Spinor Bose Condensates in Optical Traps

In an optical trap, the ground state of spin-1 Bosons such as $^{23}$Na, $^{39}$K, and $^{87}$Rb can be either a ferromagnetic or a "polar" state, depending on the scattering lengths in different angular momentum channel. The collective modes of these states have very different spin character and spatial distributions. While ordinary vortices are stable in the polar state, only those with unit circulation are stable in the ferromagnetic state. The ferromagnetic state also has coreless (or Skyrmion) vortices like those of superfluid $^{3}$He-A. Current estimates of scattering lengths suggest that the ground states of $^{23}$Na and $^{87}$Rb condensate are a polar state and a ferromagnetic state respectively.Comment: 11 pages, no figures. email : [email protected]

Lead-free Perovskite Materials for Solar Cell: An Update of Recent Trends

Solar energy has emerged as renewable energy to support human and social development. The development of low-cost, high-efficiency perovskite solar cell has attracted intensive attention because of unique properties such as band gap tenability, stability and high absorption co-efficient value. Research indicates that the power conversion efficiency of lead perovskite solar cell has increased from 3.8% to 25.2% recently. However, the main challenges in this type of solar cell was lead element. Lead is very toxic and very hard to discharge from the body. Therefore, researchers work hard to develop non or low toxic metal ions to substitute lead in solar cell. In this work, different lead-free perovskite materials (tin, germanium, caesium, copper, bismuth and antimony) and related photovoltaic behaviors were reported. The band gap, absorption efficiency, power conversion efficiency, fill factor, short circuit current, open circuit voltage and other physical properties for all of lead-free materials were highlighted. Tin based perovskites showed very high absorption coefficient. Bismuth and antimony were very stable because of +3 valence state in the atmosphere. Finally, the review also describes some challenges facing the performance of solar cells

Third-order many-body perturbation theory calculations for the beryllium and magnesium isoelectronic sequences

Relativistic third-order MBPT is applied to obtain energies of ions with two valence electrons in the no virtual-pair approximation (NVPA). A total of 302 third-order Goldstone diagrams are organized into 12 one-body and 23 two-body terms. Only third-order two-body terms and diagrams are presented here, owing to the fact that the one-body terms are identical to the previously studied third-order terms in monovalent ions. Dominant classes of diagrams are identified. The model potential is a Dirac-Hartree-Fock $V^{N-2}$ potential, and B-spline basis functions in a cavity of finite radius are employed in the numerical calculations. The Breit interaction is taken into account through second order of perturbation theory and the lowest-order Lamb shift is also evaluated. Sample calculations are performed for berylliumlike ions with Z = 4--7, and for the magnesiumlike ion P IV. The third-order energies are in excellent agreement with measurement with an accuracy at 0.2% level for the cases considered. Comparisons are made with previous second-order MBPT results and with other calculations. The third-order energy correction is shown to be significant, improving second-order correlation energies by an order of magnitude

Distribution amplitudes and decay constants for (π,K,ρ,K∗)(\pi,K,\rho,K^*) mesons in light-front quark model

We present a calculation of the quark distribution amplitudes(DAs), the Gegenbauer moments, and decay constants for $\pi,\rho,K$ and $K^*$ mesons using the light-front quark model. While the quark DA for $\pi$ is somewhat broader than the asymptotic one, that for $\rho$ meson is very close to the asymptotic one. The quark DAs for $K$ and $K^*$ show asymmetric form due to the flavor SU(3)-symmetry breaking effect. The decay constants for the transversely polarized $\rho$ and $K^*$ mesons($f^T_\rho$ and $f^T_{K^*}$) as well as the longitudinally polarized ones($f_\rho$ and $f_{K^*}$) are also obtained. Our averaged values for $f^T_V/f_V$, i.e. $(f^T_\rho/f_\rho)_{\rm av}=0.78$ and $(f^T_{K^*}/f_{K^*})_{\rm av}=0.84$, are found to be consistent with other model predictions. Especially, our results for the decay constants are in a good agreement with the SU(6) symmetry relation, $f^T_{\rho(K^*)}=(f_{\pi(K)}+f_{\rho(K^*)})/2$.Comment: 12 pages, 6figure

Analytic continuation of single-particle resonance energy and wave function in relativistic mean field theory

Single-particle resonant states in spherical nuclei are studied by an analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean field (RMF) theory. Taking the neutron resonant state $\nu 1g_{9/2}$ in $^{60}$Ca as an example, we examine the analyticity of the eigenvalue and eigenfunction for the Dirac equation with respect to the coupling constant by means of a \pade approximant of the second kind. The RMF-ACCC approach is then applied to $^{122}$Zr and, for the first time, this approach is employed to investigate both the energies, widths and wave functions for $l\ne 0$ resonant states close to the continuum threshold. Predictions are also compared with corresponding results obtained from the scattering phase shift method.Comment: 19 pages, 9 figure

Determination of Vitamin C in Fresh Fruits and Vegetables Using the Dye-titration and Microfluorometric Methods

The vitamin C content of19 types of fresh fruits and 24 vegetables was determined by the official AOAC methods of dye-titration and microfluorometry. As expected, values obtained by the latter method, which estimated ascorbic acid plus dehydroascorbic acid (DHAA), were clearly higher than those given by the titration method, which determined only ascorbic acid. There were considerable differences in the values obtained by the two methods, depending on the concentration ofDHAA in the foods. Larger differences were obtained for the vegetables. The mean recovery value obtained by the dye-titration method was significantly higher than that given by the fluorometric method (p <0.01). Reproducibility studies showed that the two methods did not give significantly different variances (p < 0.05). If only ascorbic acid values were required, the titrimetric procedure would give good results, and it may be ca"ied out rapidly using simple laboratory equipment. If a fluorometer was available, total vitamin C values, which would be more useful from the nutritional point of view, could be determined

Supergalactic winds driven by multiple superstar clusters

We present two dimensional hydrodynamic calculations of free expanding supergalactic winds, taking into consideration strong radiative cooling. Our main premise is that supergalactic winds are powered by collections of superstar clusters. Every individual superstar cluster is a source of a high metallicity radiative supersonic outflow (paper I, 2003, ApJ, 590, 791). The interaction of winds from neighboring knots of star formation is shown to lead to a collection of stationary oblique shocks and crossing shocks, able to structure the general outflow into a network of dense and cold, kpc long filaments that originate near the base of the outflow. The shocks also lead to extended regions of diffuse soft X-ray emission and furthermore, to channel the outflow with a high degree of collimation into the intergalactic medium.Comment: 10 pages, 5 figures, Accepted for publication in The Astrophysical Journa

Generalized Rayleigh and Jacobi processes and exceptional orthogonal polynomials

We present four types of infinitely many exactly solvable Fokker-Planck equations, which are related to the newly discovered exceptional orthogonal polynomials. They represent the deformed versions of the Rayleigh process and the Jacobi process.Comment: 17 pages, 4 figure

Effect of disorder on a Pomeranchuk instability

We study the effect of disorder on the order parameter equation and transition temperature of a Pomeranchuk-type Fermi-surface instability using replica mean field theory. We consider the example of a phase transition to a $d_{x^2 +y^2}$ type Fermi surface distortion, and show that, in the regime where such a transition is second order, the transition temperature is reduced by disorder in essentially the same way as that for a d-wave superconductor. We argue that observing this disorder dependence of metal-to-metal transition might be a useful indicator of a finite angular momentum Fermi surface distortion.Comment: 4.1 pages, 3 figs. Version as published in EPL. Added data of Sr3Ru2O7 to theory curves of Fig.2, and some clarification of derivation of result