Modern Physics Letters A

A new S-matrix model is proposed to describe refraction effects in the intermediate energy light nucleus elastic scattering on atomic nuclei. An analysis of experimental data on scattering of ⁴He, ⁶Li and ¹⁶O nuclei by different target nuclei is made on the basis of this model and the near-far decomposition of the scattering amplitude. Comparison of our results with those obtained by the optical model is discussed.

The chiral U(1) anomaly in d=4, N=1 supergravity is evaluated on the basis of the heat kernel method. We consider all gravitino interactions of the theory, i.e. not only the minimal coupling of gravitino and gravitational fields, but also four-gravitino interactions which are treated as two-gravitino interactions in the background field method. We show the explicit form of a new contribution from the four-gravitino interactions to the anomaly.

In recent works by Singer, Douglas, Gopakumar and Gross an application of results of Voiculescu from noncommutative probability theory to constructions of the master field for large-N matrix field theories have been suggested. It turns out that this master field becomes the Boltzmann field in the free Fock space. In this note we consider interrelations between the master field and quantum semigroups. We define the master field algebra and observe that it is isomorphic to the algebra of functions on the quantum semigroup SU_q(2) for q=0. The master field becomes a central element of the quantum group bialgebra. The quantum Haar measure on the SU_q(2) for any q gives the Wigner semicircle distribution for the master field. Coherent states on SU_q(2) become coherent states in the master field theory.

In the framework of the theory of defects/three-dimensional gravitation, a positive correction to the magnetic moment of the electron bound to a disclination in a dielectric solid is obtained.

We investigate the generalized Gross-Neveu model using the discretized light-cone quantization and we find that the vacuum of the bare theory is nontrivial in the presence of vectorial current coupling when the simplest and most natural form of quantum constraints is used. Nevertheless the vacuum of the renormalized theory is trivial.

In the thermodynamic the Bethe-Salpeter equations which are obtained contain all the terms needed to make them finite.

A sufficiently large class of vector sigma models admitting r variable singularities is defined. It is shown how quasihomogeneity induces filtrations on algebras of functions and Lie algebras of infinitesimal diffeomorphisms. From the filtrations, double scaling limits and Airy functions are derived.

Nonperturbative exact flow equations describe the scale dependence of the effective average action. We present a numerical solution for an approximate form of the flow equation for the potential in a three-dimensional N-component scalar field theory. The critical behavior, with associated critical exponents, can be inferred with good accuracy.

Factorization of string amplitudes is one way of constructing string interaction vertices. We show that correlation functions in string theory can be conveniently factorized using loop variables representing delta functionals. We illustrate this construction with some examples where one particle is off-shell. These vertices are “correct” in the sense that they are guaranteed, by construction, to reproduce S-matrix elements when combined with propagators in a well-defined way.