118616284
GENERALIZED SECOND LAW OF THERMODYNAMICS IN WARPED DGP BRANEWORLD
We investigate the validity of the generalized second law of thermodynamics on the (n - 1)-dimensional brane embedded in the (n + 1)-dimensional bulk. We examine the evolution of the apparent horizon entropy extracted through relation between gravitational equation and the first law of thermodynamics together with the matter field entropy inside the apparent horizon. We find that the apparent horizon entropy extracted through connection between gravity and the first law of thermodynamics satisfies the generalized second law of thermodynamics. This result holds regardless of whether there is the intrinsic curvature term on the brane or a cosmological constant in the bulk. The observed satisfaction of the generalized second law provides further support on the thermodynamical interpretation of gravity based on the profound connection between gravity and thermodynamics.
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.
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.
30079794
Stability of the event horizon in (2+1)-dimensional black holes.
126084815
Entropy of quantum field in toroidal black hole without brick wall
The calculation of the brick-wall model gives the entropy as two terms: one is proportional to the horizon area and the other is a constant. Then they renormalized the entropy by introducing the Newton’s constant and the entropy correction arising from the higher curvature effective gravitational action. Finally, they got the renormalized entropy whose leading term is proportional to the horizon area of the black hole and the others is precisely the one-loop correction arising from the higher curvature terms of the gravitational action. Their work confirmed the suggestion by Susskind and Uglum [25] that these divergences have the correct form to be absorbed in the Bekenstein–Hawking formula as a renormalization of Newton’s constant.
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
119774346
Heavy-element abundances and massive star formation
We investigate the observational consequences that arise for the heavy-element abundances in normal spiral galaxies from variations in the initial mass function (IMF). In particular, we calculate the oxygen yield for a given IMF, using the most recent calculations of supernova nucleosynthesis. Assuming instantaneous recycling of oxygen, we calculate the resultant oxygen abundance. The predicted and observed oxygen abundances in our Galaxy are compared, and we find that the overall abundance is well explained by the IMF determined in the solar neighborhood
54186214
Cooling gas outflows from galaxies
We study steady, radial gas outflows from galaxies in an effort to understand the way tenuous and hot gas is transported to large distances away from galaxies. In particular, we obtain solutions for outflow problems, and study the outflow topology, effects of the galaxy mass, the size of outflow regions, the efficiency of radiative cooling, and the fate of the cooled gas. Under general power-law forms for the cooling function and the gravitational field of galaxies, we show that the outflow solutions are determined by the two-parameter initial conditions. In an analogy with stellar wind or accretion problems, we demonstrate that there exists no transonic flow, but either subsonic or supersonic flows are obtainable. Solutions of the supersonic outflows are studied in detail as they are most likely to carry gas to large distances away from galaxies. We find that if gravity is weak, the outflow is characterized by the ratio of the radiative cooling time to the flow time, $t_c/t_f$. The importance of the galactic gravitational field is characterized by the fractional energy lost radiatively within the flow time in outflows with velocity equal to the circular velocity of the galaxy; if the fraction is small, gravity stops the outflow before the gas has a chance to cool radiatively. In the 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. We find that the hot gas in dwarf galaxies can either flow out as galactic winds, or cools radiatively to form clouds. In the latter case, the clouds escape the galaxies. In contrast, massive galaxies like our own tend to confine the gas. We present the surface brightness in various x-ray energy bands. We also estimate the mean
121278811
Entropies of a Toroidal Black Hole Due to Scalar and Dirac Fields
Using the thin film brick-wall model, the entropies of a toroidal black hole due to scalar and Dirac fields are investigated. The entropy due to the scalar field is one fourth of the horizon area, and that due to the Dirac field is seven eighth of the area. These results are similar to that in black holes with horizon topology S2. The cutoff in toroidal black hole is chosen as the same as one in black holes with horizon topology S2, which seems to mean that the thin film brick-wall model is universal.