28,874 research outputs found
Supersymmetry Breaking and Moduli Stabilization with Anomalous U(1) Gauge Symmetry
We examine the effects of anomalous U(1)_A gauge symmetry on soft
supersymmetry breaking terms while incorporating the stabilization of the
modulus-axion multiplet responsible for the Green-Schwarz (GS) anomaly
cancellation mechanism. In case of the KKLT stabilization of the GS modulus,
soft terms are determined by the GS modulus mediation, the anomaly mediation
and the U(1)_A mediation which are generically comparable to each other,
thereby yielding the mirage mediation pattern of superparticle masses at low
energy scale. Independently of the mechanism of moduli stabilization and
supersymmetry breaking, the U(1)_A D-term potential can not be an uplifting
potential for de Sitter vacuum when the gravitino mass is smaller than the
Planck scale by many orders of magnitude. We also discuss some features of the
supersymmetry breaking by red-shifted anti-brane which is a key element of the
KKLT moduli stabilization.Comment: 32 pages; references are adde
Two-gap superconductivity in MgB: clean or dirty?
A large number of experimental facts and theoretical arguments favor a
two-gap model for superconductivity in MgB. However, this model predicts
strong suppression of the critical temperature by interband impurity scattering
and, presumably, a strong correlation between the critical temperature and the
residual resistivity. No such correlation has been observed. We argue that this
fact can be understood if the band disparity of the electronic structure is
taken into account, not only in the superconducting state, but also in normal
transport
Loop structure of the lowest Bloch band for a Bose-Einstein condensate
We investigate analytically and numerically Bloch waves for a Bose--Einstein
condensate in a sinusoidal external potential. At low densities the dependence
of the energy on the quasimomentum is similar to that for a single particle,
but at densities greater than a critical one the lowest band becomes
triple-valued near the boundary of the first Brillouin zone and develops the
structure characteristic of the swallow-tail catastrophe. We comment on the
experimental consequences of this behavior.Comment: 4 pages, 7 figure
Comparable analysis of the distribution functions of runup heights of the 1896, 1933 and 2011 Japanese Tsunamis in the Sanriku area
Data from a field survey of the 2011 Tohoku-oki tsunami in the Sanriku area of Japan is used to plot the distribution function of runup heights along the coast. It is shown that the distribution function can be approximated by a theoretical log-normal curve. The characteristics of the distribution functions of the 2011 event are compared with data from two previous catastrophic tsunamis (1896 and 1933) that occurred in almost the same region. The number of observations during the last tsunami is very large, which provides an opportunity to revise the conception of the distribution of tsunami wave heights and the relationship between statistical characteristics and the number of observed runup heights suggested by Kajiura (1983) based on a small amount of data on previous tsunamis. The distribution function of the 2011 event demonstrates the sensitivity to the number of measurements (many of them cannot be considered independent measurements) and can be used to determine the characteristic scale of the coast, which corresponds to the statistical independence of observed wave heights
Simulation of the trans-oceanic tsunami propagation due to the 1883 Krakatau volcanic eruption
International audienceThe 1883 Krakatau volcanic eruption has generated a destructive tsunami higher than 40 m on the Indonesian coast where more than 36 000 lives were lost. Sea level oscillations related with this event have been reported on significant distances from the source in the Indian, Atlantic and Pacific Oceans. Evidence of many manifestations of the Krakatau tsunami was a subject of the intense discussion, and it was suggested that some of them are not related with the direct propagation of the tsunami waves from the Krakatau volcanic eruption. Present paper analyzes the hydrodynamic part of the Krakatau event in details. The worldwide propagation of the tsunami waves generated by the Krakatau volcanic eruption is studied numerically using two conventional models: ray tracing method and two-dimensional linear shallow-water model. The results of the numerical simulations are compared with available data of the tsunami registration
Quantum carpet interferometry for trapped atomic Bose-Einstein condensates
We propose an ``interferometric'' scheme for Bose-Einstein condensates using
near-field diffraction. The scheme is based on the phenomenon of intermode
traces or quantum carpets; we show how it may be used in the detection of weak
forces.Comment: 4 figures. Submitted to Phys. Rev.
Factorization and polarization in linearized gravity
We investigate all the four-body graviton interaction processes:
, , and with
as an elementary particle of spin less than two in the context of linearized
gravity except the spin-3/2 case. We show explicitly that gravitational gauge
invariance and Lorentz invariance cause every four-body graviton scattering
amplitude to be factorized. We explore the implications of this factorization
property by investigating polarization effects through the covariant density
matrix formalism in each four-body graviton scattering process.Comment: 45 pages, figures are included (uses pictex), RevTe
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Mechanisms of airfoil noise near stall conditions
The focus of this paper is on investigating the noise produced by an airfoil at high angles of attack over a range of Reynolds number
Re≈2×10⁵–4×10⁵. The objective is not modeling this source of noise but rather understanding the mechanisms of generation for surface pressure fluctuations, due to a separated boundary layer, that are then scattered by the trailing edge. To this aim, we use simultaneous noise and surface pressure measurement in addition to velocimetric measurements by means of hot wire anemometry and time-resolved particle image velocimetry. Three possible mechanisms for the so-called “separation-stall noise” have been identified in addition to a clear link between far-field noise, surface pressure, and velocity fields in the noise generation
Coulomb suppression of NMR coherence peak in fullerene superconductors
The suppressed NMR coherence peak in the fullerene superconductors is
explained in terms of the dampings in the superconducting state induced by the
Coulomb interaction between conduction electrons. The Coulomb interaction,
modelled in terms of the onsite Hubbard repulsion, is incorporated into the
Eliashberg theory of superconductivity with its frequency dependence considered
self-consistently at all temperatures. The vertex correction is also included
via the method of Nambu. The frequency dependent Coulomb interaction induces
the substantial dampings in the superconducting state and, consequently,
suppresses the anticipated NMR coherence peak of fullerene superconductors as
found experimentally.Comment: 4 pages, Revtex, and 2 figures. Revised and final version to appear
in Phys. Rev. Lett. (1998
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