Pre-Asymptotic Analysis of the Scattering Problem

JETP Letters - The pre-asymptotic analysis of the multichannel scattering problem for particles with an arbitrary spin and short-range interactions has been presented. The complete operator-valued...     

“Fine-tuning” renormalization and associated constants in a nonrelativistic four-fermion model

Exact solutions of a two-particle eigenvalue problem are obtained for a four-fermion contact interaction. Composite Goldstone modes are found. A relationship, is found between the renormalization procedure and the construction of self-adjoint solutions. Irkutsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 62–66, July, 1997.     

Spin waves in dilute ferromagnetic alloys of Pd-Fe type

The concentration dependence of spin waves stiffness coefficient in Pd-Fe alloys is calculated. Our results are in a good agreement with experimental results.     

Linear positive magnetoresistance and quantum interference in ferromagnetic metals

Positive, linear in field, and isotropic magnetoresistance in fields up to 60 T is found in geometrically constrained ferromagnets, such as thin films of iron, nickel, and cobalt and their granular mixtures with nonmagnetic materials. The resistivity measured as a function of temperature shows a minimum at temperatures reaching a remarkably high 92 K, followed by logarithmic dependence at low temperatures. We propose to explain both phenomena by a modified version of the quantum electron-electron interaction theory. The agreement is only qualitative while the observed magnitude of the magnetoresistance slope is much larger than the calculated one.     

Integration of the thirring model equations

It is demonstrated that an exact solution for the Thirring massless model in the canonical quantization scheme follows from its Heisenberg equations in the method of dynamic mapping and the presence of unitary nonequivalent representations of the Dirac massless field.     

On fermionic tilde conjugation rules and thermal bosonization. Hot and cold thermofields

A generalization of Ojima tilde conjugation rules is suggested, which is useful for the thermofield bosonization. The notion of hot and cold thermofields is introduced to distinguish different thermofield representations giving the correct normal form of thermofield solution for finite temperature Thirring model with correct renormalization and anticommutation properties.     

Higher order corrections to the Grimus-Stockinger formula

For the Grimus-Stockinger formula the same dimensionless parameter of asymptotic expansion is found by several ways of calculations. This parameter strongly depends on the width of wave packet.     

Unusual symmetries in the Kugel-Khomskii Hamiltonian

The Kugel-Khomskii Hamiltonian for cubic titanates describes spin and orbital superexchange interactions between d(1) ions having threefold degenerate t(2g) orbitals. Since orbitals do not couple along "inactive" axes, perpendicular to the orbital planes, the total number of electrons in |alpha> orbitals in any such plane and the corresponding total spin are both conserved. A Mermin-Wagner construction shows that there is no long-range spin ordering at nonzero temperatures. Inclusion of spin-orbit coupling allows such ordering, but even then the excitation spectrum is gapless due to a continuous symmetry. Thus, the observed order and gap require more symmetry breaking terms.