Plaintiff, Edward Snyder and Thomas Kauper survey a sample of private antitrust cases from the period 1973-1983 and review critically the recent economic literature on raising rivals\u27 costs as an exclusionary practice.
Much in Snyder and Kauper\u27s study is worthy of comment. They have given us a useful picture of private antitrust litigation during the period covered by the sample, one that may be more accurate than a reading of reported cases from that period would suggest. Moreover, their generally critical treatment of the literature on raising rivals\u27 costs is clear and focused on the need to draw administrable policy conclusions. Most noteworthy, however, is their critique of the antitrust injury doctrine as a means of controlling unmeritorious or perverse suits by competitors. Their argument on this score - based upon their analysis of the 1973-1983 data and some more recent antitrust injury decisions - is deeply flawed and does not support their conclusion that competitor suits should be abolished. We argue here that the antitrust injury requirement and related procedural devices have evolved to address the problem of perverse competitor suits. Moreover, the solution that Snyder and Kauper offer for the problem will not likely improve upon the traditional methods of the legal system
Quantum Mechanics, Common Sense and the Black Hole Information Paradox
The purpose of this paper is to analyse, in the light of information theory
and with the arsenal of (elementary) quantum mechanics (EPR correlations,
copying machines, teleportation, mixing produced in sub-systems owing to a
trace operation, etc.) the scenarios available on the market to resolve the
so-called black-hole information paradox. We shall conclude that the only
plausible ones are those where either the unitary evolution of quantum
mechanics is given up, in which information leaks continuously in the course of
black-hole evaporation through non-local processes, or those in which the world
is polluted by an infinite number of meta-stable remnants.Comment: 15 pages, Latex, CERN-TH.6889/9
Spinning Down a Black Hole With Scalar Fields
We study the evolution of a Kerr black hole emitting scalar radiation via the
Hawking process. We show that the rate at which mass and angular momentum are
lost by the black hole leads to a final evolutionary state with nonzero angular
momentum, namely .Comment: 4 pages (including 3 postscript figures), Revtex, uses epsf.tex,
twocolumn.sty and header.sty (included). Submitted to Physical Review Letter
THERMAL RADIATION FROM MAGNETIZED NEUTRON STARS: A look at the Surface of a Neutron Star.
Surface thermal emission has been detected by ROSAT from four nearby young
neutron stars. Assuming black body emission, the significant pulsations of the
observed light curves can be interpreted as due to large surface temperature
differences produced by the effect of the crustal magnetic field on the flow of
heat from the hot interior toward the cooler surface. However, the energy
dependence of the modulation observed in Geminga is incompatible with blackbody
emission: this effect will give us a strong constraint on models of the neutron
star surface.Comment: 10 pages. tar-compressed and uuencoded postcript file. talk given at
the `Jubilee Gamow Seminar', St. Petersburg, Sept. 1994
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