118685400
Revisiting $f(R)$ gravity models that reproduce $\Lambda$CDM expansion
We reconstruct an $f(R)$ gravity model that gives rise to the particular $\Lambda$CDM background evolution of the universe. We find well-defined, real-valued analytical forms for the $f(R)$ model to describe the universe both in the early epoch from the radiation to matter dominated eras and the late time acceleration period. We further examine the viability of the derived $f(R)$ model and find that it is viable to describe the evolution of the universe in the past and there does not exist the future singularity in the Lagrangian.
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.
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.
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.
30079794
Stability of the event horizon in (2+1)-dimensional black holes.
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...
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.
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
121071019
OBSERVATIONAL H(z) DATA AS A COMPLEMENTARITY TO OTHER COSMOLOGICAL PROBES
In this paper, we use a set of observational H(z) data (OHD) to constrain the Lambda CDM cosmology. This dataset can be derived from the differential ages of the passively evolving galaxies. Meanwhile, the A-parameter, which describes the Baryonic Acoustic Oscillation (BAO) peak, and the newly measured value of the Cosmic Microwave Background (CMB) shift parameter Rare used to present combinational constraints on the same cosmology. The combinational constraints favor an accelerating flat universe while the flat Lambda CDM cosmology is also analyzed in the same way. We obtain result compatible with that by many other independent cosmological observations. We find that the observational H(z) data set is a complementarity to other cosmological probes.
120034276
de Broglie–Bohm interpretation for wave function of a toroidal black hole
The mass function of a toroidal black hole as a dynamical variable is given by using Kuchar’s approach. Then the toroidal black hole is investigated by using the de Broglie–Bohm approach, and its quantum potential and quantum trajectories are obtained. In our process the vector potential of the electromagnetic field in the toroidal black hole is treated as a canonical variable.