Modern Physics Letters A

A gauge theory of spin-1/2 Dirac field in four-dimensional space-time is presented. The gauge invariant gravitational interaction is also investigated.

The three-point correlation functions with twist fields are determined for bosonic Z_N orbifolds. Both the choice of the modular background (compatible with the twist) and of the (higher) twisted sectors involved are fully general. We point out a necessary restriction on the set of instantons contributing to twist field correlation functions not obtained in previous calculations. Our results show that the theory is target space duality invariant.

An action for two-dimensional gravity conformally coupled to two dilaton-type fields is analyzed. Classically, the theory has some exact solutions. These include configurations representing black holes. A semiclassical theory is obtained by assuming that these singular solutions are caused by the collapse of some matter fields. The semiclassical equations of motion reveal then that any generic solution must have a flat geometry.

The critical behavior of the D=0 matrix model with the potential perturbed by a nonlocal term generating touchings between random surfaces is studied. It is found that the phase diagram of the model has many features of the phase diagram of discretized Polyakov’s bosonic string with higher order curvature terms included. It contains the phase of smooth (Liouville) surfaces, the intermediate phase and the phase of branched polymers. The perturbation becomes irrelevant at the first phase and dominates at the third one.

Parity and CP violation in W boson decay are discussed. It is shown that CP test is possible by measuring the angular distribution in a W boson non-suppressed two-body decay mode without the polarization measurement of the final state fermions. We found that LEP200 and next linear collider (NLC) have non-trivial sensitivity on the right-handed coupling and CP violation. LEP200 will slightly improve the present limit on the right-handed coupling in the coupling, and have sensitivity on the relative magnitude of the CP violation to the P violation up to 8×10⁻². NLC will improve the former by some factor or even an order of magnitude, and have sensitivity on the latter up to 10⁻³–10⁻².

Two-dimensional supergravity in the light-cone gauge is canonically discussed and osp(1/2) generators are written in terms of the canonical variables.

We analyze the new states that have recently been discovered in 2D string theory by E. Witten and B. Zwiebach. Since the Liouville direction is uncompactified, we show that the deformations by the new ghost number two states generate equivalent classical solutions of the string fields. We argue that the new ghost number one states are responsible for generating transformations which relate such equivalent solutions. We also discuss the possible interpretation of higher ghost number states of these.

We apply the method of coadjoint orbits of W_∞-algebra to the problem of non-relativistic fermions in one dimension. This leads to a geometric formulation of the quantum theory in terms of the quantum phase space distribution of the Fermi fluid. The action has an infinite series of expansion in the string coupling, which to leading order reduces to the previously discussed geometric action for the classical Fermi fluid based on the group w_∞ of area-preserving diffeomorphisms. We briefly discuss the strong coupling limit of the string theory which, unlike the weak coupling regime, does not seem to admit a two-dimensional space-time picture. Our methods are equally applicable to interacting fermions in one dimension.

We study the QCD vacuum orientation angles in correlation with the strong CP phases. A vacuum alignment equation of the dynamical chiral symmetry breaking is derived based on the anomalous Ward identity. It is emphasized that a chiral rotation of the quark field causes a change of the vacuum orientation and a change in the definition of the light pseudoscalar generators. As an illustration of the idea, η→2π decays are carefully studied in different chiral frames.