May 1995 arXiv papers — page 2

A. Acker, S. K. Gorny, F. Cuisinier

The central star (CSPN) of the planetary nebula M 1-25 (PN G 4.9+4.9) is classified as a [WC 6] star, the only CSPN of this subclass known at this time. A comparison with the other emission-lines CSPN (the [WC]-class and the 'weak emission-lines stars' or {\em wels}-class) shows that (1) the characteristics of this [WC 6] star fit well inside the mai

Cheongho Han, Vijay K. Narayanan, Andrew Gould

Lunar occultation can be used to measure the proper motions of some of the long time scale microlensing events, $t_{e} \gsim 70$ days, now being detected toward the Galactic bulge. The long events are difficult to explain within the context of standard models of the mass distribution and dynamics of the Galaxy. Han & Gould (1995b) have suggested that they ma

V. Mueller

A double inflationary model provides perturbation spectra with enhanced power at large scales (Broken Scale Invariant perturbations -- BSI), leading to a promising scenario for the formation of cosmic structures. We describe a series of high-resolution PM simulations with a model for the thermodynamic evolution of baryons in which we are capable of identifyi

N. Cardiel, J. Gorgas, A. Aragon-Salamanca

Through the study of two absorption spectral features in the optical range (Mg2 and the 4000 A break), we find evidence for star formation in the inner regions of cooling-flow galaxies. The application of simple stellar population models reveals that the measured indices are explained if a relatively small fraction of the total mass flow (5-17%) is forming n

A. Bochkarev, Ph. de Forcrand

We study on the lattice the correlator of heavy-quark currents in the vicinity of vanishing momentum. The renormalized charmed quark mass, the renormalized strong coupling constant and gluon condensate can be defined in terms of the derivatives of that correlator at zero momentum. We analyze quenched Monte-Carlo data on a small lattice $8^3*16$ for $β=6$. We

S. Peris, M. Perrottet, E. de Rafael

We discuss, within the framework of the Standard Model, the calculation of the two-loop electroweak contributions to the anomalous magnetic moment of the muon involving triangle fermionic loops of leptons and quarks. Because of the large ratios of masses involved, these contributions are rather large. The result we obtain differs from a previous estimate rep

F. De Jonghe, P. Termonia, W. Troost, S. Vandoren

We propose a new BRST operator for the B-twist of $N=2$ Landau-Ginzburg (LG) models. It solves the problem of the fractional ghost numbers of Vafa's old BRST operator and shows how the model is obtained by gauge fixing a zero action. An essential role is played by the anti-BRST operator,which is given by one of the supersymmetries of the $N=2$ algebra. I

G. K. Leontaris, S. Lola, G. G. Ross

Right handed neutrinos with mass of ${\cal O} \; (10^{12}-10^{13})$ GeV are required to implement the see-saw mechanism and generate neutrino masses capable of playing a role in structure formation. Moreover models of fermion masses often relate the Yukawa couplings involving these neutrinos to the up-quark Yukawa couplings. Here we study the effects of such

N. Mavromatos, D. Nanopoulos

Microtubule (MT) networks, subneural paracrystalline cytosceletal structures, seem to play a fundamental role in the neurons. We cast here the complicated MT dynamics in the form of a $1+1$-dimensional non-critical string theory, thus enabling us to provide a consistent quantum treatment of MTs, including enviromental {\em friction} effects. We suggest, thus

Glenn Barnich, Friedemann Brandt, Marc Henneaux

We analyse in detail the local BRST cohomology in Einstein-Yang-Mills theory using the antifield formalism. We do not restrict the Lagrangian to be the sum of the standard Hilbert and Yang-Mills Lagrangians, but allow for more general diffeomorphism and gauge invariant actions. The analysis is carried out in all spacetime dimensions larger than 2 and for all

Junegone Chay, Soo-Jong REY

We study the normalization of perturbative QCD corrections to the inclusive $B \rightarrow X_s γ$ decay. We propose to set the renormalization scale using the Brodsky-Lepage-Mackenzie (BLM) method. In the proposed method the scale is determined by absorbing the vacuum polarization correction from light fermions to renormalization scale but not including the

Kengo Ichiki

Granular flows in a narrow pipe are studied numerically by the model taking account of hydrodynamic effects of fluid surrounding particles. In the simulations density waves are observed over the wide range of the Stokes number, which represents the inertial effect of particles. The mechanisms of formation of the density waves are considered and two types of

R. David Dikeman, M. Shifman, N. G. Uraltsev

The photon energy distribution in the inclusive b -> s+γtransitions is a combination of two components: the first component, soft physics, is determined by the so called primordial distribution function, while the second component, perturbative physics, is governed by the hard gluon emission. A simple ansatz is suggested for the primordial distribution funct

M. G. Mustafa, A. Ansari

Within the MIT bag model picture of QCD, we have studied the stability of finite size strangelets at finite temperature with baryon number $A \leq 100$. The light quarks $u$ and $d$ are considered massless while mass of the $s$ quark is taken as $150$ MeV. Using discrete eigen energies of the non-interacting quarks in the bag, grand canonical partition funct

M. G. Mustafa, A. Ansari

Mass of a baryon as a function of temperature is calculated using colour-singlet partition function for massless quarks (with two flavours) and abelian gluons confined in a bag with a temperature dependent bag pressure constant $B(T)$. The non-perturbative aspect of QCD interaction is included through colour-singlet restriction on quark-gluon partition funct

R. A. Arndt, I. I. Strakovsky, R. L. Workman, M. M. Pavan

We present the results of energy-dependent and single-energy partial-wave analyses of $π$N elastic scattering data with laboratory kinetic energies below 2.1~GeV. Resonance structures have been extracted using Breit-Wigner fits, speed plots, and a complex plane mapping of the associated poles and zeroes. This is the first set of resonance parameters from a V

S. A. Rakityansky, S. A. Sofianos, V. B. Belyaev, V. I. Korobov

The reaction rate of the nuclear fusion d+Li6 ----> Be8*(2+,0) is estimated in the case where the nuclei are confined to each other by a muon. For the description of nuclear transitions, a method which is analogous to the Linear Combination of Atomic Orbitals has been used. Using the complex coordinate rotation method, we found that a molecular d-mu-Li6 stat

H. Grosse, C. Klimcik, P. Presnajder

We describe the self-interacting scalar field on the truncated sphere and we perform the quantization using the functional (path) integral approach. The theory posseses a full symmetry with respect to the isometries of the sphere. We explicitely show that the model is finite and the UV-regularization automatically takes place.

R. Floreanini, R. Percacci

We discuss the definition of the average effective action in terms of the heat-kernel. As an example we examine a model describing a self-interacting scalar field, both in flat and curved background, and study the renormalization group flow of some of the parameters characterizing its effective potential. Some implications of the running of these parameters

L. L. Frankfurt, E. G. Gurvich

We deduce momentum sum rules for the parton structure functions of a photon target. Non-perturbative QCD contribution to the momentum sum rules follows from conservation of the energy--momentum tensor and it is calculated through the hadronic part of the photon vacuum polarization operator. The contribution of the unresolved photon unambiguously follows from

W. Vogelsang, A. Vogt

We analyze the capability of prompt photon production in pp and pp(bar) collisions to constrain the gluon distribution of the proton, considering data from fixed-target experiments as well as collider measurements. Combined fits are performed to these large-p_T direct gamma cross sections and lepton-proton deep-inelastic scattering data in the framework of n

M. V. Ramana

We consider the contribution of new strongly interacting sector, with a characteristic scale of half a TeV, to top quark production at the Tevatron. The color-octet, isosinglet analog of the $ρ$ meson in this theory is produced copiously in hadron colliders. If the mass of this resonance is less than twice the mass of the lightest pseudo-Goldstone bosons, th

Uschi Grandel, Wolfram Weise

We investigate the role of nonperturbative quark-gluon dynamics in soft high energy processes. In order to reproduce differential and total cross sections for elastic proton-proton and proton-antiproton-scattering at high energy and small momentum transfer it turns out that we need two scales, the gluonic correlation length and a confinement scale. We find a

K. Kanaya

The effect of the strange quark in the finite temperature phase transition of QCD is studied on the lattice. Using the one-plaquette gauge action and the Wilson quark action, the transition in the chiral limit is shown to be continuous for the case of degenerate two flavors, $N_F=2$, while it is of first order for $N_F \geq 3$. For a more realistic case of m

Thomas Reisz

Linked cluster expansions provide a useful tool for both analytical and numerical investigations of lattice field theories. The expansion parameter(s) being the interaction strength(s) fields at neighboured lattice sites are coupled, they result into convergent hopping parameter like series for free energies, correlation functions and in particular susceptib

P. V. Moniz

The general theory of N=1 supergravity with supermatter is applied to a Bianchi type IX diagonal model. The supermatter is constituted by a complex scalar field and its spin-$1\over 2$ fermionic partners. The Kähler geometry is chosen to be a two-dimensional flat one. The Lorentz invariant Ansatz for the wave function of the universe is taken to be as simple

K. Held, M. Ulmke, D. Vollhardt

We present the first correlated-electron theory of metamagnetism in strongly anisotropic antiferromagnets. Quantum-Monte-Carlo techniques are used to calculate the field vs. temperature phase diagram of the infinite-dimensional Hubbard model with easy axis. A metamagnetic transition scenario with 1.~order and 2.~order phase transitions is found. The apparent

H. Frahm, M. P. Pfannmüller

We address the question how a correspondence between the particle like excitations in the one dimensional Hubbard model (i.e. ``holons'' and ``spinons'') and the free fermionic picture can be established in the limit of vanishing interaction by studying the finite size spectrum in the framework of the Bethe Ansatz. Special attention has to be

K. A. Hallberg, E. Mueller-Hartmann, C. A. Balseiro

We calculate the dynamical behaviour of a hole in various spin backgrounds in infinite dimensions, where it can be determined exactly. We consider hypercubic lattices with two different types of spin backgrounds. On one hand we study an ensemble of spin configurations with an arbitrary spin probability on each sublattice. This model corresponds to a thermal

V. Kushnir, B. Rosenstein

We develop a formalism for performing real space renormalization group transformations of the "decimation type" using perturbation theory. The type of transformations beyond $d=1$ is nontrivial even for free theories. We check the formalism on solvable case of $O(N)$ symmetric Heisenberg chain. The transformation is particularly useful to study asymp

Thomas W. Kephart, Thomas J. Weiler

We suggest that the highest energy $ \gsim 10^{20} eV$ cosmic ray primaries may be relativistic magnetic monopoles. Motivations for this hypothesis are that conventional primaries are problematic, while monopoles are naturally accelerated to $E \sim 10^{20} eV$ by galactic magnetic fields. By matching the cosmic monopole production mechanism to the observed

S. Cristiani, F. La Franca, P. Andreani, A. Gemmo

This is the first paper in a series aimed at defining a statistically significant sample of QSOs in the range $ 15 < B < 18.75$ and $ 0.3 < z < 2.2$. The selection is carried out using direct plates obtained at the ESO and UK Schmidt Telescopes, scanned with the COSMOS facility and searched for objects with an ultraviolet excess. Follow-up spectroscopy, carr

P. Andreani, S. Cristiani, F. La Franca

We have investigated the spatial distribution of quasars and its relationship with redshift by using the two-point correlation function, the variance of cell counts and the conditional density as a function of redshift. By comparing our results with those found by other authors we conclude that quasars have a correlation function with amplitude similar to or

S. Cristiani, S. D&#39;Odorico, V. D&#39;Odorico, A. Fontana

The spectra of the QSOs PKS2126-158 ($z_{em}=3.27$) and Q0055-269 ($z_{em}=3.66$) have been observed at high resolution ($2.2 - 2.7 \times 10^4$). Significant clustering, with $ξ\simeq 1$ at $Δv=100$ km s$^{-1}$, is detected in both cases for lines with $\log N_{HI} \geq 13.8$. A similar result is obtained analysing the data available in the literature for Q

Yukitoshi Kan-ya, Ryoichi Nishi, Takashi Nakamura

We investigated the dependence of the optical depth $τ$ of the microlensing events on model parameters of the Galactic halo. We only consider Galactic mass models in which the rotation curve inside the Sun is compatible with the observation and LMC is bound to the Galaxy. It is found that $τ$ varies up to a factor 2.5 from the standard spherical and flat rot

Bruce Hunt

A rational group of hermitian type is an algebraic group over the rational numbers whose symmetric space is a hermitian symmetric space. We assume such a group $G$ to be given, which we assume is isotropic. Then, for any rational parabolic $P$ in the group $G$, we find a reductive rational subgroup $N$ closely related with $P$ by a relation we call incidence

Atanas Iliev

Among smooth non-rational Fano 3-folds, the non-hyperelliptic Fano 3-fold X(10) of genus 6 has the unique property to admit a non-trivial orbit of birationally isomorphic 3-folds, inside its moduli space. Here we prove that these orbits are, in fact, the same as the fibers of the Griffiths period map for X(10). This leads upto the main result of the paper: T

Atanas Iliev

Let the threefold X be a general smooth conic bundle over the projective plane P(2), and let (J(X), Theta) be the intermediate jacobian of X. In this paper we prove the existence of two natural families C(+) and C(-) of curves on X, such that the Abel-Jacobi map F sends one of these families onto a copy of the theta divisor (Theta), and the other -- onto the

Stefan Boettcher, Maya Paczuski

We introduce a self-organized critical model of punctuated equilibrium with many internal degrees of freedom ($M$) per site. We find exact solutions for $M\rightarrow \infty$ of cascade equations describing avalanche dynamics in the steady state. This proves the existence of simple power laws with critical exponents that verify general scaling relations for

Ziv Ran

A revised version with a number of corrections and refinements.

C. P. Burgess, J. -P. Derendinger, F. Quevedo, M. Quiros

We study in detail gaugino condensation in globally and locally supersymmetric Yang-Mills theories. We focus on models for which gauge-neutral matter couples to the gauge bosons only through nonminimal gauge kinetic terms, for the cases of one and several condensing gauge groups. Using only symmetry arguments, the low-energy expansion, and general properties

P V Landshoff

Exclusive vector meson production from real and virtual photons is a good probe of pomeron physics. In particular, it sheds light on how the soft pomeron is related to nonperturbative QCD, and how it couples to heavy flavours. It also raises the question whether there are two pomerons, a soft one and a hard one.

Ch. Okonek, A. Teleman

We present the simplest non-abelian version of Seiberg-Witten theory: Quaternionic monopoles. These monopoles are associated with Spin^h(4)-structures on 4-manifolds and form finite-dimensional moduli spaces. On a Kahler surface the quaternionic monopole equations decouple and lead to the projective vortex equation for holomorphic pairs. This vortex equation

S. Kalyana Rama, Sasanka Ghosh

We look for a graviton-dilaton theory which can predict non trivial values of the PPN parameters $β$ and/or $γ$ for a charge neutral point star, without any naked singularity. With the potential for dilaton $ϕ$ set to zero, it contains one arbitrary function $ψ(ϕ)$. Our requirements impose certain constraints on $ψ$, which lead to the following generic and m

James A. Rome

Special Issue: New Stellarators New stellarators are being constructed throughout the world as part of a well-coordinated international program. This issue concentrates on the engineering and construction details of Large Helical Device (LHD), Toki, Japan Wendelstein 7-X (W7-X), Greifswald, Germany Helias Stellarator Experiment (HSX), Madison Wisconsin, USA

Victor Matveev, Robert Shrock

Although the physical properties of the 2D and 1D Ising models are quite different, we point out an interesting connection between their complex-temperature phase diagrams. We carry out an exact determination of the complex-temperature phase diagram for the 1D Ising model for arbitrary spin $s$ and show that in the $u_s=e^{-K/s^2}$ plane (i) it consists of $

Giovanni Gallavotti

Some models for developed turbulence are considered; they are shown to obey a large fluctuations theorem, and one among them also obeys a response reciprocity relation of Onsager&#39;s type. This illustrates and extends ideas and techniques developed in earlier works mainly for non equilibrium problems in statistical mechanics.

Janusz Kaluzny, Wojciech Krzeminski, Beata Mazur

BV photometry is presented for 12 RR Lyr variables discovered in the presumably young galactic globular cluster Ruprecht 106. All variables are type RRab, and their periods span a narrow range from 0.574 to 0.652 day. We report also on the discovery of 3 SX Phe variables among the cluster blue stragglers. A likely background RR Lyr variable and two foregroun

Pavel Kroupa

The stellar luminosity function derived from the sample of stars within 5.2--20~pc is the nearby luminosity function. The luminosity function obtained from deep low spatial resolution surveys to distances of typically 100--200~pc is the photometric luminosity function. We obtain and tabulate a best estimate of the parent distribution from which Malmquist cor

Beverley J. Wills, M. S. Brotherton

Radio core dominance, usually measured by R, the rest frame ratio of core to lobe flux density, has been used as an indicator of Doppler boosting of quasars&#39; radio jets and hence the inclination of the central engine&#39;s spin axis to the line of sight. The use of lobe flux density as a means of normalizing the boosted core flux density to the available

B. Ramesh

With its cometary appearance and a reflection nebula near its edge facing some bright Orion stars, the Lynd&#39;s cloud L1616 shows ample evidence for being affected by one or more of these massive stars. To estimate its mass and star formation efficiency as well as to determine if it is gravitationally bound, we mapped this cloud in J=1${\rightarrow}$0 tran

David Polarski, Alexei A. Starobinsky

The gravitational waves (GW) background generated in a double inflationary model, with two scalar fields mutually interacting through gravity only, and its relative contribution $T/S$ to large-angle temperature fluctuations of the relic microwave background are investigated in detail. The relation between $T/S$ and the slope of the GW spectrum $n_T$ is shown

Artan Boriçi, Philippe de Forcrand

We study the systematic errors of Lüscher&#39;s formulation of dynamical Wilson quarks and some of its variants, in the weak and strong coupling limits, and on a sample of small configurations at finite $β$. We confirm the existence of an optimal window in the cutoff parameter $\varepsilon$, and the exponential decrease of the error with the number of boson

A. Bottino, N. Fornengo, C. W. Kim, G. Mignola

Motivated by a recent rather surprising conclusion based on the 1992 PDG data on the pion, kaon and lepton decays that if three generations of neutrinos are assumed to be massive and mixed, the heaviest neutrino, $ν_3$, could have a mass in the range, $155~\mbox{MeV} \lsim m_3 \lsim 225~\mbox{MeV}$, we have analyzed the latest 1995 data on the leptonic decay

Manoelito M. de Souza

A new interpretation of the causality implementation in the Lienard-Wiechert solution raises new doubts against the validity of the Lorentz-Dirac equation and the limits of validity of the Minkowski structure of spacetime.

Stephen Playfer, Sheldon Stone

Rare b decays provide a unique opportunity to measure Standard Model parameters and probe beyond the Standard Model. We review here the experimentalprogress made in measuring these decays, and the importance of future measurements, including the possible observation of CP violation.

James Robinson, Andreas Albrecht

We describe an implementation of the structure functions of Babul \& Starkman, in order to quantify the ``sheet-like&#39;&#39; nature of a distribution of matter. We test this statistic on a toy model describing cosmic string wakes, and show that it does a better job than other statistics which have been proposed for distinguishing non-Gaussianity in the for

M. Ardehali

A protocol for quantum bit commitment is proposed. The protocol is feasible with present technology and is secure against cheaters with unlimited computing power as long as the sender does not have the technology to store an EPR particle for an arbitrarily long period of time. The protocol is very efficient, requiring only tens of particles.

Teiji Kunihiro

On the basis of the classical theory of envelopes, we formulate the renormalization group (RG) method for global analysis, recently proposed by Goldenfeld et al. It is clarified why the RG equation improves things.

K. A. Hallberg, C. A. Balseiro

Using numerical techniques we study the zero temperature properties of a substitutional magnetic impurity in a one-dimensional correlated system described by the Hubbard model with repulsive interaction $U$. We find that, while the static spin correlation maintains a $2k_F$ periodicity, the charge correlations show Friedel oscillations with a $4k_F$ periodic

Vikram Soni

We show that the sphaleron energy which identifies with the (instanton) potential barrier for B-violation is reduced in the presence (background) of an electroweak Z-string. We also show that for large enough Higgs coupling, $λ$, the sphaleron energy can go negative. For such $λ$, electroweak Z-strings can reduce their energy by accumulating sphaleron bound

Simon Davis

Correlation functions can be calculated on Riemann surfaces using the operator formalism. The state in the Hilbert space of the free field theory on the punctured disc, corresponding to the Riemann surface, is constructed at infinite genus, verifying the inclusion of these surfaces in the Grassmannian. In particular, a subset of the class of $O_{HD}$ surface

K. Wodkiewicz

It is shown that the Einstein, Podolsky and Rosen (EPR) correlations for arbitrary spin-s and the Greenberger, Horne and Zeilinger (GHZ) correlations for three particles can be described by nonlocal joint and conditional quantum probabilities. The nonlocality of these probabilities makes the Bell&#39;s inequalities void. A description that exhibits the relat

M. C. Cross, D. I. Meiron

The growth of domains of stripes evolving from random initial conditions is studied in numerical simulations of models of systems far from equilibrium such as Rayleigh-Benard convection. The scaling of the size of the domains deduced from the inverse width of the Fourier spectrum is studied for both potential and nonpotential models. The morphology of the do

H. Müther, G. Knehr, A. Polls

A simple method is presented to evaluate the effects of short-range correlations on the momentum distribution of nucleons in nuclear matter within the framework of the Green&#39;s function approach. The method provides a very efficient representation of the single-particle Green&#39;s function for a correlated system. The reliability of this method is establ

A. Drago, U. Tambini, M. Hjorth-Jensen

Using the Color-Dielectric model to describe quark confinement, including strange quarks and accounting for beta--equilibrium, we get masses for a static neutron star in the range $1.3\leq M/M_{\odot}\leq 1.54 $ for a radius $R\approx 9$ km. Rapid cooling through the direct URCA mechanism is obtained. The implications for the composition of neutron stars is

John H. Schwarz

Many two-dimensional classical field theories have hidden symmetries that form an infinite-dimensional algebra. For those examples that correspond to effective descriptions of compactified superstring theories, the duality group is expected to be a large discrete subgroup of the hidden symmetry group. With this motivation, we explore the hidden symmetries of

Y. Hosotani

The massive multi-flavor Schwinger model on a circle is reduced to a finite dimensional quantum mechanics problem. The model sensitively depends on the parameter $mL|\cos\onehalfθ|$ where $m$, $L$, and $θ$ are a typical fermion mass, the volume, and the vacuum angle, respectively.

Taro KASHIWA

A form of the constraints, specifying a $D$-dimensional manifold embedded in $D+1$ dimensional Euclidean space, is discussed in the path integral formula given by a time discretization. Although the mid-point prescription is privileged in the sphere $S^D$ case, it is more involved in generic cases. An interpretation on the validity of the formula is put in t

P. Berglund, P. Candelas, X. de la Ossa, E. Derrick

We consider the gauge neutral matter in the low--energy effective action for string theory compactification on a \cym\ with $(2,2)$ world--sheet supersymmetry. At the classical level these states (the \sing&#39;s of $E_6$) correspond to the cohomology group $H^1(\M,{\rm End}\>T)$. We examine the first order contribution of instantons to the mass matrix of th

Rajen Kundu

In this paper, we have calculated the lowest order splitting functions occurring in the Altarelli-Parisi equation in the light front hamiltonian formalism. Two component perturbative LFQCD in light cone gauge is our guideline and we have used LFTD-approximation for dressed quark and gluon states.

Srubabati Goswami, Kamales Kar, Amitava Raychaudhuri

We perform a three flavour analysis of the atmospheric, accelerator and reactor neutrino data from the Kamiokande, LSND and Bugey experiments respectively. Choosing the values of ${Δ{m}}^2$ obtained from two flavour fits of the first two experiments, the allowed ranges of the three generation mixing angles are determined. The accelerator experiments CHORUS a

Thomas A. Kaeding

A fit of amplitudes to the experimental branching ratios to two mesons is used to construct a new estimate of neutral $D$ mixing which includes $SU(3)$ breaking. The result is dominated by the experimental uncertainties. This suggests that the charm sector may not be as sensitive to new physics as previously thought and that long-distance calculations may no

G. P. Korchemsky, G. Sterman

We discuss the role of infrared renormalons in power corrections to hadronic cross sections, including their universality. We show how perturbative renormalon structure arises near kinematic boundaries in the thrust distribution, the Drell-Yan cross section and radiative B decays. The leading infrared renormalon in each case is associated with jet evolution.

P. Kalyniak, P. Madsen, N. Sinha, R. Sinha

We explore the detection potential of the four lepton production processes $e^{+}e^{-} \rightarrow l^{+} νl^{\prime -}\overlineν$ for anomalous contributions to the triple boson vertices at proposed future high energy colliders with center-of-mass energies of 500 GeV and 1 TeV. The predicted bounds are of the order of a few percent for the $CP$-even coupling

R. D. Ball, S. Forte

We show that a unified approach to the perturbative evolution of structure functions which sums all logarithms of Q^2 and 1/x at leading and next-to-leading order yields results in full agreement with the 1993 HERA data for F_2. This makes it possible to determine alpha_s surprisingly accurately from these data alone.

R. N. Faustov, V. O. Galkin

The exclusive rare radiative $B$-decays are studied in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. The large recoil momentum of the final vector meson allows for the expansion of the decay form factor in inverse powers of the b-quark mass. This considerably simplifies the analysis of these decay

Z. Berezhiani, R. N. Mohapatra

We suggest that recent neutrino puzzles that are the solar and atmospheric neutrino deficits as well as the possible neutrino oscillations reported by the LSND experiment and the possibility of massive neutrinos providing the hot component of the cosmological dark matter, can all be naturally explained by assuming existence of a mirror world described by an

Zurab Berezhiani

The first fermion family might play a key role in understanding the structure of flavour: a role of the mass unification point. The GUT scale running masses $\bar{m}_{e,u,d}$ are rather close, which may indicate an approximate symmetry limit. Following this observation, we present a new predictive approach based on the SUSY $SO(10)$ theory with $\tanβ\sim 1$

A. A. Bytsenko, E. Elizalde, S. D. Odintsov

The conformal anomaly for spinors and scalars on a N-dimensional hyperbolic space is calculated explicitly, by using zeta-function regularization techniques and the Selberg trace formula. In the case of conformally invariant spinors and scalars the results are very much related with those corresponding to a N-dimensional sphere.

Frederick Wilhelm

Recall that the radius of a compact metric space $(X, dist)$ is given by $rad\ X = \min_{x\in X} \max_{y\in X} dist(x,y)$. In this paper we generalize Berger&#39;s $\frac{1}{4}$-pinched rigidity theorem and show that a closed, simply connected, Riemannian manifold with sectional curvature $\geq 1$ and radius $\geq \fracπ{2}$ is either homeomorphic to the sph

B. G. Konopelchenko, I. A. Taimanov

It is shown that the equation which describes constant mean curvature surface via the generalized Weierstrass-Enneper inducing has Hamiltonian form. Its simplest finite-dimensional reduction has two degrees of freedom, integrable and its trajectories correspond to well-known Delaunay and do Carmo-Dajzcer surfaces (i.e., helicoidal constant mean curvature sur

D. A. Rabson, S. A. Trugman

Spin chirality has generated great interest recently both from possible applications to flux phases and intrinsically, as an example of a several-site magnetic order parameter that can be long-ranged even where simpler order parameters are not. Previous work (motivated by the flux phases) has focused on antiferromagnetic chiral order; we construct a model in

Yong Wang, A. H. MacDonald

Controversy concerning the pairing symmetry of high-$T_c$ materials has motivated an interest in those measurable properties of superconductors for which qualitative differences exist between the s-wave and d-wave cases. We report on a comparison between the microscopic electronic properties of d-wave and s-wave superconductors in the mixed state. Our study

Daniel ben-Avraham, Vladimir Privman, Dexin Zhong

We propose a model for diffusion-limited annihilation of two species, $A+B\to A$ or $B$, where the motion of the particles is subject to a drift. For equal initial concentrations of the two species, the density follows a power-law decay for large times. However, the decay exponent varies continuously as a function of the probability of which particle, the ho

G. Chitov, D. Senechal

The renormalization-group (RG) approach proposed earlier by Shankar for interacting spinless fermions at $T=0$ is extended to the case of non-zero temperature and spin. We study a model with $SU(N)$-invariant short-range effective interaction and rotationally invariant Fermi surface in two and three dimensions. We show that the Landau interaction function of

Leo Radzihovsky

I argue that in contrast to $B<B_ϕ$, where the Vortex Liquid (VL) freezes into the Strongly-pinned Bose Glass phase (SBG), with flux-line vortices localized by the columnar defects, for $B>B_ϕ$, the additional vortices see a significantly weaker random $z$-independent potential due to the caging by the vortices strongly pinned on the columnar defects. The re

Achille Giacometti, Amos Maritan, Jayanth R. Banavar

The effects of erosion, avalanching and random precipitation are captured in a simple stochastic partial differential equation for modelling the evolution of river networks. Our model leads to a self-organized structured landscape and to abstraction and piracy of the smaller tributaries as the evolution proceeds. An algebraic distribution of the average basi

A. Perez-Madrid, J. M. Rubi, P. Mazur

By considering an ensemble of Brownian particles suspended in a heat bath as a thermodynamic system with an internal degree of freedom it is possible to obtain the Fokker-Planck equation for Brownian motion in a temperature gradient, by applying the scheme of non-equilibrium thermodynamics. We recover explicitely the equations derived in particular by Zubare

A. Perez-Madrid, J. M. Rubi

We show that a dispersion of monodomain ferromagnetic particles in a solid phase exhibits stochastic resonance when a driven linearly polarized magnetic field is applied. By using an adiabatic approach, we calculate the power spectrum, the distribution of residence times and the mean first passage time. The behavior of these quantities is similar to their co

U. Marini Bettolo Marconi, A. Crisanti

To study the effect of slow heat conduction during phase separation, we discuss the relaxation properties of an $O(N)$ symmetric model with Phase field type dynamics, where a non conserved order parameter field couples bilinearly to a diffusive field. In the limit $N\to\infty$ we obtain an exact solution. The analysis reveals three different types of growth

Naoto Nagaosa, Mahito Kohmoto

An effective Chern-Simons theory for the Abelian quantum Hall states with edges is proposed to study the edge and bulk properties in a unified fashion. We impose a condition that the currents do not flow outside the sample. With this boundary condition, the action remains gauge invariant and the edge modes are naturally derived. We find that the integer coup

Kikuo Harigaya

Variations in the band structures of the two-dimensional C60-polymers are studied, when pi-conjugation conditions are changed. We investigate the rectangular and triangular polymers, in order to discuss metal-insulator transitions, using a semiempirical model with the Su-Schrieffer-Heeger type electron-phonon interactions. We find that electronic structures

K. A. Hallberg, P. Horsch, G. Martinez

We use the density-matrix renormalization group technique developed by White \cite{white} to calculate the spin correlation functions $<{S}_{n+l}^z{S}_n^z>=(-1)^l ω(l,N)$ for isotropic Heisenberg rings up to $N=70$ sites. The correlation functions for large $l$ and $N$ are found to obey the scaling relation $ω(l,N)=ω(l,\infty)f_{XY}^α (l/N)$ proposed by Kapl

D. Cule

The dynamics of the discrete Gaussian model for the surface of a crystal deposited on a disordered substrate is investigated by Monte Carlo simulations. The mobility of the growing surface was studied as a function of a small driving force $F$ and temperature $T$. A continuous transition is found from high-temperature phase characterized by linear response t

Kathryn A. Moler, David J. Baar, Ruixing Liang, Walter N. Hardy

The anisotropy of the magnetic field dependence of the specific heat of YBa$_2$Cu$_3$O$_{7 - {\rm δ}}$ can be used to identify different low-energy excitations, which include phonons, spin-$ \frac{1}{2}$ particles, and electronic contributions. With a magnetic field H applied perpendicular to the copper oxide planes, we find that the specific heat includes a

Manny Rayner, Pierrette Bouillon

The paper argues the importance of high-quality translation for spoken language translation systems. It describes an architecture suitable for rapid development of high-quality limited-domain translation systems, which has been implemented within an advanced prototype English to French spoken language translator. The focus of the paper is the hybrid transfer

K. H. Cook, C. Alcock, R. A. Allsman, T. S. Axelrod

The MACHO Collaboration&#39;s search for baryonic dark matter via its gravitational microlensing signature has generated a massive database of time ordered photometry of millions of stars in the LMC and the bulge of the Milky Way. The search&#39;s experimental design and capabilities are reviewed and the dark matter results are briefly noted. Preliminary ana

R. C. Thomson, P. Crane, C. D. Mackay

HST images of the western hot spot of the nearby FRII radio galaxy Pictor A resolve the hot spot into an amorphous region of highly polarized wisps. The high polarization (>~ 50%) indicates that the optical emission is synchrotron radiation and that the magnetic field structure has been well resolved. The magnetic field is oriented nearly perpendicular to th

R. C. Thomson, D. R. T. Robinson, N. R. Tanvir, C. D. Mackay

We present the first high resolution polarization map of the ultraviolet emission from the outer jet in M87. The data were obtained by the Faint Object Camera (FOC) on the Hubble Space Telescope. The polarization map has a resolution of 0.2 arcsec and was derived using data from three linearly polarized images combined with the best available calibration dat