118533325
Quasi-Single Field Inflation and Non-Gaussianities
In quasi-single field inflation models, massive isocurvature modes, that are coupled to the inflaton and have mass of order the Hubble parameter, can have nontrivial impacts on density perturbations, especially non-Gaussianities. We study a simple example of quasi-single field inflation in terms of turning inflaton trajectory. Large bispectra with a one-parameter family of novel shapes arise, lying between the well-known local and equilateral shape. The trispectra can also be very large and its magnitude tNL can be much larger than fNL2.
119725208
Holographic Gas as Dark Energy
We investigate the statistical nature of holographic gas, which may represent the quasi-particle excitations of a strongly correlated gravitational system. We find that the holographic entropy can be obtained by modifying degeneracy. We calculate thermodynamical quantities and investigate stability of the holographic gas. When applying to cosmology, we find that the holographic gas behaves as holographic dark energy, and the parameter c in holographic dark energy can be calculated from our model. Our model of holographic gas generally predicts c < 1, implying that the fate of our universe is phantom-like.
53583135
Three-dimensional two-layer outer gap model: Fermi energy-dependent light curves of the Vela pulsar
We extend the two-dimensional two-layer outer gap model to a three-dimensional geometry and use it to study the high-energy emission of the Vela pulsar. In this model, the outer gap is divided into two parts, i.e. the main acceleration region on the top of last-open field lines and the screening region around the upper boundary of the gap. In the main acceleration region, the charge density is much lower than the Goldreich–Julian charge density, and the charged particles are accelerated by the electric field along the magnetic field to emit multi-GeV photons. In the screening region, the charge density is larger than the Goldreich–Julian value to close the gap, and particles in this region are responsible for multi-100 MeV photon emission. We apply this three-dimensional two-layer model to the Vela pulsar and compare the model light curves, the phase-averaged spectrum and the phase-resolved spectra with the recent Fermi observations, which also reveals the existence of the third peak between two main peaks. The phase position of the third peak moves with the photon energy, which cannot be explained by the geometry of magnetic field structure and the caustic effects of the photon propagation. We suggest that the existence of the third peak and its energy-dependent movement results from the azimuthal structure of the outer gap.
119448285
Prospects for constraining cosmology with the extragalactic cosmic microwave background temperature
Observers have demonstrated that it is now feasible to measure the cosmic microwave background (CMB) temperature at high redshifts. We explore the possible constraints on cosmology which might ultimately be derived from such measurements. In addition to providing a consistency check on standard and alternative cosmologies, possibilities include constraints on the inhomogeneity and anisotropy of the universe at intermediate redshift $z\ensuremath{\lesssim}10,$ an independent probe of peculiar motions with respect to the Hubble flow, constraining the epoch of reionization, and the time variability of the fine structure constant. We argue that the best possibility is as a probe of peculiar motions. We show, however, that the current measurement uncertainty $(\ensuremath{\Delta}T=\ifmmode\pm\else\textpm\fi{}0.002\mathrm{K})$ in the local present absolute CMB temperature imposes intrinsic limits on the use of such CMB temperature measurements as a cosmological probe. At best, anisotropies at intermediate redshift could only be constrained at a level of $\ensuremath{\gtrsim}0.1%$ and peculiar motions could only be determined to an uncertainty of $\ensuremath{\gtrsim}311{\mathrm{km}\mathrm{}\mathrm{}\mathrm{s}}^{\ensuremath{-}1}.$ If the high z CMB temperature can only be measured with a precision comparable to the uncertainty of the local interstellar CMB temperature, then peculiar motions could be determined to an uncertainty of ${1101(1+z)}^{\ensuremath{-}1}[\ensuremath{\Delta}{T}_{\mathrm{CMB}}(z)/0.01\mathrm{K}]{\mathrm{km}\mathrm{}\mathrm{s}}^{\ensuremath{-}1}.$
121984352
The BES detector
Abstract The Beijing Spectrometer (BES) is a general purpose solenoidal detector at the Beijing Electron Positron Collider (BEPC). It is designed to study exclusive final states in e + e − annihilations at the center of mass energy from 3.0 to 5.6 GeV. This requires large solid angle coverage combined with good charged particle momentum resolution, good particle identification and high photon detection efficiency at low energies. In this paper we describe the construction and the performance of BES detector.
36793805
False vacuum decay in Jordan-Brans-Dicke cosmologies
Abstract We examine the bubble nucleation rate in a first-order phase transition taking place in a background Jordan-Brans-Dicke cosmology. We compute the leading order terms in the nucleation rate when the Jordan-Brans-Dicke field is large (i.e., late times) by means of a Weyl rescaling of the fields in the theory. We find that despite the fact that the Jordan-Brans-Dicke field (hence the effective gravitational constant) has a time dependence in the false vacuum, at late times the nucleation rate is time independent.
43062196
Development of thermionic-cathode RF electron gun at IHEP
A thermionic cathode RF electron gun has been developed at the Institute of High Energy Physics, Academia Sinica, China. The gun will accelerate and prebunch electrons emitted from a L/sub a/B/sub 6/ cathode using a high electric field in a resonant cavity. The gun was fabricated and tested, and used in the Beijing free-electron laser project. Results of experimental measurements of the injector performance of a prototype gun are also presented.<<ETX>>