33,531 research outputs found
Searching for -ray signature in WHSP blazars: Fermi-LAT detection of 150 excess signal in the 0.3-500 GeV band
A direct search of -ray emission centered on multi-frequency selected
candidates is a valuable complementary approach to the standard search adopted
in current -ray Fermi-LAT catalogs. Our candidates are part of the
2WHSP sample, that was assembled with the aim of providing targets for Imaging
Atmospheric Cherenkov Telescopes (IACT), and is currently the largest set of
high synchrotron peaked (HSP) blazars. We perform a likelihood analysis with
the Fermi Science Tools using positions from 400 2WHSP blazars as seeds of
tentative -ray sources. This enabled us to detect 150 -ray
excess signals that have not yet been reported in previous -ray
catalogs (1FGL, 2FGL, and 3FGL). By identifying new sources, we solve a
fraction of the extragalactic isotropic -ray background (IGRB)
composition, improving the description of the -ray sky. Our analysis
considers the 0.3-500 GeV energy band, integrating over 7.2 yrs of Fermi-LAT
observation and making use of the Pass 8 data release. Within the 150 2WHSPs
that showed excess -ray signature: 85 are high-significance detections
with test statistic (TS)25, and 65 are lower-significance detections with TS
between 10 to 25. We study the -ray photon spectral index distribution,
the likelihood of detection according to the synchrotron peak brightness, and
plot the measured -ray LogN-LogS of HSP blazars, also discussing the
portion of the IGRB that has been resolved by this work. We report on four
cases where we could resolve source confusion and find counterparts for
unassociated 3FGL sources with the help of high-energy TS maps together with
multi-frequency data. The 150 new -ray sources are named with the
acronym 1BIGB for the first version of the Brazil ICRANet Gamma-ray Blazar
catalog, in reference to the cooperation agreement supporting this work.Comment: Accepted for publication in A&A: September 01, 201
Holographic Butterfly Effect and Diffusion in Quantum Critical Region
We investigate the butterfly effect and charge diffusion near the quantum
phase transition in holographic approach. We argue that their criticality is
controlled by the holographic scaling geometry with deformations induced by a
relevant operator at finite temperature. Specifically, in the quantum critical
region controlled by a single fixed point, the butterfly velocity decreases
when deviating from the critical point. While, in the non-critical region, the
behavior of the butterfly velocity depends on the specific phase at low
temperature. Moreover, in the holographic Berezinskii-Kosterlitz-Thouless
transition, the universal behavior of the butterfly velocity is absent.
Finally, the tendency of our holographic results matches with the numerical
results of Bose-Hubbard model. A comparison between our result and that in the
nonlinear sigma model is also given.Comment: 41 pages, 7 figures, minor revisions, refs adde
FDserver: A web service for protein folding research
*Summary:* To facilitate the study of protein folding, we have developed a web service for protein folding rate and folding type prediction as well as for the calculation of a variety of topological parameters of protein structure, which is freely available to the community.
*Availability:* http://sdbi.sdut.edu.cn/FDserve
Probing gauge-phobic heavy Higgs bosons at high energy hadron colliders
We study the probe of the gauge-phobic (or nearly gauge-phobic) heavy Higgs
bosons (GPHB) at high energy hadron colliders including the 14 TeV LHC and the
50 TeV Super Proton-Proton Collider (SppC). We take the process , and study it at the hadron level including simulating the jet
formation and top quark tagging (with jet substructure). We show that, for a
GPHB with GeV, can be determined by adjusting the value
of in the theoretical distribution to fit the observed
distribution, and the resonance peak can be seen at the SppC for
=800 GeV and 1 TeV.Comment: 6 pages, with 7 eps files for 7 figure
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