bluuebunny/crossref_metadata_2025 huggingface dataset:
Leptonic Decays of Heavy Quarks on the Lattice
Authors: Wittig Hartmut
Published: October 2003

The status of lattice calculations of heavy-light decay constants and of the B parameter BB is reviewed. After describing the lattice approach to heavy quark systems, the main results are discussed, with special emphasis on the systematic errors in present lattice calculations. A detailed analysis of the continuum limit for decay constants is performed. The implications of lattice results on studies of CP violation in the Standard Model are discussed.
Screening in Two-Dimensional QCD
Authors: Abdalla E. , Mohayaee R. , Zadra A.
Published: October 2003

We discuss the issue of screening and confinement of external color charges in bosonized two-dimensional quantum chromodynamics. Our computation relies on the static solutions of the semiclassical equations of motion. We consider the problem with fermions in the fundamental representation, as well as arbitrary products thereof, from which the case of adjoint representation may be obtained by suitable constraints in the massless case. The mass term is treated perturbatively. Under these assumptions, we arrive at the conclusion that, in the cases considered so far (fermions in the fundamental representation or arbitrary numbers of copies thereof) screening seems to prevail. Indeed, we found no solution compatible to confinement. To confirm this result further, we outline the construction of operators corresponding to screened quarks.
Five-Brane Lagrangian with Loop Corrections in Field-Theory Limit
Authors: Saulina N. A. , Terentiev M. V. , Zyablyuk K. N.
Published: October 2003

Equations of motion and the Lagrangian are derived explicitly for dual D = 10, N = 1 supergravity considered as a field theory limit of a five-brane. It is used the mass-shell solution of heterotic string Bianchi identities obtained in the two-dimensional σ-model two-loop approximation and in the tree-level heterotic string approximation. As a result the dual supergravity Lagrangian is derived in the one-loop five-brane approximation and in the lowest six-dimensional σ-model approximation.
The Heterotic Life of the D-Particle
Authors: Danielsson Ulf H. , Ferretti Gabriele
Published: October 2003

We study the dynamics of D-particles (D0-branes) in type I' string theory and of the corresponding states in the dual heterotic description. We account for the presence of the two eight-orientifolds (eight-dimensional orientifold planes) and sixteen D8-branes by deriving the appropriate quantum mechanical system. We recover the familiar condition of eight D8-branes for each eight-orientifold. We investigate bound states and compute the phase shifts for the scattering of such states and find that they agree with the expectations from the supergravity action. In the type I' regime we study the motion transverse to the eight-orientifold and find an interesting cancellation effect.
Algebraic Bosonization: The Study of the Heisenberg and Calogero–Sutherland Models
Authors: Frau Marialuisa , Sciuto Stefano , Lerda Alberto , Zemba Guillermo R.
Published: October 2003

We propose an approach to treating (1 + 1)-dimensional fermionic systems based on the idea of algebraic bosonization. This amounts to decomposing the elementary low-lying excitations around the Fermi surface in terms of basic building blocks carrying a representation of the [Formula: see text] algebra, which is the dynamical symmetry of the Fermi quantum incompressible fluid. This symmetry simply expresses the local particle number current conservation at the Fermi surface. The general approach is illustrated in detail through two examples: the Heisenberg and Calogero–Sutherland models, which allow comparison with the exact Bethe ansatz solution.
Spectral Flow and Feigin–Fuks Parameter Space of N = 4 Superconformal Algebras
Authors: Matsuda Satoshi
Published: October 2003

The parameter space of the Feigin–Fuks representations of the N = 4 SU (2)k superconformal algebras is studied from the viewpoint of the spectral flow. The η phase of the spectral flow is nicely incorporated through twisted fermions and the spectral flow resulting from the inner automorphism of the N = 4 superconformal algebras is explicitly shown to be operating as identity relations among the generators. Conditions for the unitary representations are also investigated in our Feigin–Fuks parameter space.
Simple Calculation of Instanton Corrections in MASSIVE N = 2 SU(3) SYM
Authors: Ewen Holger , Förger Kristin
Published: October 2003

We give an explicit derivation of the Picard–Fuchs equations for N = 2 supersymmetric SU(3) Yang–Mills theory with Nf < 6 massive hypermultiplets in the fundamental representation. We determine the instanton corrections to the prepotential in the weak coupling region using the relation between Tr <ϕ2> and the prepotential. This method can be generalized straightforwardly to other gauge groups.
Field Strength Correlators for Two-Dimensional Yang–Mills Theories Over Riemann Surfaces
Authors: Nunes João P. , Schnitzer Howard J.
Published: October 2003

The path integral computation of field strength correlation functions for two-dimensional Yang–Mills theories over Riemann surfaces is studied. The calculation is carried out by Abelianization, which leads to correlators that are topological. They are nontrivial as a result of the topological obstructions to the Abelianization. It is shown in the large N limit on the sphere that the correlators undergo second order phase transitions at the critical point. Our results are applied to a computation of contractible Wilson loops.
Dirac's Observables for the Higgs Model I: The Abelian Case
Authors: Lusanna Luca , Valtancoli Paolo
Published: October 2003

We search a canonical basis of Dirac's observables for the classical Abelian Higgs model with fermions in the case of a trivial U(1) principal bundle. The study of the Gauss law first class constraint shows that the model has two disjoint sectors of solutions associated with two physically different phases. In the electromagnetic phase, the electromagnetic field remains massless: after the determination of the Dirac's observables we get that both the reduced physical Hamiltonian and Lagrangian are nonlocal. In the Higgs phase, the electromagnetic field becomes massive and in terms of Dirac's observables we get a local, but nonanalytic in the electric charge (or equivalently in the sum of the electromagnetic mass and of the residual Higgs field), physical Hamiltonian; however the associated Lagrangian is nonlocal. Some comments on the R-gauge-fixing, the possible elimination of the residual Higgs field and on the Nielsen–Olesen vortex solution close the paper.
Janis–Newman–Winicour and Wyman Solutions are the Same
Authors: Virbhadra K. S.
Published: October 2003

We show that the well-known most general static and spherically symmetric exact solution to the Einstein-massless scalar equations given by Wyman is the same as one found by Janis, Newman and Winicour several years ago. We obtain the energy associated with this space–time and find that the total energy for the case of the purely scalar field is zero.
Renormalization of Composite Operators in Non-Abelian Gauge Theories
Authors: Lee Taeyeon
Published: October 2003

Renormalization of composite operators (at zero momentum transfer) is discussed in non-Abelian gauge theories. Composite operators are inserted into Green's functions by differentiating Z, the generating functional for Green's functions, with respect to the parameters coupled to the composite operators. In the case of the field strength tensor with no coupling parameter, it is possible to have the form of [Formula: see text] by rescaling gauge fields as Aμa → Aμa/g. Then the renormalization of [Formula: see text] can be carried out by the differentiation [Formula: see text]. By doing this, the renormalization procedure is different from the previous work of Kluberg–Stern and Zuber. The procedure of this paper naturally leads to the proper basis of operators which makes the triangular renormalization matrix. Explicit forms for the relation between bare and renormalized composite operators are presented, with the dimensional regularization and minimal subtraction scheme.
Higgs Branch, Hyper-Kähler Quotient and Duality in SUSY N = 2 Yang–Mills Theories
Authors: Antoniadis I. , Pioline B.
Published: October 2003

Low-energy limits of N = 2 supersymmetric field theories in the Higgs branch are described in terms of a nonlinear four-dimensional σ-model on a hyper-Kähler target space, classically obtained as a hyper-Kähler quotient of the original flat hypermultiplet space by the gauge group. We review in a pedagogical way this construction, and illustrate it in various examples, with special attention given to the singularities emerging in the low-energy theory. In particular, we thoroughly study the Higgs branch singularity of Seiberg–Witten SU(2) theory with Nf flavors, interpreted by Witten as a small instanton singularity in the moduli space of one instanton on ℝ4. By explicitly evaluating the metric, we show that this Higgs branch coincides with the Higgs branch of a U(1) N = 2 SUSY theory with the number of flavors predicted by the singularity structure of Seiberg–Witten's theory in the Coulomb phase. We find another example of Higgs phase duality, namely between the Higgs phases of U(Nc)Nf flavors and U(Nf-Nc)Nf flavors theories, by using a geometric interpretation due to Biquard et al. This duality may be relevant for understanding Seiberg's conjectured duality Nc ↔ Nf-Nc in N = 1 SUSY SU(Nc) gauge theories.
q-Deformed Phase Space and its Lattice Structure
Authors: Wess Julius
Published: October 2003

Quantum groups lead to an algebraic structure that can be realized on quantum spaces. These are noncommutative spaces that inherit a well-defined mathematical structure from the quantum group symmetry. In turn such quantum spaces can be interpreted as noncommutative configuration spaces for physical systems. We study the noncommutative Euclidean space that is based on the quantum group SO q(3).
Production of Scalar $K\bar{K}$ Molecules in ϕ Radiative Decays
Authors: Achasov N. N. , Gubin V. V. , Shevchenko V. I.
Published: October 2003

The potentialities of the production of the scalar [Formula: see text] molecules in the ϕ radiative decays are considered beyond the narrow resonance width approximation. It is shown that BR (ϕ → γ f0(a0) → γππ(πη)) ≈ (1 ÷ 2) × 10-5, [Formula: see text] and BR (ϕ → γ (f0 + a0) → γ KSKS) < 5 · 10-8. The mass spectra in the ππ, πη, K+K- channels are calculated. The imaginary part of the amplitude ϕ → γ f0(a0) is calculated analytically. It is obtained by the phase of the scalar resonance production amplitude that causes the interference patterns in the reaction e+e- → γπ+π- in the ϕ meson mass region.
Notes on the Kinematic Structure of the Three-Flavor Neutrino Oscillation Framework
Authors: Ahluwalia D. V.
Published: October 2003

These notes present a critique of the standard three-flavor neutrino oscillation framework. The design proposal of the MINOS at Fermilab based on a two-mass eigenstate framework may require serious reconsideration if there is strong mixing between all three flavors of neutrinos. For the LSND and KARMEN neutrino oscillation experiments, the amplitude of neutrino oscillation of the "one mass scale dominance" framework vanishes for certain values of mixing angles as a result of opposite signs of two equal and opposite contributions. Recent astronomical observations leave open the possibility that one of the neutrino mass eigenstates may be nonrelativistic in some instances. Neutrino oscillation phenomenology with a superposition of two relativistic, and one nonrelativistic, mass eigenstates is constructed. It is concluded that if the transition from the nonrelativistic to the relativistic regime happens for energies relevant to the reactor and the LSND neutrino oscillation experiments, then one must consider an ab initio analysis of the existing data.
Slower-Than-Light Spin-$\frac{1}{2}$ Particles Endowed with Negative Mass Squared
Authors: Salesi Giovanni
Published: October 2003

Extending in a straightforward way the standard Dirac theory, we study a quantum mechanical wave equation describing free spinning particles — which we propose to call Pseudotachyons (PT's) — which behave like tachyons in the momentum space (p2 = -m2), but like subluminal particles (v < c) in the ordinary space. This is allowed since, as it happens in every quantum theory for spin-[Formula: see text] particles, the momentum operator, -i ∇, (that is conserved), and the velocity operator α, (that is not), are independent operators, which refer to independent quantities: [Formula: see text]. As a consequence, at variance with ordinary Dirac particles, for PT's the average velocity [Formula: see text] is not equal to the classical velocity v cl = p/ε, but actually to the velocity "dual" of v cl : εp/p2. Being reciprocal of |v cl |, the speed of PT's is therefore smaller than the light speed. Since a lot of experimental data seems to involve a negative mass squared for neutrinos, we suggest that these particles might be PT's, travelling, because of their very small mass, at subluminal speeds very close to the light one. The present theory is shown to be separately invariant under the C, P, T transformations; the covariance under Lorentz transformations is also proven. Furthermore, we derive the kinematical constraints linking 4-impulse, 4-velocity and 4-polarization of free PT's.
Enhanced Gauge Symmetry in Three-Modulus Models of Type II String and Hypergeometric Series
Authors: Suzuki Hisao
Published: October 2003

The conifold singularities in the type II string are considered as the points of phase transition. In some cases, these singularities can be understood, in the framework of the conventional field theories, as the points of enhanced gauge symmetry. We consider a class of three-modulus type II strings. It is shown the periods can be written in the form of hypergeometric series around the singular points in these models. The leading expansion around the conifold locus turns out to be described by Appell functions. In one singular point, we observe the enhanced gauge symmetry of SU(2) × SU(2) independent of the models. Around another conifold locus, however, the resulting expression of the Appell functions depends on the models. We examine the result by considering a relation between these Appell functions and underlying Riemann surfaces.
M and F Theory Instantons, N = 1 Supersymmetry and Fractional Topological Charge
Authors: Gómez César , Hernández Rafael
Published: October 2003

We analyze instanton generated superpotentials for three-dimensional N = 2 supersymmetric gauge theories obtained by compactifying on S1 N = 1 four-dimensional theories. For SU(2) with Nf = 1, we find that the vacua in the decompactification limit is given by the singular points of the Coulomb branch of the N = 2 four-dimensional theory (we also consider the massive case). The decompactification limit of the superpotential for pure gauge theories without chiral matter is interpreted in terms of 't Hooft's fractional instanton amplitudes.
Thermal Masses and Equilibrium Rates in the Quark Gluon Phase
Authors: Alam Jan-E , Roy Pradip , Sarkar Sourav , Raha Sibaji , Sinha Bikash
Published: October 2003

We apply the momentum integrated Boltzmann transport equation to study the time evolution of various quark flavors in the central region of ultrarelativistic heavy ion collisions. The effects of thermal masses for quarks and gluons are incorporated to take into account the in-medium properties of these ingredients of the putative quark gluon plasma. We find that even under very optimistic conditions, complete chemical equilibration in the quark gluon plasma appears unlikely.
Classification of Quantized Braided Groups in the Dimension 2
Authors: Hlavatý Ladislav
Published: October 2003

The quantized braided groups are determined by matrices R, Q that solve Yang–Baxter system also related to quantum doubles and nonultralocal integrable systems. A complete solution of the Yang–Baxter system for dimension 2, more precisely, all invertible 4 × 4 matrices, that provide the classification of the quantized braided groups, is given.
Fusion of Twisted Representations
Authors: Gaberdiel Matthias R.
Published: October 2003

The comultiplication formula for fusion products of untwisted representations of the chiral algebra is generalized to include arbitrary twisted representations. We show that the formulae define a tensor product with suitable properties, and determine the analogue of Zhu's algebra for arbitrary twisted representations.

As an example we study the fusion of representations of the Ramond sector of the N = 1 and N = 2 superconformal algebra. In the latter case, certain subtleties arise which we describe in detail.
Transformation of Second-Class into First-Class Constraints in Supersymmetric Theories
Authors: Barcelos-Neto J. , Oliveira W.
Published: October 2003

We use the method due to Batalin, Fradkin, Fradkina, and Tyutin (BFFT) in order to convert second-class into first-class constraints for some quantum mechanics supersymmetric theories. The main point to be considered is that the extended theory, where new auxiliary variables are introduced, has to be supersymmetric too. This leads to some additional restrictions with respect to the conventional use of the BFFT formalism.
Remarks on Renormalization of Black Hole Entropy
Authors: Kim Sang Pyo , Kim Sung Ku , Soh Kwang-Sup , Yee Jae Hyung
Published: October 2003

We elaborate the renormalization process of entropy of a nonextremal and an extremal Reissner–Nordström black hole by using the Pauli–Villars regularization method, in which the regulator fields obey either the Bose–Einstein or Fermi–Dirac distribution depending on their spin-statistics. The black hole entropy involves only two renormalization constants. We also discuss the entropy and temperature of the extremal black hole.
Geometrically Induced Gauge Structure on Manifolds Embedded in a Higher-Dimensional Space
Authors: Fujii Kanji , Ogawa Naohisa , Uchiyama Satoshi , Chepilko Nikolai Mikhailovich
Published: October 2003

We explain in a context different from that of Maraner the formalism for describing the motion of a particle, under the influence of a confining potential, in a neighborhood of an n-dimensional curved manifold Mn embedded in a p-dimensional Euclidean space Rp with p ≥ n + 2. The effective Hamiltonian on Mn has a (generally non-Abelian) gauge structure determined by the geometry of Mn. Such a gauge term is defined in terms of the vectors normal to Mn, and its connection is called the N connection. This connection is nothing but the connection induced from the normal connection of the submanifold Mn of Rp.

In order to see the global effect of this type of connections, the case of M1 embedded in R3 is examined, where the relation of an integral of the gauge potential of the N connection (i.e. the torsion) along a path in M1 to the Berry phase is given through Gauss mapping of the vector tangent to M1. Through the same mapping in the case of M1 embedded in Rp, where the normal and the tangent quantities are exchanged, the relation of the N connection to the induced gauge potential (the canonical connection of the second kind) on the (p - 1)-dimensional sphere Sp - 1 (p ≥ 3) found by Ohnuki and Kitakado is concretely established; the former is the pullback of the latter by the Gauss mapping. Further, this latter which has the monopole-like structure is also proved to be gauge-equivalent to the spin connection of Sp - 1. Thus the N connection is also shown to coincide with the pullback of the spin connection of Sp - 1. Finally, by extending formally the fundamental equations for Mn to the infinite-dimensional case, the present formalism is applied to the field theory that admits a soliton solution. The resultant expression is in some respects different from that of Gervais and Jevicki.
EPR Elements of Physical Reality in Quantum Mechanics
Authors: Thankappan V. K. , Menon Ravi K.
Published: October 2003

The concept of elements of physical reality (e.p.r.) in quantum mechanics as defined by Einstein, Podolsky and Rosen (EPR) is discussed in the context of the EPR–Bohm and the EPR–Bell experiments on a pair of spin 1/2 particles in the singlet state. It is argued that EPR's definition of e.p.r. is appropriate to the EPR–Bell experiment rather than to the EPR–Bohm experiment, and that Bohr's interpretation of e.p.r. is also consistent with such a viewpoint. It is shown that the observed correlation between the spins of the two particles in the EPR–Bell experiment is just a manifestation of the correlation that exists between the wave functions of the particles in the singlet state and a consequence of the fact that a Stern–Gerlach magnet does not change the state of a particle but only transforms its wave function into a representation defined by the axis of the magnet. As such, the correlation is suggested to be an affirmation of Einstein's concept of locality, and not an evidence for nonlocality.
Multiflavor Massive Schwinger Model with Non-Abelian Bosonization
Authors: Delphenich David , Schechter Joseph
Published: October 2003

We revisit the treatment of the multiflavor massive Schwinger model by non-Abelian bosonization. We compare three different approximations to the low-lying spectrum: (i) reading it off from the bosonized Lagrangian (neglecting interactions), (ii) semiclassical quantization of the static soliton, (iii) approximate semiclassical quantization of the "breather" solitons. A number of new points are made in this process. We also suggest a different "effective low-energy Lagrangian" for the theory which permits easy calculation of the low-energy scattering amplitudes. It correlates an exact mass formula of the system with the requirement of the Mermin–Wagner theorem.
Emergent Chiral Symmetry: Parity and Time Reversal Doubles
Authors: Balachandran A. P. , Vaidya S.
Published: October 2003

There are numerous examples of approximately degenerate states of opposite parity in molecular physics. Theory indicates that these doubles can occur in molecules that are reflection-asymmetric. Such parity doubles occur in nuclear physics as well, among nuclei with odd A ~ 219–229. We have also suggested elsewhere that such doubles occur in particle physics for baryons made up of cbu and cbd quarks.

In this article, we discuss the theoretical foundations of these doubles in detail, demonstrating their emergence as a surprisingly subtle consequence of the Born–Oppenheimer approximation, and emphasizing their bundle-theoretic and topological underpinnings. Starting with certain "low energy" effective theories in which classical symmetries like parity and time reversal are anomalously broken on quantization, we show how these symmetries can be restored by judicious inclusion of "high-energy" degrees of freedom. This mechanism of restoring the symmetry naturally leads to the aforementioned doublet structure. A novel byproduct of this mechanism is the emergence of an approximate symmetry (corresponding to the approximate degeneracy of the doubles) at low energies which is not evident in the full Hamiltonian. We also discuss the implications of this mechanism for Skyrmion physics, monopoles, anomalies and quantum gravity.
Current Issues in the Phenomenology of Particle Physics
Authors: Ellis John
Published: October 2003

The present status of the Standard Model and its experimental tests are reviewed, including indications on the likely mass of the Higgs boson. Also discussed are the motivations for supersymmetry and grand unification, searches for sparticles at LEP, neutrino oscillations, and the prospects for physics at the LHC.
Renormalization of Kernels in Stochastically Quantized Gauge-Invariant Fermionic Theories
Authors: Musayev S.
Published: October 2003

Fermionic theory coupled to the non-Abelian gauge field is stochastically quantized by means of choosing certain quasilocal gauge-covariant kernel. One-loop renormalization is carried out for the whole system of the Langevin equations which are shown to be multiplicative renormalizable. Renormalization of noise correlators agrees with that of the kernel in the Langevin equations. In the equilibrium limit β-function and mass renormalization constant reproduce standard results. It is demonstrated that the nonequilibrium theory possesses BRST invariance.
Dimensional Structural Constants from Chiral and Conformal Bosonization of QCD
Authors: Andrianov A. A. , Andrianov V. A. , Ebert D. , Feldmann T.
Published: October 2003

We derive the dimensional nonperturbative part of the QCD effective action for scalar and pseudoscalar meson fields by means of chiral and conformal bosonization. The related structural coupling constants L5 and L8 of the chiral Lagrangian are estimated using general relations which are valid in a variety of chiral bosonization models without explicit reference to model parameters. The asymptotics for large scalar fields in QCD is elaborated, and model-independent constraints on dimensional coupling constants of the effective meson Lagrangian are evaluated. We determine also the interaction between scalar quarkonium and the gluon density and obtain the scalar glueball-quarkonium potential.
Test of the Chiral Structure and FCNC in the Quark Sector by Radiative B Meson Decays
Authors: Handoko L. T. , Yoshikawa T.
Published: October 2003

We study the effects of a vector-like SU(2) quark doublet as a fourth generation. In this model we examine the chiral structure and the FCNC in the quark sector by using radiative B meson decays in the allowed region for parameters from Rb = Γqq/Γ had . We compute the ratio R = Br (b → dγ)/ Br (b → sγ) in the model which realizes a different chiral structure as well as FCNC. The constraints have been extracted from the experimental results of B meson decays, the T new parameter of oblique corrections and Rb. Under the natural assumption that the violation of the V - A structure in the light-quark sector is small, we can determine the allowed region for most of the mixings parameters and the vector-like quark masses. We show that there will be significant deviations in R from the SM prediction due to the FCNC's and the violation of the V - A structure.
To Restore the Broken Symmetry in the Nonconfining Schwinger Model
Authors: Rahaman Anisur
Published: October 2003

A new generalization of the vector Schwinger model is considered where gauge symmetry is broken at the quantum mechanical level. By proper extension of the phase space this broken symmetry has been restored in two different ways. One of these two leads to a BRST-invariant effective action. An equivalent gauge-invariant theory is reformulated even in the usual phase space also.
Finite Temperature Effects on Electromagnetic Probes of Quark–Gluon Plasma
Authors: Bhattacharyya Abhijit , Raha Sibaji , Alam Jan-E , Sinha Bikash
Published: October 2003

Effects of temperature dependence of hadronic form factors on the electromagnetic probes of Quark–Gluon Plasma (QGP) have been looked into. It has been observed that in the kinematic domain thought to be most relevant for Quark–Gluon Plasma diagnostics with electromagnetic probes (M ~ 1–4 GeV ), the space–time integrated emission rates (i.e. count rates) of dileptons and photons from the hot hadronic sector are not very sensitive to the finite temperature corrections of the form factors.
Longitudinal and Transverse Ward–Takahashi Identities, Anomaly and Schwinger–Dyson Equation
Authors: Kondo Kei-Ichi
Published: October 2003

Based on the path integral formalism, we rederive and extend the transverse Ward–Takahashi identities (which were first derived by Yasushi Takahashi) for the vector and the axial vector currents and simultaneously discuss the possible quantum anomaly for them. Subsequently, we propose a new scheme for writing down and solving the Schwinger–Dyson equation in which the transverse Ward–Takahashi identity together with the usual (longitudinal) Ward–Takahashi identity are applied to specify the fermion–boson vertex function. Within this framework, we give an example of exactly soluble truncated Schwinger–Dyson equation for the fermion propagator in an Abelian gauge theory in arbitrary dimension when the bare fermion mass is zero. It is especially shown that in two dimensions, it becomes the exact and closed Schwinger–Dyson equation which can be exactly solved.
Analytic Results in (2+1)-Dimensional Finite Temperature LGT
Authors: Billó M. , Caselle M. , D'Adda A.
Published: October 2003

In a (2 + 1)-dimensional pure LGT at finite temperature the critical coupling for the deconfinement transition scales as βc(nt) = Jcnt + a1, where nt is the number of links in the "timelike" direction of the symmetric lattice. We study the effective action for the Polyakov loop obtained by neglecting the spacelike plaquettes, and we are able to compute analytically in this context the coefficient a1 for any SU(N) gauge group; the value of Jc is instead obtained from the effective action by means of (improved) mean field techniques. Both coefficients have already been calculated in the large N limit in a previous paper. The results are in very good agreement with the existing Monte Carlo simulations. This fact supports the conjecture that, in the (2 + 1)-dimensional theory, spacelike plaquettes have little influence on the dynamics of the Polyakov loops in the deconfined phase.
Asymmetry Effects in Polarized Hadron Scattering
Authors: Chen Yaw-Hwang , Nyeo Su-Long , Wu Chung-Yi
Published: October 2003

We calculate the single-spin and double-spin asymmetry differential cross sections for the polarized hadron scattering PP → l+ l- + jet up to O(αs) by the helicity amplitude method. Numerical results of the differential cross sections, which can be used to probe the spin contents of the proton, are obtained from several sets of polarized parton distribution functions.
Notes on Curtright–Zachos Deformations of osp(1,2) and Super Virasoro Algebras
Authors: Aizawa Naruhiko , Kobayashi Tatsuo , Sato Haru-Tada
Published: October 2003

Based on the quantum superspace construction of q-deformed algebra, we discuss a supersymmetric extension of the deformed Virasoro algebra, which is a subset of the q–W∞ algebra which recently appeared in the context of two-dimensional string theory. We analyze two types of deformed super Virasoro algebra as well as their osp(1,2) subalgebras. Applying our quantum superspace structure to conformal field theory, we find the same type of deformation of affine sl(2) algebra.
High-Temperature Anyon Superconductivity
Authors: Ferrer E. J. , Hurka R. , De La Incera V.
Published: October 2003

The screening of an applied magnetic field in a charged anyon fluid at finite density (μ≠0) and temperature (T≠0) is investigated. Using the semi-infinite sample boundary conditions we find, at densities typical of high-temperature superconducting materials, that the anyon fluid exhibits a superconducting behavior. The total Meissner screening is characterized by two penetration lengths, corresponding to two short-range eigenmodes of propagation within the anyon fluid.
Surface Tension of the Induced Magnetization in the 1D Isotropic XY-Model
Authors: De Lima J. P. , Gonçalves L. L.
Published: October 2003

The surface tension of the induced magnetization in the one-dimensional isotropic ferromagnetic XY-model (s = 1/2, open chain) is considered. The magnetization domains are induced by an inhomogeneous transverse field, and the model can be exactly solved by using the Green function technique. At T = 0 the system undergoes a quantum transition in the bulk driven by the field which is associated to the induced renormalized magnetization. In this temperature limit, the surface tension is determined, and it is shown that, when properly renormalized, it follows a scaling law near the critical point, with a critical exponent μ equal to 1. A brief review is presented for the calculations of the critical exponents and it is also shown that they satisfy the known relations, provided the effective classical dimension is equal to 3. Since the dynamic exponent z is equal to 2, this result confirms the dynamic shift in the dimensionality of the system, d+z, as expected for the quantum transitions. It is also shown that, consistently with this result, the dimension d in the relation μ = (d-1)ν for classical systems should be replaced by the effective dimension d+z for quantum transitions.
Landauer Approach to Time-Dependent Transport
Authors: Chen L. Y. , Nash P. L.
Published: October 2003

Based upon the nonequilibrium Green's function formalism, we present a time-dependent Landauer approach to transport through a mesoscopic system under an ac bias voltage. The system is modeled as an elastic scatterer coupled to large electron reservoirs through perfect conducting wires (leads). The chemical potentials of the reservoirs are driven apart by the bias and, consequently, current flows through the leads from one reservoir to another. We examine the nonequilibrium statistical processes of electrons in the leads. The electronic waves are quantized on the basis of orthonormal wave packets moving along the leads, scattered by the scatterer, and coupled to the reservoirs. The time for an electron to traverse the leads between the source and the drain reservoirs plus the phase delay time caused by the scatterer is found to be the relevant time scale in the time-dependent transport. The frequency dependence of the admittance is fully investigated.
Strain-Induced Nanostructuring on Si(001) and Ge(001) Surfaces
Authors: Zandvliet H. J. W.
Published: October 2003

The ability to create structures on a nanometer scale is and will be of great fundamental and technological importance. Here I discuss a simple but elegant method, based on strain-induced self-assembling, to produce an uniform nanowire pattern. The typical width of the nanowires can be varied between 8–12 Å, whereas the averaged spacing between neighbouring nanowires can be varied in the range from 30 to 100 Å. This method can be applied to a wide range of adsorbates or etching materials on group IV semiconductor (001) surfaces. Among them are Ni/Si(001), Bi/Si(001), Ge/Si(001), Ag/Si(001), Bi/Ge(001), H 2 /Si(001) , O 2/ Si(001) , Br 2/ Si(001) and I 2/ Si(001) . Finally, the dramatic influence which strain relaxation can have on the formation of self-assembled nanostructures on surfaces is illustrated using the particular interesting Bi/Ge(001) system.
Statistics of Mesoscopic Fluctuations of Quantum Capacitance
Authors: Kumar N. , Jayannavar A. M.
Published: October 2003

The Thouless formula (G = (e2/h)(E c /Δ) for the two-probe dc conductance G of a d-dimensional mesoscopic cube is re-analysed to relate its quantum capacitance C Q to the reciprocal of the level spacing Δ. To this end, the escape time-scale τ occurring in the Thouless correlation energy (E c = ℏ/τ) is interpreted as the time constantτ = RC Q with RG ≡ 1, giving at once C Q = (e2/2π Δ). Thus, the statistics of the quantum capacitance is directly related to that of the level spacing, which is well known from the Random Matrix Theory for all the three universality classes of statistical ensembles. The basic questions of how intrinsic this quantum capacitance can arise purely quantum-resistively, and of its observability vis-à-vis the external geometric capacitance that combines with it in series, are discussed.
Interaction Effects on the Density of States in a Disordered Tunneling Superlattice
Authors: Yang Y. H.
Published: October 2003

The interaction theory has been generalized to the case of anisotropic disordered electronic systems. The interaction correction to the density of states near Fermi surface in a tunneling superlattice has been calculated in the weakly localized regime, and the dimensional crossover effect has been discussed.
A Field Emission Microscopic Study of Hydrogen Adsorption on a Stepped Tungsten Plane: W(310)
Authors: Choi D. S. , Paik S. M. , Han J. H. , Park N. G. , Kim K. S. , Whang C. N.
Published: October 2003

Using a newly developed Derivative Field Emission Current (DFEC) methods, the heat of desorption and the work-function-change of W(310) plane induced by hydrogen adsorption are measured. The average work function of the W(310) plane increases initially as the hydrogen dose increases for the low coverage region, decreases for the dose higher than about 0.7 Languimir, and saturates at about 4 Languimir. We find the eight hydrogen adsorption sites on the W(310) plane. Three of these sites are on the terrace (100) plane and the hydrogen adsorption on these sites lower the work function. The other three sites are on the step-wall (110) plane raising the work function. Last two sites are probably on the step-edge. The heats of desorption for these sites ranges from 16.6±2.0 kcal/mol for the γ2 state to 32.0±1.0 kcal/mol for the β6 state. An indirect comparison and analysis show that our findings are quite reasonable.
Heteroepitaxial Growth of c-Axis-Oriented BaTiO3:Ce/YBa2Cu3O7-x Bilayer Structure on SrTiO3(100) by Pulsed Laser Deposition
Authors: Li Chunling , Liu Yanwei , Zhou Yueliang , Chen Zhenghao , Chen Hong , Zhu Yong
Published: October 2003

c-axis-oriented BaTiO 3 :Ce/YBa 2 Cu 3 O 7-x bilayers have been epitaxially grown on the SrTiO 3(100) substrates by pulsed laser deposition. The crystal structure and epitaxial orientation of the films have been analyzed by the XRD θ/2θ, ω and ϕ scans, and the results indicate that the bilayer thin films have high degree of c-axis-oriented epitaxial crystalline structure. The surface morphology of the thin films was revealed by scanning electron microscopy (SEM). The ferroelectricity of the BaTiO 3 :Ce thin films was verified by the P-E hysteresis loop.
Influence of Silicon Intermediate Layer on Adhesion of Carbon Films
Authors: Qingrun Hou , Gao J.
Published: October 2003

The influence of silicon intermediate layer on adhesion of carbon films has been investigated by using the micro-scratch method. The carbon films with and without Si intermediate layer were grown on glass substrates by both electron beam evaporation and pulsed laser deposition. To improve the adhesion of carbon, a silicon intermediate layer was deposited by electron beam evaporation with thickness ranged from 6 to 42 nm. Variations in adhesion were found for different coating techniques and deposition conditions, especially the thickness of silicon intermediate layers. The cause of such variations was discussed.
Nematic Isotropic Phase Transition: An Alternative Formulation
Authors: Mukherjee Prabir K.
Published: October 2003

Nematic-Isotropic (N-I) phase transition is discussed in an alternative way by using Landau–de Gennes phenomenological theory. The temperature difference of T NI -T* is obtained near the tricritical point. We also obtained the value of the ratio (Q*-Q NI )/Q NI , where Q* is the order parameter at the temperature T* of the absolute stability limit of the isotropic phase and Q NI is the order parameter at the nematic-isotropic transition temperature T NI .
t–J Model with Infinite-Ranged Hopping
Authors: Li C. B. , Mattis D. C.
Published: October 2003

The complete spectrum of energy levels is found for the t–J model with infinite-range hopping (i.e. on a simplex of N sites), for arbitrary N. By comparison with free fermions on the same simplex, the two-body interactions break an important symmetry.
Exact Eigenstates in Long-Ranged t–J Model
Authors: Mattis D. C.
Published: October 2003

We present some exact eigenstates of the t–J model with infinite-range hopping (i.e. on a simplex of N sites) for arbitrary N, examine their degeneracy, obtain the low-temperature magnetic susceptibility, and observe a form of charge-spin separation.
Path Integral Calculations of Particle Self-Energy and Effective Mass in Coulomb Systems
Authors: Sa-Yakanit V. , Lakhno V. D. , Haß Klaus
Published: October 2003

The generalized path integral approach is applied to calculate the ground state energy and the effective mass of an electron-plasmon interacting system for a wide range of densities. It is shown that in the self-consistent approximation an abrupt transition between the weak coupling and the strong coupling region of interaction exists. The transition occurs at low electron densities according to a value of 418 for rs, when Wigner crystallization is possible. For densities of real metals, the electron bandwidth is calculated and a comparison with experimental results is given.
Magnetization in Ultrathin Films: Critical Exponent β for the 2D XY Model with 4-Fold Crystal Fields
Authors: Bramwell S. T. , Holdsworth P. C. W. , Rothman J.
Published: October 2003

Ultrathin XY-like magnetic films with 4-fold symmetry breaking crystal fields h4 show a universal magnetization exponent β≈0.23. This suggests that the films fall into the universality class of the isotropic XY model, which we have proposed to be characterized, in any large but finite system, by an effective exponent β = 3 π2/128 ≈0.23. This empirical conclusion is at first sight in disagreement with theoretical expectations, which would place the films in a class of nonuniversal critical behavior characteristic of h4, with β= J/8h4≫1. However, as h4 is a marginal perturbation to the 2D-XY model, crossover to critical behavior characteristic of the perturbation occurs only after rescaling to an exponentially large length scale. We argue that this is the reason for the fact that the nonuniversal behavior characteristic of the crystal fields has not yet been observed in experiment. We present Monte Carlo data to show that one should always observe the universal magnetization characteristic of the finite size 2D-XY model, although there is a possibility of observing a crossover to non-power law behavior characteristic of h4 at low temperature.
Development of a Novel Renormalization Technique in Nonrelativistic QED Based on a New Theoretical Concept
Authors: Seke J.
Published: October 2003

A new renormalization concept is introduced. By using this new concept and a novel technique based on the resolvent-operator method, it is shown, for the first time to our knowledge, that an unambiquous renormalization to all orders of the interaction can be carried out in nonrelativistic QED.
A Molecular Full-Potential LMTO Calculation for Copper Clusters
Authors: Datta Radhika Prosad , Banerjea Amitava , Mookerjee Abhijit , Bhattacharyya A. K.
Published: October 2003

We study the electronic properties of small (10–20 atoms) copper clusters using the newly-developed molecular full-potential linearized muffin-tin orbital two-centre-fit (TCF) method of Methfessel and van Schilfgaarde. The geometric structures of the clusters had earlier been determined by us through simulated annealing using the Equivalent Crystal Theory to compute total energies. We report the variation of the binding energy, as obtained from the TCF calculations, with cluster size and compare these to the binding energies determined, for the same structures, from the ECT. We also show the variation of the HOMO-LUMO gap with cluster size, and the pseudo-density of states for select cluster sizes.
The Essential Characteristics of the Pseudogapped Metallic State of High-Tc Superconductor
Authors: Zhang Liyuan , Feng Xiaobing
Published: October 2003

The pseudogapped metallic state which was recently revealed by angle-resolved photoemission experiments in the normal state of high-T c superconductor (HTS) can be interpreted with a model of non-simple metal in which there are locally correlating carrier pairs and the coexisting single itinerant carriers. The pair correlation is temperature dependent with a delocalization process with decreasing temperature down to T c , which can be revealed by the thermoelectric power S of HTS. By theoretical calculation, it is shown that a pseudogap exists in electronic energy spectrum of this two-component system in which high T c and small superconducting coherence length can be obtained in its superconducting state.
The Electron Self-Energy in a Classical Spin Model
Authors: Frenkel J. , Santos R. B.
Published: October 2003

We discuss a simple model where the electron is approximately described by a rapidly spinning disk of radius λ=ℏ/mc, such that the linear speed at its border is c. We assume that the particle's mass is uniformly distributed over the surface of the disk and its electric charge is strongly peaked around the border. It follows that the spin of the particle must be ℏ/2 and its magnetic moment should have a g factor equal to 2. We show that the electromagnetic self-energy of the particle is given by an expression which is similar to the result obtained in quantum electrodynamics.
RKKY Interaction Between Impurities in GaAs/AlAs Quantum Wells
Authors: da Cunha Lima I. C. , Filho L. G. Ferreira , Troper A.
Published: October 2003

The RKKY interaction between two magnetic impurities in a GaAs/AlAs double quantum well under a strong electric field perpendicular to the interfaces is obtained as a function of the field strength and the barrier width. We obtain a fast decrease of the exchange with the barrier width for the impurities lying in different wells. At intermediate strengths and small barrier widths, a structure is observed in the inter-well exchange.
Oxygen-Induced Nonuniformity in Surface Electrical-Potential Barrier
Authors: Sun Chang Q. , Bai Chunli
Published: October 2003

In order to quantify the behaviour of surface electrons on O-chemisorbed metal surface, as observed wtith STM and STS, we developed a model on nonuniform electrical potential barrier. The new modelling approach contains: (1) the elastic potential, the spatial variation and the energy dependence of the inelastic damping are unified by the electronic distribution; (2) the O-induced spatial-localisation and the nonuniformity in energy-state are taken into effect; (3) the single-variable parameterised functions simplify the numerical optimisation and ensure the uniqueness in solutions. Therefore, crystal structure models can be judged by comparing the shapes of the crystal-dependent-z0(E) profiles that exhibit joint features of topography and spectroscopy.
Elastic Behavior and Lattice Vibronics of bcc Phase Metals
Authors: Verma A. , Verma M. L. , Rathore R. P. S.
Published: October 2003

A model in real space has been developed by extending the generalized form of the exponential potential known as extended generalized exponential potential (EGEP) to account for (a) the correct nature of repulsive and attractive components of forces for all the separations in general and that of small separations in particular (b) the dielectric screening functions in an alternative and simpler form through the parameter m (c) the three-body forces such as volume forces in an indirect way in the framework of EGEP through the parameter n. The model is employed to compute the cohesive energy, phonon spectra and second-order elastic constants in group IV bcc metals. The predictions show good agreement with experimental findings.
Rotating Polarization Probing of Elastic and Inelastic Scatterings
Authors: Emile Olivier , Bretenaker Fabien , Le Floch Albert
Published: October 2003

The recent technical advances in the creation of rapidly rotating light polarizations are shown to provide new tools to explore elastic and inelastic scattering phenomena. In the case of inelastic scattering, the light fluoresced by atoms or molecules coherently excited by a rapidly rotating linear polarization is expected to exhibit new resonances. Such resonances, due to the transfer of coherence from light to atoms or molecules, are theoretically studied and experimentally observed. They provide simple methods to probe atomic internal constants, such as energy level life-times. The analogy between those resonances and the Hanle effect suggests new experiments in atomic physics. In the case of elastic scattering such as the one encountered during propagation through a dense turbid medium, the rotating linear polarization is shown to be an ideal tool to extract the ballistic photons from the large background of diffused light. This permits to image tiny objects embedded in a dense turbid medium, with an experimental resolution similar to the one obtained in usual homogeneous optical system.