Abstract:
Here we present an experimentally feasible quantum memory for individual polarization photon with long-lived atomic ensembles excitations. Based a process similar to teleportation, the memory is reversible. And the storage information can be effortlessly read out and transferred back to photon. Although it successes with only a probability of 1/4, it is expected valuable in various quantum information processing, especially those cases where polarized photons are employed. The physical requirements are moderate and fit the presest technique.

Abstract:
We give some necessary and sufficient conditions for p.p.-rings without identity to be reduced. Our results strengthen and extend the results of Fraser and Nicholson as well as some recent results we obtained on reduced p.p.-rings with identity.

Abstract:
Denote the 2×2 upper triangular matrix rings over ℤ and ℤp by UTM2(ℤ) and UTM2(ℤp), respectively. We prove that if a ring R is a p.p.-ring, then R is reduced if and only if R does not contain any subrings isomorphic to UTM2(ℤ) or UTM2(ℤp). Other conditions for a p.p.-ring to be reduced are also given. Our results strengthen and extend the results of Fraser and Nicholson on r.p.p.-rings.

Abstract:
A mechanism for leptogenesis at the electroweak scale was investigated in a model of dark energy and dark matter proposed by one of us (PQH). This model involves an asymptotically free gauge group SU(2)Z and an axion-like particle with an SU(2)Z-instanton-induced potential which yields a scenario for the dark energy. Furthermore, the extended particle content of this SU(2)Z model contains a possible candidate for the cold dark matter, namely, the SU(2)Z "shadow" fermion, which couples with the Standard Model lepton through a scalar "messenger field" carrying both SU(2)Z and electroweak quantum numbers. Since these shadow fermions are in a real representation of SU(2)Z, lepton number can be violated in the Yukawa sector and a lepton number asymmetry can be generated in the SU(2)Z particle's decay which is also CP-violating and "out-of-equilibrium". The asymmetry coming from the interference between the tree-level and one-loop amplitudes was calculated for both messenger scalar and shadow fermion decays. It turns out, in order to have a non-vanishing lepton asymmetry and to be consistent with the unitarity condition, some shadow fermions have to decay into lighter messenger scalars, hence could be a candidate "progenitor" for the lepton asymmetry.

Abstract:
We study whether the bias factors of galaxies can be unbiasedly recovered from their power spectra and bispectra. We use a set of numerical N-body simulations and construct large mock galaxy catalogs based upon the semi-analytical model of Croton et al. (2006). We measure the reduced bispectra for galaxies of different luminosity, and determine the linear and first nonlinear bias factors from their bispectra. We find that on large scales down to that of the wavenumber k=0.1h/Mpc, the bias factors b1 and b2 are nearly constant, and b1 obtained with the bispectrum method agrees very well with the expected value. The nonlinear bias factor b2 is negative, except for the most luminous galaxies with M<-23 which have a positive b2. The behavior of b2 of galaxies is consistent with the b2 mass dependence of their host halos. We show that it is essential to have an accurate estimation of the dark matter bispectrum in order to have an unbiased measurement of b1 and b2. We also test the analytical approach of incorporating halo occupation distribution to model the galaxy power spectrum and bispectrum. The halo model predictions do not fit the simulation results well on the precision requirement of current cosmological studies.

Abstract:
We use a set of numerical N-body simulations to study the large-scale behavior of the reduced bispectrum of dark matter and compare the results with the second-order perturbation theory and the halo models for different halo mass functions. We find that the second-order perturbation theory (PT2) agrees with the simulations fairly well on large scales of k<0.05 h/Mpc, but it shows a signature of deviation as the scale goes down. Even on the largest scale where the bispectrum can be measured reasonably well in our simulations, the inconsistency between PT2 and the simulations appears for the colinear triangle shapes. For the halo model, we find that it can only serve as a qualitative method to help study the behavior of Q on large scales and also on relatively small scales. The failure of second-order perturbation theory will also affect the precise determination of the halo models, since they are connected through the 3-halo term in the halo model. The 2-halo term has too much contribution on the large scales, which is the main reason for the halo model to overpredict the bispectrum on the large scales. Since neither of the models can provide a satisfying description for the bispectrum on scales of about 0.1h/Mpc for the requirement of precision cosmology, we release the reduced bispectrum of dark matter on a large range of scales for future analytical modeling of the bispectrum.

Abstract:
In this work, micro/nano-structured Bi_{0.5}Sb_{1.5}Te_{3}bulk thermoelectric materials were synthesized by mechanical alloying from elemental shots of Bi, Sb, and Te. Cold pressing and subsequent heat treatments with hydrogen reduction were used to form bulk solid samples with good thermoelectric properties in the temperature range around 75℃to 100℃. In comparison to crystal growth methods and chemical solution synthesis, the reported technique can be readily implemented for mass production with relatively low cost.

Abstract:
We consider the electromagnetic and transition pion form factors. Using dispersion relations we simultaneously describe both the hadronic, time-like region and the asymptotic region of large energy-momentum transfer. For the latter we propose a novel mechanism of Regge fermion exchange.

Abstract:
By means of certain limit technique, two kinds of generalized Darboux transformations are constructed for the derivative nonlinear Sch\"odinger equation (DNLS). These transformations are shown to lead to two solution formulas for DNLS in terms of determinants. As applications, several different types of high order solutions are calculated for this equation.

Abstract:
We consider the electromagnetic and transition pion form factors. Using dispersion relations we simultaneously describe both the hadronic, time-like region and the asymptotic region of large energy-momentum transfer. For the latter we propose a novel mechanism of Regge fermion exchange. We find that hadronic contributions dominate form factors at all currently available energies.