6,300 research outputs found
Work statistics across a quantum phase transition
We investigate the statistics of the work performed during a quench across a
quantum phase transition using the adiabatic perturbation theory. It is shown
that all the cumulants of work exhibit universal scaling behavior analogous to
the Kibble-Zurek scaling for the average density of defects. Two kinds of
transformations are considered: quenches between two gapped phases in which a
critical point is traversed, and quenches that end near the critical point. In
contrast to the scaling behavior of the density of defects, the scaling
behavior of the work cumulants are shown to be qualitatively different for
these two kinds of quenches. However, in both cases the corresponding exponents
are fully determined by the dimension of the system and the critical exponents
of the transition, as in the traditional Kibble-Zurek mechanism (KZM). Thus,
our study deepens our understanding about the nonequilibrium dynamics of a
quantum phase transition by revealing the imprint of the KZM on the work
statistics
Probing annihilations and decays of low-mass galactic dark matter in IceCube DeepCore array: Track events
The deployment of DeepCore array significantly lowers IceCube's energy
threshold to about 10 GeV and enhances the sensitivity of detecting neutrinos
from annihilations and decays of light dark matter. To match this experimental
development, we calculate the track event rate in DeepCore array due to
neutrino flux produced by annihilations and decays of galactic dark matter. We
also calculate the background event rate due to atmospheric neutrino flux for
evaluating the sensitivity of DeepCore array to galactic dark matter
signatures. Unlike previous approaches, which set the energy threshold for
track events at around 50 GeV (this choice avoids the necessity of including
oscillation effect in the estimation of atmospheric background event rate), we
have set the energy threshold at 10 GeV to take the full advantage of DeepCore
array. We compare our calculated sensitivity with those obtained by setting the
threshold energy at 50 GeV. We conclude that our proposed threshold energy
significantly improves the sensitivity of DeepCore array to the dark matter
signature for GeV in the annihilation scenario and
GeV in the decay scenario.Comment: 19 pages, 5 figures; match the published versio
Spin textures in slowly rotating Bose-Einstein Condensates
Slowly rotating spin-1 Bose-Einstein condensates are studied through a
variational approach based upon lowest Landau level calculus. The author finds
that in a gas with ferromagnetic interactions, such as Rb, angular
momentum is predominantly carried by clusters of two different types of
skyrmion textures in the spin-vector order parameter. Conversely, in a gas with
antiferromagnetic interactions, such as Na, angular momentum is carried
by -disclinations in the nematic order parameter which arises from spin
fluctuations. For experimentally relevant parameters, the cores of these
-disclinations are ferromagnetic, and can be imaged with polarized light.Comment: 14 pages, 12 low resolution bitmapped figures, RevTeX4. High
resolution figures available from author. Suplementary movies available from
autho
Epoch Dependent Dark Energy
We present a model in which the equation of state parameter w approaches -1
near a particular value of z, and has significant negative values in a
restricted range of z. For example, one can have w ~ -1 near z = 1, and w >
-0.2 from z = 0 to z = 0.3, and for z > 9. The ingredients of the model are
neutral fermions (which may be neutrinos, neutralinos, etc) which are very
weakly coupled to a light scalar field. This model emphasises the importance of
the proposed studies of the properties of dark energy into the region z > 1.Comment: 7pp., 2 figs. Invited talk at the 5th Int'l. Wkshp. on the Dark Side
of the Universe, 1-5 June 2009 Melbourne, DSU09; to appear in the proceeding
Tau Neutrino Astronomy in GeV Energies
We point out the opportunity of the tau neutrino astronomy for the neutrino
energy E ranging between 10 GeV and 10^3 GeV. In this energy range, the
intrinsic tau neutrino production is suppressed relative to the intrinsic muon
neutrino production. Any sizable tau neutrino flux may thus arise because of
the \nu_{\mu}\to \nu_{\tau} neutrino oscillations only. It is demonstrated
that, in the presence of the neutrino oscillations, consideration of the
neutrino flavor dependence in the background atmospheric neutrino flux leads to
the drastically different prospects between the observation of the
astrophysical muon neutrinos and that of the astrophysical tau neutrinos.
Taking the galactic-plane neutrino flux as the targeted astrophysical source,
we have found that the galactic-plane tau neutrino flux dominates over the
atmospheric tau neutrino flux for E > 10 GeV. Hence, the galactic-plane can at
least in principle be seen through the tau neutrinos with energies just greater
than 10 GeV. In a sharp contrast, the galactic-plane muon neutrino flux is
overwhelmed by its atmospheric background until E > 10^6 GeV.Comment: major revision of text and two new figures, to appear in PR
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