Observation of selective enhancement of the capture of ultracold neutrons by nuclei

The subbarrier reflection of ultracold neutrons (UCNs) from stainless steel (an alloy of iron, nickel, chromium, and titanium) is investigated by means of neutron-radiation analysis. It is found that the increase in the probability of capture of UCNs by nuclei is large compared to the standard theory. The effect is selective, the enhancement factor varying From 3 for iron to 90 for titanium. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 1, 3–8 (10 January 1997)     

On a maximal torus in subgroups of a general linear group

Let k be a field, K/k a finite extension of it of degree n. We denote G=Aut(kK), G_o=Aut(k K) and fix in K a basis ω₁,...,ω_n over k. In this basis, to any automorphism group of kK there corresponds a matrix group, which is denoted by the same symbol. Let G′≤G., In this paper, the conditions under which G′⊎G_o is a maximal torus in G′ are studied. The calculation of N_G′(G′⊎G_o) is carried out, provided that thee conditions are fulfilled. The case G′=SL (kK) is of particular interset. It is known that for Galois extensions and for extensions of algebraic number fields, G′⊎G_o is a maximal torus in G′. Bibligraphy: 2 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 227, 1995. pp. 15–22.     

On the algebraicK-theory of twisted flag varieties

The algebraicK-groups of projective homogeneous varieties are computed. The answer is given in terms ofK-groups of a semisimple algebra canonically associated with the variety. Our results generalize a result of Quillen and a result of Swan, whereK-groups of Severi-Brauer varieties and of smooth projective quadratic hypersurfaces were computed.     

Structure of MCSCF electronic energy domain

The modern version of the process of removing redundant variables in an MCSCF optimization problem is studied on the basis of the manifold theory. It is shown that there exists a simple parametrization of the MCSCF orbital manifold that is convenient for computer implementation of quasi-Newton optimization schemes. A sequential unconstrained optimization technique for minimizing electronic energy with respect to local coordinates is described.     

Construction on nonequilibrium constitution diagrams of the T-n type and their use for analysis of the temperature dependence of phase composition

An examination of the dependence of the free energy of liquid and solid phases on volume in a one-component substance is used as a basis to prove that it is possible to use a conoid law to construct phase diagrams of a new type: temperature-density of the substance (T-n). A similar approach can be applied in a more complicated case: to multicomponent systems and to phases of an arbitrary nature. An analysis is made of nonequilibrium T-n diagrams for Mg constructed in the temperature range from 200 to 1200K by the method indicated. The conditions necessary for Mg to change from equilibrium states to the region in which the liquid and solid phases coexist are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 69–72, August, 1985.