C. Cronström

A Simple and Complete Lorentz-Covariant Gauge Condition

Abstract We discuss a very simple gauge condition, for abelian or non-abelian gauge theories, which is both Lorentz-covariant and complete. Using this gauge a straightforward solution to the problem of expressing the vector potential A in terms of the field strength G is obtained.

On topological boundary characteristics in nonabelian gauge theory

We study a topological classification of gauge potentials based on an examination of the Chern–Simons surface term C(U) at appropriate boundary components of the space‐time manifold when the potential approaches a pure gauge dU U−1 at the boundary. We derive an explicit local formula for a 2‐form H(U) such that C(U)=dH(U).

Zeroes of the pion form factor

Abstract We derive a sum-rule for the modulus of the pion formfactor in the time-like region, by means of which one can test the existence of complex zeroes in the formfactor. The available data indicates that such zeroes exist.

Photon induced relativistic band structure in dielectrics

Abstract We show that an electromagnetic plane wave field induces a band structure for electron scattering in a refractive medium. This can lead to a new type of diffractive scattering of electrons in the medium.

Generalized O(1, 2) expansions of multiparticle amplitudes

Abstract We develop the formalism for making generalized O (1, 2) expansions of multiparticle amplitudes involving particles with arbitrary (nonzero) mass and spin. It is found that such expansions can be made for very general classes of amplitudes; in addition to the requirement of the existence of certain kinematic zeroes, essentially only power boundedness in the expansion variable is required. The physical meaning of the various spin and kinematic variables that occur in the expansion is analyzed in detail. A comparison between the O (1, 2) and usual Regge expansions for two-particle amplitudes is made and a fundamental difference between these two types of expansions is pointed out.

Multi-Hamiltonian structure of Lotka-Volterra and quantum Volterra models

Abstract We consider evolution equations of the Lotka-Volterra type, and elucidate especially their formulation as canonical Hamiltonian systems. The general conditions under which these equations admit several conserved quantities (multi-Hamiltonians) are analysed. A special case, which is related to the Liouville model on a lattice, is considered in detail, both as a classical and as a quantum system.

First-order Lagrangians and the Hamiltonian formalism

Abstract We consider the problem of constructing a general unconstrained Hamiltonian formalism for a system with a finite number of degrees of freedom, starting from a general first-order Lagrangian. This construction, which uses only elements of linear algebra and the theory of partial differential equations, is given in a rather explicit form. An application of the formalism to the quantization of two-dimensional real self-dual fields is given.

Third-order phase transition and superconductivity in thin films

We have found a new mean field solution in the BCS theory of superconductivity. This unconventional solution indicates the existence of superconducting phase transitions of third order in thin films, or in bulk matter with a layered structure. The critical temperature increases with decreasing thickness of the layer, and does not exhibit the isotope effect. The electronic specific heat is a continuous function of temperature with a discontinuity in its derivative.

ALGEBRAIC STRUCTURE OF WEINBERG'S FIRST SUPERCONVERGENCE CONDITION.

Abstract We show that Weinbergs first superconvergence condition for p-wave hadron interaction leads to the group SU(2) ⊎ SU(4). A few p-wave decay rates are calculated and found to agree well with experiment.

Quantization of non-abelian gauge theory. I. Gauge invariant Hamiltonian formulation

Abstract An essentially gauge invariant canonical Hamiltonian formulation is given for a non-Abelian Yang-Mills system coupled to a fermion field. The Hamiltonian contains only unconstrained dynamical variables, which in the quantum version satisfy canonical equal time commutation relations.