Conductance of quantum interference transistors in parallel and in series

We theoretically study the electronic conductance G and the current–voltage characteristics of two quantum interference transistors in parallel and in series. We use two different definitions of conductance,G ∼ T and G ∼ T / R. Neither can reproduce the classical additivity law in the case of coherent transport due to quantum interference for the elements in series and quasibound states when elements are in parallel. In the case of two transistors in series, we find that the quantityT / R only qualitatively better represents the additivity law, which is probably expected because this model avoids counting the contact resistance twice. However, for the parallel configuration of transistors, the conductance is almost additive for the majority of energies when G ∼ T, except for the single-mode regime. Possible use of these configurations in digital electronics for basic logic functions is discussed.     

Chaos in Temperature in Generic 2p-Spin Models

We prove chaos in temperature for even p-spin models which include sufficiently many p-spin interaction terms. Our approach is based on a new invariance property for coupled asymptotic Gibbs measures, similar in spirit to the invariance property that appeared in the proof of ultrametricity in Panchenko (Ann Math (2) 177(1):383–393, 2013), used in combination with Talagrand’s analogue of Guerra’s replica symmetry breaking bound for coupled systems.     

Inelasticity effects inππ production inγγ collisions

The inelasticity effects in the production of pion pairs in the processγγ→ππ for real photons are investigated using the partial wave dispersion relations. The total cross sections for different photon helicities are calculated. It is observed that this process is dominated by theππ final state interaction. A prediction for S* (997) →γγ decay width is also made. Work supported financially by CSIR, New Delhi     

LHC prospects in searches for neutral scalars in pp → γγ + jet

At hadron colliders, the γγ + jet channel provides a larger signal-to-background ratio in comparison with the inclusive γγ channel in hunting for scalars uncharged under the SM gauge group. By using NLO results for the SM Higgs boson production and corresponding background, we estimate LHC prospects in searches for the radion and sgoldstino in the γγ + jet channel. Three-body final-state kinematics allows for refined cuts. We have found that this channel could be comparable with the γγ channel in searches for new physics. The text was submitted by the authors in English.     

Phase separation in the strongly correlated Falicov-Kimball model in infinite dimensions

Phase separation in the strongly correlated Falicov-Kimball model in infinite dimensions is examined. We show that the phase separation can occur for any values of the interaction constant J^* when the site energy of the localized electrons is equal to zero. Electron-poor regions always have homogeneous state and electron-rich regions have chessboard state for , chessboard state or homogeneous state in dependence upon temperature for 0<J ^* <0.03 and homogeneous state for J ^* =0. For J ^* =0 and T=0, phase separation (segregation) occurs at .The obtained results are exact for the Bethe lattice with infinite number of the nearest neighbours. Received 1 December 1998 and Received in final form 12 April 1999     

Ferromagnetism in Hubbard model in many-electron operator representation

The Hubbard model for a metal with strong correlations is considered in the representation of many-electron X-operators. General self-consistent expressions are obtained for the one-particle Green function taking into account fluctuation corrections. The stability regions of the saturated and unsaturated ferromagnetism in the ground state on the n-U plane (n is the electron concentration and U is the Coulomb interaction parameter) are determined for various bare densities of states (semi-elliptic band and the square, cubic, and hypercubic lattices).     

Metal-insulator transition in hydrogen and in expanded alkali metals

Two methods are considered for testing the stability of an electron gas to formation of bound states round a pair of protons. In the first, the screened potential for the two protons is set up as a superposition, which is appropriate in a very high density electron gas. The condition for bound state formation is then examined in the two-centre problem. The density thus obtained is in the right density range to accord with the experiment of Hawke et al. for producing cold metallic hydrogen.This has encouraged us to attempt a more ambitious calculation, namely the investigation of the Heitler-London energy of a model H₂ molecule with screened electron-nuclear and electron-electron interactions, the screening being again through appropriate introduction of the Thomas-Fermi screening radius. The merit of this second model is that the theory contains the Heitler-London value of the dissociation energy of the free H₂ molecule in the limit when the density of the electron gas tends to zero. This feature, the binding energy of the diatomic and its importance in distinguishing the metal-insulator transition in hydrogen from those expected to occur in expanded alkali metals is stressed. The second point we stress is that, in both the models discussed above, there is a close connection with the one-centre criterion for bound state formation. Though we have not carried out detailed two-centre calculations for expanded alkali metals, nevertheless some discussion is given of the one-centre bound state criterion in these metals.Some remarks are also made on the dielectric function of molecular crystals, in relation to the insulator-metal transition.     

The role of nickel in stimulated processes in NaCl

The influence of nickel impurity upon thermostimulated (ionic conductivity, TSE, TSL, TOB) processes and absorption, ESR and luminescence of sodium chloride doped with different concentrations of nickel and irradiated with different doses of X-rays is studied. It is shown that both the concentration of nickel and the dose of X-radiation play an important role. Further, the form of TSE-, TSL- and TOB-curves in NaCl-Ni changes, to a certain degree, very similarly as in case of calcium.The authors wish to express their appreciation to Dr. M.Lébl for preparing the crystals, Dr. I.Velická for the polarographic analysis, Ing. E.Mariani for the measurements of conductivity, to K.Dolealová, E.Linhartová and I.Sváková for careful measurements and elaboration of experimental results, to L.Berkes for the ionic conductivity measurements and to K.Raksányi for the purification of the fundamental NaCl material.     

Electric quadrupole interaction of192Tl(8−) nuclei in hexagonal Tl and in tetragonal in metals

The TDPAD technique has been used to measure the electric quadrupole coupling constants for the¹⁹²Tl(8^–) isomer in hexagonal Tl at different temperatures and in tetragonal In at room temperature. The values measured weree ² qQ/h=24.0(15) MHz extrapolated toT=0K, and 33.1(16) MHz at 293K for the Tl and In hosts,respectively, The electric field gradient for Tl impurities in In was determined from systematics of isoelectric systems, yielding |Q[¹⁹²T1(8^–)]|=0.44(7)b.The almost perfect symmetry of the T1 crystalline structure makes this metal a sensitive probe to current models for electric field gradients in metals. The magnitude and temperature dependence of the field gradient in thallium metal are discussed within the framework of such models.     

Fano-type features in magnetoabsorption in semiconductors

It is shown that bulk semiconductors exhibit strongly asymmetric Fano-type resonance profiles in magnetoabsorption processes involving the formation of hot electron-hole pairs (EHPs) and accompanied by the scattering of the EHPs by defects. This result is valid for transitions to electronic states with large Landau quantum numbers, when the Coulomb interaction plays a small role. The physical reason for such a sharp change in the magnetoabsorption coefficient as compared with the expected result for the ordinary density of states in a quantizing magnetic field is that the electronic excitations are quasi-one-dimensional. The form of the resonance absorption is in good qualitative agreement with the experimental data. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 619–622 (25 April 1996)     

Electric multipole interaction of pairs in solids: Ce in LaCl3

The electric multipole interaction (EMI) is studied in general for the case of two rare earth (RE) ions interacting in host crystals possessing C_3h symmetry at the ion sites. The particular case of Ce³⁺ substituted for La³⁺ in LaCl₃ is used as an example. The splitting of two degenerate levels of such a system is studied as an application of elementary group theory, and a notation is proposed for the resulting levels. The angular dependence of the splitting due to the first term of the EMI, namely, the electric quadrupole-quadrupole interaction (EQQ), is obtained for one of the levels of the system under consideration. The ground quartet is studied for the nearest neighbor configuration (nn), and all of the multipoles in the expansion for EMI are kept. The shielding effects, which are very important in this problem, are assumed to depend on one parameter. This makes possible the study of the variation of the splittings with respect to such a parameter. The importance of terms beyond the quadrupole is brought out.     

Monogamy Relations in Terms of Tsallis-Q Entropy in any Dimensional System

Monogamy of entanglement is a fundamental property of multipartite entangled states. In this article, due to the convexity of Trρ^q with respect to q when q ≥ 1, we give a monogamy-like relation in terms of Tsallis-q entanglement entropy of assistance (TqEEA) for pure states over an n- partite any dimensional system and monogamy-like relations in terms of Tsallis-q entanglement entropy (TqEE) for mixed states for any dimensional system, we also give a lower bound for the TqEE of a four-partite pure state. At last, we show that the generalized W-class states satisfy the polygamy relation in terms of TqEE when q = 2.     

The rate of propagation of ultrasonic waves in ADP in voigt's theory

The difference measured in the rates of propagation of shear ultrasonic wavesv _zx andv _zx in an ADP crystal is one of the bases of the Laval-Raman theory of the elastic properties of crystals. In the present paper an attempt is made to obtain by calculation a similar difference in rates within the old Voigt theory by using the more perfect methods of computation of Lawson and Paillouxe. The calculations, together with an estimate of the influence of second-order effects, however, indicate that the measured differences in rates cannot be explained even in this way by means of Voigt's theory.In conclusion, the author would like to express his sincere thanks to Senior Lecturer L. Janík for cooperation in the measurements, Assistant Professor J. Tichý for kindly lending the results of his own measurements and less accessible literature, and Technician R. Suchy for assistance in adapting the experimental equipment. He is also indebted to Professor P. A. O'Brien and the head of the Czechoslovak Commercial Section in Khartoum, B. Sychra, for help in elaborating this contribution.     

Radioactivity measurements and risk assessments of spa waters in some areas in Turkey

The current study presents the results of the activity of radionuclides in spa waters, and evaluates their radiological influences on the population consuming these waters in the Central and Eastern Black Sea regions of Turkey. Since these waters are used for therapy and consumption purposes unconsciously, their radiological impact on the people was computed by taking into consideration the annual intake through ingestion of ²²⁶Ra, ²³²Th, ⁴⁰K, ¹³⁷Cs and ²²²Rn. The mean activities were estimated to be 11.35 for gross alpha, 6.23 for gross beta, 2.96 for ²²⁶Ra, 0.42 for ²³²Th, 0.069 for ¹³⁷Cs, 0.19 for ⁴⁰K, and 267 Bq L^–1 for ²²²Rn, respectively. The estimated effective doses from spa water were found to be 49.77 µSv a^–1 (²²⁶Ra), 5.95 µSv a^–1 (²³²Th), 0.07 µSv a^–1 (¹³⁷Cs), 0.83 µSv a^–1 (⁴⁰K) and 56.03 µSv a^–1 (²²²Rn). These values were evaluated and compared with related verified values from literature. Also, physico-chemical characterizations of spa water samples considered in the current study were investigated. This study would be useful for consumers and official authorities for the assessment of radiation exposure risk due to usage of the considered spa waters.     

Three-body scattering in configuration space

The asymptotic forms of the wavefunction and Faddeev components in configuration space are shown to determine uniquely the solutions of the Schrödinger or Faddeev differential equations for 2 → (2, 3) and 3 → (2, 3) processes. An antisymmetrized form of the Faddeev differential equation for three equivalent fermions is given and its angular analysis is performed in the general case of local potentials with tensor interaction for neutron-deuteron scattering. We describe a numerical method for solving the corresponding boundary value problem and apply it to scattering and break-up at E_n^1ab = 14.4 MeV in the doublet S state for the four local potentials of Malfliet and Tjon, Reid, de Tourreil and Sprung, and de Tourreil, Rouben and Sprung. For the three realistic potentials, elastic scattering amplitudes differ by 5%, and amplitudes for break-up in the two-neutron state ¹S₀ differ by less than 4%.     

Resonances in Compton-Like scattering processes in an external magnetized medium

We consider the possible resonance effects in the tree-level two-vertex amplitudes for the transitions jf → j'f' in a constant uniform magnetic field and in the presence of a magnetized plasma consisting of charged fermions for various combinations of scalar, pseudo-scalar, vector, and axial-vector vertices. As an application of the results obtained, we have investigated the scattering of a photon by magnetized-plasma electrons, γe → γe, in the resonance region and calculated the photon absorption coefficient in this reaction. The cross section for this process has been calculated and compared with the available published results.     

Normal spectral emissivity of platinum in the red and in the green in vacuum and helium

The spectral emissivity of platinum for λ=0.645 μm and λ=0.546 μm has been measured by using a De Vos blackbody in ultrahigh vacuum and in helium. Changes in enissivity brought about by heat treatment and changing ambiences, are illustrated and discussed and the results are compared with previously published data. The emissivities determined turned out to be appreciably lower than the measurements of previous investigators. The determined values for 1100<T(K)<1800 are for 0.645 μ between 0.237 and 0.249 in vacuum, and between 0.185 and 0.290 in helium; and for 0.546 μm between 0.250 and 0.312 for vacuum and between 0.219 and 0.321 in helium.     

Fluorescence of a Benzothienopyridopyrimidone in Solution and in Lipid Vesicles

Fluorescence properties of a biologically active benzothienopyridopyrimidone in solution and in lipid vesicles are reported. Assays at different pH values (0.5–10) allowed the determination of pK _a = 2.0, showing that this compound may be useful as a pH indicator for pH ≤ 4. In lipid vesicles, benzothienopyridopyrimidone locates in a water-rich environment, indicating that it can be carried in the hydrophilic region of liposomes for drug delivery applications.