Local correlations of different eigenfunctions in a disordered wire

The correlation of the local density of states 〈ρ_ɛ(r ₁)ρ_{ɛ + ω}(r ₂)〉 in quasi-one-dimensional disordered wires in a magnetic field is calculated under the assumption that |r ₁ − r ₂| is much smaller than the localization length. This amounts to finding the zero mode of the transfer-matrix Hamiltonian for the supersymmetric σ model, which is done exactly by mapping to the three-dimensional Coulomb problem. Both the regimes of level repulsion and level attraction are obtained, depending on |r ₁ − r ₂|. We demonstrate that the correlations of different eigenfunctions in the quasi-one-dimensional and strictly one-dimensional cases are dissimilar. The text was submitted by the authors in English.     

Nonadiabatic effects in the phonon spectra of superconductors

The nonadiabatic corrections to the self-energy part Σ_s(q, ω) of the phonon Green’s function are studied for various values of the phonon vectors q resulting from electron-phonon interactions. It is shown that the long-range electron-electron Coulomb interaction has no direct influence on these effects, aside from a possible renormalization of the corresponding constants. The electronic response functions and Σ_s(q, ω) are calculated for arbitrary vectors qand energy ω in the BCS approximation. The results obtained for q=0 agree with previously obtained results. It is shown that for large wave numbers q, vertex corrections are negligible and Σ_s(q, ω) possesses a logarithmic singularity at ω=2Δ, where Δ is the superconducting gap. It is also shown that in systems with nesting, Σ_s(Q, ω) (where Q is the nesting vector) possesses a square-root singularity at ω=2Δ, i.e., exactly of the same type as at q=0. The results are used to explain the recently published experimental data on phonon anomalies, observed in nickel borocarbides in the superconducting state, at large q. It is shown, specifically, that in these systems nesting must be taken into account in order to account for the emergence of a narrow additional line in the phonon spectral function S(q, ω)≈−π ⁻¹ Im D _s (q, ω), where D _s (q, ω) is the phonon Green’s function, at temperatures T<T _c . Zh. éksp. Teor. Fiz. 115, 1799–1817 (May 1999)     

Elementary muon, pion, and kaon particles as resonators for neutrino quanta. Calculations of mass ratios for e, μ, π0, π±, K 0, K ±, and ν e

Masses of a number of elementary particles are calculated on the basis of the model suggested in [1] with the use of one parameter. In this model, an electron is considered as an electric cloud enclosed inside an elastic lepton shell, electron neutrino ν _е is considered as an elastic lepton shell contracted to a minimal size, and muon, pion and kaon are considered as resonators for quanta of virtual neutrinos excited inside the elastic lepton shell. The number and type of these quanta are determined from the decay scheme for μ, π, and K: 2 for the muon (ν _е and ), 3 for the pion (ν _е , ν _μ, and ), and at least 21 for the kaon. The model allows mass ratios approximating the experimental data for these particles to be obtained for the first time, with the ratio of μ and е masses equal to (6πℏс/е ²)^2/3 ≅ 188, the ratio of π ⁰ and μ masses equal to (3/2)^2/3, and the ratio of K ⁰ and π ⁰ equal masses to 7^2/3. The calculated e, μ , π ⁰, and K ⁰ masses are in the 0.547:105.707:134.963:493.87 (MeV) ratios (normalized by the neutral pion mass). This is in good agreement with the available experimental data. The mass ν _е (≅ 0.02 eV) is also estimated in this model, and the variety of K-meson decay schemes is naturally explained as a result of the variety of excited intrinsic neutrino field structures with the same energy. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–29, January, 2009.     

Large-scale amplification of a magnetic field by turbulent helicity fluctuations

In this paper the procedure of large-scale averaging of the magnetic-field diffusion equation with the α-term curlα(r,t)B(r,t) is used to show that a nonuniform distribution of the turbulent helicity fluctuations (more precisely, the fluctuations of the coefficient α) with a zero average value gives rise to large-scale amplification of the initial magnetic field. A detailed study is carried out of the dependence of the resulting large-scale α effect on the characteristics of the correlator 〈〈α(r, t)α(r″,t″)〉〉 in a rotating medium with a nonuniform distribution of the angular velocity ω=ω(ρ,z) (ρ is the distance for the rotation axis z). The effect of helicity fluctuations and the diffusion coefficient on the turbulent diffusion process is also investigated. Zh. éksp. Teor. Fiz. 116, 85–104 (July 1999)     

Detection of (<Emphasis Type="Italic">C</Emphasis> + <Emphasis Type="Italic">A</Emphasis>)-type dislocation self-blocking in magnesium

The self-blocking effect predicted theoretically and then observed in intermetallides is established for a pure metal, namely, for magnesium. This effect can be observed only for magnesium single crystals whose axis is parallel to the c axis and whose yield stress behavior σ _y (T) has a temperature anomaly. For such single crystals, the self-blocking of the (c + a)-type edge dislocations is established during pyramidal slip of type II. The self-blocking is proved by dislocation extension along the preferred direction without external stress. In this case, the á 1[`1]00 ñ \left\langle {1\bar{1}00} \right\rangle directions appear preferred. TEM images of (c + a) dislocations extended along the preferred directions are presented. It is demonstrated that two effects – temperature anomaly of σ _y (T) and dislocation self-blocking – have the common nature: a two-valley potential relief of the dislocation. A model of two-valley relief of the (c + a) dislocations in Mg is proposed.     

Magnetization of optically polarized gas atoms by an optical pulse train

The properties of the density matrix and the multipole moments arising in oriented and aligned atoms with zero nuclear spin through the interaction with strong resonant ultrashort pulses with wave vector k ₀ and circular or linear polarization have been found. Calculations have been made for the time-dependent light-induced magnetization μ(t′) of a gas of pre-oriented and prealigned atoms following the passage of a weak resonant elliptically polarized pulse with frequency ω and wave vector k collinear with k ₀. It is shown that for oriented atoms, μ(t′) is an even function of the detuning from resonance, ω-ω _ba, and can be split into two terms whose directions are a consequence of symmetry and are determined by the vectors k ₀ and k as well as by the direction of rotation of the electric fields corresponding to the pulses. For aligned atoms the vector μ(t′) is collinear with k, and the first term is an even function of ω-ω _ba. However, the second term is an odd function of ω-ω _ba and reverses direction when the sign of ω-ω _ba changes, as well as when the orientation of the axes of the polarization ellipse is changed. It is shown that if a series of weak linearly polarized pulses pass through the gas, the light-induced magnetization of the oriented and aligned gas atoms can be decomposed into three factors: the first determines the direction and is a consequence of the symmetry; the second (with the dimensions of magnetic moment) depends on the characteristics of the resonant transitions; and the third is a universal function of t′ and ω-ω _ba that does not depend on the underlying characteristics of the resonant transition. These vector factors and the universal functions are in principle different for oriented and aligned atoms. Zh. éksp. Teor. Fiz. 111, 63–92 (January 1997)     

Universality of a dynamical percolative approach to 1/f γ noise

A dynamical percolative model explaining the universality of 1/ f ^γ noise is reported. Exponents γ ranging from 0 to 2 are obtained under the hypothesis that noise originates from random switching events between two ON-OFF states in elemental parts (switchers) of a physical system. The usual noise behaviour with γ very close to 1 in an arbitrarily wide frequency range is obtained assuming a statistical distribution of switcher relaxation time τ proportional to τ ^-1 , as in McWhorter's model. The impact of these results with respect to recent self-organised criticality models is discussed. Received 6 November 2000 and Received in final form 22 May 2001     

The Al-Pd-Mn quasicrystalline approximant -phase revisited

A detailed investigation of the Fourier space of several Al-Pd-Mn samples with composition Al-72.6 at. %, Pd-22.9 at. %, Mn-4.5 at. % is reported. In the phase diagram of the Al-Pd-Mn ternary alloy, this composition corresponds to the so-called ξ' phase which was described as an icosahedral quasicrystalline approximant. By re-examining the Fourier space by means of X-ray diffraction (powder patterns and single crystal precession patterns), complex structures in close relation with the ξ'-phase have been observed. These long-range order complex structures are described as resulting from a periodic perturbation of the ξ' structure along the c direction. Two states with periodicities c (3 + τ) and c (5 + τ) have been observed in this study (τ: golden mean). Structural models based on periodic arrangements of “defects” layers separating layers of phase are proposed. These two states are certainly intermediate states between the phase and the metastable decagonal quasicrystalline phase. Received 11 April 2002 / Received in final form 24 June 2002 Published online 17 September 2002     

Laser-induced fluorescence measurements of a 3 Π metastable carbon monoxide in a high enthalpy flow

Excitation of carbon monoxide molecules has been carried out in a cold cell and in a low-pressure plasma jet using an ArF narrow-band excimer laser. The different excitation models are discussed and the relevance of atomic carbon absorption into the laser cavities is pointed out. Excitation spectra of Cameron bands have been obtained in a room-temperature cell and compared with calculated spectra. A value of the constant σ related to the interaction strength between a ³ Π( v = 2) state and its neighbouring singlet states is derived: 0≤σ≤0.05. The fluorescence spectrum following broad band excitation of CO has been observed both in UV and visible. Similar experiments carried out in a high enthalpy flow have allowed to point out the presence of a ³ Π metastable carbon monoxide. A method for relative measurements of this species concentration is proposed. Received 9 April 2001 and Received in final form 13 June 2001     

Study of excitation transfer Li (3 D → 3 P ) occurring in optical collisions with rare gas atoms experimentally

By selective optical excitation of collision pairs and observation of the reemitted fluorescence information is obtained on the role of the molecular channels involved in inelelastic collisions. As an example case we have studied experimentally the Li( 3 D → 3 P) excitation transfer in Li(3D)X systems with X = Ne, Ar by means of the optical collision process Li (2 P ) + X + h ν→ LiX (3 D Λ) → Li (3 P , 3 D ) + X where LiX (3 D Λ) collision molecules dissociate into Li(3P, 3D) atoms following laser excitation h ν of Li (2 P ) + X pairs. For this purpose we measured the Li 3P/3D population ratio by the fluorescence from these levels as function of the laser detuning Δν from the Li(2P-3D) transition and the rare gas pressure, and determined from this the 3P/3D excitation ratio B (Δν) for single collision conditions. The experiments were performed using two step cw laser excitation of gaseous mixtures Li + X at temperatures around 600 K in the detuning range |Δν| ? 100 cm^-1. The B (Δν) profiles obtained display strong blue-red wing asymmetries both for Li ^* Ne and Li ^* Ar. This reflects different dissociation probabilities from the 3 D Σ or 3 D (Π,Δ) states that are initially prepared by blue wing or red wing excitation, respectively. The results are qualitatively discussed in terms of new ab initio potentials for the two systems. Received 23 February 2000 and Received in final form 5 July 2000     

Hamiltonian dynamics of vortex lines in hydrodynamic-type systems

It is shown that the degeneracy of the noncanonical Poisson bracket operating on the space of solenoidal vector fields that arises due to the freezing-in of the curl of the velocity [E. A. Kuznetsov and A. V. Mikhailov, Phys. Lett. A 77, 37 (1980)] is lifted when the vorticity Ω is represented in terms of vortex lines. This representation makes it possible to integrate the equation of motion of the vorticity for a system with the Hamiltonian H=∫∣Ω∣d r. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 12, 1015–1020 (25 June 1998)     

Quasi-long-range order in the random anisotropy Heisenberg model

The random field and random anisotropy N-vector models are studied with the functional renormalization group in 4−ε dimensions. The random anisotropy Heisenberg (N=3) model has a phase with an infinite correlation length at low temperatures and weak disorder. The correlation function of the magnetization obeys a power law 〈m(r ₁)m(r ₂)〉∼|r ₁−r ₂|^{− 0.62ε}. The magnetic susceptibility diverges at low fields as χ∼H ^−1+0.15ε. In the random field N-vector model the correlation length is finite at arbitrarily weak disorder for any N>3. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 130–135 (25 July 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Anisotropic momentum transfer in low-dimensional electron systems in a magnetic field

In low-dimensional systems with an asymmetric quantizing potential, an asymmetric electron energy spectrum ε(p)≠ε(−p), where p is the electron momentum, arises in the presence of a magnetic field. A consequence of such an energy spectrum is that momentum transfer to the electron system in mutually opposite directions in the presence of an external perturbation is different. Therefore, in the presence of a standing electromagnetic wave momentum is transferred from the wave to the electrons, which gives rise to a new type of electromotive force. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 551–555 (25 October 1997)     

Microscopic three-cluster study of the low-energy 9 Be photodisintegration

The ⁹Be and ⁹B nuclei are investigated in a microscopic three-cluster model involving α + α + n (or α + α + p) configurations. The ⁸Be (0 ⁺ , 2 ⁺ ) + n and ⁵He (3/2 ^- , 1/2 ^- ) + α (or mirror) channels are included by taking account of the unstable nature of ⁸Be and ⁵He. Spectroscopic properties of ⁹Be and ⁹B are analyzed. We show that the ⁵He + α configurations cannot be neglected to derive accurate results. The ⁹Be(γ,αα)n photodisintegration cross-section is shown to be mainly determined by ⁸Be + n channels at low energies, but ⁵He + α channels become important beyond E _γ≈ 4 MeV. Received: 7 September 2001 / Accepted: 19 November 2001     

A Way To Discover Maxwell's Equations Theoretically

The Coulomb force, established in the rest frame of a source-charge Q, when transformed to a new frame moving with a velocity V has a form F = q E + q v × B, where E = E′_∥ + γE′_⊥ and B = (1/c ²)v × E and E′ is the electric field in the rest frame of the source. The quantities E and B are then manifestly interdependent. We prove that they are determined by Maxwell's equations, so they represent the electric and magnetic fields in the new frame and the force F is the well known from experiments Lorentz force. In this way Maxwell's equations may be discovered theoretically for this particular situation of uniformly moving sources. The general solutions of the discovered Maxwell's equations lead us to fields produced by accelerating sources.     

Effects of two strong fields in resonant four-wave mixing

An explicit solution is obtained for the four-wave mixing ω₄=ω₁−ω ₂+ω₃ of two strong fields E ₁, E ₃ and two weak fields E ₂, E ₄ in a four-level system with large Doppler broadening. Resonance of the intensity dependence of the mixing coefficient is found around equal Rabi frequencies, E ₁·d ₁=E ₃·d ₃, where d _1,3 are the dipole moments of the corresponding transitions. The effect is interpreted as a crossing of quasi-energy levels. Up to 6 peaks appear in the dependence of the conversion coefficient on the detuning of the probe field E ₂. The unexpected additional pair of peaks is a consequence of averaging over velocities. The results permit interpretation of the saturation behavior found in recent experiments on mixing in sodium vapor. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 777–782 (25 December 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

The widths of single-particle states of anisotropic, strongly correlated electron systems in solids

The damping γ(ε) of electron states in crystals is investigated beyond the phase transition point related to a rearrangement of the Fermi surface. Attention is focused on the alteration of the standard Landau theory due to the emergence of a flat portion in the spectrum ξ(p) of single-particle excitations as a result of the rearrangement. In the limit ε →0, the width γ(ε) of the states in the region of the Brillouin zone where the dispersion of ξ(p) is of an ordinary order of magnitude is found to depend on ε almost linearly, in contrast to the Fermi-liquid-theory result γ(ε)∼ε². Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 759–765 (10 December 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Preparation, magnetoresistance and magnetocaloric effect of two-layered perovskite La 2.5- x K 0.5+ x Mn 2 O 7+δ

Polycrystalline two-layered perovskite La_2.5-xK_0.5+xMn₂O _{7 + δ} (0 < x < 0.5) samples have been prepared by a modified sol-gel method and their magnetoresistance and magnetocaloric effects have been studied. A large deviation between the metal-insulator (MI) transition temperature (T _ρ ) and the magnetic transition temperature (T_C) is observed. Large magnetoresistance (MR) effects with Δρ/ρ of ∼40% at 12 kOe are obtained in wide temperature ranges. The maximum of the magnetic entropy change peaks at its Curie temperature (T_C), far above its MI transition temperature (T _ρ ). The large magnetic entropy change (∼1.4 J/kg.K) is obtained in the sample La_2.5-xK_0.5+xMn₂O _{7 + δ} (x = 0.35) upon 10 kOe applied magnetic field. Received 2 May 2002 / Received in final form 1st October 2002 Published online 19 December 2002 RID="a" ID="a"e-mail: wzhong@ufp.nju.edu.cn     

Packing of molecules and hole formation in lyotropic systems

A vector field q (the order parameter of the molecular packing) describing the packing (specifically, the orientation) of membrane-forming amphiphilic molecules is introduced to describe the structures of lyotropic phases constructed from membranes. In the general case q·n≠0 (where n is the unit normal vector) and therefore the singularities of the vector field q are not determined uniquely by the topology of the surface. The condition q·n=0 signifies disruption of the packing of the molecules. This corresponds to holes, which can form in membranes when lyotropic systems are diluted. As an illustration, the simplest type of such singularities, in which the distribution of the field q around a hole is described by a part of an instanton with unit topological charge, is studied. It is shown that such a distribution guarantees the existence of a local minimum under the condition that the tension per unit length λ of the hole boundary is small compared with the deformation energy of the field q: λh/K≪l (K is the modulus of the orientational elasticity of the field q and h is the thickness of the membrane). The radius of the hole which is formed equals L≈2.52(K/λh)^1/3 and the energy E≈59.79K(λh/K)^1/3. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 8, 575–580 (25 October 1996)