1,507 research outputs found
Super Landau Models on Odd Cosets
We construct d=1 sigma models of the Wess-Zumino type on the SU(n|1)/U(n)
fermionic cosets. Such models can be regarded as a particular supersymmetric
extension (with a target space supersymmetry) of the classical Landau model,
when a charged particle possesses only fermionic coordinates. We consider both
classical and quantum models, and prove the unitarity of the quantum model by
introducing the metric operator on the Hilbert space of the quantum states,
such that all their norms become positive-definite. It is remarkable that the
quantum n=2 model exhibits hidden SU(2|2) symmetry. We also discuss the planar
limit of these models. The Hilbert space in the planar n=2 case is shown to
carry SU(2|2) symmetry which is different from that of the SU(2|1)/U(1) model.Comment: 1 + 33 pages, some typos correcte
Theoretical and experimental study of high-pressure synthesized B20-type compounds Mn(Co,Rh)Ge
The search and exploration of new materials not found in nature is one of
modern trends in pure and applied chemistry. In the present work, we report on
experimental and \textit{ab initio} density-functional study of the
high-pressure-synthesized series of compounds Mn(Co,Rh)Ge. These
high-pressure phases remain metastable at normal conditions, therewith they
preserve their inherent noncentrosymmetric B20-type structure and chiral
magnetism. Of particular interest in these two isovalent systems is the
comparative analysis of the effect of (Co) and (Rh) substitution for
Mn, since the orbitals are characterized by higher localization and
electron interaction than the orbitals. The behavior of
Mn(Co,Rh)Ge systems is traced as the concentration changes in the
range . We applied a sensitive experimental and theoretical
technique which allowed to refine the shape of the temperature dependencies of
magnetic susceptibility and thereby provide a new and detailed
magnetic phase diagram of MnCoGe. It is shown that both systems
exhibit a helical magnetic ordering that very strongly depends on the
composition . However, the phase diagram of MnCoGe differs from
that of MnRhGe in that it is characterized by coexistence of two
helices in particular regions of concentrations and temperatures.Comment: 12 pages, 11 figure
Analysis of the time reserve influence on the technological cell productivity
Time redundancy, widely used in technical systems, is one of the methods to improve the reliability and efficiency of technical systems. In this paper, the effect of instantly replenishing the time reserve on the productivity of a technical system is considered. Formulas of productivity of a technological cell in cases of random, constant and exponential time reserve are received, numerical results are given
Orientational Order-Disorder Effects in Molecular Crystals as Evidenced by Low-Frequency Raman Spectra
The studies of reorientational motions of molecules in crystals
of organic compounds by low-frequency Raman spectroscopy are
briefly reported. Some examples illustrate the efficiency of the
investigation of order-disorder phenomena in organic crystals by
the temperature dependence of low-frequency vibrational spectra
combined with simultaneous calculations of the molecular dynamics
by the atom-atom potentials (AAP) method. The conditions have been determined which are necessary in order to affect the low-frequency Raman spectra by anisotropy of molecular reorientations in crystals
Strong-Coupling Superconductivity of CeIrSi with the Non-centrosymmetric Crystal Structure
We studied the pressure-induced superconductor CeIrSi with the
non-centrosymmetric tetragonal structure under high pressure. The electrical
resistivity and ac heat capacity were measured in the same run for the same
sample. The critical pressure was determined to be = 2.25 GPa,
where the antiferromagnetic state disappears. The heat capacity
shows both antiferromagnetic and superconducting transitions at pressures close
to . On the other hand, the superconducting region is extended to
high pressures of up to about 3.5 GPa, with the maximum transition temperature
= 1.6 K around GPa. At 2.58 GPa, a large heat capacity
anomaly was observed at = 1.59 K. The jump of the heat capacity in
the form of is 5.7 0.1.
This is the largest observed value among previously reported superconductors,
indicating the strong-coupling superconductivity. The electronic specific heat
coefficient at is, however, approximately unchanged as a function
of pressure, even at .Comment: This paper will be published in J. Phys. Soc. Jpn. on the August
issue of 200
Reachability problems for PAMs
Piecewise affine maps (PAMs) are frequently used as a reference model to show
the openness of the reachability questions in other systems. The reachability
problem for one-dimentional PAM is still open even if we define it with only
two intervals. As the main contribution of this paper we introduce new
techniques for solving reachability problems based on p-adic norms and weights
as well as showing decidability for two classes of maps. Then we show the
connections between topological properties for PAM's orbits, reachability
problems and representation of numbers in a rational base system. Finally we
show a particular instance where the uniform distribution of the original orbit
may not remain uniform or even dense after making regular shifts and taking a
fractional part in that sequence.Comment: 16 page
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