33,531 research outputs found

    Searching for γ\gamma-ray signature in WHSP blazars: Fermi-LAT detection of 150 excess signal in the 0.3-500 GeV band

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    A direct search of γ\gamma-ray emission centered on multi-frequency selected candidates is a valuable complementary approach to the standard search adopted in current γ\gamma-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 γ\gamma-ray sources. This enabled us to detect 150 γ\gamma-ray excess signals that have not yet been reported in previous γ\gamma-ray catalogs (1FGL, 2FGL, and 3FGL). By identifying new sources, we solve a fraction of the extragalactic isotropic γ\gamma-ray background (IGRB) composition, improving the description of the γ\gamma-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 γ\gamma-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 γ\gamma-ray photon spectral index distribution, the likelihood of detection according to the synchrotron peak brightness, and plot the measured γ\gamma-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 γ\gamma-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

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    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 O(N)O(N) nonlinear sigma model is also given.Comment: 41 pages, 7 figures, minor revisions, refs adde

    FDserver: A web service for protein folding research

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    *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

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    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 pp→ttˉttˉpp\to t\bar t t\bar t, 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 MH<800M^{}_H<800 GeV, MHM^{}_H can be determined by adjusting the value of MHM^{}_H in the theoretical pT(b1)p^{}_T(b_1) distribution to fit the observed pT(b1)p^{}_T(b_1) distribution, and the resonance peak can be seen at the SppC for MHM^{}_H=800 GeV and 1 TeV.Comment: 6 pages, with 7 eps files for 7 figure
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