arXiv subjects

Wu-Sheng Dai

Publications and source records attributed to Wu-Sheng Dai.

68 records · Page 4Linked to original sources

arXiv2007

Gentile statistics with a large maximum occupation number

In Gentile statistics the maximum occupation number can take on unrestricted integers: $1 1 the Bose-Einstein case is not recovered from Gentile statistics as n goes to % N . Attention is also concentrated on the contribution of the ground state which was ignored in related literature. The thermodynamic behavior of a $% ν$-dimensional Gentile ideal gas of particle of dispersion $E=\frac{p^{s}%}{2m}$, where $ν$ and s are arbitrary, is analyzed in detail. Moreover, we provide an alternative derivation of the partition function for Gentile statistics.

cond-mat.stat-mech↗

arXiv2007

Intermediate-statistics quantum bracket, coherent state, oscillator, and representation of angular momentum (su(2)) algebra

In this paper, we first discuss the general properties of an intermediate-statistics quantum bracket, $[ u,v]_{n}=uv-e^{i2π/(n+1)}vu$, which corresponds to intermediate statistics in which the maximum occupation number of one quantum state is an arbitrary integer, $n$. A further study of the operator realization of intermediate statistics is given. We construct the intermediate-statistics coherent state. An intermediate-statistics oscillator is constructed, which returns to bosonic and fermionic oscillators respectively when $n\to \infty $ and $n=1$. The energy spectrum of such an intermediate-statistics oscillator is calculated. Finally, we discuss the intermediate-statistics representation of angular momentum ($su(2)$) algebra. Moreover, a further study of the operator realization of intermediate statistics is given in the Appendix.

quant-ph↗

arXiv2006

The difference of boundary effects between Bose and Fermi systems

In this paper, we show that there exists an essential difference of boundary effects between Bose and Fermi systems both for Dirichlet and Neumann boundary conditions: at low temperatures and high densities the influence of the boundary on the Bose system depends on the temperature but is independent of the density, but for the Fermi case the influence of the boundary is independent of the temperature but depends on the density, after omitting the negligible high-order corrections. We also show that at high temperatures and low densities the difference of the influence of the boundary between Bose and Fermi systems appears in the next-to-leading order boundary contribution, and the leading boundary contribution is independent of the density. Moreover, for calculating the boundary effects at high temperatures and low densities, since the existence of the boundary modification causes the standard virial expansion to be invalid, we introduce a modified virial expansion.

cond-mat.stat-mech↗

arXiv2006

The equation of state for two-dimensional hard-sphere gases: Hard-sphere gases as ideal gases with multi-core boundaries

The equation of state for a two-dimensional hard-sphere gas is difficult to calculate by usual methods. In this paper we develop an approach for calculating the equation of state of hard-sphere gases, both for two- and three-dimensional cases. By regarding a hard-sphere gas as an ideal gas confined in a container with a multi-core (excluded sphere) boundary, we treat the hard-sphere interaction in an interacting gas as the boundary effect on an ideal quantum gas; this enables us to treat an interacting gas as an ideal one. We calculate the equation of state for a three-dimensional hard-sphere gas with spin $j$, and compare it with the results obtained by other methods. By this approach the equation of state for a two-dimensional hard-sphere gas can be calculated directly.

cond-mat.stat-mech↗

arXiv2004

A representation of angular momentum (SU(2)) algebra

This paper seeks to construct a representation of the algebra of angular momentum (SU(2) algebra) in terms of the operator relations corresponding to Gentile statistics in which one quantum state can be occupied by $n$ particles. First, we present an operator realization of Gentile statistics. Then, we propose a representation of angular momenta. The result shows that there exist certain underlying connections between the operator realization of Gentile statistics and the angular momentum (SU(2)) algebra.

cond-mat.stat-mech↗

arXiv2004

Geometry effects in confined space

In this paper we calculate some exact solutions of the grand partition functions for quantum gases in confined space, such as ideal gases in two- and three-dimensional boxes, in tubes, in annular containers, on the lateral surface of cylinders, and photon gases in three-dimensional boxes. Based on these exact solutions, which, of course, contain the complete information about the system, we discuss the geometry effect which is neglected in the calculation with the thermodynamic limit $V\to \infty $, and analyze the validity of the quantum statistical method which can be used to calculate the geometry effect on ideal quantum gases confined in two-dimensional irregular containers. We also calculate the grand partition function for phonon gases in confined space. Finally, we discuss the geometry effects in realistic systems.

cond-mat.stat-mech↗

arXiv2003

Quantum statistics of ideal gases in confined space

In this paper, the effects of boundary and connectivity on ideal gases in two-dimensional confined space and three-dimensional tubes are discussed in detail based on the analytical result. The implication of such effects on the mesoscopic system is also revealed.

quant-ph↗

arXiv2002

Comment on "Bose-Einstein condensation in low-dimensional traps"

We show that the critical temperature of a one-dimensional gas confined by a power-law potential should be lower than that in the paper of Vanderlei Bagnato and Daniel Kleppner. Moreover, a sketch of the critical temperature is given in some more details.

quant-ph↗

arXiv2002

Electromagnetic Transition in Waveguide with Application to Lasers

The electromagnetic transition of two-level atomic systems in a waveguide is calculated. Compared with the result in free space, the spontaneous emission rate decrease because the phase space is smaller, and meanwhile, some resonance appears in some cases. Moreover, the influence of non-uniform electromagnetic field in a waveguide on absorption and stimulated emission is considered. Applying the results to lasers, a method to enhance the laser power is proposed.

quant-ph↗

arXiv2000

Electromagnetic radiation of baryons containing two heavy quarks

The two heavy quarks in a baryon which contains two heavy quarks and a light one, can constitute a scalar or axial vector diquark. We study electromagnetic radiations of such baryons, (i) Ξ_{(bc)_1} -> Ξ_{(bc)_0}+γ, (ii) Ξ_{(bc)_1}^* -> Ξ_{(bc)_0}+γ, (iii) Ξ_{(bc)_0}^{**}(1/2, l=1) -> Ξ_{(bc)_0}+γ, (iv) Ξ_{(bc)_0}^{**}(3/2, l=1) -> Ξ_{(bc)_0}+γand (v) Ξ_{(bc)_0}^{**}(3/2, l=2) -> Ξ_{(bc)_0}+γ, where Ξ_{(bc)_{0(1)}}, Ξ^*_{(bc)_1} are S-wave bound states of a heavy scalar or axial vector diquark and a light quark, and Ξ_{(bc)_0}^{**}(l is bigger than 1) are P- or D-wave bound states of a heavy scalar diquark and a light quark. Analysis indicates that these processes can be attributed into two categories and the physical mechanisms which are responsible for them are completely distinct. Measurements can provide a good judgment for the diquark structure and better understanding of the physical picture.

hep-ph↗

arXiv1999

Non-Spectator Diquark Effects on Lifetimes of Λ_b, Ω_{b}^{()} and Weak Decay Rates of Σ_{b}^{()}, Ξ_{b}^{(*)}

The difference of τ_{_B} and τ_{_{Λ_b}} indicates the role of the light flavors. We calculate the lifetimes of B-meson and Λ_b based on the weak effective Hamiltonian while assuming the heavy baryon is constructed by a heavy b-quark and a diquark containing two light quarks. In this scenario, we use the information of the measured ratio τ_{_{Λ_b}}/τ_{_B} as input to predict rates of the inclusive weak decays of Σ_{b}^{(*)} and Ξ_{b}^{(*)} into non-bottom final states. We find that these rates of Σ_{b}^{(*)} and Ξ_{b}^{(*)} are much larger than that of B-mesons and Λ_b. We also give the predictions for the lifetimes of Ω_b and Ω_{b}^{*}. Phenomenological implication of our result is discussed.

hep-ph↗

arXiv1998

Determine the parameter Bk of the K0-K0bar system by means of the precise Cabibbo-Kobayashi-Maskawa matrix elements

Taking use of the relation between weak CP phase and the other three mixing angles in Cabibbo-Kobayashi-Maskawa matrix postulated by us before, the uncertainty coming from the weak interaction can be reduced, furthermore, by means of the relation between the calculation result about mixing parameter epsilon from the box diagrams and the related experimental data in K0-K0bar system, the parameter Bk can be extracted. We take Vud, Vub and Vtb as inputs, when we let them vary in the ranges 0.9745<=Vud<=0.9760, 0.0018<=Vub<=0.0045 and 0.9991<=Vtb<=0.9993, we find the permitted window for Bk is 0.444<=Bk<=1.242. With the more precise measurment on the CKM matrix elements in the future, we can determine Bk more precisely.

hep-ph↗

arXiv1998

Non-Spectator Contributions to Inclusive Charmless $B$ Decays

The light quarks inside $B$ mesons are usually treated as spectators and do not affect the decay rates which are assumed to be purely due to b quark decays. In this paper we calculate the non-spectator contributions to inclusive charmless $B$ decays due to the spectator effects. We find that the non-spectator contributions to the branching ratio for $\bar B^0$ are small ($<2\times 10^{-4}$), but the contributions to $ΔS = 0$ and $ΔS = -1$, $B^-$ decay branching ratios can be as large as $-7.5\times 10^{-4}$ and $2\times 10^{-3}$, respectively. These contributions may play an important role in rare charmless $B$ decays.

hep-ph↗

arXiv1996

Study on $ν_μ$, $ν_τ$ Decays and CP-Non Invariance at Early Epoch of the Universe

We study the $ν_μ$ and $ν_τ$ decays in the early epoch of the universe. If $m_{ν_τ}>2m_e$, there would be a CP asymmetry between $ν_τ\rightarrow e^++e^-+ν_e$ and $\barν_τ \rightarrow e^++e^-+\barν_e$. The resultant CP non-invariance is a function of temperature and density and can reach $10^{-7}$ for a reasonable temperature range, but it is noticed that if $m_{ν_τ}>2m_μ\sim 200$ MeV, the CP non-invariance can be much larger.

hep-ph↗