Analysis of intermediate boson spectra from FIR data for HTSC and heavy fermion systems

Calculations of the effect of intermediate bosons on the optical properties of the normal state are used to analyze the spectra of these bosons. For high temperature superconductors these spectra are in agreement with the standard electron-phonon model (the end of the spectrum is near 800 cm^–1) with a moderate coupling constant =1–1.5. For the heavy fermion compound UPt₃ the spectrum of intermediate bosons is consistent with neutron data for spin fluctuations.This work was partially supported by ISF and RFFI (No 94-02-04186a) grants.     

High frequency curvature oscillations in <Emphasis Type="Italic">F</Emphasis>(<Emphasis Type="Italic">R</Emphasis>) gravity

It is argued that F(R) modified gravity generically leads to high frequency curvature oscillations in astrophysical systems with rising mass/energy density. Potentially observational manifestations of such oscillations are discussed. In particular, gravitational repulsion in finite-size objects, forbidden in standard General Relativity, is shown to exist. Also an alternation of density perturbation evolution is found out. The latter is induced by excitation of a parametric resonance and by the so-called antifriction phenomenon. These new features could lead to strong reshaping of the usual Jeans instability.     

Transport properties of lithium in the gas phase

The collision cross section of lithium atoms is determined by generalizing empirical data on the and of Na, K, Rb, and Cs vapors and quantum calculations of the potential curves of Li₂. The ₁ and ₁ of Li vapors are calculated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 6, pp. 993–998, December, 1980.     

Computation of extreme eigenvalues in higher dimensions using block tensor train format

We consider approximate computation of several minimal eigenpairs of large Hermitian matrices which come from high-dimensional problems. We use the tensor train (TT) format for vectors and matrices to overcome the curse of dimensionality and make storage and computational cost feasible. We approximate several low-lying eigenvectors simultaneously in the block version of the TT format. The computation is done by the alternating minimization of the block Rayleigh quotient sequentially for all TT cores. The proposed method combines the advances of the density matrix renormalization group (DMRG) and the variational numerical renormalization group (vNRG) methods. We compare the performance of the proposed method with several versions of the DMRG codes, and show that it may be preferable for systems with large dimension and/or mode size, or when a large number of eigenstates is sought.     

Method of Determining the Elastic Characteristics of Graphene and Other 2D Nanoallotropes

Semiconductors - To calculate and design nanoelectronic and nanophotonic devices, in which graphenes and graphene-like 2D nanoallotropes of carbon, silicon, and binary III–V compounds are...     

Simulation of technological systems in custom production

Russian Engineering Research -     

Thermoluminescence centres created selectively in MgO crystals by fast neutrons

A possibility of using the thermoluminescent detection of collision-created interstitial centres in MgO by the TL peak at 700 K, arising at the radiative recombination of anion interstitials with F+ centres, for the selective detection of fast neutrons in mixed neutron-gamma fields, is examined. Selectivity and sensitivity of such a detector are discussed. For the present time, the sensitivity of the thermoluminescent detection of anion interstitials created by neutron irradiation is comparable to that of the EPR detection of F+ centres, the main limitations of the thermoluminescence method being connected with the background thermoluminescence and absence of suitable luminescence centres in this temperature region, when undoped and untreated MgO crystals are used. Possible ways to overcome these shortcomings are discussed.