bluuebunny/crossref_metadata_2025 huggingface dataset:
AN ANALYTICAL SOLUTION OF A SECOND KIND VOLTERRA INTEGRAL EQUATION REPRESENTING THE CONTRIBUTION OF GRAVITATIONAL WAVES TO THE POLARIZATION OF THE COSMIC MICROWAVE BACKGROUND
Authors: GIBILISCO MARINA
Published: November 2004

Volterra integral equations of the second kind have a remarkable importance in many physical problems. In this paper, I shall discuss the particular case of a Volterra equation whose solution represents the polarization of the cosmic microwave background (CMB) induced by cosmological gravitational waves. The analytical study of the radiative transfer equation, written in the Chandrasekhar formalism, is performed after a change of variables that follows the formalism developed by Polnarev in 1980. Then, the problem turns into the solution of a second kind Volterra equation, containing the gravitational wave spectrum in its source term. An analytical solution for this Volterra equation can be found if its kernel has a polynomial or an exponential form: in these cases, respectively, the methods of the resolvent and of the iterated kernels can be successfully applied; the solution thus determined represents the polarization of the CMB photons induced by cosmological gravitational waves.

The calculated polarization degree for the CMB is plotted versus the wave number k of the gravitational waves inducing the polarization. In the case of an exponential kernel, i.e. for a Universe fast reionized at small redshift (z≤20), I obtain a remarkable polarization peak at small k (k≤4); such a degree of polarization for the CMB should be observable at angular scales near 9°, thus providing also a test for many reionization models. On the contrary, for a standard ionization history, a CMB polarization comparable in magnitude to the one predicted above could only be observed at small angular scales (θ≤2°).
TWISTORS AND EINSTEIN-CARTAN THEORY
Authors: DE SABBATA VENZO , XIN YU
Published: November 2004

After showing that through space-time defects in the presence of torsion we have a way towards the quantization of space-time, we consider the strong analogy between twistors and torsion, both transforming invariantly under the SL (2, C) group, which indicates that twistor theory seems to constitute a mathematical/geometrical basis for the commutation relation between torsion and curvature.
STUDYING STRUCTURE OF ELECTROWEAK CORRECTIONS
Authors: HIOKI ZENRŌ
Published: November 2004

Several different effects in electroweak quantum corrections are explored separately through the latest data on the weak-boson masses. The leading-log approximation, the improved-Born approximation and the nondecoupling top-quark effects are studied without depending on the recent CDF data about mt, and the results are given in a form independent, of the Higgs mass. On the other hand, the bosonic and the nondecoupling Higgs effects are examined by fully taking account of those CDF data. It is emphasized that future precision measurements of MW and mt are considerably significant not only for further studies of the electroweak theory at higher confidence level but also for new-physics searches beyond it.
HYPERON RADIATIVE DECAYS
Authors: LACH J. , ŻENCZYKOWSKI P.
Published: November 2004

We review the experimental and theoretical status of weak radiative hyperon decays. Our discussion centers on a controversy over the validity of Hara’s theorem, which was originally expected to be respected by these decays. After presenting the hadron level theorem we describe experiments that have provided convincing evidence against its applicability to these decays. In the theoretical part we juxtapose the hadron level and quark level approaches and discuss the violation of Hara’s theorem in the latter. We review quark model phenomenology, which offers a promising description of experimental data. Measurements that should be made to settle the theoretical controversy are pinpointed. The importance of radiative hyperon decays in understanding the nonlocal composite nature of hadrons is stressed.
A STUDY OF QUARK-HADRON PHASE TRANSITION
Authors: CHAKRABARTI B. , DEVI T.L. REMA , BHATTACHARYA A.
Published: November 2004

The anomalous behavior of the thermodynamic co-ordinates along with the hadronic critical temperature (Tc) is studied and the properties of the surrounding vacuum are investigated in the framework of the Ginzburg-Landau theory of superconductivity, with interesting conclusions.
TOPOLOGICAL σ MODELS AND LARGE N MATRIX INTEGRAL
Authors: EGUCHI TOHRU , HORI KENTARO , YANG SUNG-KIL
Published: November 2004

In this paper we describe in some detail the representation of the topological CP1 model in terms of a matrix integral which we have introduced in a previous article. We first discuss the integrable structure of the CP1 model and show that it is governed by an extension of the one-dimensional Toda hierarchy. We then introduce a matrix model which reproduces the sum over holomorphic maps from arbitrary Riemann surfaces onto CP1. We compute intersection numbers on the moduli space of curves using a geometrical method and show that the results agree with those predicted by the matrix model. We also develop a Landau-Ginzburg (LG) description of the CP1 model using a superpotential eX + et0,Q e-X given by the Lax operator of the Toda hierarchy (X is the LG field and t0,Q is the coupling constant of the Kähler class). The form of the superpotential indicates the close connection between CP1 and N=2 supersymmetric sine-Gordon theory which was noted sometime ago by several authors. We also discuss possible generalizations of our construction to other manifolds and present an LG formulation of the topological CP2 model.
CHROMOGRAVITY: QCD-INDUCED DIFFEOMORPHISMS
Authors: NE’EMAN YUVAL , ŠIJAČKI DJORDJE
Published: November 2004

We expand the QCD gluon field [Formula: see text] around a constant “pure gauge” solution [Formula: see text] in the IR sector, i.e. [Formula: see text] and provide a mathematical definition for an “IR limit” in which the frequencies of the fluctuating field [Formula: see text] vanish. We prove that in this limit, SU (3) color gauge transformations become equivalent to space-time diffeomorphisms. A gravity-like contribution is then shown to emerge from the overall “n-gluon exchange” component in the expansion of the generating functional of QCD Green functions, with the two-gluon term acting like the metric field in gravity. This QCD-induced “chromogravity” provides an effective long range action, i.e. longer-ranged than the contribution of quark-antiquark (meson) exchanges. We conjecture chromogravity to be responsible for many of the features of the hadron spectrum and of color confinement, issues for which there is as yet no proof in QCD (including lattice calculations), beyond general qualitative arguments. The method exhibits a smooth transition to the perturbative and semiperturbative treatment of high energy hadron scattering, including the emergence of the Pomeranchuk trajectory.
UNCERTAINTY RELATION FOR A QUANTUM OPEN SYSTEM
Authors: HU B.L. , ZHANG YUHONG
Published: November 2004

We derive the uncertainty relation for a quantum open system consisting of a Brownian particle interacting with a bath of quantum oscillators at finite temperature. We examine how the quantum and thermal fluctuations of the environment contribute to the uncertainty in the canonical variables of the system. We show that upon contact with the bath (assumed to be ohmic in this paper) the system evolves from a quantum-dominated state to a thermal-dominated state in a time which is the same as the decoherence time in similar models in the discussion of quantum to classical transition. This offers some insight into the physical mechanisms involved in the environment-induced decoherence process. We obtain closed analytic expressions for this generalized uncertainty relation under the conditions of high temperature and weak damping, separately. We also consider under these conditions an arbitrarily squeezed initial state and show how the squeeze parameter enters in the generalized uncertainty relation. Using these results we examine the transition of the system from a quantum pure state to a nonequilibrium quantum statistical state and to an equilibrium quantum statistical state. The three stages are marked by the decoherence time and the relaxation time, respectively. With these observations we explicate the physical conditions under which the two basic postulates of quantum statistical mechanics become valid. We also comment on the inappropriate usage of the word “classicality” in many decoherence studies of quantum to classical transition.
CENTRAL POTENTIALS AND EXAMPLES OF HIDDEN ALGEBRA STRUCTURE
Authors: BRIHAYE Y. , DEVAUX N. , KOSINSKI PIOTR
Published: November 2004

We propose two generalizations of the Coulomb potential equation of quantum mechanics and investigate the occurrence of algebraic eigenfunctions for the corresponding Schrödinger equations. Some relativistic counterparts of these problems are also discussed.
SIMPLE NON-ABELIAN FINITE FLAVOR GROUPS AND FERMION MASSES
Authors: FRAMPTON P.H. , KEPHART T.W.
Published: November 2004

The use of non-Abelian discrete groups G as family symmetries is discussed in detail. Out of all such groups up to order g=31, the most appealing candidates are two subgroups of SU(2): the dicyclic (double dihedral) group G=Q6= (d) D3(g=12) and the double tetrahedral group [Formula: see text]. Both can allow a hierarchy t>b, τ>c>s, μ>u, d, e. The top quark is uniquely allowed to have a G symmetric mass. Sequential breaking of G and radiative corrections give the smaller masses. Anomaly freedom for gauging G⊂ SU (2) is a strong constraint in assignment of fermions to representations of G.
DIFFUSION MECHANISMS AT fcc METAL SURFACES — EMBEDDED ATOM METHOD CALCULATIONS
Authors: LIU CHUN-LI
Published: November 2004

Recent development in theoretical investigations using computer simulation techniques and the embedded atom method (EAM) on diffusion processes critical to nucleation and growth of thin films at fcc metal surfaces is reviewed. Through these investigations, interactions between adatoms and substrate, adatoms and steps, and clusters and substrate and the effect of these interactions on dynamic diffusion processes are further understood. The results from these theoretical investigations are generally consistent with available experimental data and have provided explanations for some experimental observations. Some predictions made a few years ago from these studies have been confirmed by the latest experiments.
THEORY OF POLYMER RELAXATION TIMES IN SEMI-DILUTE SOLUTIONS
Authors: SHIWA YASUHIRO
Published: November 2004

The explicit crossover behavior of the longest relaxation time for the dilute and semi-dilute polymer solutions is presented. Gradual reduction of the excluded-volume and the hydrodynamic interaction due to screening is taken into account along with the entanglement effect. The result reveals a continuous approach to a reptation-like asymptote with increasing concentration.
ON A MAPPING BETWEEN HARD-CORE POTENTIAL MODELS FOR NEMATOGENS AND CONTINUOUS ONES
Authors: ROMANO S.
Published: November 2004

Hard-core nematogenic models can be studied using Onsager’s theory, and, on the other hand, continuous interaction potentials can be investigated using the molecular field approach pioneered by Maier and Saupe. Comparison between these treatments shows a certain formal similarity, reflecting their common variational root; on this basis, hard-core potential models can be mapped on separable continuous ones, via their excluded volume. As a specific example, we have, therefore, considered hard spherocylinders and hence the continuous potential model(s) [Formula: see text] here uj denotes the unit vector defining particle orientation, xj denotes the coordinate vector of its center of mass, and ∊ is a positive quantity setting temperature and energy scales(i.e. T*=kBT/∈). The |sin| function can be expanded in a series of Legendre polynomials of even order, with a dominant P2 term; particles’ centers of mass were associated with a simple-cubic lattice, the function ɸ(r) was truncated at nearest-neighbor separation, and values of the two parameters p and q were chosen so as to make contact with the Lebwohl-Lasher lattice model, i.e. [Formula: see text]. The resulting pair potential was studied by molecular field theory and by computer simulation; molecular field theory predicts a first-order transition at [Formula: see text], whereas the result obtained by simulation was [Formula: see text]; comparison with the Lebwohl-Lasher model shows that the higher-order interactions contained in the potential tend to increase the transition temperature towards its molecular field limit.
MAGNETIC PROPERTIES OF BINARY DISORDERED ALLOY
Authors: MANDAL K. , GHATAK S.K.
Published: November 2004

A model binary alloy Ax B1−x where A and B represent ferromagnetic and paramagnetic transition metal respectively is considered within the framework of periodic Anderson model, and the effects of d-level disorder and variation of electron concentration due to alloying on the magnetic properties are investigated. The phase boundary, thermal behavior of magnetization and susceptibility of the alloy are obtained using HF approximation for the Coulomb interaction and the virtual crystal approximation for d-level disorder. The ferromagnetic state of alloy vanishes at a critical concentration xc which depends on d-band width, strength of s-d hybridization and the Coulomb interaction. The re-entrant magnetic phase is found within a small region of x for alloy with narrow d-band. For x≲xc, the magnetic properties resemble that of spin-glass system. For x≪xc, the alloy behaves like a Pauli paramagnet. The re-entrant and spin-glass-like phases are associated with the increase in d-level population as temperature decreases. Local moment for x≃1 decreases with temperature up to Tc whereas the reverse is the situation for alloy exhibiting spin-glass-like behavior.
SPONTANEOUS FLUX AND FLUX TRAPPED IN MESOSCOPIC CYLINDERS
Authors: SZOPA M. , ZIPPER E.
Published: November 2004

Persistent currents in mesoscopic cylinders made of a very clean metal and with nearly flat Fermi surface are studied. It is shown that the inclusion of the orbital magnetic interaction between electrons can lead to spontaneous currents (spontaneous fluxes) and to flux trapping if the number of interacting electrons is large enough. The free energy of the cylinder is discussed and the self-consistent formulas for the quantized flux in the cylinder is derived. It is argued that the properties of such mesoscopic cylinders are to some extent similar to the properties of superconducting samples.
W INFINITE SYMMETRIES IN THE HIERARCHICAL QUASIPARTICLE STATES (LOWEST LANDAU LEVEL STATES) OF THE FRACTIONAL QUANTUM HALL SYSTEMS
Authors: CHEN YI-XIN , MA ZHONG-SHUI , SU ZHAO-BIN
Published: November 2004

We investigate the W infinite symmetries in the theory of general fractional quantum Hall effects by using the lowest Landau level constraint approach. We find that there does exist a W infinite symmetric algebra for the fractional quantum Hall system with all the quasiparticles being restricted to the lowest Landau level. The corresponding generators can be used to generate the new degenerate wavefunctions of the lowest Landau level states by means of Laughlin and Halperin wavefunctions. Meanwhile, we find there still exists another W infinite symmetric algebra in the system, whose generators are used to generate the degenerate wavefunctions of the lowest Landau level for the anti-quasiparticles. We conclude that the FQH system can effectively be described by quasiparticle features or anti-quasiparticle features. We also show that the local part of the W infinite symmetric algebras is the magnetic translation operator of the general fractional quantum Hall system. We finally construct the operators of the single mode wave density excitations in the system and discuss their operator product relations.
CONSTRAINED ANNEALING FOR SYSTEMS WITH QUENCHED DISORDER
Authors: PALADIN GIOVANNI , PASQUINI MICHELE , SERVA MAURIZIO
Published: November 2004

We review a method for the study of systems with quenched disorder, such as Ising models with random field or coupling, by means of annealed averages where appropriate constraints are imposed. It allows one to understand the role of the intensive variables of the disorder (mean magnetic field, impurities concentration, frustration…) and improves the annealed approximation of the quenched free energy.

The constrained annealing can be obtained by introducing generalized Gibbs-like potential depending on Lagrangian multipliers associated to the intensive variables of the disorder. The minimum of the potential gives a lower bound of the quenched free energy which can be a very accurate estimate for a proper choice of the constraints.

The method is first applied to one-dimensional Ising models with random magnetic fields. In this case the frustration is properly taken into account and the quenched free energy density is estimated with a precision higher than the numerical results. As a first step to higher dimensional model we then introduce an Ising model with two competing interactions: nearest neighbour random couplings and a positive infinite range coupling. At low temperature the model exhibits a new type of non-trivial ‘ferrimagnetic’ order in a region of low temperatures and intermediate disorder strength. The qualitative features of the model (in particular the phase transition line between ferromagnetic and ferrimagnetic phases) is reproduced by the constrained annealing.

Finally we apply our method to d-dimensional Ising models with random nearest neighbour coupling. In this case, we also introduce an alternative new way to obtain constrained annealed averages without recurring to the Lagrange multipliers. It requires to perform quenched averages on small volumes, in a analytic or numerical way. We thus give a sequence of converging lower bounds for the quenched free energy. In particular, in 2d the known analytic estimates are considerably improved.
PHASE DIAGRAM FOR A LUTTINGER LIQUID COUPLED TO PHONONS IN ONE DIMENSION
Authors: MARTIN THIERRY , LOSS DANIEL
Published: November 2004

We consider a one-dimensional system consisting of electrons with short-ranged repulsive interactions and coupled to small-momentum transfer acoustic phonons. The interacting electrons are bosonized and described in terms of a Luttinger liquid which allows us to calculate exactly the one- and two-electron Green function. For non-interacting electrons, the coupling to phonons alone induces a singularity at the Fermi surface which is analogous to that encountered for electrons with an instantaneous attractive interaction. The exponents which determine the presence of singlet/triplet superconducting pairing fluctuations, and spin/charge density wave fluctuations are strongly affected by the presence of the Wentzel-Bardeen singularity, resulting in the favoring of superconducting fluctuations. For the Hubbard model the equivalent of a phase diagram is established, as a function of: the electron-phonon coupling, the electron filling factor, and the on-site repulsion between electrons. The Wentzel-Bardeen singularity can be reached for arbitrary values of the electron-phonon coupling constant by varying the filling factor. This provides an effective mechanism to push the system from the antiferromagnetic into the metallic phase, and finally into the superconducting phase as the electron filling factor is increased towards half-filling.
NON-ADIABATIC ELIMINATION OF VARIABLES IN STOCHASTIC PROCESSES BY MEANS OF PATH INTEGRAL AND INFLUENCE FUNCTIONAL METHODS
Authors: WIO HORACIO S. , BUDDE C. , BRIOZZO C. , COLET P.
Published: November 2004

We present a novel scheme for the non-adiabatic elimination of variables in stochastic processes, based on a path integral representation of the probability density and the use of an influence functional. We analyze in particular the case of multivariate Fokker-Planck equations, or equivalently a set of coupled Langevin equations driven by white noises, and discuss some examples where exact or approximate results are obtained.
FIRST ORDER PHASE TRANSITIONS, WHEN AND FROM WHERE DO THEY EMERGE? —THE CASE OF GELS
Authors: SEKIMOTO KEN
Published: November 2004

We briefly review the recent theoretical understanding of the first order phase transition undergone by gels with an emphasis on physical concepts, deliberately excluding details of modeling and analytic methods. The density of a gel changes discontinuously at the transition point. A variety of features of the transition result from the basic fact that the inhomogeneity of the density of the gel inevitably causes shear deformation. This deformation, on the one hand, reflects the geometry of the sample and, on the other hand, may alter the transition temperature.
SELF-CONSISTENT THEORY OF ELASTIC PROPERTIES OF STRONGLY ANHARMONIC CRYSTALS I: GENERAL TREATMENT AND COMPARISON WITH COMPUTER SIMULATIONS AND EXPERIMENT FOR FCC CRYSTALS
Authors: ZUBOV V.I. , SANCHEZ J.F. , TRETIAKOV N.P. , YUSEF A.E.
Published: November 2004

Based on the correlative method of an unsymmetrized self-consistent field,16–23 we have derived expressions for elastic constant tensors of strongly anharmonic crystals of cubic symmetry. Each isothermal elastic constant consists of four terms. The first one is the zeroth approximation containing the main anharmonicity (up to the fourth order). The second term is the quantum correction. It is important at temperatures below the De-bye characteristic temperature. Finally, the third and fourth terms are the perturbation theory corrections which take into account the influence of the correlations in atomic displacements from the lattice points and that of the high-order anharmonicity respectively. These corrections appear to be small up to the melting temperatures. It is sufficient for a personal computer to perform all our calculations with just a little computer time. A comparison with certain Monte Carlo simulations and with experimental data for Ar and Kr is made. For the most part, our results are between. The quasi-harmonic approximation fails at high temperatures, confirming once again the crucial role of strong anharmonicity.
FQHE AND JAIN’S APPROACH ON THE TORUS
Authors: CRISTOFANO G. , MAIELLA G. , MUSTO R. , NICODEMI F.
Published: November 2004

By using the explicit knowledge of the lowest energy single particle wave functions in the presence of an arbitrary magnetic field, we extend to the case of a torus Jain’s idea of looking at the FQHE as a manifestation of an integer effect for composite fermions. We show that this can be realized thanks to a redefinition of the vacuum state that is explicitly collective in nature. We also discuss the relationship of this approach with the hierarchical scheme and with the characterization of the Hall states in terms of W1+∞ algebras and 2D conformal field theories.
THE VAN HOVE SINGULARITY IN HIGH Tc SUPERCONDUCTORS
Authors: HORBACH M.L. , KAJÜTER H.
Published: November 2004

Experimental indications for the role of the van Hove singularity (vHs) in the electronic density of states of high Tc superconductors are discussed. It is argued that

(i) like the resistivity, the measured temperature and doping dependences of the normal state electronic specific heat of YBCO are consistent with the existence of a vHs and

(ii) the doping dependence of Tc in the underdoped and optimally doped regimes may be accounted for mainly by a vHs.

Further, we discuss the suppression of the quasiparticle scattering rate below Tc, and the coherence lengths in the hole-doped materials and NCCO. Assuming that the same mechanism for superconductivity operates in the electron-doped and the hole-doped cuprates, we argue that the bosonic mode that causes the superconductivity is strongly influenced by the doping in the overdoped regime. We further argue that this boson involves an energy scale larger than that of phonons and is only weakly coupled to the charge carriers.
MODE-COUPLING THEORY, DYNAMIC SCALING, AND TWO-DIMENSIONAL TURBULENCE
Authors: NANDY MALAY K. , BHATTACHARJEE JAYANTA K.
Published: November 2004

A self-consistent mode-coupling scheme, along with dynamic scaling ideas, is used to obtain a renormalized perturbation theory in the Eulerian framework from Wyld’s perturbation theory of the forced Navier-Stokes equation. For the force-correlation behaving as k−(d−4+y), the Kolmogorov and Kraichnan-Batchelor scaling spectra of two-dimensional turbulence for the inverse energy cascade, [Formula: see text] and the direct entropy cascade, [Formula: see text], are obtained for y=4 and y=6 respectively, including the logarithmic correction for the latter. Unlike the usual Eulerian formulations (e.g. the direct-interaction approximation), the theory is finite in the energy regime, while it becomes marginal in the enstrophy regime, leading to the logarithmic correction. Calculations yield C=6.447 and C′=1.923 at one-loop order, which are in exact agreement with those of field-theoretic renormalization group calculations [P. Olla, Phys. Rev. Lett. 67, 2465 (1991)]. However, a self-consistent treatment of the logarithmic scalings in E(k) and the inverse response-time yields a different value: C′=2.201. The theory is free of any external parameter; the choice of y(=4 or 6) is dictated by the condition of conserved transfer of energy or enstrophy.
PROPERTIES OF HEAT FLUX FUNCTIONS AND A LINEAR THEORY OF HEAT FLUX
Authors: WANG LIQIU
Published: November 2004

The symmetry and positive definiteness of thermal conductivity tensor K are used to derive some properties of heat flux functions ɸi (i=0, 1, 2). All ɸi are shown to be real-valued. Both ɸ0 and ɸ2 are found to be positive definite, and ɸ1 is constrained between −(ɸ0 + ɸ2) and (ɸ0 + ɸ2). By assuming heat flux vector q to be a linear function of temperature gradient ∇θ and velocity strain tensor D, ɸi reduce to three coefficients which are independent of D and ∇θ.
SPIN FLUCTUATION THEORY FOR TEMPERATURE-INDUCED FERROMAGNETISM IN ITINERANT ANTIFERROMAGNETS AND PARAMAGNETS
Authors: POVZNER A.A. , LIKHACHEV D.V.
Published: November 2004

The possible occurrence of “temperature-induced ferromagnetism” in itinerant antiferromagnets with spin-density wave and strong paramagnets is discussed on the basis of spin fluctuation theory taking account of the effect of large ferromagnetic spin fluctuations. It is shown that the presence of a point of inflexion of the density of states near the Fermi level leads to the appearance of temperature-induced ferromagnetic order parameter in the itinerant electron systems. In addition the influence of this order parameter on the antiferromagnetic transition temperature is demonstrated and new mechanism of the magnetic phase transition is studied in relation to the magnetism of TiBe 2.
MANY-PHOTON EFFECTS IN INELASTIC LIGHT SCATTERING: THEORY AND MODEL APPLICATIONS
Authors: CINI MICHELE , D’ANDREA A. , VERDOZZI C.
Published: November 2004

A new formalism, based on the method of Excitation Amplitudes, is presented in order to set up a theory of the second harmonic generation (SHG) and other Inelastic Light Scattering phenomena, like the dynamical Start effect, when many-photon effects are considered. We develop the quantum theory and its semiclassical limit on equal footing, and show that the maximum intensity of the Second Harmonic fields does not generally correspond exactly to twice the incident frequency. The most interesting case occurs in highly polarizable systems when the exciting field is strong enough to produce appreciable many-photon effects, yet there are still observable quantum fluctuations. The inclusion of electron-photon coupling to all orders then leads to new effects, including a contribution of the Dynamical Stark Effect to the SHG response, as shown by model calculations.
MAGNETIC LAYER THICKNESS DEPENDENCE OF THE INTERLAYER EXCHANGE COUPLING
Authors: BLOEMEN P. J. H. , VAN DE VORST M. T. H. , DE JONGE W. J. M. , JOHNSON M. T. , COEHOORN R.
Published: November 2004

Recent progress in the research on interlayer exchange coupling, focusing on the effect of the magnetic layer, is reviewed. Several theoretical works have shown that the exchange coupling does not just involve an interaction localized at the interfaces, but the electronic properties of the sandwich as a whole. The important prediction that the strength of the exchange coupling should oscillate as a function of the magnetic layer thickness has been confirmed recently for the Co/Cu(100) and the Fe/Cr(100) system. The oscillation periods are strongly believed to be related to wave vectors that span extremal parts of the spin-resolved Fermi surfaces of the ferromagnets.
GAP-LABELING PROPERTIES OF THE ENERGY SPECTRUM FOR TWO-DIMENSIONAL FIBONACCI QUASILATTICES
Authors: LIU YOUYAN , SRITRAKOOL WICHIT , FU XIUJUN
Published: November 2004

We have analytically obtained the occupation probabilities on subbands of the hierarchical energy spectrum and the step heights of the integrated density of states for two-dimensional Fibonacci quasilattices. Based on the above results, the gap-labeling properties of the energy spectrum are found, which claim that the step height is equal to {mτ}, where the braces denote the fractional part, and m is an integer that can be used to label the corresponding energy gap. Numerical results confirm these results very well.
LATTICE MELTING AT STRUCTURAL PHASE TRANSITIONS
Authors: HARRIS M. J. , DOVE M. T.
Published: November 2004

Lattice melting is an unusual effect that occurs at the continuous structural phase transition belonging to the m = 2 universality class. Renormalization group theoretical studies have shown that the mean-squared atomic displacements are expected to diverge at this transition, much as they do in a conventional liquid–solid transition. However, in the m = 2 transition they diverge continuously, and only along one crystallographic direction. The end result is still that the crystalline long range order is destroyed completely at T c , but unlike a conventional melting transition it recovers after the transition is passed. The current theoretical understanding of this effect is reviewed together with a discussion of the search for an experimental realization. Recent experiments that show that the ferroelastic transition in anhydrous Na 2 CO 3 is the first known to show ideal lattice melting are detailed.
PATH INTEGRAL DERIVATION OF AN EXACT MASTER EQUATION
Authors: LAWANDE S. V. , LAWANDE Q. V.
Published: November 2004

The Feynman propagator in coherent states representation is obtained for a system of a single harmonic oscillator coupled to a reservoir of N oscillators. Using this propagator, an exact master equation is obtained for the evolution of the reduced density matrix for the open system of the oscillator.
IMPLICATIONS OF INTERPOLATIVE QUANTUM STATISTICS — A REVIEW
Authors: RAMANATHAN R.
Published: November 2004

A review of the interpolative quantum statistics is presented. It is shown, by imposing a positivity condition on the distribution function, that this statistics subsumes Gentile's intermediate statistics and is far richer than Gentile's statistics, apart from being a genuine quantum statistics. It is also capable of accounting for the possible very small violations of statistics in physical processes. It is finally pointed out that this statistics offers an elegant and useful parametrization of Haldane's 'statistical interaction', while retaining all the interesting features of the latter. Some of the statistical mechanics that these distribution functions lead to are also examined.
MULTIAFFINE SCALING IN ONE-DIMENSIONAL DISORDERED SYSTEMS
Authors: MANNA SUSIL K. , BASU CHAITALI , MOOKERJEE ABHIJIT
Published: November 2004

The multiaffine analysis is used to study the internal structures of the transmittance in three different cases: a homogeneous random chain in the mesoscopic regime, an inhomogeneous random chain and a random chain in the presence of an external electric field. We find large fluctuations of transmittance in all three different types of systems and these obey anisotropic multiaffine scaling. This method provides a unified description of transmittance fluctuations in very different systems.
SYNTHESIS AND CHARACTERIZATION OF LaBaCa2Cu3Oy SUPERCONDUCTOR
Authors: JEYABALAN K. , ASOKAMANI R. , NATARAJAN S. , KALIYAPERUMAL L. K.
Published: November 2004

We report here the synthesis and characterization of a new superconducting oxide LaBaCa 2 Cu 3 O y. The T c value of the compound is measured to be 25 K. XRD studies reveal that the compound possesses orthorhombic structure.
RENORMALIZATION OF POTENTIAL SCATTERING IN A ONE-DIMENSIONAL NON-LUTTINGER LIQUID: CONDUCTION AND X-RAY FERMI-EDGE SINGULARITY
Authors: YUE DONGXIAO
Published: November 2004

We review some of our recent results on the potential scattering in a weakly interacting one-dimensional(1D) electron gas. The technique we developed is a poor man's renormalization group procedure in the scattered wave basis. This technique can treat the renormalizations of the scattering on the barrier and the scattering between the electrons in a coherent way, and it allows us to find the scattering amplitudes on a localized potential of arbitrary strength for electrons at any energy. The obtained phase shifts are used to study the Fermi-edge singularity in an interacting 1D electron system, where anomalous exponent of the power-law singularity in the vicinity of the edge is found. The transmission coefficient is directly related to the conductance of a 1D channel by the Landauer formula. Simple formulas that describe the conductance at any temperature are derived. In spin-[Formula: see text] systems, the electron–electron backscattering induces renormalizations of the interaction constants, which causes the low-temperature conductance to deviate from the results of the Luttinger liquid theory. In particular, the temperature dependence of the conductance may become nonmonotonic. In the presence of a magnetic field, backscattering gives rise to a peak in the differential conductance at bias equal to the Zeeman splitting.
SPECIAL POLYNOMIALS IN PROBLEMS OF QUANTUM OPTICS
Authors: ORLOV YURII N. , VEDENYAPIN VICTOR V.
Published: November 2004

For a general Raman-type model describing the decay of a pumping mode into p components special polynomials are introduced. Asymptotic properties of those polynomials are discussed when the number of excitations tends to infinity. In the investigation of interaction between radiation and media, a number of mathematical complexities arises. The simplest example is the modeling of radiation scattering by excitations of a crystal lattice. Some of the contradictions are caused by the peculiarities of the second quantization method, which is used effectively for quadratic Hamiltonians only. Another problem is the determination of the energy states of the investigated media, which is a problem of eigenvalues. Mathematically we are to examine some system of polynomials connecting each other by a recurrency, which is analogous to the classical case. In this paper we consider the mathematical problems arising therein.
DIFFUSION OF LIGHT ADATOMS ON SOLID SURFACES
Authors: CHEN L. Y. , YING S. C.
Published: November 2004

We present a brief review of a theoretical approach to the diffusion of light adatoms that covers the entire range from the classical regime of thermally activated hopping to the low temperature regime of quantum tunneling between adjacent sites. We compare our theoretical results with recent experimental data for the system H/Ni(100). We also contrast our results with those obtained from the quantum transition state approach.
APPLICATIONS OF COLLISIONALLY EXCITED AUTOIONIZATION ELECTRON SPECTROSCOPY: CASE STUDIES OF Na ADSORPTION AND OXYGEN COADSORPTION ON METAL SURFACES
Authors: XU FANG
Published: November 2004

We discuss the mechanism and applications of the low energy collisionally excited projectile and target atom autoionization electron spectroscopy through illustration of the representative case studies of Na adsorption and O 2 coadsorption on polycrystalline Cr, Pt, and Al substrates using 700 eV Ne + ion impact. We show that it is possible to determine the surface electrostatic potentials with the detected electron kinetic energies, to monitor the evolution of the local valence charge distribution around the excitation sites with the coverage dependence of the Ne 2p 41 D -3 P singlet-to-triplet conversion rate, and to establish the overlayer growth morphology with the variation of the widths and relative intensities of the transition lines. We demonstrate the great potential of this surface analysis technique in the studies of interface formation involving alkali metal overlayers.
PARTICLE COARSENING IN Fe(Cu) ALLOYS
Authors: RANA ANWAR MANZOOR , ANSARI M. IQBAL
Published: November 2004

Particle coarsening behavior in Fe(Cu) alloys has been studied by electrical resistivity measurements at different ageing temperatures. Measured resistivity data for these alloys were analyzed by discussing the electrical resistivity behavior during thermal ageing and theories of diffusion-controlled coarsening of precipitates. Some important parameters such as the precipitate radius r, solute concentration C, diffusivity D, etc. were calculated and compared with the previous results obtained with Transmission Electron Microscopy (TEM) and Small Angle Neutron Scattering (SANS) techniques.
SHOT NOISE SUPPRESSION IN QUANTUM POINT CONTACT STRUCTURES
Authors: CHEN L. Y. , YING S. C.
Published: November 2004

The shot noise power spectrum of a quantum point contact structure is investigated based upon a time-dependent Landauer approach. The system is modeled by an open conducting channel coupled with two infinite reservoirs. When the channel length L ≫ ξ (the coherence length of an electron wave packet), all the channel states moving from source to drain are fully occupied while all the opposite ones are empty. Consequently, shot noise is suppressed to zero along with conductance quantization. For L ~ ξ, however, while the conductance is still well quantized, the shot noise is only partially suppressed to a nonzero fraction of its full level, in agreement with recent experimental data.
VIRIAL EXPANSION FOR AN ε-DEFORMED SYSTEM
Authors: R-MONTEIRO MARCO A. , RODITI ITZHAK , RODRIGUES LIGIA M. C. S.
Published: November 2004

We compute the virial expansion of an ideal quantum q gas equation of state for small values of the deformation parameter.
DYNAMICS OF A NONDEGENERATE TWO-PHOTON JAYNES–CUMMINGS MODEL
Authors: D'SOUZA RICHARD , JAYARAO ARUNDHATI S.
Published: November 2004

A generalized Jaynes–Cummings model including the Stark shifts is investigated where the transition is mediated by two different modes of photons. For two different types of correlated field states, the pair coherent states and two-mode SU(1, 1) coherent states, the effect of including the Stark shift on the dynamical behavior of atomic inversion, atomic squeezing parameters, second order coherence function, and photon number distribution is investigated. Our results indicate significant changes in the behavior of these quantities for large and small average photon number  in the presence and absence of Stark shift and depending on the type of correlated field involved.
HIGH PRESSURE STUDY OF La3Ni2B2Nx
Authors: CAO Y. , MENG R. L. , CHU C. W.
Published: November 2004

The pressure effect on the superconducting transition temperature (T c ) of the newly discovered compound with a nominal composition La 3 Ni 2 B 2 N x with a T c ~14 K has been determined up to 1.5 GPa. T c was found to decrease linearly at a rate of –0.9 K/GPa, which is much greater than that of similar superconducting compounds, LuNi 2 B 2 C and Lu 2 Ni 2 B 2 C 2, while the compound resistivity remains unchanged. Reasons for the observation remain unknown.
GROWTH PATTERN OF SILICON CLUSTERS
Authors: BAHEL ATUL , PAN JUN , RAMAKRISHNA MUSHTI V.
Published: November 2004

Tight-binding molecular dynamics simulated annealing technique is employed to search for the ground state geometries of silicon clusters containing 11–17 atoms. These studies revealed that layer formation is the dominant growth pattern in all these clusters. Fullerene-like precursor structures consisting of fused pentagon rings are also observed. The atoms in all these clusters exhibit pronounced preference for residing on the surface.
ON THE INTERATOMIC CORRELATIONS AND MEAN SQUARE RELATIVE ATOMIC DISPLACEMENTS IN AN ANHARMONIC MODEL OF THE CLOSE-PACKED CRYSTAL
Authors: ZUBOV V. I. , PASCUAL M. F. , RODRIGUES C. G.
Published: November 2004

The correlative method of unsymmetrized self-consistent field (CUSF) is used to study the interatomic correlations and mean square displacements in anharmonic crystals. In the first order of CUSF we have derived the formula for the atomic mean square displacement and quadratic correlation between displacements of two nearest neighbors along the line passing through their centers [Formula: see text] where n is the dimensionality of a lattice and Z is the coordinational number. In the second order of CUSF we have calculated the quadratic correlation moments and mean square relative displacements in the two-dimensional model of an anharmonic crystal with hexagonal lattice. The results are compared with those for square lattice obtained previously.
THE METHOD OF INTER-PARTICLE DISTRIBUTION FUNCTIONS FOR DIFFUSION-REACTION SYSTEMS IN ONE DIMENSION
Authors: BEN-AVRAHAM DANIEL
Published: November 2004

Diffusions limited reactions in confined geometries exhibit all aspects of nonequilibrium dynamics, such as anomalous kinetics, self-organization and dynamical phase transitions, and have therefore been the subject of extensive research in recent years. In this paper we review the method of interparticle distribution functions (IPDF) which was originally introduced for deriving the exact kinetics of the diffusion-limited coalescence process, A+A→A, in one dimension. We explain the IPDF method and review variants of the coalescence model which can be solved exactly through this technique. We then consider strategies for approximations based on the IPDF method and review applications to coalescence with finite reaction rates (away from the strictly diffusion-controlled regime), many-body reactions (nA→mA), and the contact process. We conclude with a discussion of open, interesting problems and possible ways to their solution.
SPIRAL CHOLESTERICS: SURFACE EFFECTS
Authors: MITOV M. , SIXOU P.
Published: November 2004

The helicoidal structure of the cholesteric phase can be untwisted by the electric field effect. We have shown that spiral-shaped structures could nucleate at the threshold of the field-induced homeotropic state from filaments (linked to the twisted state) embedded in a homeotropic pseudo-nematic matrix (untwisted cholesteric). In this article, we show that confinement and anchoring conditions influence the dynamical behavior and the existence of spiral patterns induced in cholesteric liquid crystals materials by an electric field.
IONIZATION OF CHARGE-ANTICHARGE PAIRS IN ULTRATHIN PALLADIUM FILMS
Authors: LIU YING , PRICE JOHN C.
Published: November 2004

The electrical conductance and I–V characteristics of ultrathin Pd films prepared by low temperature deposition have been measured in situ. An Arrhenius behavior was found for the electrical conductance. A crossover between regimes with different activation energies was observed at a temperature TK. Below TK, the I–V characteristics of the film were found to be nonlinear. These observations are explained using a charge Kosterlitz-Thouless-Berezinskii transition picture which involves the ionization of charge-anticharge pairs.
EXACTNESS OF FERMIONIC LINEARIZATION SCHEME WITH CLIFFORD VARIABLES IN d=∞
Authors: MONTORSI ARIANNA
Published: November 2004

We show that the fermionic linearization scheme for dealing with strongly correlated electron systems — when implemented with Clifford variables — becomes exact in the d=∞ limit, at least for Hubbard-like models. In this case, the model is mapped exactly into a single-site problem. The conditions under which such a feature allows to obtain an exact solution are also discussed.
SUPER-RECURRENCE PHENOMENON RELEVANT TO THE PHASE IN THE NONLINEAR SCHRÖDINGER EQUATION
Authors: YANG Y. , TAN Y. , ZHANG W.Y. , ZHENG C.Y.
Published: November 2004

The nonlinear Schrödinger equation with spatially periodic boundary conditions is numerically solved by means of the spectrum method. It is found that with the initial condition carefully chosen, the phase recurrence just appears when the amplitudes have the nineteenth recurrences to the initial condition. This phenomenon is called as the phase super-recurrence. Using a simple perturbation model, the amplitude recurrence period Ta and the phase change ∆φa in the period Ta are estimated, and a good agreement between this estimation and the numerical results of the nonlinear Schrödinger equation is shown.
A qp-DEFORMED ANHARMONIC OSCILLATOR WITH THE Uqp(U2) ⊃ Uqp(O2) SYMMETRY AND ITS APPLICATION TO VIBRATIONAL MOLECULAR SPECTRA
Authors: ZHOU HUAN-QIANG , ZHANG XIN-MING , HE JING-SONG
Published: November 2004

A qp-deformed anharmonic oscillator with the Uqp(U2) ⊃ Uqp(O2) symmetry is presented for describing vibrational spectra of diatomic molecules. The energy formula is tested on the vibrational spectra in the state [Formula: see text] of H2 obtained through the Rydberg-Klein-Rees (RKR) method.
METAL-INSULATOR TRANSITION OF CuO IN YBCO/CuO/YBCO JUNCTION
Authors: OGUSHI T. , KOBA S. , HIROSE M. , HIGO S. , KAWANO I. , NAKAO A.
Published: November 2004

A resistive transition of CuO sandwiched with Y 1 Ba 2 Cu 3 O 7–δ films has been studied. It shows a zero resistive transition around the critical temperature of Y 1 Ba 2 Cu 3 O 7–δ. The metal-insulator (or high resistivity) transition has been observed for thicker samples depending on the measuring current.
FINITE-SIZE SCALING FOR THE SPHERICAL MODEL WITH LONG-RANGE INTERACTION
Authors: NOJIMA K.
Published: November 2004

The finite-size scaling property of the correlation length for the spherical model with long-range interaction is examined above the critical temperature. The analysis is performed below the upper critical dimension.
GENERALIZED TEMPLATE FOR PERIOD DOUBLINGS
Authors: ARIMITSU T. , MOTOIKE T.
Published: November 2004

It is shown how one can derive the formula for the local crossing number with the help of the symbolic dynamics with two letters knowing that, on the extended (ξ, η)-template, any period-doubling sequences in continuous dynamical systems is characterized by the periodic block [Formula: see text] The formulas of the global crossing number and of the linking number are derived in terms of the local crossing number which can be extracted from the power spectrum of periodic orbits. The topological characterization of periodic orbits in continuous dynamical systems has come to be at hand for experimenters as well as for theorists. The formulas are applied to the situations of the numerical experiments for particular systems, and the results are investigated in connection with the concept of the irreducible and reducible templates. It is also shown how the formulas can be applicable to the forced Lorenz system, the Brusselator equation, the parametric pendulum, T(2, 5) resonant torus knot and P(7, 3, −2) pretzel knot.
EXPERIMENTAL STUDY OF THE SOLITONS IN NONLINEAR DIATOMIC MACRO-LATTICE
Authors: LOU SEN-YUE , HUANG GUOXIANG
Published: November 2004

For a one-dimensional damped and parametrically driven diatomic-like macro-pendulum lattice, five types of the lower cutoff and upper cutoff stable soliton and kink excitations have been observed. Especially, the gap soliton which has been studied widely in physics is first observed in macro-experiments. The experimental results can be well explained qualitatively by a nonlinear Schrödinger theory after neglecting the nonuniformity effects of the pendulums.