Super-horizon Perturbations and CMBA

We provided a gedanken experiment and argued that since observers inside a given Hubble volume could not detect the super horizon perturbation modes as real perturbations, these modes could only affect the average value of the cosmic microwave background (CMB), but not its anisotropy properties (CMBA) in that Hubble volume.Comment: 1 pages, 1 figure

Primordial Power Spectrum's Calculation and the Upper Bound on the Number of E-foldings of Inflation

In numerical calculations of the primordial power spectrum of perturbations produced during inflation, for very little wavenumber $k$s, to implement the initial conditions required of the perturbation mode functions consistently, we must let the universe experience more e-foldings of inflation than that required of it to solve the horizon, flatness and other pre-inflation problems. However, if the number of e-foldings of inflation has an upper bound, then for perturbations at scales greater than some critical value, the initial conditions required of the mode functions cannot be implemented physically. Because at the inflation beginning point, these perturbation modes lie outside the horizon. We propose that such perturbations do not contribute to the Cosmological Microwave Background Anisotropy (CMBA). Under this proposition, the exceptional lowness of the observed little $l$ muli-poles of CMBA is reproduced numerically. In Linde's $\phi^2$ model, the upper bound on the number of e-foldings of inflation is determined to be 65 approximately.Comment: 5 pages, 4 figure

A Question About Standard Cosmology and Extremely Dense Stars' Collapsing

We ask if the conventional variable separation techniques in the studying of standard cosmology and the collapsing of extremely dense stars introduce Newton's absolute space-time concepts. If this is the case, then a completely relative cosmology is needed. We build the basic frame-works for such a cosmology and illustrate that, the observed luminosity-distance v.s. red-shift relations of supernovaes can be explained naturally even without any conception of dark energies.Comment: 4 and half pages, 1 figures, two column style

Yang-Type Monopoles In 5 Dimensional Curved Space-Time

Motivated by Gibbons and Townsend's recent work, we construct Yang-Type monopoles in maximally symmetric space-time. We then analyze the dependence of horizon structure of the space-times around the 5-dimensional monopoles on the relative strength of gravitations to Yang-Mills interactions. We also analyze the stability of the monopoles against tensor type perturbations on metrics.Comment: 10 pages, 2 figure

Viscosity and jet quenching from holographic model

We consider the backreaction of the fundamental flavor degrees of freedom on the AdS$_5$-Schwarz background, and calculate their contributions to the shear viscosity and jet-quenching parameter of the thermal quark-gluon plasma.Comment: 5 pages, minor changes and references adde

Thermodynamics of Chiral Fermion System in a Uniform Magnetic Field

We construct the grand partition function of the system of chiral fermions in a uniform magnetic field from Landau levels, through which all thermodynamic quantities can be obtained. Taking use of Abel-Plana formula, these thermodynamic quantities can be expanded as series with respect to a dimensionless variable $b=2eB/T^{2}$. We find that the series expansions of energy density, pressure, magnetization intensity and magnetic susceptibility contain a singular term with $\ln b^{2}$, while particle number density, entropy density and heat capacity are power series of $b^{2}$. The asymptotic behaviors of these thermodynamic quantities in extreme conditions are also discussed.Comment: 30 pages, 7 figure

An Ignored Assumption of Λ\LambdaCDM Cosmology and An Old Question: Do We Live On The "Center" of The Universe?

We point out that $\Lambda$CDM cosmology has an ignored assumption. That is, the $\Lambda$ component of the universe moves synchronously with ordinary matters on Hubble scales. If cosmological constant is vacuum energy, this assumption may be very difficult to be understood. We then propose a new mechanism which can explain the accelerating recession of super-novaes. That is, considering the pressures originating from the random moving (including Hubble recession) of galaxy clusters and galaxies. We provide an new analytical solution of Einstein equation which may describe a universe whose pressures originating from the random moving of galaxy clusters and galaxies are considered.Comment: two column style, 4 page

Spherical Collapse Model

We studied the spherical collapse model in the flat $\Lambda$CDM cosmology and provided exact and analytical formulaes for the calculation of the two important parameters in the application of Press-Schechter theory, the critical density contrast and the ratio of cluster/background densities at the virialization point in terms of a media variable which can be solved precisely by numerical methods.Comment: part of the numerical results changed, two typoes correcte

Spherical Collapse Model And Dark Energy(I)

In existing literatures about the top-hat spherical collapse model of galaxy clusters formation in cosmology containing dark energies, dark energies are usually assumed not to cluster on this scale. But all these literatures ignored the current describing the flowing of dark energies outside the clusters which should exist under this assumption, so the conclusions of these literatures are worth further explorations. In this paper we study this model in QCDM or Phantom-CDM cosmologies(flat) by assuming that dark energies will cluster synchronously with ordinary matters on the scale of galaxy clusters so the dark energy current flowing outside the clusters does not exist at all and find that in this case, the key parameters of the model exhibit rather non-trivial and remarkable dependence on the equation of state coefficients of dark energies. We then apply the results in Press-Scheter theory and calculate the number density of galaxy clusters and its evolutions. We find that this two quantities are both affected exponentially by the equation of state coefficients of dark energies. We leave the study of this model with the assumption that dark energies do not cluster on the scale of galaxy clusters at all as the topic of another paper where similar conclusions will be obtained also.Comment: two column style, 10 pages, 9 figure

Mass transportation of thermally driven nanotube nanomotors with defects

Thermally driven nanotube nanomotors provide linear mass transportation controlled by a temperature gradient. However, the underlying mechanism is still unclear where the mass transportation velocity in experiment is much lower than that resulting from simulations. Considering that defects are common in fabricated nanotubes, we use molecular dynamics simulations to show that the mass transportation would be considerably impeded by the potential barriers or wells induced by the defects, which provides a possible picture to understand the relative low value at microscopic level. The optimal structure and the factors which would affect the performance are discussed. The result indicates considering defects is helpful in designing nanotube nanomotor and other new nanomotor-based devices.Comment: 5 pages, 5 figure