April 1995 arXiv papers — page 6

Tsunefumi Tanaka, William A. Hiscock

The vacuum expectation value of the stress-energy tensor $\left\langle 0\left| T_{μν} \right|0\right\rangle$ is calculated in several multiply connected flat spacetimes for a massive scalar field with arbitrary curvature coupling. We find that a nonzero field mass always decreases the magnitude of the energy density in chronology-respecting manifolds such as

L. A. de Vaulchier, J. P. Vieren, Y. Guldner, N. Bontemps

We have measured the penetration depth $λ(T)$ on $\rm YBa_{2}Cu_{3}O_{7}$ thin films from transmission at 120, 330 and 510~GHz, between 5 and 50~K. Our data yield simultaneously the absolute value and the temperature dependence of $λ(T)$. In high quality films $λ(T)$ exhibits the same linear temperature dependence as single crystals, showing its intrinsic na

N. Menyhard, G. Odor

A family of nonequilibrium kinetic Ising models, introduced earlier, evolving under the competing effect of spin flips at {\it zero temperature} and nearest neighbour random spin exchanges is further investigated here. By increasing the range of spin exchanges and/or their strength the nature of the phase transition 'Ising-to-active' becomes of (dyna

Kikuo Harigaya

Variations in the band structures of C60-polymers are studied, when pi-conjugation conditions are changed. We look at band structures in order to discuss a metal-insulator transition, using a semi-empirical model with the Su-Schrieffer-Heeger type electron-phonon interactions. We find that electronic structures change among direct-gap insulators and the meta

GARY STEIGMAN

Observations of interstellar lithium provide a valuable complement to studies of lithium in Pop I and Pop II stars. Large corrections for unseen LiII and for non-gas phase lithium have provided obstacles to using interstellar data for abundance determinations. An approach to surmounting these difficulties is proposed and is applied to the Galaxy and the LMC.

David J. D. Earn, J. A. Sellwood

The stability of a galaxy model is most easily assessed through N-body simulation. Particle-mesh codes have been widely used for this purpose, since they enable the largest numbers of particles to be employed. We show that the functional expansion technique, originally proposed by Clutton-Brock for other simulation problems, is in fact superior for stability

Hermann Hessling

Under which conditions does a jet appear as a particle--like signal from the hidden realm of quarks and gluons? Motivated by this question jet clustering conditions are formulated, in order to characterize jet clustering algorithms, which can be used for a determination of particle--like jets. Jets are understood as particle--like, if they behave like free p

David A. Buote, John C. Tsai

We quantify the morphologies and dynamical states of 59 galaxy clusters using the power-ratio technique of Buote & Tsai applied to ROSAT PSPC X-ray images. The clusters exhibit a particularly strong $P_2/P_0 - P_4/P_0$ correlation in the $1h^{-1}_{80}$ Mpc aperture which may be interpreted as an evolutionary track; the location of a cluster on the correlatio

M. B. Spencer et. al

We report on a measurement of the decay $K_L\rightarrowμ^+μ^-γ$ from Fermilab experiment E799. We observe $207$ candidate signal events with an estimated background of $10.5 \pm 4.0$ events and establish $B(K_L\rightarrowμ^+μ^-γ) = (3.23\pm 0.23(stat) \pm 0.19(sys))\times 10^{-7}$. This provides the first measurement of the $Kγγ^*$ form factor in the muonic

S. Dimopoulos, G. F. Giudice, N. Tetradis

We postulate that the orientation of the soft supersymmetry-breaking terms in flavor space is not fixed by tree level physics at the Planck scale; it is a dynamical variable which depends on fields that have no tree level potential. These fields can be thought of as either moduli or as the Nambu-Goldstone bosons of the spontaneously broken flavor symmetry wh

E. Ramos, J. Roca

We prove that particle models whose action is given by the integrated $n$-th curvature function over the world line possess $n+1$ gauge invariances. A geometrical characterization of these symmetries is obtained via Frenet equations by rephrasing the $n$-th curvature model in $\reals^d$ in terms of a standard relativistic particle in $S^{d-n}$. We ``prove by

Michael P. Brenner, Detlef Lohse, T. F. Dupont

An air bubble trapped in water by an oscillating acoustic field undergoes either radial or nonspherical pulsations depending on the strength of the forcing pressure. Two different instability mechanisms (the Rayleigh--Taylor instability and parametric instability) cause deviations from sphericity. Distinguishing these mechanisms allows explanation of many fe

S. Majid

We clarify the relation between the `bosonisation' construction (due to the author) which can be used to turn a Hopf algebra $B$ in the category of $H$-modules or $H$-comodules into an equivalent ordinary Hopf algebra, and a version of Radfords theorem (also due in this form to the author) which does the same for $B$ in the category of crossed $H$-module

Michael J. Dinneen, Paul R. Hafner

The results of computer searches for large graphs with given (small) degree and diameter are presented. The new graphs are Cayley graphs of semidirect products of cyclic groups and related groups. One fundamental use of our ``dense graphs'' is in the design of efficient communication network topologies.

Jonathan Berry, Mark Goldberg

This paper presents the results of an experimental study of graph partitioning. We describe a new heuristic technique, path optimization, and its application to two variations of graph partitioning: the max_cut problem and the min_quotient_cut problem. We present the results of computational comparisons between this technique and the Kernighan-Lin algorithm,

Maria Girardi, William B. Johnson

A bounded linear operator between Banach spaces is called {\it completely continuous} if it carries weakly convergent sequences into norm convergent sequences. Isolated is a universal operator for the class of non-completely-continuous operators from $L_1$ into an arbitrary Banach space, namely, the operator from $L_1$ into $\ell_\infty$ defined by $$ T_0 (f

Rick G. Faber

We prove that for every closed locally convex subspace $E$ of $L_0$ and for any continuous linear operator $T$ from $L_0$ to $L_0/E$ there is a continuous linear operator $S$ from $L_0$ to $L_0$ such that $T = QS$ where $Q$ is the quotient map from $L_0$ to $L_0/E$.

Fred Cooper

We review the closed time path formalism of Schwinger using a path integral approach. We apply this formalism to the study of pair production from strong external fields as well as the time evolution of a nonequilibrium chiral phase transition.

Vu B Ho

It is observed that, at short range, the field equations of general relativity admit a line element that takes the form of Yukawa potential. The result leads to the possibility that strong interaction may also be described by field equations that have the same form as that of general relativity. It is then shown how such field equations may arise from the co

G. Blaylock, Abe Seiden, Y. Nir

In current searches for D0 anti-D0 mixing, the time evolution of ``wrong-sign'' decays is used to distinguish between a potential mixing signal and the dominant background from doubly-Cabibbo-suppressed decays. A term proportional to $ΔMt$ in the expression for the time evolution is often neglected in theoretical discussions and experimental analyses

T. Gisiger, M. B. Paranjape

We present the study of the influence of the leading contribution from the kinetic energy of the Skyrme Lagrangian on the scattering of low energy nucleons. This classical kinetic energy for the 2-body system is computed using the product ansatz and is correct for low energy, well separated Skyrmions. We quantize the rotational degrees of freedom of the Skyr

Glennys R. Farrar

I advocate the virtues of a very economical version of the minimal supersymmetric standard model which avoids cosmological problems often encountered in dynamical SUSY-breaking and solves the SUSY-CP problem. Imposing $m_Z=91$ GeV and $m_t \sim 175$ GeV implies that scalar masses are generally $100-200$ GeV. The gluino and photino are massless at tree level.

Paolo Cea, Leonardo Cosmai

We investigate the dual superconductivity hypothesis in pure SU(2) lattice gauge theory. We focus on the dual Meissner effect by analyzing the distribution of the color fields due to a static quark-antiquark pair. We find evidence of the dual Meissner effect both in the maximally Abelian gauge and without gauge fixing. We measure the London penetration lengt

Paul R. Anderson, William A. Hiscock, Daniel J. Loranz

The stress-energy tensor of a free quantized scalar field is calculated in the extreme Reissner-Nordström black hole spacetime in the zero temperature vacuum state. The stress-energy appears to be regular on the event horizon, contrary to the suggestion provided by two-dimensional calculations. An analytic calculation on the event horizon for a thermal state

Katarina Uzelac, Anwar Hasmy, Rémi Jullien

Phase transitions inside the pores of an aerogel are investigated by modelizing the aerogel structure by diffusion-limited cluster-cluster aggregation on a cubic lattice in a finite box and considering $q$-states Potts variables on the empty sites interacting via nearest-neighbours. Using a finite size scaling analysing of Monte-Carlo numerical results, it i

Th. M. Nieuwenhuizen

Aspects of the dynamical glass transition are considered within a mean field spin glass model. At the dynamical transition the the system condenses in a state of lower entropy. The difference, the information entropy or complexity, is calculated by analysis of the metastable (TAP) states. It increases for lower temperatures, showing that more and more free e

E. Amic, J. M. Luck, Th. M. Nieuwenhuizen

The multiple scattering of scalar waves in diffusive media is investigated by means of the radiative transfer equation. This approach amounts to a resummation of the ladder diagrams of the Born series; it does not rely on the diffusion approximation. Quantitative predictions are obtained, concerning various observables pertaining to optically thick slabs, su

Alex Kamenev, Yuval Oreg

The diagrammatic linear response formalism for the Coulomb drag in two--layer systems is developed. This technique can be used to treat both elastic disorder and intralayer interaction effects. In the absence of intralayer electron--electron correlations we reproduce earlier results, obtained using the kinetic equation and the memory--function formalism. In

Th. M. Nieuwenhuizen

The static free energy of glassy systems can be expressed in terms of the Parisi order parameter function. When this function has a discontinuity, the location of the step is determined by maximizing the free energy. In dynamics a transition is found at larger temperature, while the location of the step satisfies a marginality criterion. It is shown here tha

P. Collet, A. Galves, A. Lopes

Using the Thermodynamic Formalism, we introduce a Gibbsian model for the identification of regular grammars based only on positive evidence. This model mimics the natural language acquisition procedure driven by prosody which is here represented by the thermodynamical potential. The statistical question we face is how to estimate the incidenc e matrix of a s

Shuly Wintner, Nissim Francez

This paper describes an abstract machine for linguistic formalisms that are based on typed feature structures, such as HPSG. The core design of the abstract machine is given in detail, including the compilation process from a high-level language to the abstract machine language and the implementation of the abstract instructions. The machine's engine sup

V. M. Lipunov, K. A. Postnov, M. E. Prokhorov, I. E. Panchenko

Evolution of the coalescence rate of double neutron stars (NS) and neutron star -- black hole (BH) binaries are computed for model galaxies with different star formation rates. Assuming gamma-ray bursts (GRB) to originate from NS+NS or NS+BH merging in distant galaxies, theoretical logN--logS distributions and <V/V_max> tests of gamma-ray bursts (GRB) are ca

Uta Fritze - v. Alvensleben, Andi Burkert

From spectrophotometric and chemical evolutionary modelling of interacting and merging galaxies we predict abundances of burst stars and of globular clusters (GCs) that may be formed in strong bursts. Observations of young GCs in merger remnants confirm the predicted metallicities. We investigate their formation as a result of a strong star burst with a high

Geir Ellingsrud, Joseph Le Potier, Stein A. Stromme

We compute the Donaldson numbers $q_{17}(CP^2)=2540$ and $q_{21}(CP^2)=233208$.

Abhay Ashtekar, Jerzy Lewandowski, Donald Marolf, Jose Mourao

Quantization of diffeomorphism invariant theories of connections is studied. A solutions of the diffeomorphism constraints is found. The space of solutions is equipped with an inner product that is shown to satisfy the physical reality conditions. This provides, in particular, a quantization of the Husain-Kuchař model. The main results also pave way to quant

J. C. R. Magueijo

We propose an analytic method for predicting the large angle CMBR temperature fluctuations induced by model textures. The model makes use of only a small number of phenomenological parameters which ought to be measured from simple simulations. We derive semi-analytically the $C^l$-spectrum for $2\leq l\leq 30$ together with its associated non-Gaussian cosmic

Evgenyi A. Ivanov

Starting from the action of $(4,4)$ $2D$ twisted multiplets in the harmonic superspace with a double set of $SU(2)$ harmonic variables, we present its generalization which provides an off-shell description of a wide class of $(4,4)$ sigma models with torsion and non-commuting left and right complex structures. The distinguishing features of the action constr

Julio Abad, Miguel Rios

A general fusion method to find solutions to the reflection equation in higher spin representations starting from the fundamental one is shown. The method is illustrated by applying it to obtaining the $K$ diagonal boundary matrices in an alternating spin $1/2$ and spin $1$ chain. The hamiltonian is also given. The applicability of the method to higher rank

Th. M. Nieuwenhuizen

In certain mean field models for spin glasses there occurs a one step replica symmetry breaking pattern. As an example of general $1/N$-corrections in such systems, the fluctuations in the internal energy are calculated. For this specific quantity the outcome is known from the specific heat. It is shown that the correct result can be derived by assuming that

Nicola Maggiore, Olivier Piguet, Mathieu Ribordy

We consider a N=2 supersymmetric Yang-Mills-Chern-Simons model, coupled to matter, in the Wess-Zumino gauge. The theory is characterized by a superalgebra which displays two kinds of obstructions to the closure on the translations: field dependent gauge transformations, which give rise to an infinite algebra, and equations of motion. The aim is to put the fo

J. -P. Kneib, Y. Mellier, R. Pello, J. Miralda-Escude

A mass model of the rich cluster A2218 is presented based on optical and new near-infrared images of arc(let)s and the ROSAT/HRI X-ray map. A lensing model is proposed with two dark matter clumps, centered on the two bright galaxies around which the various arcs are observed. Two of them, close to the most massive clump around the brightest galaxy, are requi

Tomohiro Matsuda

We analyze the gaugino condensation in the effective theory for N=1 SU(N) Supersymmetric QCD with $N_{f}$ flavors. It is known that taking the vacuum expectation value of the matter field to be infinite, we can show that gaugino condensation can occur. At such a limit we should consider only pure supersymmetric Yang-Mills theory. But when we include an inter

B. Abdesselam, D. Arnaudon, A. Chakrabarti

The Gelfand--Zetlin basis for representations of $U_q(sl(N))$ is improved to fit better the case when $q$ is a root of unity. The usual $q$-deformed representations, as well as the nilpotent, periodic (cyclic), semi-periodic (semi-cyclic) and also some atypical representations are now described with the same formalism.

W. Q. Chao, C. S. Gao, Y. B. He

We present a phenomenological study of the $x_F$ dependence of quarkonium production in high energy proton-nucleus collisions. The \xf~dependence of comover contributions is introduced to account for the observed quarkonium suppression at low $x_F$. Combining comover contributions, nuclear shadowing effect, energy loss mechanism and nuclear absorption togeth

K. Berndl, M. Daumer, D. Dürr, S. Goldstein

Bohmian mechanics is the most naively obvious embedding imaginable of Schrödinger&#39;s equation into a completely coherent physical theory. It describes a world in which particles move in a highly non-Newtonian sort of way, one which may at first appear to have little to do with the spectrum of predictions of quantum mechanics. It turns out, however, that a

Y. Ben-Aryeh, C. Brif

We assert that state reduction processes in different types of photodetection experiments are described by using different kinds of ladder operators. A special model of discrete photodetection is developed by the use of superoperators which are based on the Susskind-Glogower raising and lowering operators.

I. S. Towner, J. C. Hardy

Beta-decay and muon-capture experiments in nuclei are reviewed. The conserved vector current hypothesis is confirmed through the observed constancy of the vector coupling constant determined from the superallowed Fermi transitions and from the measurement of the weak-magnetism term in mirror Gamow-Teller transitions. The axial-vector and pseudoscalar couplin

George Gasper, Walter Trebels

Sufficient ultraspherical multiplier criteria are refined in such a way that they are comparable with necessary multiplier conditions. Also new necessary conditions for Jacobi multipliers are deduced which, in particular, imply known Cohen type inequalities. Muckenhoupt&#39;s transplantation theorem is used in an essential way.

George Gasper, Walter Trebels

A Lemma of Riemann--Lebesgue type for Fourier--Jacobi coefficients is derived. Via integral representations of Dirichlet--Mehler type for Jacobi polynomials its proof directly reduces to the classical Riemann--Lebesgue Lemma for Fourier coefficients. Other proofs are sketched. Analogous results are also derived for Laguerre expansions and for Jacobi transfor

Michael J. Dinneen, Vance Faber, Michael R. Fellows

Cayley graph techniques are introduced for the problem of constructing networks having the maximum possible number of nodes, among networks that satisfy prescribed bounds on the parameters maximum node degree and broadcast diameter. The broadcast diameter of a network is the maximum time required for a message originating at a node of the network to be relay

D. Stoll, M. Thies

The Higgs mechanism is reconsidered in the canonical Weyl gauge formulation of quantized gauge theories, using an approach in which redundant degrees of freedom are eliminated. As a consequence, its symmetry aspects appear in a different light. All the established physics consequences of the Higgs mechanism are recovered without invoking gauge symmetry break

R. Banerjee, H. J. Rothe, K. D. Rothe

We study the connection between the Green functions of the Maxwell-Chern-Simons theory and a self-dual model by starting from the phase-space path integral representation of the Deser-Jackiw master Lagrangian. Their equivalence is established modulo time-ordering ambiguities.

R. Banerjee, Heinz J. Rothe

We convert the self-dual model of Townsend, Pilch, and Nieuwenhuizen to a first-class system using the generalized canonical formalism of Batalin, Fradkin, and Tyutin and show that gauge-invariant fields in the embedded model can be identified with observables in the Maxwell-Chern-Simons theory as well as with the fundamental fields of the self-dual model. W

G. Cognola, L. Vanzo, S. Zerbini

The first quantum corrections to the entropy for an eternal 4-dimensional extremal Reissner-Nordström black hole is investigated at one-loop level, in the large mass limit of the black hole, making use of the conformal techniques related to the optical metric. A leading cubic horizon divergence is found and other divergences appear due to the singular nature

D. L. Bennett, C. D. Froggatt, H. B. Nielsen

Constants of Nature that have nongeneric values pose a riddle often referred to as the finetuning problem. The conspicuous values assumed by many physical constants (e.g., the vanishing effective cosmological constant, the smallness of the Higgs mass compared to the Planck scale, the finestructure constants, $Θ_{QCD}$) seem to coincide with values that are o

A. Bialas, R. Peschanski

The initial-state radiation of soft colour dipoles produced together with a single QCD Pomeron exchange (BFKL) in onium-onium scattering is calculated in the framework of Mueller&#39;s approach. The resulting dipole production grows with increasing energy and reveals an unexpected feature of a power-law tail at appreciably large transverse distances from the

E. Dudas, S. Pokorski, C. A. Savoy

We classify all the phenomenologically viable fermion mass matrices coming from a spontaneously broken abelian symmetry $ U(1)_X, $ with one and two additional chiral fields of opposite charges $ X=\pm 1. $ We find that the non-trivial Kähler metric can fill zeroes of the fermion mass matrices up to phenomenologically interesting values. A general anomaly an

Tomohiro Matsuda

We re-examine the so-called Nambu-Jona-Lasinio mechanism suggested by Song, Xu and Chin in breaking the supersymmetry in the Wess-Zumino model and show that this mechanism cannot be justified without assuming special effects between fermions. The fermion condensation suggested by them corresponds to an unstable vacuum configuration. As a result, there is no

Clifford M. Will

We survey the role of stable clocks in general relativity. Clock comparisons have provided important tests of the Einstein Equivalence Principle, which underlies metric gravity. These include tests of the isotropy of clock comparisons (verification of local Lorentz invariance) and tests of the homogeneity of clock comparisons (verification of local position

G. Esposito, A. Yu. Kamenshchik, I. V. Mishakov, G. Pollifrone

This paper studies the linearized gravitational field in the presence of boundaries. For this purpose, $ζ$-function regularization is used to perform the mode-by-mode evaluation of BRST-invariant Faddeev-Popov amplitudes in the case of flat Euclidean four-space bounded by a three-sphere. On choosing the de Donder gauge-averaging term, the resulting $ζ(0)$ va

Anwar Hasmy, Marie Foret, Eric Anglaret, Jacques Pelous

A numerical simulation of silica aerogels is performed using diffusion-limited cluster-cluster aggregation of spheres inside a cubic box (with periodic boundary conditions). The volume fraction $c$ is taken to be sufficiently large to get a gel structure at the end of the process. In the case of monodisperse spheres, the wavevector dependent scattered intens

Anwar Hasmy, Rémi Jullien

Numerical simulations of Diffusion-Limited and Reaction-Limited Cluster-Cluster Aggregation processes of identical particles are performed in a two-dimensional box. It is shown that, for concentrations larger than a characteristic gel concentration, the morphology of the resulting spanning cluster at the gel time $t_g$ exhibits a crossover length $L_c$ betwe

Anwar Hasmy, René Vacher, Rémi Jullien

Fractal aggregates are built on a computer using off-lattice cluster-cluster aggregation models. The aggregates are made of spherical particles of different sizes distributed according to a Gaussian-like distribution characterised by a mean $a_0$ and a standard deviation $σ$. The wave vector dependent scattered intensity $I(q)$ is computed in order to study

A. I. Larkin, M. C. Marchetti, V. M. Vinokur

A sharp maximum in the critical current $J_c$ as a function of temperature just below the melting point of the Abrikosov flux lattice has recently been observed in both low and high temperature superconductors. This peak effect is strongest in twinned crystals for fields aligned with the twin planes. We propose that this peak signals the breakdown of the col

A. Hädicke, W. Krech

The Andreev current through an ultrasmall NIS junction is calculated in a systematic way by means of a nonlinear response approach basing on the elementary Hamiltonian of quasiparticle tunneling. The voltage dependence of current and differential conductance as well as the Andreev conductance are derived for low- and high-impedance environments, respectively

Ronald Dickman, Alex Yu. Tretyakov

An apparent violation of hyperscaling at the endpoint of the critical line in the Domany-Kinzel stochastic cellular automaton finds an elementary resolution upon noting that the order parameter is discontinuous at this point. We derive a hyperscaling relation for such transitions and discuss applications to related examples.

C. M. Canali, V. E. Kravtsov

It is shown that the two-level correlation function $R(s,s&#39;)$ in the invariant random matrix ensembles (RME) with soft confinement exhibits a &#34;ghost peak&#34; at $s\approx -s&#39;$. This lifts the sum rule prohibition for the level number variance to have a Poisson-like term ${\rm var}(n)=ηn$ that is typical of RME with broken U(N) symmetry. Thus we

P. W. Brouwer, C. W. J. Beenakker

A random-matrix theory is presented which shows that breaking time-reversal symmetry by itself does {\em not} suppress the weak-localization correction to the conductance of a disordered metal wire attached to a superconductor. Suppression of weak localization requires applying a magnetic field as well as raising the voltage, to break both time-reversal symm

P. W. Brouwer, C. W. J. Beenakker

Numerical simulations of conduction through a disordered microbridge between a normal metal and a superconductor have revealed an anomalous insensitivity of the conductance fluctuations to a magnetic field. A theory for the anomaly is presented: Both an exact analytical calculation (using random-matrix theory) and a qualitative symmetry argument (involving t

A. Fairhall, O. Gat, V. S. L&#39;vov, I. Procaccia

Kraichnan&#39;s model of passive scalar advection in which the driving velocity field has fast temporal decorrelation is studied as a case model for understanding the appearance of anomalous scaling in turbulent systems. We demonstrate how the techniques of renormalized perturbation theory lead (after exact resummations) to equations for the statistical quan

B. Kaulakys, G. Vektaris

A theoretical and numerical analysis of the transition from chaotic to nonchaotic behavior in an ensemble of particles with different initial conditions which move according to Newton&#39;s equations in a bounding potential and are driven by an identical sequence of random forces (see S. Fahy and D. R. Hamann, Phys. Rev. Lett. {\bf 69}, 761 (1992)) is presen

Carlos C. Rodriguez

Robert Machol&#39;s surprising result, that from a single observation it is possible to have finite length confidence intervals for the parameters of location-scale models, is re-produced and extended. Two previously unpublished modifications are included. First, Herbert Robbins nonparametric confidence interval is obtained. Second, I introduce a technique f

H. C. Spruit, R. Stehle, J. C. B. Papaloizou

We investigate the stability to nonaxisymmetric perturbations of an accretion disc in which a poloidal magnetic field provides part of the radial support against gravity. Interchange instability due to radial gradients in the magnetic field are strongly stabilized by the shear flow in the disc. For smooth field distributions this instability is restricted to

A. Burkert

Recent observations indicate that dark matter haloes have flat central density profiles. Cosmological simulations with non-baryonic dark matter predict however self similar haloes with central density cusps. This contradiction has lead to the conclusion that dark matter must be baryonic. Here it is shown that the dark matter haloes of dwarf spiral galaxies r

Paul Bode, Edmund Bertschinger

We have developed a code which links scalar-mode fluctuations in the early universe with those observable at the present time by integrating the coupled, linearized, Einstein, Boltzmann, and fluid equations in a perturbed flat Robertson-Walker spacetime. The results are useful both for calculations of the cosmic microwave background anisotropy and the linear

A. Aparicio, J. Cepa, C. Gallart, H. Castaneda

The stellar content of the Im galaxy NGC 2366 is discussed on the basis of CCD BVR photometry. The three brightest blue and red stars have been used to estimate its distance, obtaining a balue of 2.9 Mpc. The spatial distribution of the young stellar population is discussed in the light of the integrated color indices and the color-magnitude diagrams of diff

Teiji Kunihiro

We show on the basis of an effective theory of QCD that a wide variety of observables in the hadron world is governed by the chiral symmetry together with an interplay between the axial anomaly and the explicit symmetry breaking due to the current quark mass. We also discuss the nature of the chiral transition at finite temperature and related dynamical phen

Jesus Pando, Li-Zhi Fang

A wavelet space-scale decomposition (SSD) analysis of large scale structures in the universe has been developed. The SSD method of identifying and measuring structures in the spatial distribution of objects has been demonstrated. The position and strength (richness) of the identified clusters can be described by the corresponding coefficient of the wavelet t

Gil Zumbach

For various two dimensional non linear $σ$ models, we present a direct comparison between the $β$ functions computed with the $2+ε$ renormalization group and the $β$ functions measured by Monte Carlo simulations. The theoretical and measured $β$ functions match each other nicely for models with a trivial topology, yet they disagree clearly for models contain

Andreas S. Kronfeld

Lattice fermions have well-known difficulties with chiral symmetry. To evade them it is possible to couple continuum fermions to lattice gauge fields, by introducing an interpolation of the latter. Following this line of thinking, this paper presents two Euclidean formulations of the effective action that appears after functional integration over fermion fie

G. L. Fogli, E. Lisi

An analysis of the existing data on the atmospheric neutrino anomaly is presented, focused on the statistical significance that can be attributed to its experimental evidence. Our approach is alternative to the usual analyses in terms of the $μ/e$ ratio of event rates. In fact, we perform a comparison between data and expectations, by {\em separating\/} the

H1 Collaboration

Photoproduction of 2-jet events is studied with the H1 detector at HERA. Parton cross sections are extracted from the data by an unfolding method using leading order parton-jet correlations of a QCD generator. The gluon distribution in the photon is derived in the fractional momentum range $0.04\le x_γ\le 1$ at the average factorization scale $75$ GeV$^2$.

S. D. Bass

General arguments suggest that the non-perturbative background field in QCD may have a non-trivial spin structure. We discuss how this effect may be manifest in semi-inclusive measurements of fast pions in polarised deep inelastic scattering.

L. Smrcka, P. Vasek, J. Kolacek, T. Jungwirth

We have found that Fermi contours of a two-dimensional electron gas at $\rmGaAs/Al_xGa_{1-x}As$ interface deviate from a standard circular shape under the combined influence of an approximately triangular confining potential and the strong in-plane magnetic field. The distortion of a Fermi contour manifests itself through an increase of the electron effectiv

Subir Sachdev, N. Read, R. Oppermann

We introduce an effective field theory for the vicinity of a zero temperature quantum transition between a metallic spin glass (``spin density glass&#39;&#39;) and a metallic quantum paramagnet. Following a mean field analysis, we perform a perturbative renormalization-group study and find that the critical properties are dominated by static disorder-induced

C. Brif

Statistical and phase properties and number-phase uncertainty relations are systematically investigated for photon states associated with the Holstein-Primakoff realization of the SU(1,1) Lie algebra. Perelomov&#39;s SU(1,1) coherent states and the eigenstates of the SU(1,1) lowering generator (the Barut-Girardello states) are discussed. A recently developed

S. Z. Levendorskii, A. Sudbery

We show that a Yangian construction based on the algebra of an infinite number of harmonic oscillators (i.e. a vibrating string) terminates after one step, yielding the Virasoro algebra.

V. R. Manfredi, L. Salasnich

Using a classical analytical criterion (that of curvature) and numerical results (Poincarè sections and spectral statistics), a transition order--chaos--order in the roto--vibrational model of atomic nuclei has been shown. Numerical calculations were performed for some deformed nuclei.

E. Comay

Elements of a new model of strong interactions are described. The model is based on an extension of electrodynamics that is derived from a regular Lagrangian density. Here the electric and magnetic fields of Maxwell equations play a symmetric role. It is shown that results are in accordance with general properties of nuclear and nucleon systems.

Aviezri S. Fraenkel

The ``losing positions&#34; of certain combinatorial games constitute linear error detecting and correcting codes. We show that a large class of games that can be cast in the form of *annihilation games*, provides a potentially polynomial method for computing codes (*anncodes*). We also give a short proof of the basic properties of the previously known *lexi

Richard Costambeys, Paul Mansfield

We show that the one-instanton sector moduli-space divergence of the O(3) Sigma Model leads to an unacceptable dependence of Green&#39;s functions on the arbitrary way that the field is split into a quantum fluctuation about a classical background. Since the divergence is associated with the degeneration of field configurations to those of the zero-instanton

Z. Hasiewicz, Z. Jaskolski

The classical and the quantum massive string model based on a modified BDHP action is analyzed in the range of dimensions $1<d<25$. The discussion concerning classical theory includes a formulation of the geometrical variational principle, a phase-space description of the two-dimensional dynamics, and a detailed analysis of the target space geometry of class

Saurya Das, Parthasarathi Majumdar

We discuss an approach to compute two-particle scattering amplitudes for spinless particles colliding at Planckian centre-of-mass energies, with increasing momentum transfer away from the eikonal limit. For electrically neutral particles, the amplitude exhibits poles on the imaginary squared cm energy axis at locations that are distinct from those appearing

I. Yu. Karataeva, S. L. Lyakhovich

The regularization scheme is proposed for the constrained Hamiltonian formulation of the gauge fields coupled to the chiral or axial fermions. The Schwinger terms in the regularized operator first-class constraint algebra are shown to be consistent with the covariant divergence anomaly of the corresponding current. Regularized quantum master equations are st

John K. Elwood, Mark B. Wise, Martin J. Savage

We calculate all of the form factors for the one-photon, $K_L \rightarrow π^+ π^- γ^* \rightarrow π^+ π^- e^+e^-$ contribution to the $K_L \rightarrow π^+ π^- e^+e^-$ decay amplitude at leading order in chiral perturbation theory. These form factors depend on one unknown constant that is a linear combination of coefficients of local ${\cal O}(p^4)$ operators

A. Vogt

Precise determinations of the strong coupling constant in hadronic collisions demand sets of parton densities spanning a sufficiently wide range of values for the QCD scale parameter Lambda. For such applications, we supplement the recent GRV parametrization by five sets of dynamically generated parton distributions for Lambda-values corresponding to alpha_{

G. P. Salam

The colour dipole multiplicity distribution is analysed for the wave function of a heavy onium state at small $x$. Numerical results for the average multiplicity and the effect of cutoffs on its power growth are presented. Then, the full multiplicity distribution is analysed: the second multiplicity moment is derived and the tail of the distribution is shown

J. Edsjo, P. Gondolo

Weakly-interacting massive particles (WIMPs) annihilating in the center of the Sun or the Earth may give rise to energetic neutrinos which might be discovered by astronomical neutrino detectors. The angular distribution of the neutrino-induced muons is considered in detail via Monte Carlo simulations. It is shown that large underground Čerenkov neutrino tele

Bernard PIRE

The theoretical framework of hard exclusive reactions is reviewed with special emphasis on the Elfe project program. Perturbative QCD studies have shown that factorization properties allow to separate well-defined non perturbative objects which are crucial in the understanding of confinement dynamics from perturbatively calculable hard processes. The applica

T. Gousset, B. Pire, J. P. Ralston

We study a new mechanism for hadronic helicity flip in high energy hard exclusive reactions. The mechanism proceeds in the limit of perfect chiral symmetry, namely without any need to flip a quark helicity. The fundamental feature of the new mechanism is the breaking of rotational symmetry of the hard collision by a scattering plane in processes involving in