Modern Physics Letters A

We generalize the Walecka model for nuclear matter by including the π-field. It is found that a finite mean π-field may lower the energy per nucleon even in the nuclear matter of subnormal density. A mean π-field may significantly change the nuclear equation of state. The importance of considering the π-field in the relativistic mean field theory for nuclear matter is therefore emphasized.

The classical (1,0) superparticle in a curved superspace is considered. The minimal set of constraints to be imposed on the background for correct inclusion of interaction is found. The most general form of Siegel-type local fermionic symmetry is presented. Gauge algebra of the model is shown to be closed off-shell (by means of adding one trivial symmetry) and deformed as compared to the flat one. The form and algebraic structure of local symmetries of the theory are shown not to be deformed (in comparing with the flat case) in the (1,0) supergravity background only.

We study the relation between lattice construction and surgery construction of three-dimensional topological field theories. We show that a class of the Chung-Fukuma-Shapere theory on the lattice has representation theoretic reformulation which is closely related to the Altschuler-Coste theory constructed by surgery. There is a similar relation between the Turaev-Viro theory and the Reshetikhin-Turaev theory.

The Drinfeld-Sokolov formalism is extended to the case of operator-valued affine Lie algebra to derive nonlinear integrable dynamical systems in (2+1) dimensions. The Poisson structure of these integrable equations are also worked out. While from the first- and second-order flows we get some new integrable equations in (2+1) dimensions, the KP equation is seen to result from the third-order flow. Complete integrability of such equations and the existence of the bi-Hamiltonian structure are demonstrated.

The charged 2-D black hole is visualized as presenting a potential barrier V^out(r*) to incoming tachyon wave. Since this takes the complicated form, an approximate form V^APP(r*) is used for scattering analysis. We calculate the reflection and transmission coefficients for scattering of tachyon off the charged 2-D black hole. The Hawking temperature is also derived from the reflection coefficient by Bogoliubov transformation. In the limit Q→0, we recover the Hawking temperature of the 2-D dilaton black hole.

We propose a model which can be regarded as a mean field approximation for pure lattice QCD and chiral field. It always possesses a phase transition between a strong-coupling phase (where it reduces to a one-plaquette integral) and a nontrivial weak-coupling one. For the U(N) gauge group, it is equivalent to some hermitian multi-matrix model. This analogy allows us to determine possible large-N critical regimes thus generalizing the Gross-Witten phase transition in the one-plaquette model.

It is shown that the approximation of the narrow widths of the f₀ and a₀ resonances, which is used in both theoretical and experimental investigations of the radiative decays ϕ→γa₀ and ϕ→γf₀, is not valid. We will explain that there is a need to take into account the corrections for finite widths.

Hamiltonian lattice gauge models based on the assignment of the Heisenberg double of a Lie group to each link of the lattice are constructed in arbitrary spacetime dimensions. It is shown that the corresponding generalization of the gauge-invariant Wilson line observables requires to attach to each vertex of the line a vertex operator which goes to the unity in the continuum limit.