黄克孙与杨振宁

介绍了物理学家兼诗人黄克孙先生的著作和经历,特别考察了他与杨振宁先生的特殊友情以及在玻色气方面的合作研究详情。

Dynamics of an Ultracold Bose Gas in Funnel-Shaped Potential

In this paper we develop a variational theory to study the dynamic properties of ultracold Bose gas ina funnel external potential.We obtain one-dimensional nonlinear equation which describes the dynamics of transversetight confined bosonic gas from three-dimension to one-dimension,and find one-dimensional s-wave scattering lengthwhich depends on the shape of transverse confining potential.If the funnel trapping potential is strong enough at zerotemperature,all transverse excitations are frozen.We find the dynamic equation which describes the Tonks-Girardeaugas and present a qualitative analysis of the experimental accessibility of the Tonks-Girardeau gas with funnel-trappedalkalic atoms.

Functional Integral Approach to Transition Temperature of a Homogeneous ImperfectBose Gas

A functional integral approach (FIA) is introduced to calculate the transition temperature of a uniform imperfect Bose gas. With this approach we find that the transition temperature is higher than that of the corresponding ideal gas. We obtain the expression of the transition temperature shift as , where n is the density of particle number and a is the scattering length. The result has never been reported in the literature.

Effect of Spatial Dimension and External Potential on Joule-Thomson Coefficients of Ideal Bose Gases

Based on the form of the n-dimensional generic power-law potential, the state equation and the heat capacity, the analytical expressions of the Joule-Thomson coefficient （3TC） for an ideal Bose gas are derived in n-dimensional potential. The effect of the spatial dimension and the external potential on the JTC are discussed, respectively. These results show that： （i） For the free ideal Bose gas, when n/s ≤ 2 （n is the spatial dimension, s is the momentum index in the relation between the energy and the momentum）, and T → Tc （Tc is the critical temperature）, the JTC can obviously improve by means of changing the throttle valve＇s shape and decreasing the spatial dimension of gases. （ii） For the inhomogeneous external potential, the discriminant △= [1 - y∏^ni=1（kT/εi）^1/tiГ（1/ti＋1）] （k is the Boltzmann Constant, T is the thermodynamic temperature, ε is the external field＇s energy）, is obtained. The potential makes the JTC increase when △ 〉 0, on the contrary, it makes the JTC decrease when A 〈△. （iii） In the homogenous strong external potential, the JTC gets the maximum on the condition of kTεi〈〈1.

Fragmented condensates of singly trapped dipolar Bose gases

By employing the method of the multiconfigurational time-dependent Hartree for bosons,we investigate the ground state properties of a singly trapped dipolar gas of spinless bosons.We show that the repulsive interactions favor the formation of the fragmented ground state.In particular,we find the formation of the fragmented state is mainly due to the interaction energies associated with the one-and two-particle exchanges between orbitals.We also obtain the stability diagram of the system and find that the stability of the system is significantly enhanced by the appearance of the fragmentation.

quantum gases power law potential grand potential condensation hierarchy

The changes in characteristics of Bose condensation of ideal Bose gas due to an external generic power law potential U =∑~d_（i=1）ci｜xi/ai｜~（ni） are studied carefully. Detailed calculation of Kim et al.（J. Phys. Condens. Matter 11（1999） 10269） yielded the hierarchy of condensation transitions with changing fractional dimensionality. In this manuscript, some theorems regarding specific heat at constant volume CV are presented. Careful examination of these theorems reveal the existence of hidden hierarchy of the condensation transition in trapped systems as well.

Collective Excitations of Low Dimensional Trapped Bose-Condensed Gas

In this paper, we investigate excited characteristic of the weakly interacting quasi-one-dimensional （11）） and quasi-two-dimensional （2D） Bose-Einstein condensation （BEC） in harmonic potential trap. The energ3, spectrum and the analytical expression of the sound velocity are obtained and analyzed. Compared with 3-Dimensional homogeneous Bose-condensed gas occasion, the sound velocity of 21） Bose-Einstein condensation in harmonic potential trap is smaller.

Magnetic lattices for ultracold atoms and degenerate quantum gases

We review recent developments in the use of magnetic lattices as a complementary tool to optical lattices for trapping periodic arrays of ultracold atoms and degenerate quantum gases. Recent advances include the realisation of Bose–Einstein condensation in multiple sites of a magnetic lattice of one-dimensional microtraps, the trapping of ultracold atoms in square and triangular magnetic lattices,and the fabrication of magnetic lattice structures with submicron period suitable for quantum tunnelling experiments.Finally, we describe a proposal to utilise long-range interacting Rydberg atoms in a large spacing magnetic lattice to create interactions between atoms on neighbouring sites.

Virial Coefficients from Unified Statistical Thermodynamics of Quantum Gases Trapped under Generic Power Law Potential in d Dimension and Equivalence of Quantum Gases

From the unified statistical thermodynamics of quantum gases, the virial coefficients of ideal Bose and Fermi gases, trapped under generic power law potential are derived systematically. From the general result of virial coefficients, one can produce the known results in d = 3 and d = 2. But more importantly we found that, the virial coefficients of Bose and Fermi gases become identical(except the second virial coefficient, where the sign is different)when the gases are trapped under harmonic potential in d = 1. This result suggests the equivalence between Bose and Fermi gases established in d = 1(J. Stat. Phys. DOI 10.1007/s10955-015-1344-4). Also, it is found that the virial coefficients of two-dimensional free Bose(Fermi) gas are equal to the virial coefficients of one-dimensional harmonically trapped Bose(Fermi) gas.