bluuebunny/crossref_metadata_2025 huggingface dataset:
TIME IN THE SEMICLASSICAL APPROXIMATION TO QUANTUM GRAVITY COUPLED WITH A BACKGROUND SCALAR FIELD AND KALUZA-KLEIN THEORY
Authors: OHKUWA YOSHIAKI
Published: November 2004

We consider the semiclassical approximation to quantum gravity coupled with a background scalar field and a quantum matter field. We define the semiclassical time variable and write down the Schrödinger equation for the quantum matter field. This can be rewritten into the form whose time variable is the original time coordinate, when the relation of Hamilton-Jacobi holds. It is shown that the four-dimensional semiclassical time with a background scalar field is related to the five-dimensional semiclassical time without it by means of the Kaluza-Klein dimensional reduction.
OPERATOR REGULARIZATION AND CHERN-SIMONS THEORY TO TWO-LOOP ORDER
Authors: McKEON D.G.C. , WONG S.K.C.
Published: November 2004

We examine the two-loop radiative corrections in non-Abelian Chern-Simons theory using operator regularization. With this technique, no regulating parameters are introduced into the initial action; consequently, ∈αβγ is unambiguously defined, circumventing a major difficulty encountered when using dimensional regularization. By employing the DeWitt expansion of off-diagonal matrix elements occurring in the regulated two-loop generating functional, it is shown that the beta function is zero at two-loop order.
STRING FIELD THEORY OF TWO-DIMENSIONAL QCD ON A CYLINDER: A REALIZATION OF W∞ CURRENT ALGEBRA
Authors: DHAR AVINASH , LAKDAWALA PORUS , MANDAL GAUTAM , WADIA SPENTA R.
Published: November 2004

We consider two-dimensional QCD on a cylinder, where space is a circle of length L. We formulate the theory in terms of gauge-invariant gluon operators and multiple-winding meson (open string) operators. The meson bilocal operators satisfy a W∞ current algebra. The gluon sector (closed strings) contains purely quantum-mechanical degrees of freedom. The description of this sector in terms of nonrelativistic fermions leads to a W∞ algebra. The spectrum of excitations of the full theory is therefore organized according to two different algebras: a wedge subalgebra of W∞ current algebra in the meson sector and a wedge subalgebra of W∞ algebra in the glueball sector. In the large N limit the theory becomes semiclassical and an effective description for the gluon degrees of freedom can be obtained. We have solved the effective theory of the gluons in the small L limit. We get a glueball spectrum which coincides with the “discrete states” of the (Euclidean) c=1 string theory. We remark on the implications of these results for (a) QCD at finite temperature and (b) string theory.
TIME IN THE CHAOTIC INFLATION MODEL AND NUMERICAL CALCULATIONS
Authors: OHKUWA YOSHIAKI , KITAZOE TETSURO , MIZUMOTO YOSHIHIKO
Published: November 2004

The time variable is considered in the quantum gravity theory and calculated explicitly in the framework of the chaotic inflationary scenario where the scalar matter field has a contribution to the time variable in addition to the gravity field. The time formulated under the semiclassical approximation is a natural extension of that in the classical orbital motion. A perturbation method is introduced in terms of the scalar mass to obtain analytically solvable expressions for the time. The Wheeler-DeWitt equation is solved numerically to ensure that the semiclassical approximation is well justified. We examine the obtained time in detail and find that it is reasonable to consider it as time in the region where the semiclassical approximation is well justified.
ADELIC HARMONIC OSCILLATOR
Authors: DRAGOVICH BRANKO
Published: November 2004

Using the Weyl quantization we formulate one-dimensional adelic quantum mechanics, which unifies and treats ordinary and p-adic quantum mechanics on an equal footing. As an illustration the corresponding harmonic oscillator is considered. It is a simple, exact and instructive adelic model. Eigenstates are Schwartz-Bruhat functions. The Mellin transform of the simplest vacuum state leads to the well-known functional relation for the Riemann zeta function. Some expectation values are calculated. The existence of adelic matter at very high energies is suggested.
HEAVY MESON RADIATIVE DECAYS AND LIGHT VECTOR MESON DOMINANCE
Authors: JAIN PANKAJ , MOMEN ARSHAD , SCHECHTER JOSEPH
Published: November 2004

Electromagnetic interactions are introduced in the effective chiral Lagrangian for heavy mesons which includes light vector particles. A suitable notion of vector meson dominance is formulated. The constraints on the heavy meson-light vector and heavy meson-light pseudoscalar coupling constants are obtained using experimental D*→Dγ branching ratios. These constraints are compared with values estimated from semileptonic transition amplitudes as well as from extension of the light meson coupling pattern. Application to the heavy baryon spectrum in the “bound state” model is made.
REDUCTION OF TODA LATTICE HIERARCHY TO GENERALIZED KdV HIERARCHIES AND THE TWO-MATRIX MODEL
Authors: ARATYN H. , NISSIMOV E. , PACHEVA S. , ZIMERMAN A.H.
Published: November 2004

Toda lattice hierarchy and the associated matrix formulation of the 2M-boson KP hierarchies provide a framework for the Drinfeld-Sokolov reduction scheme realized through Hamiltonian action within the second KP Poisson bracket. By working with free currents, which Abelianize the second KP Hamiltonian structure, we are able to obtain a unified formalism for the reduced SL (M+1, M−k) KdV hierarchies interpolating between the ordinary KP and KdV hierarchies. The corresponding Lax operators are given as superdeterminants of graded SL (M+1, M−k) matrices in the diagonal gauge and we describe their bracket structure and field content. In particular, we provide explicit free field representations of the associated W(M, M−k) Poisson bracket algebras generalizing the familiar nonlinear WM+1 algebra. Discrete Bäcklund transformations for SL (M+1, M−k) KdV are generated naturally from lattice translations in the underlying Toda-like hierarchy. As an application we demonstrate the equivalence of the two-matrix string model to the SL (M+1, 1) KdV hierarchy.
PLANCKIAN SCATTERING OF NON-ABELIAN GAUGE PARTICLES
Authors: KAR SUPRIYA , MAHARANA JNANADEVA
Published: November 2004

We present a systematic study of high energy scattering of non-Abelian gauge particles in (3+1)-dimensional Einstein gravity using semiclassical techniques of Verlinde and Verlinde. It is shown that the BRST gauge invariance of the Yang-Mills action in the presence of quantum gravity in the Planckian energy regime is maintained and the vertex operator is invariant under BRST transformations. The presence of gravitational shock wave describing the gauge particles is discussed in the resulting (3+1)-dimensional effective theory of Yang-Mills gravity.
GAUGINO CONDENSATION IN THE CHIRAL AND LINEAR REPRESENTATIONS OF THE DILATON
Authors: GAIDA INGO , LÜST DIETER
Published: November 2004

String effective theories with N=1 supersymmetry in four dimensions are the subject of this discussion. Gaugino condensation in the chiral representation of the dilaton is reviewed in the truncated formalism in the UK(1) superspace. By the use of the supersymmetric duality of the dilaton the same investigation is made in the linear representation of the dilaton. We show that for the simple case of one gaugino condensate the results concerning supersymmetry breaking are independent of the representation of the dilaton.
TOTAL WIDTHS OF LIGHT HADRONS: AN INCLUSIVE VIEW
Authors: MITRA A.N. , SHARMA ANJU
Published: November 2004

The total width of a [Formula: see text] hadron is modeled by the rate at which it dissociates into a pair of quasifree quarks brought about by “soft” and “hard” gluon exchanges, under the ansatz of a short time zone for the existence of such a state. A crucial ingredient in this regard is the quark’s mass function for which a nonperturbative formula is obtained via dynamical breaking of the chiral symmetry of an input vector-exchange-like four-fermion Lagrangian, facilitated by the knowledge that for a chirally invariant Lagrangian this quantity is also equal to the pion-quark vertex function in the chiral limit (Mπ⇒0). The mass function so employed is based on a Bethe-Salpeter (BS) model with a vectorexchange-like kernel (chirally invariant) which is precalibrated to the spectroscopy of [Formula: see text] and qqq hadrons, and also predicts a value of [Formula: see text] fully consistent with QCD sum rules. The predicted widths show a good overlap with available data from L>1 to J=5, while limitations of phase space resist applicability of the said mechanism due to the onset of hadronic selection rules for certain L≤1 states.
DIFFERENTIAL RENORMALIZATION FOR CURVED SPACE AND FINITE TEMPERATURE
Authors: COMELLAS JORDI , HAAGENSEN PETER E. , LATORRE JOSÉ I.
Published: November 2004

We derive, based only on simple principles of renormalization in coordinate space, closed renormalized amplitudes and renormalization group constants at one- and two-loop orders for scalar field theories in general backgrounds. This is achieved through a renormalization procedure we develop exploiting the central idea behind differential renormalization, which needs as the only inputs the propagator and the appropriate Laplacian for the backgrounds in question. We work out this coordinate space renormalization in some detail, and subsequently back it up with specific calculations for scalar theories both on curved backgrounds, manifestly preserving diffeomorphism invariance, and at finite temperature.
A POSSIBLE EXPLANATION OF THE NEGATIVE VALUES OF $m_{\nu _c }^2 $ OBTAINED FROM THE β SPECTRUM SHAPE ANALYSES
Authors: CHENGRUI CHING , TSOHSIU HO , DONGQI LIANG , YAJUN MAO , SHIPING CHEN , HANCHENG SUN
Published: November 2004

By comparing the results obtained using the same experimental data of CIAE but different theoretical formula fits it is pointed out that the negative value of [Formula: see text] most likely stemmed from the inaccuracy of the theoretical formula of the β spectrum.
COLORED EXTENSIONS OF GLq(2) QUANTUM GROUP AND RELATED NONCOMMUTATIVE PLANES
Authors: BASU-MALLICK B.
Published: November 2004

An infinite-dimensional quantum group, containing the standard GLq(2) and GLp,q(2) cases as different subalgebras, is constructed by using a colored braid group representation. It turns out that all algebraic relations occurring in this “colored” quantum group can be expressed in the Heisenberg-Weyl form, for a nontrivial choice of corresponding basis elements. Moreover a novel quadratic algebra, defined through Kac-Moody-like generators, is obtained by making some power series expansion of related monodromy matrix elements. The structure of invariant noncommutative planes associated with this “colored” quantum group has also been investigated.
DRELL-YAN PRODUCTION AT COLLIDER ENERGIES
Authors: VAN NEERVEN W.L.
Published: November 2004

We present some results of the Drell-Yan cross sections dσ/dm and σtot which includes the [Formula: see text] contribution to the coefficient function. In particular we study the total cross section σtot for vector boson production and dσ/dm for low invariant masses m of the lepton pairs at large hadron collider energies. This study includes a detailed discussion of the dependence of the cross sections on the chosen scheme [Formula: see text] versus DIS) and the factorization scale.
PROMPT PHOTON PRODUCTION IN p-p COLLISIONS
Authors: CLEYMANS J. , QUACK E. , REDLICH K. , SRIVASTAVA D.K.
Published: November 2004

A systematic study of the inclusive photon cross-section in p-p collisions is presented. The dependence of the γ rates on the renormalization and factorization scales is discussed. A comparison is made with experimental data for centre-of-mass energies ranging from 23 GeV to 1.8 TeV. Predictions of the cross-sections are given for two different sets of structure functions for RHIC and LHC energies.
HEAVY QUARK PRODUCTION IN pp COLLISIONS
Authors: McGAUGHEY P.L. , QUACK E. , RUUSKANEN P.V. , VOGT R. , WANG X.-N.
Published: November 2004

A systematic study of the inclusive single heavy quark and heavy-quark pair production cross sections in pp collisions is presented for RHIC and LHC energies. We compare with existing data when possible. The dependence of the rates on the renormalization and factorization scales is discussed. Predictions of the cross sections are given for two different sets of parton distribution functions.
PHYSICAL REALIZATION OF THE JIMBO-MIWA THEORY OF THE MODIFIED KORTEWEG-DE VRIES EQUATION ON A THIN ELASTIC ROD: FERMIONIC THEORY
Authors: MATSUTANI SHIGEKI
Published: November 2004

Recently we found that the Dirac operator on a thin elastic rod is identical with the Lax operator of the modified Korteweg-de Vries (MKdV) equation while the thin elastic rod is governed by the MKdV equation. In this article, we will show the physical relation between the Hirota bilinear method and the Dirac field in a thin rod on two-dimensional space, along the lines of the Jimbo-Miwa construction of the MKdV soliton.
THE PERTURBATIVE αs CORRECTIONS TO THE $K^0 - \bar K^0 $ MIXING MATRIX ELEMENT
Authors: PIVOVAROV A.A.
Published: November 2004

The leading αs corrections to the B parameter of the [Formula: see text] mixing matrix element are calculated within the sum rules method. Numerical estimates given in the framework of the factorization hypothesis for vacuum expectation values of four-quark local operators show a decrease of the [Formula: see text] matrix element from the factorized value by about 20% at the normalization point μ~1 GeV. The nonanalytical dependence of the B parameter on the kaon mass mK (~a, log mK) is discovered in the chiral limit.
TOWARDS COMPLEX (RATIONAL) POWERS OF FREE FIELDS, GENERALIZED βγ SYSTEMS AND NONPOLYNOMIAL QUANTUM FIELD THEORY
Authors: ANDREEV OLEG
Published: November 2004

The βγ system is generalized by complex (rational) powers of the fields, which leads to a corresponding extension of the Fock space. Two different approaches to computing the Green functions of the physical operators are proposed. First, the complex (rational) powers are defined via an integral representation, which allows one to compute the conformal blocks, Green functions and structure constants of OPA. Next, an approach based on a system of recursion equations for the Green functions is developed. A number of solutions of the system are found. As a result, a new class of 2D quantum field theories is constructed.
THE LATTICE QUANTUM PHASE SPACE AND THE YANG-BAXTER EQUATION
Authors: DJEMAI A.E.F.
Published: November 2004

In this work we show that, in the sense of Ref. 17, it is possible to construct the quantum group which preserves the quantum symplectic structure introduced in the context of the matrix Hamiltonian formalism defined in Ref. 9. We also study the braiding existing behind the lattice quantum phase space, and present another type of nontrivial solution to the resulting Yang-Baxter equation.
CRITICAL TEMPERATURE AND AMPLITUDE RATIOS FROM A FINITE TEMPERATURE RENORMALIZATION GROUP
Authors: VAN EIJCK M.A. , O’CONNOR DENJOE , STEPHENS C.R.
Published: November 2004

We study λφ4 theory using an environmentally friendly finite temperature renormalization group. We derive flow equations, using a fiducial temperature as flow parameter, develop them perturbatively in an expansion free from ultraviolet and infrared divergences, then integrate them numerically from zero to temperatures above the critical temperature. The critical temperature, at which the mass vanishes, is obtained by integrating the flow equations, and is determined as a function of the zero temperature mass and coupling. We calculate the field expectation value and the minimum of the effective potential as functions of temperature and derive some universal amplitude ratios which connect the broken and symmetric phases of the theory. The latter are found to be in good agreement with those of the three-dimensional Ising model obtained from high and low temperature series expansions.
TOPOLOGICAL YANG-MILLS THEORY WITH VECTOR AND ANTISYMMETRIC TENSOR FIELDS
Authors: HWANG DAE SUNG
Published: November 2004

We study a system composed of vector and second rank antisymmetric tensor gauge fields in the superconnection framework. We incorporate the matrix derivative of non-commutative geometry in order to induce the topological Yang-Mills theory. In this structure we get the BRST and anti-BRST transformation rules from one horizontality condition, and obtain the topological classical action naturally from the extended field strength. We obtain its quantum action through the BRST formalism.
SYMPLECTIC QUANTIZATION OF A REDUCIBLE THEORY
Authors: BARCELOS-NETO J. , SILVA M.B.D.
Published: November 2004

We use the symplectic formalism to quantize the Abelian antisymmetric tensor gauge field. It is related to a reducible theory in the sense that all of its constraints are not independent. A procedure like ghost-of-ghost of the BFV method has to be used, but in terms of Lagrange multipliers.
SOLITONS IN A BILOCAL FIELD THEORY
Authors: HENDERSON R.J. , RAJEEV S.G.
Published: November 2004

We obtain a bilocal classical field theory as the large N limit of the chiral Gross-Neveu (or non-Abelian Thirring) model. Exact classical solutions that describe topological solitons are obtained. It is shown that their mass spectrum agrees with the large N limit of the spectrum of the chiral Gross-Neveu model.
ALGEBRAIC RENORMALIZATION OF N=2 SUPER YANG-MILLS THEORIES COUPLED TO MATTER
Authors: MAGGIORE NICOLA
Published: November 2004

We study the algebraic renormalization of N=2 supersymmetric Yang-Mills theories coupled to matter. A regularization procedure preserving both the BRS invariance and the supersymmetry is not known yet, so it is necessary to adopt the algebraic method of renormalization, which does not rely on any regularization scheme. The whole analysis is reduced to the solution of cohomology problems arising from the generalized Slavnov operator which summarizes all the symmetries of the model. Besides unphysical renormalizations of the quantum fields, we find that the only coupling constant of N=2 supersymmetric Yang-Mills theories can get quantum corrections. Moreover, we prove that all the symmetries defining the theory are algebraically anomaly-free.
(N, p, q) HARMONIC SUPERSPACE
Authors: HARTWELL G.G. , HOWE P.S.
Published: November 2004

A family of harmonic superspaces associated with four-dimensional Minkowski space-time is described. Applications are made to free massless supermultiplets, invariant integrals and super-Yang-Mills theory. Generalization to curved space-times is performed, with emphasis on conformal supergravities.
REALIZATION OF BORCHERDS ALGEBRAS
Authors: MAROTTA V. , SCIARRINO A.
Published: November 2004

A vertex operator realization of generalized Kac-Moody algebras introduced by Borcherds is presented in the case of a single imaginary simple root. The structure of the fundamental representations is discussed. The possible relevance of the Borcherds algebra in many-particle field theory and in string theory is briefly discussed.
OFF-SHELL FORMULATION OF N=2 SUPER YANG-MILLS THEORIES COUPLED TO MATTER WITHOUT AUXILIARY FIELDS
Authors: MAGGIORE NICOLA
Published: November 2004

N=2 supersymmetric Yang-Mills theories coupled to matter are considered in the Wess-Zumino gauge. The supersymmetries are realized nonlinearly and the anticommutator between two susy charges gives, in addition to translations, gauge transformations and equations of motion. The difficulties hidden in such an algebraic structure are well known: almost always auxiliary fields can be introduced in order to put the formalism off-shell, but still the field-dependent gauge transformations give rise to an infinite-dimensional algebra quite hard to deal with. However, it is possible to avoid all these problems by collecting into a unique nilpotent operator all the symmetries defining the theory, namely ordinary BRS, supersymmetries and translations. According to this method the role of the auxiliary fields is covered by the external sources coupled, as usual, to the nonlinear variations of the quantum fields. The analysis is then formally reduced to that of ordinary Yang-Mills theory.
A NEW QUANTUM VORTEX OPERATOR AND ITS CORRELATION FUNCTIONS
Authors: MARINO E.C.
Published: November 2004

A new local and gauge-invariant quantum vortex operator is constructed in three-dimensional gauge field theories. The correlation functions of this operator are evaluated exactly in pure Maxwell theory and by means of an expansion around a constant absolute value of the Higgs field in the Abelian Higgs model. In the broken symmetry phase of the latter an explicit expression for the mass of the quantum vortices is obtained from the long distance exponential decay of the two-point function.
QUATERNION HIGGS AND THE ELECTROWEAK GAUGE GROUP
Authors: LEO S. DE , ROTELLI P.
Published: November 2004

We show that, in quaternion quantum mechanics with a complex geometry, the minimal four Higgs of the unbroken electroweak theory naturally determine the quaternion invariance group which corresponds to the Glashow group. Consequently, we are able to identify the physical significance of the anomalous Higgs scalar solutions. In addition, we introduce and discuss the complex projection of the Lagrangian density.
INCLUSION OF $Z \to b\bar{b}$ VERTEX CORRECTIONS IN PRECISION ELECTROWEAK TESTS ON THE Sp(6)L× U(1)Y MODEL
Authors: PARK GYE T. , KUO T.K.
Published: November 2004

We extend our previous work on the precision electroweak tests in the Sp (6)L× U (1)Y family model to include for the first time the important [Formula: see text] vertex corrections encoded in a new variable ∊b, utilizing all the latest LEP data. We include in our analysis the one-loop EW radiative corrections due to the new bosons in terms of ∊1,b and ΔΓZ. We find that the correlation between ∊1 and ∊b makes the combined constraint much stronger than the individual ones. The model is consistent with the recent CDF result of [Formula: see text] but it; cannot accommodate mt≳195 GeV .
PROPERTIES OF THE W BOSON FROM THE FERMILAB TEVATRON
Authors: KOPP SACHA E.
Published: November 2004

The experimental knowledge of the charged intermediate vector boson, the W, is reviewed. Measurements of the electroweak properties of the W boson, such as its mass, decay width, couplings to fermions, and leptonic branching ratios, are summarized. As well, I review production properties of the W as measured in [Formula: see text] collisions and how they can be used as tests of perturbative QCD. I also discuss new particle searches that make use of the W signature, such as new charged electroweak bosons and the now-confirmed discovery of the top quark.
ON THE SYMMETRIES OF TOPOLOGICAL QUANTUM FIELD THEORIES
Authors: BAULIEU LAURENT
Published: November 2004

We display properties of the general formalism which associates with any given gauge symmetry a topological action and a system of topological BRST and anti-BRST equations. We emphasize the distinction between the antighosts of the geometrical BRST equations and the antighosts occurring in field theory. We propose a transmutation mechanism between these objects. We illustrate our general presentation by examples.
SUPERSYMMETRIC TWO-BOSON EQUATION, ITS REDUCTIONS AND THE NONSTANDARD SUPERSYMMETRIC KP HIERARCHY
Authors: BRUNELLI J.C. , DAS ASHOK
Published: November 2004

In this paper, we review various properties of the supersymmetric Two-Boson (sTB) system. We discuss the equation and its nonstandard Lax representation. We construct the local conserved charges as well as the Hamiltonian structures of the system, and show how this system leads to various other known supersymmetric integrable models under appropriate field redefinition. We discuss the sTB and the supersymmetric nonlinear Schrödinger (sNLS) equations as constrained, nonstandard supersymmetric Kadomtsev-Petviashvili (sKP) systems and note that the nonstandard sKP systems naturally unify all the KP and mKP flows while leading to a new integrable supersymmetrization of the KP equation. We construct the nonlocal conserved charges associated with the sTB system and show that the algebra of charges corresponds to a graded, cubic algebra. Also, we note that the sTB system has a hidden supersymmetry making it an N=2 extended supersymmetric system.
2D GRAVITY COUPLED TO TOPOLOGICAL MINIMAL MODELS
Authors: MUKHERJEE AVIJIT
Published: November 2004

We discuss the properties of genus 0 correlation functions of a topological minimal model (the model Ak+1) coupled to 2D topological gravity. The action of the twisted minimal model is perturbed by nontrivial couplings to gravitational descendants, which, in turn, are constructed entirely from the fields in the matter sector of the theory. We develop an explicit formulation, in terms of orthogonal polynomials, for investigating the large phase space of the theory. Some useful identities for correlation functions (valid on the large phase space) of the theory are established and the puncture and dilaton equations of topological gravity are obtained as special cases of these general relations. Finally, we obtain an important relation expressing the gravitational couplings in terms of the couplings in the small phase space (i.e. the couplings to the chiral primaries). Thus eventually we are able to solve for the coordinates (couplings) of the large phase space in terms of the Landau-Ginzburg superpotential characterizing the matter sector of the model.
A FOUR-FERMION LATTICE MODEL
Authors: RANDJBAR-DAEMI S. , STRATHDEE J.
Published: November 2004

The weak coupling limit of an Ising type model on the F4 lattice is examined. It is shown that by imposing some constraints on the Ising couplings, one can express the weak coupling limit as a multidimensional Berezin integral with local symmetries, We explore the possibility of deriving a fermion propagator by a self-consistent, Nambu-Jona-Lasinio type of calculation. We argue that at low energies this model describes Dirac fermions coupled to Yang-Mills fields.
INTERACTING OPEN p-BRANES
Authors: ISHIKAWA SUMIO , IWAMA YASUHIRO , MIYAZAKI TADASHI , YAMANOBE MOTOWO
Published: November 2004

The Kalb-Ramond action, derived for interacting strings through an action-at-a-distance force, is generalized to the case of interacting p-dimensional objects (p-branes) in D- dimensional space-time. The openp-brane version of the theory is especially taken up. On account of the existence of their boundary surface, the fields mediating interactions between open p-branes are obtained as massive gauge fields, quite in contrast to massless gauge ones for closedp-branes.
ELECTRON NUCLEAR DOUBLE RESONANCE SPECTROSCOPY OF SOLITONS AND POLARONS IN CONJUGATED POLYMERS
Authors: KURODA SHIN-ICHI
Published: November 2004

Novel elementary excitations such as solitons and polarons in conjugated polymers carry unpaired electrons. In this case electron nuclear double resonance (ENDOR) of protons on the conjugated chain provides a unique method to observe their wavefunctions. This information has two significant meanings. Firstly, it gives the spatial extension of solitons and polarons, the quantity that is essential in examining the reality of these self-localized excitations. Secondly, it directly probes the degree of electron correlation. In the case of finite electron correlation, negative spin sites appear in the spin-density distribution. The unique and detailed determination of the wavefunctions containing such information can be made only after the careful studies of oriented polymers because of the non-single-crystalline nature of these materials. In this article I review our ENDOR studies on solitons in polyacetylene and polarons in poly(paraphenylene vinylene), performed using stretch-oriented samples. All the analyses are based on the properties of π-electrons which show characteristic anisotropy in oriented samples. The observed spin distributions are compared with theoretical results as well as shown as the basis for further analyses of conjugated polymers.
QUANTUM BAYESIAN NETS
Authors: TUCCI ROBERT R.
Published: November 2004

We begin with a review of a well-known class of networks, Classical Bayesian (CB) nets (also called causal probabilistic nets by some). Given a situation which includes randomness, CB nets are used to calculate the probabilities of various hypotheses about the situation, conditioned on the available evidence. We introduce a new class of networks, which we call Quantum Bayesian (QB) nets, that generalize CB nets to the quantum mechanical regime. We explain how to use QB nets to calculate quantum mechanical conditional probabilities (in case of either sharp or fuzzy observations), and discuss the connection of QB nets to Feynman Path integrals. We give examples of QB nets that involve a single spin-[Formula: see text] particle passing through a configuration of two or three Stern—Gerlach magnets. For the examples given, we present the numerical values of various conditional probabilities, as calculated by a general computer program specially written for this purpose.
SCALING OF THE TIME-DEPENDENT SELF-DIFFUSION COEFFICIENT
Authors: ESPAÑOL PEP , ZÚÑIGA IGNACIO
Published: November 2004

The advent of the new light scattering technique of Diffusing Wave Spectroscopy has aroused great interest on the very short time scale dynamics of colloidal particles in suspension. Here we review some advances in the experimental, computer simulation and theoretical fronts on the problem of the dynamics of Brownian particles at time scales where hydrodynamic transient effects become very important. We also present some open questions regarding the scaling of the time-dependent self-diffusion coefficient and propose possible ways of attacking them.
ATOMIC SCATTERING FACTORS FOR CARBON AND SILICON ATOMS BOUND IN CRYSTALS
Authors: SAPRA G.K. , BHASIN V.S. , KOTHARI L.S. , SRIVASTAVA M.P. , LAL KRISHAN
Published: November 2004

We derive a general expression for the atomic scattering factors of carbon and silicon atoms bound in crystals, based on a realistic charge distribution, having a tetrahedral lobed structure. We show that the scattering factors, for arbitrary orientation of the momentum transfer vector, are not only anisotropic but also complex. We are thus able to explain the observed intensity of (222) ‘forbidden’ reflection in diamond without the use of any free parameters.
STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF Bi4Sr3Ca3CuyOw AND Bi4Sr3Ca3Cu4−xMxOz(M=Fe, Cr AND Mn) GLASS CERAMICS
Authors: ZACHARIAS E. , SINGH R.
Published: November 2004

The synthesis of glass ceramic superconductors of Bi 4 Sr 3 Ca 3 Cu y O w(3≤y≤6) and Bi 4 Sr 3 Ca 3 Cu 4−x M x O z ( M=Fe , Cr , Mn and 0≤x≤0.2) compositions is reported. The 4334 sample is found to be the optimum composition to obtain Bi-2212 superconducting phase. X ray diffraction studies indicate that the solid solubility of 3d metal ions in the 4334 system is limited to x=0.05 in the case of Fe and Cr and x=0.1 in the case of Mn. A systematic decrease in Tc with increasing dopant concentration is observed from resistivity as well as AC susceptibility measurements. Tc depression rates, however, are found to differ for different dopants. XRD studies indicate the decrease in c lattice parameter with increase in dopant content. The systematics of the superconducting transition is discussed in view of Tc depression rates.
ON THE THERMODYNAMICS OF AN ANHARMONIC CRYSTAL WITH HIGH ANISOTROPY
Authors: ZUBOV V.I. , LOBO M.P. , RABELO J.N.T.
Published: November 2004

The correlative method of the unsymmetrized self-consistent field is used to study the atomic properties of a simple model of an anharmonic crystal with strong anisotropy, namely, a crystal with primitive hexagonal (PH) lattice. The self-consistent potential, Helmholtz free energy and mean-square atomic displacements are obtained in the case of weak anharmonicity. Equations of state are derived and solved. The internal energy and specific heats are calculated. The first quantum corrections are expressed in terms of the de Boer parameter included. An influence of anharmonicity is analyzed. The thermal expansion of the model considered is very anisotropic but the quantum corrections to the lattice parameters are isotropic. The results of calculations are compared with those for one- and two-dimensional models and for the isotropic crystal with the same coordination number as in the PH lattice, i.e. a body-centered cubic crystal. Other things being equal, the coefficient of volume expansion and specific heats of anisotropic crystals are greater than those of isotropic ones. A possibility of studying the strong anharmonicity in anisotropic crystals is discussed.
EXPERIMENTAL OBSERVATIONS OF SELF-AFFINE SCALING AND KINETIC ROUGHENING AT SUB-MICRON LENGTHSCALES
Authors: KRIM J. , PALASANTZAS G.
Published: November 2004

Experimental observations of self-affine scaling and kinetic roughening at sub-micron length scales are reviewed for thin solid films and ion-beam eroded surfaces.
MAGNETIC AND SUPERCONDUCTING PROPERTIES OF HIGH-Tc SUPERCONDUCTORS
Authors: VIJAYARAGHAVAN R. , GUPTA L.C.
Published: November 2004

High-Tc superconductors, distorted-perovskite cuprates, are derived, by means of suitable doping, from a Mott-insulating and antiferromagnetic parent material. The most important ingredient of their structure is the stacks of Cu-O planes which carry superconductivity. Magnetic, transport and other properties that characterize the supercon-ducting state are very unusual and highly anisotropic. Density of states at the Fermi level in these materials is rather small but Tc is very high (highest reported Tc~125 K). In the high-Tc systems that contain magnetic moment bearing rate earth (RE)-atoms, antiferromagnetic ordering (TN<2 K) of RE-moments coexists with superconductivity. Some of them are ideal two-dimensional magnetic systems. Flux line lattices in these materials have rather unusual structural properties. There are both hole-type as well as electron-type superconductors. The available experimental evidence does not favour odd-parity pairing. It is not yet clear, however, whether even-parity pairing is d-wave or s-wave type. Antiferromagnetic fluctuations may be possible mechanism of Cooper pairing. Anyonic superconductivity is ruled out.
BELL INEQUALITIES VIEWED IN TERMS OF EUCLIDEAN GEOMETRY AND GROUP THEORY
Authors: TUCCI ROBERT R.
Published: November 2004

This paper presents a new, computer-implementable algorithm for determining Bell inequalities. The algorithm is very general: one can use it to derive the Bell inequalities for any of the experiments that are usually considered for this purpose, such as the Bohm-Bell experiment, the Clauser-Horne experiment, or the experiments with spin 1, 3/2, 2 and 5/2 particles proposed by Mermin, Schwarz and Garg. As an example, this paper applies the algorithm to the Clauser-Horne experiment. The algorithm, which is based on simple notions from n-dimensional Euclidean geometry, gives a simple geometrical interpretation to the Bell inequalities. The algorithm allows one to demonstrate that a set of Bell inequalities is complete. The algorithm uses special hidden variables that were first used by Wigner and Belinfante. This paper also shows how to use finite group theory to express a set of Bell inequalities in a form that makes its invariance under relabellings explicit.
EFFECT OF MULTIPLE PHONON BRANCHES ON THE PHASE TRANSITIONAL BEHAVIOR OF A TWO-DIMENSIONAL POLARON GAS
Authors: MUKHOPADHYAY SOMA , CHATTERJEE ASHOK
Published: November 2004

Using an all-coupling variational method and the random phase approximation, it is shown that a two-dimensional polaron gas exhibiting no localization-delocalization transition with a single optical phonon branch may undergo such a transition in the presence of an additional phonon branch. However, if the system already shows a transition, with a single phonon branch, then the effect of an additional branch is just to enhance the low-mobility self-trapped phase of the polaron.
DISSIPATION AND MEMORY CAPACITY IN THE QUANTUM BRAIN MODEL
Authors: VITIELLO GIUSEPPE
Published: November 2004

The quantum model of the brain proposed by Ricciardi and Umezawa is extended to dissipative dynamics in order to study the problem of memory capacity. It is shown that infinitely many vacua are accessible to memory printing in a way that in sequential information recording the storage of a new information does not destroy the previously stored ones, thus allowing a huge memory capacity. The mechanism of information printing is shown to induce breakdown of time-reversal symmetry. Thermal properties of the memory states, as well as their relation with squeezed coherent states, are finally discussed.
NAGAOKA FERROMAGNETISM AS A TEST OF SLAVE-FERMION AND SLAVE-BOSON APPROACHES
Authors: BOIES DANIEL , JACKSON F.A. , TREMBLAY A.-M.S.
Published: November 2004

The ferromagnetic to paramagnetic transition in the Nagaoka (U=∞) limit of the Hubbard Hamiltonian is used to test the applicability of slave-boson and slave-fermion (Schwinger boson) functional-integral approaches. Within the slave-fermion formalism to one-loop order, the ferromagnetic phase is stable to spin-wave, gauge field, and longitudinal fluctuations over a doping interval that is much too large compared with other approaches. Furthermore, nonbipartite lattices such as hcp or fcc lattices are ferromagnetic for t>0 over a wider doping interval than for t<0, in qualitative disagreement with all other types of calculations. It is possible to remedy all these defects in order to reach agreement, at least qualitatively, with previous studies. It suffices to take the point of view that in the U=∞ limit it is best to represent the paramagnetic phase as the mean-field solution of the slave-boson representation, and the ferromagnetic phase as the mean-field solution of the slave-fermion representation. The transition between both phases is taken to occur at the critical hole doping where the ground state energies are equal. This seems to give the best possible comparison with other approaches, despite the lack of a variational principle justifying comparisons of energies between slave-fermion and slave-boson representations. On bipartite lattices, the critical hole density found analytically by this procedure, δc=1/3, is identical to the critical density obtained in the Kotliar-Ruckenstein slave-boson approach. This value of δc is also close to various other estimates. Nevertheless, non-bipartite lattices with t>0 remain ferromagnetic over a small but finite doping interval, in quantitative disagreement with some other approaches.
SOME INVESTIGATIONS OF THE PHYSICAL PROPERTIES OF (Ga, In)As-GaAs HETEROSTRUCTURES GROWN WITH BUILT-IN PIEZOELECTRIC FIELD
Authors: GIL B. , BIGENWALD P. , MOORE K.J. , BORING P. , WOODBRIDGE K.
Published: November 2004

The properties of single and double (Ga,ln)As-GaAs strained-layer quantum wells embedded in (pin) diodes are studied. These properties are found to be orientation-dependent, mainly due to the existence of a strong internal piezoelectric field in the (Ga,ln)As layers when the growth axis is polar. We first calculate how large the influences of the (pin) and piezoelectric field are to produce carrier tunnelling out of the active part of the heterostructure. This enables us to compute the carrier’s lifetime in the heterostructures and the corresponding resonance widths. Next, we compare the binding energies of interacting electron and hole pairs in double quantum wells with or without internal piezo electric fields. We show that the exciton binding energy is less sensitive to the piezoelectric field than the oscillator strength. Under photo excitation, many body-effects and bandgap renormalization can be easily produced in strained-layer quantum wells with internal built-in piezo-electric fields. We illuminated at low temperature single and double Ga 0.92 ln 0.08 As-GaAs strained layer quantum wells grown either along the (001) or (111) direction, and tuned over several decades the densities of photo-injected carriers. The comparison between experimental data and the results of a Hartree calculation including the space charge effects reveals that many body interactions are efficiently photo-induced in the (111)-grown samples. Moreover, we show that the tunnelling of the two lowest-lying heavy-hole levels can be stimulated for moderate carrier densities making such structures promissive in order to realise self electrooptic effect device (SEED) modulators.
NONLINEAR FLUX DIFFUSION IN SUPERCONDUCTORS
Authors: GUREVICH A.
Published: November 2004

A review of recent results on nonlinear diffusion of magnetic flux in high-Tc superconductors is given. Making use of a universality of thermally-activated flux diffusion, one can formulate the problem of macroscopic flux dynamics in terms of directly measured quantities. A hierarchy of flux creep time-scales and their dependence on initial and boundary conditions is considered. The essential effect of the sample geometry on the flux creep dynamics is discussed for a thin plate in a parallel and perpendicular magnetic field, which corresponds to local and nonlocal regimes of nonlinear flux diffusion, respectively. Both transient and steady-state regimes of flux creep are discussed. Instabilities of flux diffusion in anisotropic superconductors are considered which are give rise to a dissipative transition of the uniform critical state to either static macrovortex structures or magnetic flux turbulence. Manifestations of nonlinear flux diffusion in observed macroscopic electrodynamics of high-Tc superconductors are discussed.
UNIFIED VARIATIONAL PRINCIPLES FOR THE VON NEUMANN, MASTER AND BOLTZMANN-BLOCH EQUATIONS AND THE T-MATRIX
Authors: HATTORI MASUMI , NAKANO HUZIO
Published: November 2004

The variational principle of irreversible processes, which was previously presented for the von Neumann equation as a stationarity problem and then converted into a maximum problem by contracting the density matrix perturbatively, is reinvestigated w.r.t. the contraction of the density matrix. The present contraction relies on the T-matrix theory of scattering, where no perturbational consideration enters. By taking the electron transport in solids as a typical example, the contraction is performed in two steps: the even component of the density matrix as to time reversal is eliminated first and then the off-diagonal elements in the scheme of diagonalizing the unperturbed Hamiltonian. The maximum problem thus obtained is for the diagonal elements of the odd component of the density matrix. The maximum condition gives the master equation, which is reduced to the Boltzmann-Bloch equation in the scheme of one-body picture. It is noticeable in this equation that the collision term is given in terms of the T-matrix in scattering theory.
Tc ENHANCEMENT OF La1.8Sr0.2CaCu2O6-δ BY KMnO4 OXIDATION
Authors: YANG S. T. , CHEN L. Q. , WU F. , JIA S. L. , HUANG Y. Z. , ZHU W. J. , ZHAO Z. X.
Published: November 2004

The superconducting transition temperature of La 1.8 Sr 0.2 CaCu 2 O 6-δ has been enhanced by oxidation at 80°C using saturated KMnO 4 solution. The samples treated for 0, 1, and 10 h have oxygen contents of 5.92, 5.96, and 5.98, respectively. The corresponding T c (onset) determined from resistivity measurements were <4.2, 54, and 60 K.
DYNAMICAL SCALING OF ANHARMONIC LATTICES AT THE ONSET OF FRACTURE
Authors: OLIVEIRA F. A.
Published: November 2004

We investigate the dynamical renormalization properties of an anharmonic lattice. At the onset of fracture, we map this lattice into a transformed lattice with disorder. By studying the properties of the transformed lattice, we get analytical results for the dynamical scaling of the lattice. From these, we obtain the transformed memory of the lattice and we discuss how these results may be used to interpret simulations and experiments.
ELASTIC BEHAVIOR OF GERMANIUM-SUBSTITUTED LITHIUM FERRITES
Authors: PURUSHOTHAM Y. , REDDY P. VENUGOPAL , KISHAN PRAN , KUMAR NITENDAR
Published: November 2004

The longitudinal and shear wave velocities of germanium-substituted lithium ferrites were determined at room temperature by the pulse transmission technique. Young's (E) and rigidity (n) moduli have been corrected to theoretical density by a power equation. The zero porous corrected values of both the elastic moduli (Young's and rigidity) are found to increase with increasing germanium concentration. A linear relationship between the Debye temperature and the average sound velocity has also been observed.
EXPERIMENTAL STUDY OF THE EFFECT OF AN ACHROMATIC HALF-WAVE PLATE ON THE POLARIZATION STATE VECTOR OF CORRELATED TWO-PHOTON RADIATION FROM METASTABLE ATOMIC DEUTERIUM
Authors: SHEIKH Z. A. , DUNCAN A. J. , HAMDY H. , HAJI-HASSAN T.
Published: November 2004

We report the results of an experiment which, for the first time, demonstrates the action of an achromatic half-wave plate on the polarization state of the two-photon radiation emitted by atomic deuterium in the metastable 2S1/2 state. The results agree with the quantum mechanical predictions and confirm the hypothesis of Breit and Teller that the fine and hyperfine interaction plays no role in the emission process.
THE USE OF MARKERS AND NUCLEAR MICROANALYSIS TO MONITOR ATOMIC TRANSPORT INDUCED BY ION BOMBARDMENT IN SOLIDS
Authors: THOMÉ LIONEL , GARRIDO FRÉDÉRICO
Published: November 2004

This paper describes an original methodology developed to study the atomic transport in a solid target bombarded with energetic ions. This methodology is based on the use of heavy marker atoms introduced in the near-surface layer of the investigated target and the analysis via nuclear microanalysis techniques of the modifications of the marker profile due to ion bombardment. Results obtained in the case of low- or medium-energy (<10 keV/u ) ion irradiation, leading to the well-known ion-beam-mixing process induced by nuclear elastic collisions, are reported in the first part. The second part deals with the less-investigated case of very-high-energy (>1 MeV/u ) ion irradiation, where a dramatic plastic deformation mechanism induced by electronic excitation has been recently discovered.
SCANNING TUNNELING MICROSCOPY OF FERRITIN NANOSTRUCTURES
Authors: YAU S.-T. , ZHOU YAN
Published: November 2004

In molecular electronics, components and circuits are made of biological molecules.1 It is important to study how the molecules arrange themselves on a substrate and to arrange them artificially. The ferritin molecule is a good candidate for making molecular devices. Previously, transmission electron microscopy was used to image only the metallic core of the ferritin molecule. We use scanning tunneling microscopy to study the behavior of ferritin deposited on a surface by imaging its protein shell. We have observed different kinds of ferritin aggregates as well as single molecules under different deposition conditions. For the first time ordered self-assemble of ferritin aggregates was observed. The aggregates were also found to be arranged in artificially made patterns. We suggest a possible mechanism of the formation of the observed structures.
REFLECTANCE EFFECTS CAUSED BY REFRACTIVE INDEX GRADIENTS IN DIAMOND CELL SAMPLES OF H2 AND Al2O3
Authors: MAO HO-KWANG , EGGERT JON H. , HEMLEY RUSSELL J.
Published: November 2004

At high pressures, optical spectroscopic techniques are the principal means for probing dense solid hydrogen, including both its vibrational and electronic excitations. Ruoff et al. [Phys. Rev.B47, 11039 (1993)] proposed that refractive index gradients of H 2 samples loaded with 5% Al 2 O 3 powder in diamond anvil cells could cause a 4% rise in infrared reflectivity which interfered with the measurements on hydrogen reported by Mao et al. [Phys. Rev. Lett.65, 484 (1990)]. We have analyzed this alternative proposal, including computer simulations of the appropriate sample configuration. Our calculations show that effects of a graded index on the rise of reflectivity from 1.0 to 0.5 eV are less than 0.1% and are therefore insignificant.