41,223 research outputs found
Charmless , decays in the QCD factorization approach
The charmless , ~(where and 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
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 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 -component B(C) type Toda hierarchy which is
proved to have symmetries of a coupled algebra ( -folds
direct product of the positive half of the quantum torus algebra ).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 -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 -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 -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
In this paper, we consider two different subjects: the algebra of universal
characters (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 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 .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 () 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 and
yr, the delay time of SNe Ia has wide range from 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
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