118559036
Le Châtelier–Braun principle in cosmological physics
Assuming that dark energy may be treated as a fluid with a well-defined temperature, close to equilibrium, we argue that if nowadays there is a transfer of energy between dark energy and dark matter, it must be such that the latter gains energy from the former and not the other way around.
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.
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.
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.
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.
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.
111424651
Ion Transportation Study for Thick Gas Electron Multipliers
Ion back flow(IBF) is defined as the ions that are generated during multiplication in a thick-gas-electron-multiplier (THGEM) detector flow along the electric field. In order to suppress the IBF effect, we study ion transportation for THGEMs with various high voltages and geometrical parameters. By measuring the currents of all the electrodes of the THGEMs, the effective gain and ion back flow ratio are calculated. The measurement and simulation results reveal that with a staggered triple THGEM configuration, ion back flow can be suppressed to 1% with a proper working high voltage. The gain of the staggered configuration is less than that of the aligned configuration by 5% under the same high voltage condition. The design and the results are presented.
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...
119434810
Ly-alpha forests and cooling outflow from dwarf galaxies
We propose that cooling outflows from star-forming dwarf galaxies that are spatially correlated with but unbound to bright galaxies may account for the low column QSO Ly$\alpha$ forests, providing an explanation for both the heavy elements recently detected in them and the large sizes associated with them. Thus, we suggest that structure formations in the early universe on scales where matters collapse gravitationally and the gas forms stars are responsible for the Ly$\alpha$ forests (cf. the mini-halo model). Supernovae shock the interstellar gas to high temperature, and the resulting gas outflows from the dwarfs owing to their shallow potential wells. The gas cools radiatively as the radiative cooling time shortens because of adiabatic expansion. Subsequent thermal instability results in condensation of clouds. The clouds inherit the kinetic energy of the flow and coast to large distances, providing regions of the absorbing gas with sizes of up to hundreds of kpc. We calculate the Ly$\alpha$ absorption line profiles and the neutral column distribution, and show that they are consistent with observations. We suggest that the Ly$\alpha$ forests are caused by the faint blue galaxies found in the deep extragalactic surveys.
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.