21,903 research outputs found
Fermi Variability Study of the Candidate Pulsar Binary 2FGL~J0523.3-2530
The Fermi source 2FGL~J0523.32530 has recently been identified as a
candidate millisecond pulsar binary with an orbital period of 16.5 hrs. We have
carried out detailed studies of the source's emission properties by analyzing
data taken with the Fermi Large Area Telescope in the 0.2--300 GeV energy
range. Long-term, yearly variability from the source has been found, with a
factor of 4 flux variations in 1--300 GeV. From spectral analysis, we find an
extra spectral component at 2--3 GeV that causes the source brightening. While
no orbital modulations have been found from the Fermi data over the whole
period of 2008--2014, orbital modulation in the source's 2 GeV emission is
detected during the last 1.5 yrs of the Fermi observation. Our results support
the millisecond pulsar binary nature of 2FGL~J0523.32530. Multi-wavelength
observations of the source are warranted in order to find any correlated flux
variations and thus help determine the origin of the long-term variability,
which currently is not understood.Comment: 8 pages, 5 figures, comments from Referee were incorporated, accepted
for publication in Ap
The T2K Indication of Relatively Large theta_13 and a Natural Perturbation to the Democratic Neutrino Mixing Pattern
The T2K Collaboration has recently reported a remarkable indication of the
\nu_\mu -> \nu_e oscillation which is consistent with a relatively large value
of \theta_{13} in the three-flavor neutrino mixing scheme. We show that it is
possible to account for such a result of \theta_{13} by introducing a natural
perturbation to the democratic neutrino mixing pattern, without or with CP
violation. A testable correlation between \theta_{13} and \theta_{23} is
predicted in this ansatz. We also discuss the Wolfenstein-like parametrization
of neutrino mixing, and comment on other possibilities of generating
sufficiently large \theta_{13} at the electroweak scale.Comment: RevTeX 8 page
Active Ontology: An Information Integration Approach for Dynamic Information Sources
In this paper we describe an ontology-based information integration approach that is suitable for highly dynamic distributed information sources, such as those available in Grid systems. The main challenges addressed are: 1) information changes frequently and information requests have to be answered quickly in order to provide up-to-date information; and 2) the most suitable information sources have to be selected from a set of different distributed ones that can provide the information needed. To deal with the first challenge we use an information cache that works with an update-on-demand policy. To deal with the second we add an information source selection step to the usual architecture used for ontology-based information integration. To illustrate our approach, we have developed an information service that aggregates metadata available in hundreds of information services of the EGEE Grid infrastructure
Universal Elasticity and Fluctuations of Nematic Gels
We study elasticity of spontaneously orientationally-ordered amorphous
solids, characterized by a vanishing transverse shear modulus, as realized for
example by nematic elastomers and gels. We show that local heterogeneities and
elastic nonlinearities conspire to lead to anomalous nonlocal universal
elasticity controlled by a nontrivial infared fixed point. Namely, at long
scales, such solids are characterized by universal shear and bending moduli
that, respectively, vanish and diverge at long scales, are universally
incompressible and exhibit a universal negative Poisson ratio and a non-Hookean
elasticity down to arbitrarily low strains. Based on expansion about five
dimensions, we argue that the nematic order is stable to thermal fluctuation
and local hetergeneities down to d_lc < 3.Comment: 4 RevTeX pgs, submitted to PR
Rephasing Invariants of CP and T Violation in the Four-Neutrino Mixing Models
We calculate the rephasing invariants of CP and T violation in a favorable
parametrization of the 4x4 lepton flavor mixing matrix. Their relations with
the CP- and T-violating asymmetries in neutrino oscillations are derived, and
the matter effects are briefly discussed.Comment: RevTex 9 pages. Slight changes. Phys. Rev. D (in press
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