1,031 research outputs found
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
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
Cosmic Strings Stabilized by Fermion Fluctuations
We provide a thorough exposition of recent results on the quantum
stabilization of cosmic strings. Stabilization occurs through the coupling to a
heavy fermion doublet in a reduced version of the standard model. The study
combines the vacuum polarization energy of fermion zero-point fluctuations and
the binding energy of occupied energy levels, which are of the same order in a
semi-classical expansion. Populating these bound states assigns a charge to the
string. Strings carrying fermion charge become stable if the Higgs and gauge
fields are coupled to a fermion that is less than twice as heavy as the top
quark. The vacuum remains stable in the model, because neutral strings are not
energetically favored. These findings suggest that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: Based on talk by HW at QFEXT 11 (Benasque, Spain), 15p, uses
ws-ijmpcs.cls (incl
A Vertex Correction in the Gap Equation for the High Temperature Superconductors
We show that the Migdal theorem is obviously violated in the high Tc cuprates
and the vertex correction should be included, in particular, in the gap
equation, in order to be consistent with the anomalously strong inelastic
scattering in the ``hot spots'', which is observed from the various normal
state experiments. The vertex correction is obtained by utilizing the
generalized Ward identity, which is shown to hold in the important scattering
channel for the pairing interaction in the high Tc cuprates. As a result, we
find a strong enhancement of Tc from the vertex correction despite of the
strong pair breaking effect due to the inelastic scattering.Comment: 5 pages, 2 figure
Acute coronary syndrome in diclofenac sodium-induced type I hypersensitivity reaction : Kounis syndrome
Drug-induced type I hypersensitivity reactions are frequent. Sometimes, acute coronary syndrome (ACS) can be registered in such patients, which may have a serious impact on the course and management of the allergic reaction. Because of potentially atypical ACS clinical presentations, the ECG is an obligatory diagnostic tool in any allergic reaction. Coronary artery spasm is the pathophysiological basis of ACS, triggered by the action of potent vasoactive mediators (histamine, neutral proteases, arachidonic acid products) released from the cells involved in type I hypersensitivity. Allergic angina and allergic myocardial infarction are referred to as Kounis Syndrome. We describe herein a case of ACS in a patient with registered systemic immediate hypersensitivity reaction which developed following the muscular administration of diclofenac sodium.peer-reviewe
Fermionic Zero Modes on Domain Walls
We study fermionic zero modes in the domain wall background. The fermions
have Dirac and left- and right-handed Majorana mass terms. The source of the
Dirac mass term is the coupling to a scalar field . The source of the
Majorana mass terms could also be the coupling to a scalar field or a
vacuum expectation value of some other field acquired in a phase transition
well above the phase transition of the field . We derive the fermionic
equations of motion and find the necessary and sufficient conditions for a zero
mode to exist. We also find the solutions numerically. In the absence of the
Majorana mass terms, the equations are solvable analytically. In the case of
massless fermions a zero energy solution exists and we show that although this
mode is not discretely normalizable it is Dirac delta function normalizable and
should be viewed as part of a continuum spectrum rather than as an isolated
zero mode.Comment: 6 pages, 3 figures, matches version published in PR
Vanishing Dimensions and Planar Events at the LHC
We propose that the effective dimensionality of the space we live in depends
on the length scale we are probing. As the length scale increases, new
dimensions open up. At short scales the space is lower dimensional; at the
intermediate scales the space is three-dimensional; and at large scales, the
space is effectively higher dimensional. This setup allows for some fundamental
problems in cosmology, gravity, and particle physics to be attacked from a new
perspective. The proposed framework, among the other things, offers a new
approach to the cosmological constant problem and results in striking collider
phenomenology and may explain elongated jets observed in cosmic-ray data.Comment: v1: 5 pages revtex, 1 eps figure; v2: includes extensive discussion
on violation of Lorentz invariance, featured in a Nature editorial [Nature
466 (2010) 426] http://www.nature.com/news/2010/100720/full/466426a.html; v3:
discussion expanded, matching journal versio
Using quasars as standard clocks for measuring cosmological redshift
We report hitherto unnoticed patterns in quasar light curves. We characterize
segments of quasars' light curves with the slopes of the straight lines fit
through them. These slopes appear to be directly related to the quasars'
redshifts. Alternatively, using only global shifts in time and flux, we are
able to find significant overlaps between the light curves of different pairs
of quasars by fitting the ratio of their redshifts. We are then able to
reliably determine the redshift of one quasar from another. This implies that
one can use quasars as standard clocks, as we explicitly demonstrate by
constructing two independent methods of finding the redshift of a quasar from
its light curve.Comment: References added, Published in Phys. Rev. Let
Holes in the walls: primordial black holes as a solution to the cosmological domain wall problem
We propose a scenario in which the cosmological domain wall and monopole
problems are solved without any fine tuning of the initial conditions or
parameters in the Lagrangian of an underlying filed theory. In this scenario
domain walls sweep out (unwind) the monopoles from the early universe, then the
fast primordial black holes perforate the domain walls, change their topology
and destroy them. We find further that the (old vacuum) energy density released
from the domain walls could alleviate but not solve the cosmological flatness
problem.Comment: References added; Published in Phys. Rev.
- …