118376307
Search for GeV Gamma‐Ray Bursts with the ARGO‐YBJ Detector in Scaler Mode
The ARGO‐YBJ experiment is a full coverage array made of Resistive Plate Chambers (RPCs) operated in streamer mode to detect the extensive array showers (EASs). With large field of view (>2sr) and high duty cycle (>90%), the ARGO‐YBJ detector is the right ground‐based apparatus to detect VHE GRBs, while the high altitude (4300 m a.s.l) and scaler working mode enable it to detect GRBs in the GeV region as high energy follow‐up observation of satellites such as SWIFT. If a GRB signal is detected, the four scaler channels, which correspond to different energy thresholds, can provide further information on the energy spectrum and its cut‐off. More than 40 SWIFT GRBs were in ARGO‐YBJ field of view, no significant excess was detected till now.
118403311
Geometry and optics calibration of WFCTA prototype telescopes using star light
The Large High Altitude Air Shower Observatory project is proposed to study high energy gamma ray astronomy ( 40 GeV-1 PeV ) and cosmic ray physics ( 20 TeV-1 EeV ). The wide field of view Cherenkov telescope array, as a component of the LHAASO project, will be used to study energy spectrum and compositions of cosmic ray by measuring the total Cherenkov light generated by air showers and shower maximum depth. Two prototype telescopes have been in operation since 2008. The pointing accuracy of each telescope is crucial to the direction reconstruction of the primary particles. On the other hand the primary energy reconstruction relies on the shape of the Cherenkov image on the camera and the unrecorded photons due to the imperfect connections between photomultiplier tubes. UV bright stars are used as point-like objects to calibrate the pointing and to study the optical properties of the camera, the spot size and the fractions of unrecorded photons in the insensitive areas of the camera.
118578178
Observations of very high energy gamma-ray emission from AGNs with the ground-based EAS arrays
The ground-based EAS array is usually operated with a high duty cycle (> 90%) and a large field of view (∼ 2sr), which can continuously monitor the sky. It is essential and irreplaceable to understand the gamma-ray emission mechanism and intrinsic physics progress of the variable source AGN. The EAS arrays, AS-γ experiment (since 1990) and ARGO-YBJ experiment (since 2007), have continuously monitored the northern sky at energies above 3 TeV and 0.3 TeV, respectively. They have made substantial contributions for long-term monitoring of Mrk 421 and Mrk 501. In this paper, we will review the results obtained by the EAS arrays. The next generation of EAS array, LHAASO project, will boost the sensitivity of current EAS array at least up to 30 times with a much wider energy range from 40 GeV to 1 PeV. Beside increasing the number of VHE gamma-ray sources, it will guide us look sight into the properties of jet, and throw light on the determining of the EBL, intergalactic magnetic fields, and the validity of the Lorentz Invariance.
115310371
Preliminary results of the Moon shadow with ARGO-YBJ
122334116
Notes on holographic superconductor models with the nonlinear electrodynamics
Abstract We investigate systematically the effect of the nonlinear correction to the usual Maxwell electrodynamics on the holographic dual models in the backgrounds of AdS black hole and AdS soliton. Considering three types of typical nonlinear electrodynamics, we observe that in the black hole background the higher nonlinear electrodynamics correction makes the condensation harder to form and changes the expected relation in the gap frequency, which is similar to that caused by the curvature correction. However, in strong contrast to the influence of the curvature correction, we find that in the AdS soliton background the nonlinear electrodynamics correction will not affect the properties of the holographic superconductor and insulator phase transitions, which may be a quite general feature for the s-wave holographic superconductor/insulator system.
118374075
A new approach to the vacuum of inflationary models
A new approach is given for the implementation of boundary conditions used in solving the Mukhanov–Sasaki equation in the context of inflation. The familiar quantization procedure is reviewed, along with a discussion of where one might expect deviations from the standard approach to arise. The proposed method introduces a (model-dependent) fitting function for the z″/z and a″/a terms in the Mukhanov–Sasaki equation for scalar and tensor modes, as well as imposes the boundary conditions at a finite conformal time. As an example, we employ a fitting function and compute the spectral index, along with its running, for a specific inflationary model, which possesses background equations that are analytically solvable. The observational upper bound on the tensor to scalar ratio is used to constrain the parameters of the boundary conditions in the tensor sector as well. An overview on the generalization of this method is also discussed.
17776491
Noncommutativity as a possible origin of the ultrahigh energy cosmic ray and the TeV-photon paradoxes
In this paper, we present a general modified dispersion relation derived from q-deformed noncommutative theory and apply it to the ultrahigh energy cosmic ray and the TeV-photon paradoxes — threshold anomalies. Our purpose is not only trying to solve these puzzles by noncommutative theory but also to support noncommutative theory through the coincidence of the region in the parameter space for resolving the threshold anomalies with the one from the q-deformed noncommutative theory.
14192602
Vacuum energy density and cosmological constant in dS brane-world
We discuss the vacuum energy density and the cosmological constant of dS5 brane-world with a dilaton field. It is shown that a stable AdS4 brane can be constructed and gravity localization can be realized. An explicit relation between the dS bulk cosmological constant and the brane cosmological constant is obtained. The discrete mass spectrum of the massive scalar field in the AdS4 brane is used to acquire the relationship between the brane cosmological constant and the vacuum energy density. The vacuum energy density in the brane gotten by this method is in agreement with astronomical observations.
195822336
CURRENT STATUS OF THE PROPOSED SHANGHAI SYNCHROTRON RADIATION FACILITY
The Shanghai Synchrotron Radiation Facility (SSRF) was proposed by the Chinese Academy of Sciences and the Shanghai Municipal Government in 1995. The estimated total budget is around US$100 M, and the operation is scheduled to begin in the end of 2003. The whole SSRF project is still awaiting final approval, but its R&D has been approved. The SSRF is a third-generation synchrotron light source designed to produce high brightness VUV and soft X-ray in the energy region of 10 eV~3 keV and high flux X-ray with moderate brightness in the energy region of 3~30 keV. It consists of the injector (including a 100 MeV Linac and a 2.2-2.5 GeV Booster), the 2.2-2.5 GeV storage ring and the synchrotron radiation experimental facilities. In this paper, the main parameters and features of the SSRF are presented.