Charmless BcB_{c} →\to PPPP, PVPV decays in the QCD factorization approach

The charmless $B_{c}$ $\to$ $PP$, $PV$~(where $P$ and $V$ denote the light pseudoscalar and vector mesons, respectively) decays can occur only via the weak annihilation diagrams within the Standard Model and provide, therefore, an ideal place to probe the strength of annihilation contribution in hadronic $B_{u,d,s}$ decays. In this paper, we study these kinds of decays in the framework of QCD factorization, by adopting two different schemes: scheme I is similar to the method usually adopted in the QCD factorization approach, while scheme II is based on the infrared behavior of gluon propagator and running coupling. For comparison, in our calculation, we adopt three kinds of wave functions for $B_{c}$ meson. It is found that: (a) The predicted branching ratios in scheme I are, however, quite small and are almost impossible to be measured at the LHCb experiment. (b) In scheme II, by assigning a dynamical gluon mass to the gluon propagator, we can avoid enhancements of the contribution from soft endpoint region. The strength of annihilation contributions predicted in scheme II is enhanced compared to that obtained in scheme I. However, the predicted branching ratios are still smaller than the corresponding ones obtained in the perturbative QCD approach. The large discrepancies among these theoretical predictions indicate that more detailed studies of these decays are urgently needed and will be tested by the future measurements performed at the LHCb experiment.Comment: 25 pages, revtex

Search for the gravitational wave memory effect with the Parkes Pulsar Timing Array

Gravitational wave bursts produced by supermassive binary black hole mergers will leave a persistent imprint on the space-time metric. Such gravitational wave memory signals are detectable by pulsar timing arrays as a glitch event that would seem to occur simultaneously for all pulsars. In this paper, we describe an initial algorithm which can be used to search for gravitational wave memory signals. We apply this algorithm to the Parkes Pulsar Timing Array data set. No significant gravitational wave memory signal is founded in the data set.Comment: Proceedings of IAUS 291 "Neutron Stars and Pulsars: Challenges and Opportunities after 80 years", J. van Leeuwen (ed.); 3 pages, no figur

Quantum torus algebras and B(C) type Toda systems

In this paper, we construct a new even constrained B(C) type Toda hierarchy and derive its B(C) type Block type additional symmetry. Also we generalize the B(C) type Toda hierarchy to the $N$-component B(C) type Toda hierarchy which is proved to have symmetries of a coupled $\bigotimes^NQT_+$ algebra ( $N$-folds direct product of the positive half of the quantum torus algebra $QT$).Comment: 13 Pages, accepted for publication in the Journal of Nonlinear Scienc

Algebraic formulas for the structure constants in symmetric functions

Littlewood-Richardson rule gives the decomposition formula for the multiplication of two Schur functions, while the decomposition formula for the multiplication of two Hall-Littlewood functions or two universal characters is also given by the combinatorial method. In this paper, using the vertex operator realizations of these symmetric functions, we construct the algebraic forms of these decomposition formulas

A Class of Linear-Quadratic-Gaussian (LQG) Mean-Field Game (MFG) of Stochastic Delay Systems

This paper investigates the linear-quadratic-Gaussian (LQG) mean-field game (MFG) for a class of stochastic delay systems. We consider a large population system in which the dynamics of each player satisfies some forward stochastic differential delay equation (SDDE). The consistency condition or Nash certainty equivalence (NCE) principle is established through an auxiliary mean-field system of anticipated forward-backward stochastic differential equation with delay (AFBSDDE). The wellposedness of such consistency condition system can be further established by some continuation method instead the classical fixed-point analysis. Thus, the consistency condition maybe given on arbitrary time horizon. The decentralized strategies are derived which are shown to satisfy the $\epsilon$-Nash equilibrium property. Two special cases of our MFG for delayed system are further investigated.Comment: 16 page

Coupled Hall-Littlewood functions, vertex operators and the qq-boson model

In this paper, we firstly give the definition of the coupled Hall-Littlewood function and its realization in terms of vertex operators. Then we construct the representation of the two-site generalized $q$-boson model in the algebra of coupled Hall-Littlewood functions. Finally, we find that the vertex operators which generate coupled Hall-Littlewood functions can also be used to obtain the partition function of the A-model topological string on the conifold.Comment: 16 Page

Universal Character, Phase Model and Topological Strings on C3\mathbb C^3

In this paper, we consider two different subjects: the algebra of universal characters $S_{[\lambda,\mu]}({\bf x},{\bf y})$ (a generalization of Schur functions) and the phase model of strongly correlated bosons. We find that the two-site generalized phase model can be realized in the algebra of universal characters, and the entries in the monodromy matrix of the phase model can be represented by the vertex operators $\Gamma_i^\pm(z) (i=1,2)$ which generate universal characters. Meanwhile, we find that these vertex operators can also be used to obtain the A-model topological string partition function on $\mathbb C^3$.Comment: 13 Page

Donors of Persistent Neutron-star Low-mass X-ray Binaries

Properties of X-ray luminosities in low-mass X-ray binaries (LMXBs) mainly depend on donors. We have carried out a detailed study of donors in persistent neutron-star LMXBs (PLMXBs) by means of a population synthesis code. PLMXBs with different donors have different formation channels. Our numerical simulations show that more than 90% of PLMXBs have main sequence (MS) donors, and PLMXBs with red giant (RG) donors via stellar wind (Wind) are negligible. In our model, most of neutron stars (NSs) in PLMXBs with hydrogen-rich donors form via core-collapse supernovae, while more than 90% of NSs in PLMXBs with naked helium star (He) donors or white dwarf (WD) donors form via an evolution-induced collapse via helium star ($1.4 \leq M_{\rm He}/M_\odot \leq 2.5$) or an accretion-induced collapses for an accreting ONeMg WD.Comment: 9 pages, 4 figure

An Alternative Symbiotic Channel to Type Ia Supernovae

By assuming an aspherical stellar wind with an equatorial disk from a red giant, we investigate the production of Type Ia supernovae (SNe Ia) via symbiotic channel. We estimate that the Galactic birthrate of SNe Ia via symbiotic channel is between $1.03\times 10^{-3}$ and $2.27\times 10^{-5}$ yr$^{-1}$, the delay time of SNe Ia has wide range from $\sim$ 0.07 to 5 Gyr. The results are greatly affected by the outflow velocity and mass-loss rate of the equatorial disk. Using our model, we discuss the progenitors of SN 2002ic and SN 2006X.Comment: 11pages, 11 figurs. accepted for publication in MNRA

Electronic properties of SnTe-class topological crystalline insulator materials

The rise of topological insulators in recent years has broken new ground both in the conceptual cognition of condensed matter physics and the promising revolution of the electronic devices. It also stimulates the explorations of more topological states of matter. Topological crystalline insulator is a new topological phase, which combines the electronic topology and crystal symmetry together. In this article, we review the recent progress in the studies of SnTe-class topological crystalline insulator materials. Starting from the topological identifications in the aspects of the bulk topology, surface states calculations and experimental observations, we present the electronic properties of topological crystalline insulators under various perturbations, including native defect, chemical doping, strain, and thickness-dependent confinement effects, and then discuss their unique quantum transport properties, such as valley-selective filtering and helicity-resolved functionalities for Dirac fermions. The rich properties and high tunability make SnTe-class materials promising candidates for novel quantum devices.Comment: 15 pages, 15 figures, invited revie