General vacuum solution for Brans-Dicke-Bianchi type V

In this paper we have obtained the general vacuum solution for Bianchi type V in the Brans-Dicke theory. It is shown that for the special case=0, the sourceless scalar field is dynamically an essential factor which determines the cosmological expansion parametersR _i and the singularity does not occur whent=0. For this solution there is no antigravity (>0), which disagrees with other solutionsa for BDT-Bianchi type V     

Associated production of φ-mesons and strange particles and double φ-meson production BIS-2 collaboration

Associated production of-mesons and strange particles by neutrons at energies of 30–70 GeV has been analysed. It has been found that at least 67% of inclusive-meson production in the kinematic regionx _F>0.1 andp _T<1 GeV/c proceeds via OZI-allowed processes with extra strange particles. Double-meson production has also been observed and its cross section in the full kinematic region is estimated to be 15 ± 9b.The authors are grateful to A. M. Baldin, E. I. Maltsev, I. A. Savin for supporting these investigations; H. Bottcher, Ch. Spiering and L. V. Schreiber for useful discussions; E. M. Likhacheva, L. V. Silvestrov, V. E. Simonov, G. G. Takhtamyshev, N. V. Vlasov for their participation in the experiment.     

Inertial effects on the escape rate of a particle driven by colored noise: An instanton approach

A recent calculation, in the weak-noise limit, of the rate of escape of a particle over a one-dimensional potential barrier is extended by including an inertial term in the Langevin equation. Specifically, we consider a system described by the Langevin equation , where is a Gaussian colored noise with mean zero and correlator (t)(t')=(D/)exp(–|t–t'|/). A pathintegral formulation is augmented by a steepest descent calculation valid in the weak-noise (D0) limit. This yields an escape rateexp(–S/D), where the actionS is the minimum, over paths characterizing escape over the barrier, of a generalized Onsager-Machlup functional, the extremal path being an instanton of the theory. The extremal actionS is calculated analytically for smallm and for general potentials, and numerical results forS are displayed for various ranges ofm and for the typical case of the quartic potentialV(x)=–x ₂/2+x ₄/4.     

Interaction between the nucleon and muon currents in elastic neutrino-nucleon interactions

The spin relations of neutrino-nucleon interaction with the formation of a muonv(V) N N are investigated within the framework of the two-component and four-component theories of two neutrinos under the assumption of a point neutrino. The difference between the predictions of the two theories is identified. It is shown that the four-component theory of two neutrinos, unlike the two-component theory, accommodates the V + A variant of interaction between the muon current (v) and the barion current.The authors are grateful to Prof. A. A. Sokolov and to R. Sh. Yakh'yaev for evaluating the results.     

Radiation by relativistic dipoles. II

In a continuation of an earlier study, the electromagnetic fields of a point magnetic moment — a magneton — in uniform rectilinear motion, with a given spin precession, are analyzed. It is shown that the same equations can be found through Lorentz transformations from the corresponding expressions in the rest frame. The relationship between the electric and magnetic fieldsE andH radiated by a point magnetic dipole moment and a point electric dipole moment is derived through the use of dual transformations of the electromagnetic field tensor. It is assumed that each moment is in relativistic and otherwise arbitrary motion. In the relativistic case, as in the nonrelativistic case, the switch is accompanied by the replacementsHE, E-H. A covariant formalism is developed for describing the electromagnetic fields in the wave zone. The electromagnetic field tensor associated with the radiation is analyzed.V. V. Kuibyshev Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 73–78, March, 1993.     

The Chiral Bag Model and properties of the πNΔ system

The effective Hamiltonian for theN system is proposed in the framework of the Chiral Bag Model (CBM). The taking into account of gluonic and pionic correctinos to the pion-nucleon coupling constantg _N and the-decay axial constantg _A leads tog _N 13·5,g _A 1·28 which are in good agreement with experimental data.Presented at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.I wish to thank Gulamov K. G., Shelest V. P. and Zinoviev G. M. for useful discussions.     

On the homology of lattice vibrations of alkali metals

Investigations of the dependence of lattice vibrations of alkali metals on their interatomic distance,r reveal that they satisfy an empirical relation,Mv ² r =(q), a constant which depends on, with q=2·48 ± 0·19 at all wave vectors and hence are homologous. It is shown that the observed crossover of [00] branches of lithium is not an anomalous property, but only manifests itself in alkali metals with smaller interatomic distance due to small variations of . The role played by interatomic distance which is closely related to that of the electron gas constantC in producing a crossover and a possible reason for the observed homology are discussed.The authors are grateful to Professor B. Sharan and Mr. S. B. Rajendraprasad for many valuable and stimulating discussions. One of the authors (M. S.) is greatly indebted to Professor D. M. Sen, principal, and Professor L. V. Sud of Regional Engineering College, Kurukshetra, for granting him study leave.     

Rotational symmetry of solutions of some nonlinear problems in statistical mechanics and in geometry

The method of moving planes is used to establish a weak set of conditions under which the nonlinear equation –u(x)=V(|x|)e ^u(x) ,x² admits only rotationally symmetric solutions. Additional structural invariance properties of the equation then yield another set of conditions which are not originally covered by the moving plane technique. For instance, nonmonotonicV can be accommodated. Results for –u(y)=V(y)e ^u(y) –c, withyS ², are obtained as well. A nontrivial example of broken symmetry is also constructed. These equations arise in the context of extremization problems, but no extremization arguments are employed. This is of some interest in cases where the extremizing problem is neither manifestly convex nor monotone under symmetric decreasing rearrangements. The results answer in part some conjectures raised in the literature. Applications to logarithmically interacting particle systems and geometry are emphasized.     

Kramers time in weakly nonpotential systems

We consider a bistable Fokker-Planck system with a known stationary distribution and a small nonpotential part in the drift force. We perform a perturbation calculation of its Kramers time, _K, and compare it with the corresponding time, _K ⁽⁰⁾ , for the potential system which has the same stationary distribution. We show that _K/ _K ⁽⁰⁾ depends only on the properties of the drift force close to the saddle-point.The authors would like to dedicate this work to their colleagues Y. Orlov, R. Nazarian, and V. Brailovski.     

Nonlinear scattering with nonlocal interaction

We consider the scattering problem for the Hartree type equation in ⁿ withn2:

Pattern formation in systems with nonlocal interactions

One-dimensional lattices with harmonic coupling between neighboring lattice sites and an on-site anharmonic potential V()=A²ⁿ⁺² + ⁿ⁺² + C² + D are examined in the displacive limit. Kink solutions, interpolating between the coexistent phases =0 and =±(C/A)^1/2n at theT=0 first-order phase transition pointB ²=4AC,A, C>0,B<0,D=0 are found in simple analytic form and their dependence on the degree of anharmonicity (n=2, 4, 6, ...) is discussed. It is shown that, at the phase transition point, the kinks are accompanied by a continuous spectrum of periodic nonlinear excitations (periodons) having finite energy density.Work supported by the Swiss National Science Foundation     

Compatibility of higher rho-resonances with the pion form factor data

A realistic pion form factor model respecting the usual fundamental principles supplemented by reasonable assumptions is constructed by means of conformai mapping having some specific uniformization properties. The model includes the contributions of higher rho-resonances without any conflict with analyticity, provides a certain flexibility for the asymptotic behaviour and depends just on the physical parameters. The best fit of all existing data is achieved with(770),'(1600) and the asymptoticst ^–3/2. The predicted values of the pion charge radius, P-wave isovector scattering length, as well as theI=J = 1 scattering amplitude at the experimental measurable region coincide with the world averaged data.Dedicated to the 30th anniversary of the Joint Institute of Nuclear Research.The authors are indebted to Prof. V. A. Meshcheryakov, Dr. S. B. Gerasimov and Dr. D. Krupa for many stimulating and illuminating discussions.     

Deviation of 1/f voltage fluctuations from scale-similar Gaussian behavior

Recent measurements on thin metal films suggest a pulse model of resistance fluctuations in which scale similarity and power law spectra are only approximate. We show that such a pulse model is consistent with stationary Gaussian resistance fluctuations. This is to be contrasted with the phenomenological behavior, of fluctuations near phase transitions and in turbulent fluids where the fluctuations are non-Gaussian, but exhibit scale similarity of deep physical origin. We then critically examine other tests of the Gaussian behavior of the fluctuating voltageV(t) across a resistor. These include the relaxation of the conditional mean V(t)¦V(0)=V ₀, and the spectrum ofV ²(t). We consider also the question of time reversal invariance. We further ask under what conditions 1/f noise can be measured through fluctuations of the Johnson noise power with no applied voltage. We emphasize that this possibility, suggested and observed by Voss and Clarke, requires thatV(t) contain a non-Gaussian component.     

On the interpretation of the thickness dependence of the coercive field of BaTiO3 single crystals

It is shown in the paper that the thickness dependence of the coercive field of unetched and of successively etched BaTiO₃ single crystals can be explained by the presence of a ferroelectric surface layer with decreased permittivity. In contrast to the Merz model [1], which considered a homogeneous layer, the authors assume that the permittivity inside the layer gradually decreases in the direction to the surface. By using experimental results it has been found for the constant, characterizing (according to [1]) the thickness dependence of the coercive field of unetched crystals, that=1.6 V, which is in satisfactory agreement with experiment.The authors thank V. Dvoák C.Sc, J. Fousek C.Sc, and Z. Málek C.Sc. for stimulating discussions.     

Chromaticity-stable organic white light-emitting devices based on mixed pyridine–phenol boron complex

We demonstrate molecular organic white light-emitting devices (LEDs), using vacuum-deposited thin films of N,N-diphenyl-N,N-bis(1-naphthyl)-(1,1-biphenyl)-4,4-diamine (NPB) as the hole-transporting layer, 1,6-bis(2-hydroxyphenyl)pyridine boron complex ((dppy)BF) as the emitting layer, tris-(8-hydroxyquinoline)aluminum (Alq) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as the red-emitting layer. The white light comes from three components: exciplex emission at the interface between NPB and (dppy)BF, which covers the wide range from 500 to 700 nm, blue emission from bulk NPB and (dppy)BF and red emission from DCJTB. The chromaticity of the devices can be tuned by varying the thickness of (dppy)BF and doped Alq layers. The Commission Internationale De L'Eclairage (CIE) coordinates of emitted light vary from (0.31, 0.335) to (0.32, 0.345) when forward voltages change from 10 to 20 V, which are just adjacent to the white-light equi-energy point (0.33, 0.33). The brightness and luminous efficiency are 150 cd/m² and 0.3l m/W at 12 V, respectively.     

Absence of long-range order with long-range potentials

A particular form of Mermin's inequality is analyzed for repulsive inverse power potentials [V(r)=e ² r ^–m/m] in ad-dimensional space. For long-range potentials (m d) the system is put into a stabilizing background. Long-range order is shown to be excluded ford (m + 2)/2 whenm d, while for short-range potentials (m > d) we recover Mermin's result (d 2). For Coulomb systems (m=d – 2) and the experimentally studied electron surface layer (d = 2,m=1), long-range order cannot be excluded by the present argument.     

High-Efficiency White Light Emission Using a Phosphorescent Sensitizer in Organic Light-Emitting Devices

We have fabricated white organic light-emitting devices by using the phosphorescent material fac tris (2-phenylpyridine) iridium [Ir(ppy₃)] as a sensitizer, as a result, the efficiency of these devices is improved dramatically. Ir(ppy)₃ and the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7- tetramethyljulolidyl-9-enyl)(DCJTB) are co-doped into 4,4-N,N-dicarbazole-biphenyl (CBP) host, whose thickness affects both color and efficiency of the devices. Tris (8-hydroxyquinoline) aluminum (Alq) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine or BCP) are used as electron-transporting and exciton-blocking layers, respectively, and N,N-diphenyl-N,N-bis(1-naphthyl)-(1,1-biphenyl)-4,4-diamine (NPB) as a blue light-emitting as well as hole-transporting layer. The maximum efficiencies of the devices with 15 and 20 nm co-doped BCP tuning layer are 7.5 and 8.6 cd/A, respectively, and the former presents fairly pure white emission with CIE coordinates of (0.33, 0.32) at 10 V, which is very stable at various biases (10–19 V).     

The measurements of the FMR of a MgMn ferrite film

The aim of this work was to study ferromagnetic resonance in the single crystal ferrite film with a small halfwidth of the resonance lineH _hkl in the bandsX, K andQ. The changes of the resonance static magnetic fields, the effective magnetization, the magnetocrystalline anisotropy field andH _hkl with the temperature and frequency were investigated.The author wishes to express her thanks to Dr. S. Krupika, CSc, Dr. Z. Frait, DrSc., Ing. J. Kantrek, CSc. and Dr. R. Gerber, CSc. for their valuable discussions. The author is also grateful to Mr. M. Janatka for carrying out the electron diffraction, and Ing. V. ik for his experimental assistance.     

Feynman path integrals and the trace formula for the Schrödinger operators

We study Schrödinger operators of the form on ^d , whereA ² is a strictly positive symmetricd×d matrix andV(x) is a continuous real function which is the Fourier transform of a bounded measure. If _n are the eigenvalues ofH we show that the theta function is explicitly expressible in terms of infinite dimensional oscillatory integrals (Feynman path integrals) over the Hilbert space of closed trajectories. We use these explicit expressions to give the asymptotic behaviour of (t) for smallh in terms of classical periodic orbits, thus obtaining a trace formula for the Schrödinger operators. This then yields an asymptotic expansion of the spectrum ofH in terms of the periodic orbits of the corresponding classical mechanical system. These results extend to the physical case the recent work on Poisson and trace formulae for compact manifolds.Partially supported by the USP-Mathematisierung, University of Bielefeld (Forschungsprojekt Unendlich dimensionale Analysis)     

Noncoassociative twisting: Its application to κ-Poincaré algebra

It is shown that the use of noncoassociative coproduct allows us to simplify the structure of-Poincaré algebra — it contains nondeformedD=3 Euclidean quasi-bialgebra. We obtain by the dual construction the commuting, nonassociativeD=4 space-time.Presented at the 4th international Colloquium Quantum Groups and Integrable Systems, Prague, 22–24 June, 1995I would like to thank Profs. J. Lukierski and V.N. Tolstoy for valuable comments.