119393190
SLOWLY ROTATING PROTO STRANGE STARS IN QUARK MASS DENSITY- AND TEMPERATURE-DEPENDENT MODEL
Employing the Quark Mass Density- and temperature-dependent model and the Hartle's method, we have studied the slowly rotating strange star with uniform angular velocity. The mass–radius relation, the moment of inertia and the frame dragging for different frequencies are given. We found that we cannot use the strange star to solve the challenges of Stella and Vietri for the horizontal branch oscillations and the moment of inertia I45/(M/Ms)>2.3. Furthermore, we extended the Hartle's method to study the differential rotating strange star and found that the differential rotation is an effective way to get massive strange star.
124897627
Different Quantum Entropies for Two Kinds of Extreme Two-Dimensional Lowe–Strominger Black Holes*
It is shown that both the classical entropy of two-dimensional extremal Lowe–Strominger black hole and the quantum entropy of the scalar field in the background of this black hole are different by using Hawking's treatment as wel as Zaslavskii's treatment respectively. This result supports our previous suggestion that there are two kinds of extreme black holes in the nature. A new divergent term emerges in the quantum entropy in Zaslavskii's treatment and its physical meaning has been discussed.
119186601
Various types of phase transitions in the AdS soliton background
We study the basic holographic insulator and superconductor phase transition in the AdS soliton background by generalizing the spontaneous breaking of a global U(1) symmetry to occur via Stuckelberg mechanism. We construct the soliton solutions with backreaction and examine the effects of the backreaction on the condensation of the scalar hair in the generalized Stuckelberg Lagrangian. We disclose rich physics in various phase transitions. In addition to the AdS soliton configuration, we also examine the property of the phase transition in the AdS black hole background.
118997018
Probing the curvature of the Universe from supernova measurement
We study the possibility to probe the spatial geometry of the Universe by supernova measurement. We illustrate with an accelerating universe model with infinite-volume extra dimensions, for which the 1σ level supernova results indicate that the Universe is closed.
30079794
Stability of the event horizon in (2+1)-dimensional black holes.
118198563
Dark Energy: Relating the Evolutions of the Universe from the Past to the Future
Using the evolution history of the universe, one can make constraint on the parameter space of dynamic dark energy models. We discuss two different parameterized dark energy models. Our results further restrict the combined constraints obtained from supernova and the first-year Wilkinson-microwave-anisotropy-probe observations. From the allowed parameter space, it is found that our universe will experience an eternal acceleration. We also estimate the bound on the physically relevant regions both in the re-inflationary and inflationary phases.
207876412
STUDY OF THE SIGNAL PROCESSING SYSTEM FOR CAVITY BEAM POSITION MONITOR
A prototype of cavity beam position monitor (CBPM), with resonant frequency of 5712MHz [1] and high Q, has been installed in the Shanghai deep ultraviolet freeelectron laser source (SDUV-FEL) facility. A plug & play CBPM signal processor based on broadband oscilloscope embedded IOC (input output controller) and FFT (fast Fourier transform) technique has been developed to do quick evaluation of prototype [2]. According to the evaluation results, a series of simulation using Monte Carlo simulation method, have been carried out as a guideline for the design of dedicated CBPM signal processing system. An RF front end for a prototype of CBPM with resonant frequency of 4700MHz and low Q using the microwave devices is developed and relevant digital signal process algorithms are implemented in MATLAB. Systematic test in lab has been done to evaluate the performance. We got a resolution of 2.8 μm when the continuous sine input signal is 6dBm. INTRODUCTION The free electron laser (FEL) operating in high gain harmonic generation (HGHG) or self-amplified spontaneous emission (SASE) regime required such high beam position resolution that the electron beam could overlap the generated photon beam stringently and pass through the entire undulator section together. CBPM, which can achieve nano scale resolution as reported [3][4][5], is important and indispensable for the free electron laser (FEL) facility. The Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) facility is operating for cascaded HGHG FEL [6]. According to the relevant references, two types of CBPM with high or low Q, which has something to do with signal intensity, regression time and bandwidth, were developed and used in FEL facilities. For different CBPMs, the different signal process system would be designed. A beam test based on broadband oscilloscope embedded IOC has been done for high-quality-factor CBPM with resonant frequency of 5712MHz. The typical algorithms, such as fitting and digital down convert (DDC)[7], are used in most CBPM signal process systems. We decided to use the FFT technique to implement the beam position measurement. The optimal data length for the FFT technique has been simulated by using signal of beam test. Right now, a prototype of CBPM, not in vacuum, was newly manufactured with 4.7GHz resonant frequency and low Q. And the corresponding CBPM electronics were developed. As we would evaluate performance of two types of CBPM and choose one of them to be used in the future FEL facility, the electronics cover the two prototypes. SYSTEM SETUP The CBPM electronics consist of a dedicated RF (radio frequency) front end and a commercial data acquisition board. RF front end based on the RF receiver architecture is absolutely essential to convert the RF signals to intermediate frequency (IF). Table 1 shows the detail about the selection in our system design. Table 1: Parameters of CBPMs and RF Front End Prototype 1 Prototype 2 Resonant freq. 5.712GHz 4.700GHz
119197867
Constraints on smoothness parameter and dark energy using observational H(z) data
With large-scale homogeneity, the universe is locally inhomogeneous, clustering into stars, galaxies and larger structures. Such property is described by the smoothness parameter α which is defined as the proportion of matter in the form of intergalactic medium. If we consider the inhomogeneities over a small scale, there should be modifications of the cosmological distances compared to a homogenous model. Dyer and Roeder developed a second-order ordinary differential equation (D-R equation) that describes the angular diameter distance-redshift relation for inhomogeneous cosmological models. Furthermore, we may obtain the D-R equation for observational H(z) data (OHD). The density-parameter ΩM, the state of dark energy ω, and the smoothness-parameter α are constrained by a set of OHD in a spatially flat ΛCDM universe as well as a spatially flat XCDM universe. By using a χ2 minimization method, we get α = 0.81+0.19−0.20 and ΩM = 0.32+0.12−0.06 at the 1σ confidence level. If we assume a Gaussian prior of ΩM = 0.26 ± 0.1, we get α = 0.93+0.07−0.19 and ΩM = 0.31+0.06−0.05. For the XCDM model, α is constrained to α ≥ 0.80 but ω is weakly constrained around −1, where ω describes the equation of state of the dark energy (pX = ωρX). We conclude that OHD constrains the smoothness parameter more effectively than the data of SNe Ia and compact radio sources.
16859067
THE MASS FUNCTION OF DARK MATTER HALOES IN A COSMOLOGICAL MODEL WITH A RUNNING PRIMORDIAL POWER SPECTRUM
We present the first study on the mass functions of Jenkins et al. (J01) and an estimate of their corresponding largest virialized dark halos in the Universe for a variety of dark-energy cosmological models with a running spectral index. Compared with the PL–CDM model, the RSI–CDM model can raise the mass abundance of dark halos for small mass halos at lower redshifts, but it is not apparent on scales of massive mass halos. Particularly, this discrepancy increases largely with the decrease of redshift, and the RSI–CDM model can suppress the mass abundance on any scale of halo masses at higher redshift. As for the largest mass of virialized halos, the spatially flat ΛCDM models give more massive mass of virialized objects than other models for both of PL–CDM and RSI–CDM power spectral indexs, and the RSI–CDM model can enhance the mass of largest virialized halos for all of models considered in this paper. So we probably distinguish the PL–CDM and RSI–CDM models by the largest virialized halos in the future...
121864290
A compact positron annihilation lifetime spectrometer
Using LYSO scintillator coupled on HAMAMATSU R9800 (a fast photomultiplier) to form the small size gamma-ray detectors, a compact lifetime spectrometer has been built for the positron annihilation experiments. The system time resolution FWHM=193 ps and the coincidence counting rate similar to 8 cps/mu Ci were achieved. A lifetime value of 219 +/- 1 ps of positron annihilation in well annealed Si was tested, which is in agreement with the typical values published in the previous lectures.
119239888
Physical design of superconducting magnet for ADS injection I
A superconducting solenoid prototype magnet for Accelerator Driven Subcritical System (ADS) Injection I has been designed and fabricated, which has also been tested in a liquid Helium state inside a vertical Dewar in the Haerbin institute of Technology in November 2012. The design current was 210 A, when the test current reached 400 A no quench occurred so the solenoid magnet was forced to quench by the embedded heaters. The integral field strength, leakage field at the nearby upstream and downstream superconducting spoke cavities all meet the design requirements. At the same time, it also checked the reliability of the vertical test Dewar and the quenched detection system. The superconducting prototype magnet has accumulated valuable experiences for the coming batch magnets production and cryogenic test.