652 research outputs found
Information-preserving black holes still do not preserve baryon number and other effective global quantum numbers
It has been claimed recently that the black hole information-loss paradox has
been resolved: the evolution of quantum states in the presence of a black hole
is unitary and information preserving. We point out that, contrary to some
claims in literature, information-preserving black holes still violate baryon
number and any other quantum number which follows from an effective (and thus
approximate) or anomalous symmetry.Comment: Honorable Mention on Gravity Essay Competition 2005; Published in the
special Essay issue of Int.J.Mod.Phy
Energy flux through the horizon in the black hole-domain wall systems
We study various configurations in which a domain wall (or cosmic string),
described by the Nambu-Goto action, is embedded in a background space-time of a
black hole in and higher dimensional models. We calculate energy fluxes
through the black hole horizon. In the simplest case, when a static domain wall
enters the horizon of a static black hole perperdicularly, the energy flux is
zero. In more complicated situations, where parameters which describe the
domain wall surface are time and position dependent, the flux is non-vanishing
is principle. These results are of importance in various conventional
cosmological models which accommodate the existence of domain walls and strings
and also in brane world scenarios.Comment: references added, accepted for publication in JHE
Why black hole production in scattering of cosmic ray neutrinos is generically suppressed
It has been argued that neutrinos originating from ultra-high energy cosmic
rays produce black holes deep in the atmosphere in models with TeV-scale
quantum gravity. Such black holes would initiate quasi-horizontal showers of
particles far above the standard model rate, so that the Auger Observatory
would observe hundreds of black hole events. This would provide the first
opportunity for experimental study of microscopic black holes. However, any
phenomenologically viable model with a low scale of quantum gravity must
explain how to preserve protons from rapid decay mediated by virtual black
holes. We argue that unless this is accomplished by the gauging of baryon or
lepton number, the suppression of proton decay will also suppress quantum
gravity mediated lepton-nucleon scattering, and hence black hole production by
scattering of ultra-high energy cosmic ray neutrinos in the atmosphere. We
demonstrate this explicitly for the split fermion solution to the problem of
fast proton decay.Comment: typo corrected, journal reference adde
Production of black holes and their angular momentum distribution in models with split fermions
In models with TeV-scale gravity it is expected that mini black holes will be
produced in near-future accelerators. On the other hand, TeV-scale gravity is
plagued with many problems like fast proton decay, unacceptably large
neutron-antineutron oscillations, flavor changing neutral currents, large
mixing between leptons, etc. Most of these problems can be solved if different
fermions are localized at different points in the extra dimensions. We study
the cross-section for the production of black holes and their angular momentum
distribution in these models with "split" fermions. We find that, for a fixed
value of the fundamental mass scale, the total production cross section is
reduced compared with models where all the fermions are localized at the same
point in the extra dimensions. Fermion splitting also implies that the bulk
component of the black hole angular momentum must be taken into account in
studies of the black hole decay via Hawking radiation.Comment: accepted for publication in Phys. Rev.
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