bluuebunny/crossref_metadata_2025 huggingface dataset:
MASS GENERATION FOR NON-ABELIAN GAUGE FIELDS WITHOUT SCALARS
Authors: CAENEPEEL DIDIER , LEBLANC MARTIN
Published: November 2004

We present an alternative to the Higgs mechanism for generating masses for non-Abelian gauge fields in 3+1 dimensions. The initial Lagrangian is composed of a fermion with current-current and dipole-dipole type self-interactions minimally coupled to non-Abelian gauge fields. The mass generation occurs when we perform a fermionic functional integration. We show that by fine-tuning the coupling constants, the effective theory may be written as a BΛF type theory describing massive non-Abelian gauge fields.
SPECTRA OF HEAVY FLAVOR HADRONS BASED ON HEAVY QUARK EFFECTIVE THEORY
Authors: YU-BING DONG
Published: November 2004

In this paper, the spectra of heavy flavor hadrons, such as heavy flavor mesons [Formula: see text], baryons (QQq and Qqq) and multiquark systems [Formula: see text], are studied systematically based on the heavy quark effective theory. The calculated results of [Formula: see text] are compared with the predictions of the potential model.
AN EXAMPLE OF HIGHER WEIGHT SUPERPOTENTIAL INTERACTION IN THE HETEROTIC STRING ON ORBIFOLDS
Authors: ERDENEBAYAR D.
Published: November 2004

An explicit orbifold example of the nonzero correlation functions related to the additional contribution to the induced mass term for Higgs particles at low energies is given. We verify that they form finite-dimensional representations of the target space modular transformation SL 2(Z). This action of the modular group is shown to be consistent with its action on the fixed point set defining the twisted fields.
CLASSICAL YANG-MILLS THEORY WITH FERMIONS II: DIRAC’S OBSERVABLES
Authors: LUSANNA LUCA
Published: November 2004

For pure Yang-Mills theory on Minkowski space-time, formulated in functional spaces where the covariant divergence is an elliptic operator without zero modes, and for a trivial principal bundle over the fixed time Euclidean space with a compact, semisimple, connected and simply connected structure Lie group, a Green function for the covariant divergence has been found. It allows one to solve the first class constraints associated with Gauss’ laws and to identify a connection-dependent coordinatization of the trivial principal bundle. In a neighborhood of the global identity section, by using canonical coordinates of the first kind on the fibers, one has a symplectic implementation of the Lie algebra of the small gauge transformations generated by Gauss’ laws and one can make a generalized Hodge decomposition of the gauge potential one-forms based on the BRST operator. This decomposition singles out a pure gauge background connection (the BRST ghost as Maurer-Cartan one-form on the group of gauge transformations) and a transverse gauge-covariant magnetic gauge potential. After an analogous decomposition of the electric field strength into the transverse and the longitudinal part, Dirac’s observables associated with the transverse electric and magnetic components are identified as their restriction to the global identity section of the trivial principal bundle. The longitudinal part of the electric field can be re-expressed in terms of these electric and magnetic transverse parts and of the constraints without Gribov ambiguity. The physical Lagrangian, Hamiltonian, non-Abelian and topological charges have been obtained in terms of transverse Dirac’s observables, also in the presence of fermion fields, after a symplectic decoupling of the gauge degrees of freedom; one has an explicit realization of the abstract “Riemannian metric” on the orbit space. Both the Lagrangian and the Hamiltonian are nonlocal and nonpolynomial; like in the Coulomb gauge they are not Lorentz-invariant, but the invariance can be enforced on them if one introduces Wigner covariance of the observables by analyzing the various kinds of Poincare orbits of the system and by reformulating the theory on suitable spacelike hypersurfaces, following Dirac. By extending to classical relativistic field theory the problems associated with the Lorentz noncovariance of the canonical (presymplectic) center of mass for extended relativistic systems, in the sector of the field theory with P2>0 and W2≠0 one identifies a classical invariant intrinsic unit of length, determined by the Poincare Casimirs, whose quantum counterpart is the ultraviolet cutoff looked for by Dirac and Yukawa: it is the Compton wavelength of the field configuration (in an irreducible Poincare representation) multiplied by the value of its spin.
ALGEBRAIC CHARACTERIZATION OF ANOMALIES IN CHIRAL ${\mathcal W}_3$ GRAVITY
Authors: CARVALHO MARCELO , VILAR LUIZ CLAUDIO QUEIROZ , SORELLA S.P.
Published: November 2004

The anomalies which occur in chiral [Formula: see text] gravity are characterized by solving the BRS consistency condition.
MODIFIED TETRAHEDRON EQUATIONS AND RELATED 3D INTEGRABLE MODELS, I
Authors: BOOS H.E. , MANGAZEEV V.V. , SERGEEV S.M.
Published: November 2004

Using a modified version of the tetrahedron equations we construct a new family of N- state three-dimensional integrable models with commuting two-layer transfer matrices. We investigate a particular class of solutions to these equations and parametrize them in terms of elliptic functions. The corresponding models contain one free parameter, k—an elliptic modulus.
EXTENDED ANALYSIS OF THE “PENGUIN” PART OF THE K→ππ AMPLITUDE
Authors: PENIN A.A. , PIVOVAROV A.A.
Published: November 2004

We make an attempt to clarify the role of the annihilation or “penguin” mode in the description of the K→ππ decay within the Standard Model. Attention is centered on new operators in the effective ΔS=1 Hamiltonian and the violation of factorization for mesonic matrix elements of the local four-quark operators. We propose a regular method to evaluate the mesonic matrix elements of K→ππ transitions based on the study of three-point correlators via QCD sum rules using the chiral effective theory as an underlying low energy model for strong interaction. Matrix elements of the QCD penguin operator are calculated within this approach. The total “penguin” contribution is found to be relatively large, which improves the theoretical description of the ΔI=1/2 rule in nonleptonic kaon decays.
CONSTRAINT ALGEBRAS IN GAUGE-INVARIANT SYSTEMS
Authors: NIROV KH. S.
Published: November 2004

A Hamiltonian description is constructed for a wide class of mechanical systems having local symmetry transformations depending on time derivatives of the gauge parameters of arbitrary order. The Poisson brackets of the Hamiltonian and constraints with each other and with an arbitrary function are explicitly obtained. The constraint algebra is proved to be of the first class.
RARE b DECAYS
Authors: PLAYFER STEPHEN , STONE SHELDON
Published: November 2004

Rare b decays provide a unique opportunity to measure Standard Model parameters and probe beyond the Standard Model. We review here the experimental progress made in measuring these decays, and the importance of future measurements, including the possible observation of CP violation.
“MODULI SPACE” OF ASYMPTOTICALLY ANTI-DE-SITTER SPACE-TIMES IN 2+1 DIMENSIONS
Authors: EZAWA KIYOSHI
Published: November 2004

Setting an ansatz that the metric is expressible by a power series of the inverse radius and taking a particular gauge choice, we construct a “general solution” of (2+1)-dimensional Einstein equations with a negative cosmological constant in the case where the space-time is asymptotically anti-de-Sitter. Our general solution turns out to be parametrized by two centrally extended quadratic differentials on S1. In order to include three-dimensional black holes naturally in our general solution, it is necessary to exclude the region inside the horizon. We also discuss the relation of our general solution to the moduli space of flat [Formula: see text] connections.
LINEAR WAVE EQUATIONS AND EFFECTIVE LAGRANGIANS FOR WIGNER SUPERMULTIPLETS
Authors: DAHM R. , KIRCHBACH M.
Published: November 2004

The relevance of the contracted SU(4) group as a symmetry group of the pion-nucleon scattering amplitudes in the large Nc limit of QCD raises the problem of the construction of effective Lagrangians for SU(4) supermultiplets. In this study we suggest effective Lagrangians for self-conjugate representations of SU(4) in exploiting isomorphism between SO(6) and its universal covering SU(4). The model can be viewed as an extension of the linear σ model with SO(6) symmetry in place of SO(4) and generalizes the concept of the linear wave equations for particles with arbitrary spin. We show that the vector representation of SU(4) reduces on the SO(4) level to a complexified quaternion. Its real part gives rise to the standard linear σ model with a hedgehog configuration for the pion field, whereas the imaginary part describes vector meson degrees of freedom via purely transversal ρ mesons for which a helical field configuration is predicted. As a minimal model, baryonic states are suggested to appear as solitons of that quaternion.
EXPERIMENTAL CONSEQUENCES OF ONE-PARAMETER NO-SCALE SUPERGRAVITY MODELS
Authors: LOPEZ JORGE L. , NANOPOULOS D.V. , ZICHICHI A.
Published: November 2004

We consider the experimental predictions of two one-parameter no-scale SU (5)× U (1) supergravity models with string-inspired moduli and dilaton seeds of supersymmetry breaking. These predictions have been considerably sharpened with the new information on the top-quark mass from the Tevatron, and the actual measurement of the B(b→sγ) branching ratio from CLEO. In particular, the sign of the Higgs mixing parameter μ is fixed. A more precise measurement of the top-quark mass above (below) ≈160 GeV would disfavor the dilaton (moduli) scenario. Similarly a measurement of the lightest Higgs-boson mass above 90 GeV (below 100 GeV) would disfavor the dilaton (moduli) scenario. At the Tevatron with 100 pb−1, the reach into parameter space is significant only in the dilaton scenario [Formula: see text] via the trilepton and top-squark signals. At LEPII the dilaton scenario could be probed up to the kinematical limit via chargino and top-squark pair production, and the discovery of the lightest Higgs boson is guaranteed. In the moduli scenario, only selectron pair production looks promising. We also calculate the supersymmetric contribution to the anomalous magnetic moment of the muon.
TWISTING OF N=1 SUSY GAUGE THEORIES AND HETEROTIC TOPOLOGICAL THEORIES
Authors: JOHANSEN A.
Published: November 2004

It is shown that D=4N=1 SUSY Yang-Mills theory with an appropriate supermultiplet of matter can be twisted on a compact Kähler manifold. The conditions for cancellation of anomalies of BRST charge are found. The twisted theory has an appropriate BRST charge. We find a nontrivial set of physical operators defined as classes of the cohomology of this BRST operator. We prove that the physical correlators are independent of the external Kähler metric up to a power of a ratio of two Ray-Singer torsions for the Dolbeault cohomology complex on a Kähler manifold. The correlators of local physical operators turn out to be independent of antiholomorphic coordinates defined with a complex structure on the Kähler manifold. However, a dependence of the correlators on holomorphic coordinates can still remain. For a hyper-Kähler metric the physical correlators turn out to be independent of all coordinates of insertions of local physical operators.
TOPOLOGICAL FIELD THEORY OF VORTICES OVER CLOSED KÄHLER MANIFOLD
Authors: LEE HYUK-JAE
Published: November 2004

We show that the vortex equations of the n-dimensional closed Kähler manifolds can be derived from Einstein-Hermitian equations of the (n+1)-dimensional closed Kähler manifolds by setting invariance under translation in the (n+1)th component direction. We construct the topological theory about the vortex pair model through the dimensional reduction of the topological BRST structure.
THE PROPER TIME FORMALISM, GAUGE INVARIANCE AND THE EFFECTS OF A FINITE WORLD SHEET CUTOFF IN STRING THEORY
Authors: SATHIAPALAN B.
Published: November 2004

We discuss the issue of going off-shell in the proper time formalism. This is done by keeping a finite world sheet cutoff. We construct one example of an off-shell covariant Klein-Gordon type interaction. For a suitable choice of the gauge transformation of the scalar field, gauge invariance is maintained off-mass-shell. However, at the second order in the gauge field interaction, one finds that [U(1)] gauge invariance is violated due to the finite cutoff. Interestingly, we find, to the lowest order, that by adding a massive mode with appropriate gauge transformation laws to the sigma model background, we can restore gauge invariance. The gauge transformation law is found to be consistent, to the order calculated, with what one expects from the interacting equation of motion of the massive field. We also extend some previous discussion on applying the proper time formalism for propagating gauge particles, to the interacting (i.e. Yang-Mills) case.
BLACK HOLES IN TWO-DIMENSIONAL DILATON GRAVITY AND NONLINEAR KLEIN-GORDON SOLITON
Authors: JOHNG HYEON-MIN , SHIN HAK-SOO , SOH KWANG-SUP
Published: November 2004

Two-dimensional dilaton gravity coupled to a Klein-Gordon matter field with a quartic interaction term is considered. The theory has a classical solution which exhibits black hole formation by a soliton. The geometry of a black hole induced by a soliton is investigated.
EXACT SOLUTIONS OF THE FLUX-CREEP MODEL AND SOLITON-FLUX DYNAMICS AND THEIR APPLICATION IN TYPE-II SUPERCONDUCTORS
Authors: MA Y.L. , LI H.F. , DAI X.X.
Published: November 2004

Recently, much attention has been focused on the exactly solvable model of flux-creep in high-Tc superconductors. In this paper, the exact solution of the flux-creep model based on both thermal-activation and quantum-tunneling flux-creep theories is explicitly given. For a typical weakly periodical or quartic pinning potential and/or flux-flux interaction in a viscous medium, both classical motion in the thermal-activation region and quantum motion in the quantum-tunneling region are semi-classically analyzed, and the dependencies of activation energy and crossover temperature on several important parameters of the system are studied in more detail. The exact and explicit expression of the flux relaxation rate is derived for the full parameter range. We calculate the flux relaxation rate as a function of temperature and the current density as a function of time and find that this simple phenomenological theory is very effective in accounting for the experimental observations obtained in both high-Tc and low-Tc superconductors.
MAGNETIC FIELD AND HISTORY DEPENDENCE OF THE HARMONIC SUSCEPTIBILITY IN A GRANULAR SUPERCONDUCTOR
Authors: MANZOOR SADIA , HASANAIN S.K. , NOMAN M.A. , BHATTI G.S.
Published: November 2004

We report on the generation of harmonics of the ac susceptibility in a typical Y(123) granular superconductor. The intergrain harmonic response has been studied at T=77 K as a function of the ac field, both with and without superposed dc fields. We find that our results can be adequately described by the Anderson-Kim model. The effect of superposed dc fields on the ac field dependence of the even and odd harmonics has been qualitatively explained. Magnetic history dependence has ben studied in the field cooled and remnant states. Effects of field cooling indicate that the intergrain fields in this case are slightly smaller than for the corresponding zero field cooled condition. Remnant field studies clearly show the role of trapped flux in generating even harmonics.
QUANTUM THEORY OF LANDAU AND PEIERLS ELECTRONS FROM THE CENTRAL EXTENSIONS OF THEIR SYMMETRY GROUPS
Authors: DIVAKARAN P.P. , RAJAGOPAL A.K.
Published: November 2004

By Wigner’s theorem on symmetries, the total state space of a quantum system whose symmetries form the group G is the collection of all projective unitary representations of G; these are, in turn, realised as certain unitary representations of the set of all central extensions of G by U(1). Exploiting this relationship, we present in this paper a new approach to the quantum mechanics of an electron in a uniform magnetic field B, in the plane (the Landau electron) and on the 2-torus in the presence of a periodic potential V whose periodicity is that of an N×N lattice (the Peierls electron). For the Landau electron, G is the Euclidean group E(2) whose central extensions arise from the Heisenberg Lie group central extensions, determined by B, of the translation subgroup. The state space is a unitary representation of the direct product of two such groups corresponding to B and -B and the Hamiltonian is a unique element of the universal enveloping algebra of the centrally-extended E(2). The complete quantum theory of the Landau electron follows directly. For the Peierls electron, lattice translation-invariance is possible only if the flux per unit cell Φ takes rational values with denominator N. The state space is a unitary representation of the direct product of a finite Heisenberg group, which is a central extension of the translation group, and a Heisenberg Lie group, both characterised by Φ. The following new results are rigorous consequences. In the empty lattice limit V=0, the energy spectrum is the Landau spectrum with degeneracy equal to the total flux through the sample. As V moves away from zero, every Landau level splits into NΦ discrete sublevels, each of degeneracy N. More generally, for V≠0 of any strength and (periodic) form, and B such that Φ is nonintegral, every point in the spectrum has multiplicity N. The degeneracy is thus proportional to the linear size rather than the area of the sample. Throughout the paper, vector potentials and gauges are dispensed with and many misconceptions thereby removed.
FROM FREE CLUSTERS TO CLUSTER-ASSEMBLED MATERIALS
Authors: MELINON P. , PAILLARD V. , DUPUIS V. , PEREZ A. , JENSEN P. , HOAREAU A. , PEREZ J.P. , TUAILLON J. , BROYER M. , VIALLE J.L. , PELLARIN M. , BAGUENARD B. , LERME J.
Published: November 2004

In this paper the specific properties of free clusters and the formation of new cluster-assembled materials using the low energy cluster beam deposition (LECBD) technique are discussed. Recent results obtained for free clusters are summarized with special attention to new observed structures. As for the specific structures and properties of cluster-assembled materials, two main aspects are specially emphasized: the memory effect of the free cluster properties leading to the formation of new phases and the effect of the specific nanostructure of the cluster-assembled materials related to the random cluster stacking mechanism characteristic of the LECBD. These effects and the corresponding potential applications are illustrated using some selected examples: new diamond-like carbon films produced by fullerene depositions (memory effect) and grain effect on the magnetic properties of cluster-assembled transition metal films.
ONE MODEL OF SINGULAR RELATIVISTIC LAGRANGIAN
Authors: LASERRA E. , STRIANESE M. , PAVLOTSKY I.P.
Published: November 2004

The so-called no-interaction theorem of D.G. Currie, T.F. Jordan, E.C. Sudarshan, H. Leutwyler, G. Marmo and N. Mukunda makes it possible to construct relativistic quasiclassical particle dynamics in the post-Galilean approximation only. It is obtained that in this approximation the Lagrangians are singular on some surfaces of the phase space. These peculiarities have different physical and mathematical nature from the ones studied by P.M.A. Dirac, where Hessians vanish in the whole phase-space. The dynamical properties are essentially peculiar on the studied singular surfaces. These properties, in our opinion, can be related with some physical phenomena.

In the present paper the general situation is first described. As the whole problem is large and difficult we examined in detail just typical one- and two-dimensional models in the second part of the paper.
(ALMOST) EVERYTHING YOU ALWAYS WANTED TO KNOW ABOUT THE CONDUCTANCE OF MESOSCOPIC SYSTEMS
Authors: KAMENEV ALEX , GEFEN YUVAL
Published: November 2004

We present a systematic analysis of the average complex conductance of an ensemble of disordered mesoscopic conductors. It is argued that multiply connected Aharonov-Bohm rings are particularly amenable to this study, and reflect certain general features of the problem. Two ingredients are shown to be crucial in this context: (i) the ratio between the mean level spacing and the inelastic broadening of each level and (ii) the type of the statistical ensemble employed. Correspondingly, we distinguish between continuous and discrete spectrum limits and between canonical and grand canonical statistical ensembles. The conductance varies qualitatively as either of these two ingredients is changed. Analytical results for the conductance as a function of the magnetic flux, frequency and temperature are obtained in each limiting case. In particular, the sign of the d.c. (ω→0) magnetoconductance may change between the two limits. We also discuss the effect of electron-electron interaction.
ON THE QUANTUM KAGOMÉ ANTIFERROMAGNET
Authors: ASAKAWA HITOSHI , SUZUKI MASUO
Published: November 2004

The purpose of the present paper is to review investigations of the antiferromagnetic Heisenberg model on the kagomé lattice and to propose some schemes based on the spin-wave theory by which physical properties of the present model can be better understood. By means of our schemes, it is shown that the linear-spin-wave flat mode of the present model comes from the semi-local symmetry of the linear-spin-wave Hamiltonian, where the flat mode has an excitation-spectrum with ω≡0 for all k. It is also shown that the inclusion of higher-order quantum fluctuations may break the symmetry and thereby the flat mode may be lifted up.
EFFECT OF THE NONEQUILIBRIUM DISTRIBUTION FUNCTION ON THE ENERGY LOSS RATE OF HOT ELECTRONS IN A SEMICONDUCTOR
Authors: XING D.Y. , YANG J. , TING C.S.
Published: November 2004

The closed time path Green’s function method is used to derive the nonequilibrium distribution functions of acoustic phonons and excitations of hot electrons, renormalized by the electron-phonon interaction in the random phase approximation, and to calculate the power dissipation of hot electrons. It is shown that the energy loss channel of hot electrons would vanish unless a relaxation rate corresponding to the decay of one acoustic phonon into two or more bare acoustic phonons via the anharmonic interaction is explicitly included in the phonon propagator. The effect due to the anharmonic interaction on the energy loss rate of hot electrons has also been studied.
DISSIPATIVE STRUCTURES IN A DOUBLE PLASMA ON AN EXCITED SEMICONDUCTOR: NEAR ONE-DIMENSIONAL SYSTEMS
Authors: ESPERIDIÃO A.S.C. , ANDRADE R.F.S.
Published: November 2004

The formation of dissipative structures in a double plasma of electron and holes, generated on a semiconductor sample by submitting it to a continuous laser beam, is investigated. The equations of motion for the quasi-particles are obtained after the nonequilibrium statistical operator method and constitute an infinite system of coupled differential equations. When the kinetics of the system is one-dimensional, the search for the eigen-values of the linear stability analysis matrix, in the [Formula: see text] limit, reduces to an equation of 8th degree. The results show that the doped system is intrinsically unstable with respect to the intensity of the laser and that the bifurcation from the stable state to the dissipative structure is from a stable to an unstable node.
EPR STUDIES OF HIGH-Tc SUPERCONDUCTORS AND RELATED SYSTEMS
Authors: PUNNOOSE ALEX , SINGH R.J.
Published: November 2004

A detailed and systematic review of the EPR studies of high-Tc superconductors and their related and parent systems are presented. The various EPR signals reported from the high-Tc oxides and from their related cuprates are summarized. The experimental evidences highlighted by various workers claiming the EPR silence of copper in the high-Tc materials are also reviewed. Various theoretical models suggested by several workers to explain the observed unusual EPR silence of copper in the high-Tc superconductors are critically discussed.
TIME-DEPENDENT PROPERTIES FOR NEURAL NETWORKS WITH CONTINUOUS SPIN VARIABLES
Authors: BANERJEE VARSHA , PURI SANJAY
Published: November 2004

We present a continuous-time neural network model which consists of neurons with a continuous input-output relation. We use a computationally efficient discrete-time equivalent of this model to study its time-dependent properties. Detailed numerical results are presented for the behavior of the relaxation time to a target pattern as a function of the storage capacity of the network.
GAP FORMATION PROBABILITY OF THE α-ENSEMBLE
Authors: CHEN YANG , ERIKSEN KASPER JUEL
Published: November 2004

In this paper we employ the continuum approximation of Dyson to determine the asymptotic gap formation probability in the spectrum of N×N Hermitian matrices associated with orthogonal polynomials that are solutions of indeterminate moment problems. We have shown that the probability, Eβ[J], that an interval J is free of eigenvalues is [Formula: see text]

where

[Formula: see text]
FOUR-PARTICLE ANYON EXCITON: BOSON APPROXIMATION
Authors: Portnoi M. E. , Rashba E. I.
Published: November 2004

A theory of anyon excitons consisting of a valence hole and three quasielectrons with electric charges –e/3 is presented. A full symmetry classification of the k = 0 states is given, where k is the exciton momentum. The energy levels of these states are expressed by quadratures of confluent hypergeometric functions. It is shown that the angular momentum L of the exciton ground state depends on the distance between the electron and hole confinement planes and takes the values L = 3n, where n is an integer. With increasing k the electron density shows a spectacular splitting on bundles. At first a single anyon splits off of the two-anyon core, and finally all anyons become separated.
ELECTRICAL RESISTIVITY OF LIQUID-QUENCHED AMORPHOUS ALLOYS
Authors: NAQVI S. M. M. R. , RIZVI S. DABIR H. , RAZA S. MOHSIN , GORMANI MUSHTAQ AHMAD , FAROOQUI N.
Published: November 2004

Electrical resistivity measurements of amorphous ( Fe x Co 100-x)83 B 17 alloys in the temperature range 40 K < T < 300 K have been obtained. We observed from the analysis of the resistivity data that there is no s-d interaction or Js-d coupling. An empirical relationship for estimating Θ D is suggested from the normalized electrical resistivity data, which holds good both for theoretical and estimated Θ D . For s-d interaction or Js-d coupling to occur in ferromagnetic amorphous alloys, ordering of ferromagnetic domains, i.e. Heisenberg interaction in a disordered matrix, would require temperatures of T ≤ Θ D /50 ≃ 0.02 Θ D .
FUNCTIONAL INTEGRAL OF ANTIFERROMAGNETIC SPIN FLUCTUATIONS IN HIGH-TEMPERATURE SUPERCONDUCTORS
Authors: KRUCHININ S. P.
Published: November 2004

The Schwinger–Dyson equations and equation for free energy are derived in the approximation of weak coupling interaction for antiferromagnetic spin fluctuations in high temperature superconductors. For the calculations the method of functional integrals was used. The thermodynamic of the system is calculated near T c and the evaluations of the parameter ∆C/γT c are given.
ORBITING OF FREE, CLASSICAL ELECTRONS IN THE FIELD OF TWO SLOWLY APPROACHING CHARGES
Authors: JAKAS M. M. , HERNÁNDEZ-CABRERA A. J. , ACEITUNO P.
Published: November 2004

The motion of a free, classical, spinless electron in the field of two nuclei during low velocity atomic collisions is investigated. It is found that if one neglects the bremmstrahlung and interactions with other electrons, a free electron can orbit around the two nuclei with a surprisingly high stability. A maximum energy, however, appears above which such an orbiting becomes unstable. The connection between these findings and the acceleration of electrons by means of the Fermi shuttle effect is also discussed.
NEW INCARNATIONS OF INFINITE STATISTICS
Authors: PANIGRAHI P. K. , CHATURVEDI S. , SRINIVASAN V.
Published: November 2004

In this paper, we present two new realizations of infinite statistics and construct their respective number operators in a simple manner. One of the realizations assumes the individual oscillators to be bosonic but the mutually commutation relationship (CR) to be of the quonic form. Interestingly, the system of mutually commuting oscillators satisfying individual relations of the type [Formula: see text] (no sum over i) is shown to describe a collection of bosons. This demonstrates that for these examples the mutual CRs between the oscillators decide the statistics.
NOVEL TRANSPORT BEHAVIOR FOUND IN THE DISSIPATIVE REGIME OF SUPERCONDUCTORS
Authors: KUNCHUR MILIND N.
Published: November 2004

As the transport current density J in a superconductor is increased beyond its critical value J c , dissipation sets in resulting in a finite resistivity. The superconducting state itself, however, persists up to the pair-breaking value J d , where the kinetic energy associated with the current overcomes the condensation energy. Within this dissipative regime between J c and J d , the transport behavior displays a series of interesting physical phenomena (free flux flow, pair-breaking effect, etc.) as the Lorentz force and kinetic energy associated with the current sequentially overcome various intrinsic (e.g., pair-condensation and interlayer-coupling) and extrinsic (e.g., flux pinning) interactions relevant to the superconducting state. This review discusses these phenomena in the context of recent experiments where the existence of these effects was demonstrated in high-T c superconductors for the first time. Also described are the general principles of the pulsed-current technique used to extend transport measurements to the required high current densities and power-dissipation levels.
EFFECT OF THE SECOND PHASE ON CRITICAL CURRENT DENSITY IN Nb-ADDED YBCO FILMS
Authors: JIA JUN-HUI , QI ZHEN-ZHONG
Published: November 2004

Thin films of YBCO with or without Nb added were prepared on (100) ZrO 2 single crystalline substrate by dc magnetron sputtering method. A phase of YBa 2 NbO 6 was found to form not only in the target materials of YBCO but also in the sputtered thin films. The second phase of YBa 2 NbO 6 in the superconducting films destroyed a match relation between the lattice of YBCO and the lattice of ZrO 2 substrate. The measurements of critical current density J c under magnetic field (H // c axis, up to 5T) showed that the J c in Nb-added YBCO films reduced more apparently than that in YBCO films. It is concluded that the existence of second phase of YBa 2 NbO 6 in superconducting phase does not play a rule of flux pinning.
LONG TIME ASYMPTOTICS OF DIFFUSION IN A RANDOM MEDIUM
Authors: WANG XIAO-HONG , WANG KE-LIN
Published: November 2004

Based upon the assumption that the trajectory of a particle subjected to a thermal noise and to a divergenceless random force has the Gaussian distribution, the long time asymptotics of the particle displacement are analyzed. The results are in agreement with that of the renormalization group analysis.
STRUCTURAL AND THERMODYNAMIC PROPERTIES OF 3d TRANSITION METALS: PSEUDOPOTENTIAL THEORY REVISITED
Authors: OSMAN S. M. , RAHMAN S. M. MUJIBUR
Published: November 2004

Structural and thermodynamic properties of 3d transition metals are calculated in terms of the pseudopotential theory. The s − p and d electrons are treated in a pseudoadiabatic approximation in such a way that the s − p and d electrons are treated separately under the same footing. The s − p electrons are treated in terms of the conventional second order pseudopotential theory, while the tightly bound d electrons are treated in terms of the Wills–Harrison prescription that makes use of the Friedel rectangular electron density of states (DOS) model. The predictions of the structural phase stability and other relevant thermodynamic properties are found to be consistent with experiments for almost all of the metals.
DAMAGE HEALING IN SINGLE COMPONENT IRREVERSIBLE REACTION PROCESSES
Authors: ALBANO EZEQUIEL V.
Published: November 2004

The spreading of a globally distributed damage, created in the stationary regime, is studied in single component irreversible reaction processes on one-dimensional lattices. Each model exhibits an irreversible phase transition between a stationary reactive state and an inactive (absorbing) state. It is found that the processes are immune in the sense that even 100% of initial damage is healed within a finite healing period (T H ). Within the reactive regime, T H diverges when approaching criticality and the corresponding exponent is independent of the process, i.e. it seems to be universal for one-component systems.
PERCOLATION STUDIES IN SmBa2SbO6–YBa2Cu3O7−δ COMPOSITE SYSTEM
Authors: WARIAR P. R. S. , KOSHY J. , KURIAN J. , YADAVA Y. P. , DAMODARAN A. D.
Published: November 2004

Percolation behavior of normal state resistivity and superconductivity of SmBa 2 SbO 6– YBa 2 Cu 3 O 7−δ have been studied. The normal state and superconducting percolation threshold values of the composite are both found to be around 22% of YBa 2 Cu 3 O 7−δ in the system. The X-ray diffraction and resistivity measurements on the above percolation system have shown that there is no detectable reaction between SmBa 2 SbO 6 ceramic and YBa 2 Cu 3 O 7−δ superconductor even when the two substances are mixed thoroughly and sintered at 1020°C. The values of exponent 't' and 'u' describing the transport properties of the system are found to be 1.66 and 0.66 which agree with the theoretically expected value for a perfect composite system. The implications of the results are discussed.
RANDOM WALKS ON KEBAB LATTICES: LOGARITHMIC DIFFUSION ON ORDERED STRUCTURES
Authors: CASSI D. , REGINA S.
Published: November 2004

Kebab lattices are ordered lattices obtained matching an infinite two-dimensional lattice to each point of a linear chain. Discrete time random walks on these structures are studied by analytical techniques. The exact asymptotic expressions of the mean square displacement and of the RW Green functions show an unexpected logarithmic behavior that is the first example of such kind of law on an ordered structure. Moreover the probability of returning to the origin shows the fastest long time decay ever found for recursive random walks.
GROUND-STATE PROPERTIES OF THE SPIN-1/2 ANTIFERROMAGNETIC HEISENBERG MODEL ON A CUBIC LATTICE BY A MONTE CARLO METHOD
Authors: SAUERWEIN R. A. , DE OLIVEIRA M. J.
Published: November 2004

The spin-1/2 antiferromagnetic Heisenberg model with spatial anisotropy is studied on a cubic lattice by a Monte Carlo Method. Two types of spatial anisotropies are considered: planar and axial. The staggered magnetization m† and the ground state energy per site ∊0 are obtained as a function of the anisotropy. In the isotropic case we have obtained m† = 0.429 ± 0.001 in units where the saturated value is 0.5 and ∊0 = –0.899 ± 0.001.
STRAIN RELAXATION IN SEMICONDUCTOR HETEROSTRUCTURES
Authors: FISCHER A. , KÜHNE H.
Published: November 2004

A brief review is presented for our new approach in equilibrium theory for strain relaxation in metastable heteroepitaxial semiconductor structures, one which includes the elastic interaction between straight misfit dislocations and the lattice mismatch accommodation by tetragonal distortion of the cubic lattice cells. This approach provides an equilibrium theory which correctly predicts critical strained layer thicknesses and completely describes the strain relief via plastic flow and the phenomenon of work hardening in lattice mismatched epilayers. Experimentally observed values of critical layer thickness and strain relief are discussed and compared with our theoretical predictions.
TRANSITIONS FROM SMECTIC C* TO ISOTROPIC PHASE IN AN APPLIED ELECTRIC FIELD
Authors: CUCULESCU I. , ALEXE-IONESCU A. L. , BENA R. , GHIZDEANU C. , STOIAN V. , BARBERO G. , TH. IONESCU A.
Published: November 2004

The transition temperatures from smectic C* to isotropic phase of a liquid crystal have been recorded as a function of an applied electric field. In addition to recent investigations on the phase transitions from smectic C* to smectic A in an electric field, we have found, in our case, a decrease of the transition temperature with the electric field. An explanation has been suggested to this behavior and a formula has been obtained which fits well the experimental points.
CALCULATION OF THE FLORY EXPONENTS BY A SELF-CONSISTENT METHOD
Authors: WANG XIAO-HONG , WANG KE-LIN
Published: November 2004

The polymers that have no ends and interact with a background tangent field u(x, t) are considered to act as the random walk subjected to a thermal noise η(t) and to a divergenceless random force u(x, t). Batchelor's suggestion for the diffusive behaviors of a single particle immersed in turbulent flows in extended to the case of polymers conformation. Based upon the assumption that the particle displacement has the Gaussian distribution for the long diffusion time, Flory's exponents are calculated to be ν = 1/2 for d ≥ 4 and ν = 3/(d+2) for d ≤ 4, in agreement with that of Kamien by the dynamical renormalization group method.
ELECTROLUMINESCENCE ENHANCEMENT IN A DELTA-DOPED QUANTUM WELL OF A BIPOLAR RESONANT TUNNELING DIODE
Authors: SHENG HANYU
Published: November 2004

An analytical model of a δ-doped quantum well is developed. The results show that by using δ-doped quantum well structures, the area densities of the electrons and holes in the conduction and valence bands, respectively, can be increased by four orders of magnitudes compared with the n-i-p structure. Therefore the electroluminescence enhancement can be expected for the bipolar resonant tunneling diode of δ-doped quantum well.
FINITE SIZE CORRECTIONS IN THE FERROMAGNETIC PHASE OF THE RANDOM ENERGY MODEL
Authors: ROUHANI S. , SAAKIAN D.
Published: November 2004

The ferromagnetic phase of the random energy model was investigated for all values of the parameters. Finite size corrections to the free energy were calculated and the fine structure of the phase diagram, areas with the same size corrections, in the ferromagnetic phase was found.
INEQUIVALENT REPRESENTATIONS OF A q-OSCILLATOR ALGEBRA IN A QUANTUM q-GAS
Authors: R-MONTEIRO M. , RODRIGUES L. M. C. S.
Published: November 2004

We study the consequences of inequivalent representations of a q-oscillator algebra on a quantum q-gas. As in the "fundamental" representation of the algebra, the q-gas presents the Bose-Einstein condensation phenomenon and a λ-point transition. The virial expansion and the critical temperature of condensation are very sensible to the representation chosen; instead, the discontinuity in the λ-point transition is unaffected.
HARTREE–FOCK GROUND STATE OF THE COMPOSITE FERMION METAL
Authors: SITKO PIOTR , JACAK LUCJAN
Published: November 2004

Within the Hartree–Fock approximation the ground state of the composite fermion metal is found. We observe that the single-particle energy spectrum is dominated by the logarithmic interaction exchange term which leads to an infinite jump of the single-particle exchange at the Fermi momentum. It is shown that the Hartree–Fock result brings no corrections to the RPA Fermi velocity.
LOCALIZATION LENGTHS IN HARMONIC CHAINS WITH CORRELATED DISORDER
Authors: GINANNESCHI P. MURATORE , PETRI A. , VULPIANI A.
Published: November 2004

We show that the localization properties of harmonic chains with correlated random coupling constants kj are strongly dependent on frequency. Using different processes for the generation of the coupling sequence {kj} we observe two regimes: a regular one, where the localization length ξ is roughly proportional to the correlation length l of {kj}, and an anomalous one, in which there is not a proportionality relation and where one can have non intuitive behaviors, e.g. ξ does not increase for increasing l.
ELECTRODYNAMICAL COHERENCE IN WATER: A POSSIBLE ORIGIN OF THE TETRAHEDRAL COORDINATION
Authors: DEL GIUDICE EMILIO , GALIMBERTI ALBERTO , GAMBERALE LUCA , PREPARATA GIULIANO
Published: November 2004

In the conceptual framework of Coherent Quantum Electrodynamics we show that the molecules of the liquid phase are described by individual quantum states that differ from those in which the molecules find themselves while in the gas phase. We suggest that tetrahedral coordination emerges from such individual configurations.
CONTROLLED VERTICAL AND LATERAL MANIPULATION OF SINGLE ATOMS AND MOLECULES WITH THE SCANNING TUNNELING MICROSCOPE
Authors: NEU BJÖRN , MEYER GERHARD , RIEDER KARL-HEINZ
Published: November 2004

We report on the successful controlled vertical manipulation of single Xe atoms with the scanning tunneling microscope (STM) at a temperature of 15 K. In transferring Xe atoms from the Cu(211) substrate to the STM tip and releasing them back to the surface we used a technique similar to that employed previously by Eigler and collaborators. We demonstrate that with the well defined Xe-tip the substrate is imaged with appreciably better resolution. We show further that nanostructures built at 15 K with CO molecules by employing lateral manipulation are much more stable than those produced at 30 K, on which we reported previously. As an important consequence such structures can be produced quicker and with larger precision.
MUTUAL TRANSFER OF SQUEEZING EFFECT IN COUPLED TWO-PHOTON LASERS
Authors: GOMES A.R. , BASEIA B. , MARQUES G.C.
Published: November 2004

We investigate the mutual influence of two interacting 2-photon lasers, each subsystem being modelled as a quadratic oscillator in terms of the ladder operators âi, [Formula: see text] owing to the generation and transfer of squeezing effect. We find an exact solution for this coupled system which allows us to obtain the variances in the conjugate operators ẑi, [Formula: see text]. The results are exhibited in several plots showing the influence of the involved parameters. The second oscillator exhibits squeezing even if its nonlinear term is absent, due to the transference of the effect originated in the first (nonlinear) oscillator. Concerning this effect, the oscillators compete or cooperate depending on the parameters range; for some parameter range the system becomes unstable, as shown in numerical plots.
PAIRING SYMMETRY AND ISOTOPE EFFECT IN HIGH-TEMPERATURE SUPERCONDUCTOR
Authors: JACAK L. , BUJKIEWICZ L.
Published: November 2004

It is demonstrated that various forms of the 2D pairing parameter lead to an unusual type of the isotope effect quite distinct from the ordinary BCS behavior. The special form of the local pairing in the real space is considered in order to better use the density of states singularities and explain critical lattice distortion for high-temperature superconductors. The isotope effect is also studied for the recently suggested weak coupling theory with the order parameter antisymmetric in energy with respect to Fermi level.
THERMOELECTRIC POWER IN Nd1.85Ce0.15CuO4–y
Authors: RUAN K.Q. , WANG N.L. , WANG R.P. , CHONG Y. , DENG M. , ZHOU W. , CAO L.Z.
Published: November 2004

Nd 1.85 Ce 0.15 CuO 4–y samples were prepared by annealing at various temperatures under different atmospheres. It is found that the superconducting samples exhibit positive thermoelectric power while the nonsuperconducting samples show negative values. A negative slope (dS/dT<0) in the temperature dependent thermoelectric power is observed for T>240 K. This result is discussed.
TEMPERATURE AND DOPING LEVEL DEPENDENCE OF DELAYED RADIATION INDUCED CONDUCTIVITY IN CHROMIUM POLYACRYLATE
Authors: RAUF A. , REHMAN S.U. , KHWAJA FARID A.
Published: November 2004

The radiation induced conductivity of post-irradiated chromium polyacrylate (CrPA) is investigated as a function of exposure rate, temperature, doping level (concentration) and field strength. The samples are irradiated with 5.5 MeV 241AM, α-source. The exposure rate is varied from 5.96×108 particles/cm2 to 3.58×109 particles/cm2. It is noted that the radiation induced conductivity in this material increases exponentially, passes through a maximum and then falls off with the increase of temperature and exposure rate. The conduction has been analyzed on the basis of the Onsager model.
VERTEX FUNCTION OF A STRONGLY INTERACTING ELECTRON-HOLE PAIR NEAR THE FERMI SURFACE
Authors: GARAVELLI S.L. , FERRAZ A. , HENDERSON J.A. , OHMURA Y.
Published: November 2004

In this work we calculate and compare all the second- and third-order diagrams of the irreducible part K of the electron-hole scattering function for strongly interacting particles near the Fermi surface. We show that the exchange ladder diagrams for K are indeed the most singular diagrams up to this order of perturbation theory in the proximity of the Fermi surface. From this result emerges a new low energy scale parameter and a new effective coupling constant associated with the strongly interacting regime. The summation of exchange ladder diagrams to infinite order produces a purely imaginary pole in K. As a result the vertex function Γ diverges and the Fermi liquid becomes unstable in this strongly interacting regime.
SQUEEZED VACUUM INTERFEROMETRY
Authors: PARIS MATTEO G.A.
Published: November 2004

A high-sensitive interferometric scheme is presented. It is based on homodyne detection and squeezed vacuum phase properties. The resulting phase sensitivity scales as δϕ≃[Formula: see text] with respect to input photons number.
MERCURY-BASED SUPERCONDUCTORS WITH QUASI-NORMAL OCCUPANCY
Authors: MORENO M. , MÉNDEZ-MORENO R.M. , OROZCO S. , ORTÍZ M.A.
Published: November 2004

A model with anomalous occupancy is applied to Hg-based cuprate superconductors. The anomaly consists of a small energy gap near the Fermi surface, the scale of the gap anomaly is of order of the cutoff (v.g. Debye) energy. Values of the anomalous occupancy parameters for Hg-based superconductors are obtained for different values of the ratio R and the effective coupling constant, within the weak coupling. As these materials have the highest transition temperature known for layered copper-oxide superconductors, they serve as a new testing ground for various proposed models.
DETERMINING THE DELAY TIME OF THE TWO-DIMENSIONAL RECONSTRUCTION FOR ORDINARY DIFFERENTIAL EQUATIONS
Authors: ZHI-AN YANG , SHI-GANG CHEN , GUANG-RUI WANG
Published: November 2004

The second order Jacobian J has been calculated and the delay time τ for the two-dimensional reconstruction of ordinary differential equations has been determined according to the first maximum of the absolute value of J. This method reveals more features about reconstruction than others, and is used in the Rössler and the forced Brusselator equation.
EFFECTS OF DIELECTRIC MISMATCH ON DENSITY OF IMPURITY STATES AND OPTICAL ABSORPTION SPECTRA ASSOCIATED WITH IMPURITIES IN QUANTUM WELLS
Authors: DENG ZHEN-YAN , GUO JING-KUN
Published: November 2004

We calculate the effects of image potential due to dielectric mismatch on the density of impurity states and optical absorption spectra associated with impurities in GaAs/AlAs quantum wells. It is found that the effects of image potential on the density of impurity states and optical absorption spectra are significant, especially when the width of quantum well becomes small. The effects of impurity-ion image potential on the density of impurity states are much larger than those of electron image potential, but the effects of the impurity ion and electron image potentials on the optical absorption spectra are of the same order and opposite. The results also indicate that the effects of image potential on acceptors are comparable with those on donors.