Li Xi-Guo

Gravitational Corrections to Energy-Levels of a Hydrogen Atom

The first-order perturbations of the energy levels of a hydrogen atom in central internal gravitational field are investigated. The internal gravitational field is produced by the mass of the atomic nucleus. The energy shifts are calculated for the relativistic 1S, 2S, 2P, 3S, 3P, 3D, 4S, and 4P levels with Schwarzschild metric. The calculated results show that the gravitational corrections are sensitive to the total angular momentum quantum number.

Isospin Effects of the Mean Field and Two-Body Collision on the Fragmentation Process

Isospin effects of the mean field and two-body collision on the fragmentation as well as their dependences on the momentum-dependent interaction at intermediate energy heavy ion collisions are studied by using an isospin-dependent quantum molecular dynamics model. We find the prominent isospin effects of the multiplicity of the intermediate mass fragments Nimf, where Nimf depends sensitively on the isospin effect of the in-medium nucleon-nucleon cross section and weakly on the variation of symmetry potential in the intermediate energy region. The momentum dependence interaction enhances the sensitivity of Nimf on the isospin effect of two-body collision.

Isospin Effect of Coulomb Interaction on Momentum Dissipation in Intermediate Energy Heavy Ion Collisions

We investigate the isospin effect of Coulomb interaction on the momentum dissipation or nuclear stopping in the intermediate energy heavy ion collisions by using the isospin-dependent quantum molecular dynamics model. The calculated results show that the Coulomb interaction induces obviously the reductions of the momentum dissipation. We also find that the variation amplitude of momentum dissipation induced by the Coulomb interaction depends sensitively on the form and strength of symmetry potential. However, the isospin effect of Coulomb interaction on the momentum dissipation is less than that induced by the in-medium nucleon–nucleon cross section. In this case, Coulomb interaction does not change obviously the isospin effect of momentum dissipation induced by the in-medium two-body collision. In particular, the Coulomb interaction is preferable for standing up the isospin effect of in-medium nucleon–nucleon cross section on the momentum dissipation and reducing the isospin effect of symmetry potential on it, which is important for obtaining the feature about the sensitive dependence of momentum dissipation on the in-medium nucleon–nucleon cross section and weakly on the symmetry potential.

Topological Structure of Vortex Solution in Jackiw-Pi Model

By using phi-mapping method, we discuss the topological structure of the self-duality solution in Jackiw-Pi model in terms of gauge potential decomposition. We set up relationship between Chern-Simons vortex solution and topological number, which is determined by Hopf index and Brouwer degree. We also give the quantization of flux in this case. Then, we study the angular momentum of the vortex, which can be expressed in terms of the flux.Abstract By using φ -mapping method, we discuss the topological structure of the self-duality solution in Jackiw-Pi model in terms of gauge potential decomposition. We set up relationship between Chern-Simons vortex solution and topological number which is determined by Hopf index and Brouwer degree. We also give the quantization of flux in this case. Then, we study the angular momentum of the vortex, it can be expressed in terms of the flux.

Gasser–Leutwyler Coefficients of Chiral Lagrangian for Pseudoscalar Goldstone Bosons

Based on the Dyson-Schwinger equations in rainbow approximation for quark propagator with an effective gluon propagator, and on the parametrized fully dressed quark propagator proposed by us, the unknown Gasser-Leutwyler coefficients of the chiral Lagrangian for pseudoscalar Goldstone bosons, Li, are predicted respectively. The predicted values of Li in the two different ways are not only in reasonable agreement each other but also in agreement with empirical values used widely in literature and the values predicted by many other theoretical models with QCD characteristics. The compatible results of Gasser-Leutwyler coefficients predicted by our parameterized quark propagator,in turn, clearly verify its extensive validity.

Decomposition of Noncommutative U(1) Gauge Potential

We investigate the decomposition of noncommutative gauge potential i, and find that it has inner structure, namely, i can be decomposed in two parts, i and i, where i satisfies gauge transformations while i satisfies adjoint transformations, so dose the Seiherg–Witten mapping of noncommutative U(1) gauge potential. By means of Seiberg–Witten mapping, we construct a mapping of unit vector field between noncommutative space and ordinary space, and find the noncommutative U(1) gauge potential and its gauge field tensor can be expressed in terms of the unit vector field. When the unit vector field has no singularity point, noncommutative gauge potential and gauge field tensor will equal ordinary gauge potential and gauge field tensor

Angular momentum of a brane-world model*

In this paper we discuss the properties of the general covariant angular momentum of a five-dimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of the inflationary RS model are all zero while the others are non-zero, which agrees with the results from ordinary RS model.In this paper we discuss the properties of the general covariant angular momentum of a five-dimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of are all zero while the others are non-zero, which agrees with the results from ordinary RS model.

Connection Between Quantum–Classical Correspondence and Long-Range Correlations in Quantum Spectra

Based on the Berry–Tabor trace formula, a semiclassical quantization condition for the periodic orbits in a two-dimensional uncoupled oscillator system and the correspondence relation between the quantum levels and classical trajectories of the system have been studied in detail. Making use of the quantum–classical correspondence relation, it has been found that if a set of quantum levels corresponds to the periodic orbits with the same topology structure M(M1,M2), there will be long-range correlations among these quantum levels.