1,298 research outputs found
Some Remarks on Producing Hopf Algebras
We report some observations concerning two well-known approaches to
construction of quantum groups. Thus, starting from a bialgebra of
inhomogeneous type and imposing quadratic, cubic or quartic commutation
relations on a subset of its generators we come, in each case, to a q-deformed
universal enveloping algebra of a certain simple Lie algebra. An interesting
correlation between the order of initial commutation relations and the Cartan
matrix of the resulting algebra is observed. Another example demonstrates that
the bialgebra structure of sl_q(2) can be completely determined by requiring
the q-oscillator algebra to be its covariant comodule, in analogy with Manin's
approach to define SL_q(2) as a symmetry algebra of the bosonic and fermionic
quantum planes.Comment: 6 pages, LATEX, no figures, Contribution to the Proceedings of the
4th Colloquium "Quantum Groups and Integrable Systems" (Prague, June 1995
On the oscillation properties of eigenfunctions of Sturm--Liouville problem with singular coefficients
In the paper we consider singular spectral Sturm--Liouville problem
, , where function
is uniformly positive, generalized functions are real-valued and unitary matrix
is diagonal. The main goal is to prove that well-known (for smooth case) facts
about number and distribution of zeros of eigenfunctions hold in general case.Comment: 7 page
Dynamic spin susceptibility in the t-J model
A relaxation-function theory for the dynamic spin susceptibility in the
-- model is presented. By a sum-rule-conserving generalized mean-field
approximation (GMFA), the two-spin correlation functions of arbitrary range,
the staggered magnetization, the uniform static susceptibility, and the
antiferromagnetic correlation length are calculated in a wide region of hole
doping and temperaturs. A good agreement with available exact diagonalization
(ED) data is found. The correlation length is in reasonable agreement with
neutron-scattering experiments on La_{2-\delta}Sr_\delta)CuO_4. Going beyond
the GMFA, the self-energy is calculated in the mode-coupling approximation. The
spin dynamics at arbitrary frequencies and wave vectors is studied for various
temperatures and hole doping. At low doping a spin-wave-type behavior is found
as in the Heisenberg model, while at higher doping a strong damping caused by
hole hopping occurs, and a relaxation-type spin dynamics is observed in
agreement with the ED results. The local spin susceptibility and its (\omega/T)
scaling behavior are calculated in a reasonable agreement with experimental and
ED data.Comment: 13 pages, 14 figure
FIRST DATA ON THE CONCENTRATIONS AND DISTRIBUTION OF NOBLE METALS IN NI-CU SULFIDE ORES OF THE SOUTH MAKSUT DEPOSIT (EAST KAZAKHSTAN)
The magmatic sulfide deposits in the Central Asian orogenic belt are hosted in a series of mafic–ultramafic intrusions in the Maksut zone (E Kazakhstan), the Kalatongke and the Huangshan zones in Xinjiang (NW China) and the Hongqiling zone in NE China. In the Maksut zone there are several intrusions, the best studied from which is the South Maksut intrusion with Cu–Ni–PGE mineralization.The magmatic sulfide deposits in the Central Asian orogenic belt are hosted in a series of mafic–ultramafic intrusions in the Maksut zone (E Kazakhstan), the Kalatongke and the Huangshan zones in Xinjiang (NW China) and the Hongqiling zone in NE China. In the Maksut zone there are several intrusions, the best studied from which is the South Maksut intrusion with Cu–Ni–PGE mineralization
Optical and dc conductivities of cuprates: Spin-fluctuation scattering in the t-J model
A microscopic theory of the electrical conductivity within
the t-J model is developed. An exact representation for is
obtained using the memory-function technique for the relaxation function in
terms of the Hubbard operators, and the generalized Drude law is derived. The
relaxation rate due to the decay of charge excitations into particle-hole pairs
assisted by antiferromagnetic spin fluctuations is calculated in the
mode-coupling approximation. Using results for the spectral function of spin
excitations calculated previously, the relaxation rate and the optical and dc
conductivities are calculated in a broad region of doping and temperatures. The
reasonable agreement of the theory with experimental data for cuprates proves
the important role of spin-fluctuation scattering in the charge dynamics.Comment: 13 pages,15 figures, v.2, publication referenc
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