122210021
The interaction between dark energy and dark matter
In this review we first present a general formalism to study the growth of dark matter perturbations in the presence of interactions between dark matter(DM) and dark energy(DE). We also study the signature of such interaction on the temperature anisotropies of the large scale cosmic microwave background (CMB). We find that the effect of such interaction has significant signature on both the growth of dark matter structure and the late Integrated Sachs Wolfe effect(ISW). We further discuss the potential possibility to detect the coupling by cross-correlating CMB maps with tracers of the large scale structure. We finally confront this interacting model with WMAP 5-year data as well as other data sets. We find that in the 1σ range, the constrained coupling between dark sectors can solve the coincidence problem.
30079794
Stability of the event horizon in (2+1)-dimensional black holes.
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.
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.
59425513
Bunch by Bunch Beam Diagnostics in SSRF
A set of broadband beam instruments including filling pattern monitor, scope based BPM processor and streak camera has been implemented in the storage ring of SSRF. Several parameters such as charge, lifetime, transverse position, betatron tune and beam length, can be measured for individual bunch by these devices. The operation experience and measurement results will be introduced. The preliminary effort to retrieve wake field information from these measurements will be presented as well. INTRODUCTION Shanghai Synchrotron Radiation Facility (SSRF), as a 3.5 GeV third generation light source, started user operation with seven beamlines since 2009 [1]. Couple thousands of experiment proposals have been performed during past three years. Meanwhile almost the same number of proposals were rejected or delayed due to limited beamlines and beam time. In order to take full advantage of SSRF an upgrade project of adding more than twenty beamlines has been planed. Lots of in vacuum insertion devices with small gap will involve in this upgrading. Beam instability introduced by multibunch interaction will be a very series issue in this case. Study of machine impedance and wake field became a high priority job. Several broad band instruments with bunch by bunch capability was developed and implemented for this purpose and showed very good potential in recent machine studies. Table 1 shows the primary specification of broad band diagnostics devices equipped in SSRF ring. Table 1: Specification of Bunch by Bunch Instruments Measurement Devices Resolution Charge Button pickup + digitizer 0.1% Position Button pickup + Scope 50 um Length Streak Camera 2 ps During a typical SSRF user shift, beam in storage ring will be filled up to 210 mA with equivalent 500 bunches then decays to 140 mA. A lots of history data produced by above instruments have been accumulated. Detailed analyze of these data will give us some knowledge of multi-bunch interaction.
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.
119450767
Gas at Large Distances from Galaxies and QSO Absorption Lines
We present the calculations of steady, spherical gas outflows from galaxies in an effort to understand the effects of the galaxy mass on the flow properties such as the size of the outflow regions, the efficiency of radiative cooling, and the fate of the cooled gas. We show that there exist no transonic flows but either subsonic or supersonic flows are obtainable, in an analogy with the stellar wind or accretion problems. Solutions of the supersonic outflows are studied in detail as they are most likely to carry gas to large distances away from galaxies. In case the gas does cool radiatively, the cooled gas is most likely to form clouds via various instabilities. The clouds coast farther away from the galaxy because of the finite kinetic energy they inherit. Depending on the initial energies, the clouds can either leave the galaxy or fall back ballistically. Applications of the calculations to dwarf and normal galaxies are made, and we argue that normal galaxies like our own should have relatively small gaseous halos formed through this mechanism. We discuss the implications of cold clouds from dwarf galaxies on recent observations of the QSO absorption line systems. For massive galaxies, satellites provide alternative ways to form large gaseous halos. We show how dynamical friction can increase tidal stripping of the gas as the satellite spirals in toward the primary, and that the gas ejected from satellites may account for the QSO heavy element absorption lines.
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.