March 1996 arXiv papers — page 8

Agnieszka Zalewska, Kacper Zalewski

The masses of the yet undiscovered baryons containing single $c$ or $b$ quarks are estimated from the known masses using the following rules: equal distances in mass between the isomultiplets forming sextets, equal mass differences between the corresponding spin one-half baryons containing $c$ and $b$ quarks, hyperfine splittings inversely proportional to th

J. -L. Meunier, R. Peschanski

We compute analytically the effects of energy conservation on the self-similar structure of parton correlations in QCD jets. The calculations are performed both in the constant and running coupling cases. It is shown that the corrections are phenomenologically sizeable. On a theoretical ground, energy conservation constraints preserve the scaling properties

Koichi Yamawaki

We give an introduction to the dynamical symmetry breaking with large anomalous dimension. This is the basis of tightly bound composite Higgs models such as walking technicolor, strong ETC technicolor and top quark condensate, which are all characterized by the large anomalous dimension, γ_m \simeq 1 (walking technicolor), 1<γ_m<2 (strong ETC technicolor) an

Morimitsu Tanimoto

We have studied structures of the neutrino flavor mixing matrix focusing on the neutrino oscillations at CHORUS and NOMAD as well as the one at LSND(or KARMEN). We have assumed two typical neutrino mass hierarchies $m_3\simeq m_2\gg m_1$ and $m_3\gg m_2\gg m_1({\rm or}\simeq m_1)$. Taking into account the see-saw mechanism of neutrino masses, the reasonable

Dongsheng Du, Xiulin Li, Yadong Yang

We study the decay $B_c \rightarrow D_s^* γ$. There are two mechanisms contributing to the process. One proceeds through the short distance $b{\rightarrow}sγ$ transition and the other occurs through weak annihilation accompanied by a photon emission.The electromagnetic penguin contribution is estimated by perturbative QCD and found to be $4.68\times10^{-18}$

She-Sheng Xue

Within the framework of the ``Rome approach&#39;&#39; for a lattice chiral gauge theory, the four-quark interaction with flavour symmetry is included. We analyse spontaneous symmetry breaking and compute composite modes and their contributions to the ground state energy. As a result, it is shown that the emergence of a heavy quark family is the energetically

Hisashi Onozawa, Takashi Mishima, Takashi Okamura, Hideki Ishihara

A new algorithm for computing the accurate values of quasinormal frequencies of extremal Reissner-Nordström black holes is presented. The numerically computed values are consistent with the values earlier obtained by Leaver and those obtained through the WKB method. Our results are more precise than other results known to date. We also find a curious fact th

P. Baird, J. C. Wood

Equivalences between conformal foliations on Euclidean $3$-space, Hermitian structures on Euclidean $4$-space, shear-free ray congruences on Minkowski $4$-space, and holomorphic foliations on complex $4$-space are explained geometrically and twistorially; these are used to show that 1) any real-analytic complex-valued harmonic morphism without critical point

Dirk Endesfelder

The scattering approach to quantum transport through a disordered quasi-one-dimensional conductor in the insulating regime is discussed in terms of its transfer matrix $\bbox{T}$. A model of $N$ one-dimensional wires which are coupled by random hopping matrix elements is compared with the transfer matrix model of Mello and Tomsovic. We derive and discuss the

Joonhyun Yeo, M. A. Moore

We present in detail a nonperturbative method for vortex liquid systems. This method is based on the resummation of an infinite subset of Feynman diagrams, the so-called parquet graphs, contributing to the four-point vertex function of the Ginzburg-Landau model for a superconductor in a magnetic field. We derive a set of coupled integral equations, the parqu

Achille Giacometti, K. P. N. Murthy

The properties of a particle diffusing on a one-dimensional lattice where at each site a random barrier and a random trap act simultaneously on the particle are investigated by numerical and analytical techniques. The combined effect of disorder and traps yields a decreasing survival probability with broad distribution (log-normal). Exact enumerations, effec

V. Karimipour, Kh. Saaidi

We perform a detailed analysis of the statistical properties of Poisson networks and show that the metric and topological properties of random cellular structures, can not be derived from simple models of random networks based on a poisson point distribution [1]. In particular we show that Lewis and Aboav-Wieare laws are not obeyed in these network.

Joao A. N. Filipe, Geoff J. Rodgers

We investigate the kinetics of systems in which particles of one species undergo binary fragmentation and pair annihilation. In the latter, nonlinear process, fragments react at collision to produce an inert species, causing loss of mass. We analyse these systems in the reaction-limited regime by solving a continuous model within the mean-field approximation

A. A. Shanenko

This paper presents the Thomas-Fermi approach generalized to consider the particle correlations in many-body systems with non-Coulomb interaction potentials. The key points of the generalization consist in using integral formulation and extracting the pair distribution function. The latter has been found to obey the integral equation which, in the classical

Y. Arikabe, M. Kuwabara, Y. Ono

The dynamical behavior of an acoustic polaron in typical non-degenerate conjugated polymer, polydiacetylene, is numerically studied by using Su-Schrieffer-Heeger&#39;s model for the one dimensional electron-lattice system. It is confirmed that the velocity of a polaron accelerated by a constant electric field shows a saturation to a velocity close to the sou

Norbert E. Fuchs, Rolf Schwitter

Attempto Controlled English (ACE) allows domain specialists to interactively formulate requirements specifications in domain concepts. ACE can be accurately and efficiently processed by a computer, but is expressive enough to allow natural usage. The Attempto system translates specification texts in ACE into discourse representation structures and optionally

F. Perez-Bernal, R. Bijker, A. Frank, R. Lemus

The relation between algebraic and traditional calculations of molecular vibrations is investigated. An explicit connection between interactions in configuration space and the corresponding algebraic interactions is established.

A. Frank, R. Lemus, R. Bijker, F. Perez-Bernal

We apply the Anharmonic Oscillator Symmetry Model to the description of vibrational excitations in ${\cal D}_{3h}$ and ${\cal T}_d$ molecules. A systematic procedure can be used to establish the relation between the algebraic and configuration space formulations, by means of which new interactions are found in the algebraic model, leading to reliable spectro

Vijay K. Narayanan, Andrew Gould, D. L. DePoy

We present H and K photometry of 42,000 stars in an area of 250 arcmin$^{2}$ centered on the Galactic center. We use the photometry to construct a dereddened K band luminosity function (LF) for this region, excluding the excessively crowded inner 2&#39; of the Galaxy. This LF is intermediate between the LF of Baade&#39;s window and the LF of inner 2&#39; of

Karl Rakos, James Schombert

Rest frame Stromgren photometry (3500A, 4100A, 4750A and 5500A) is presented for 509 galaxies in 17 rich clusters between z=0 and z=1 as a test of color evolution. Our observations confirm a strong, rest frame, Butcher-Oemler effect where the fraction of blue galaxies increases from 20% at z=0.4 to 80% at z=0.9. We also find that a majority of these blue clu

G. A. Kriss, J. H. Krolik, C. Otani, B. R. Espey

We obtained X-ray spectra of the Seyfert 1 galaxy NGC~3516 in March 1995 using ASCA. Simultaneous far-UV observations were obtained with HUT on the Astro-2 shuttle mission. The ASCA spectrum shows a lightly absorbed power law of energy index 0.78. The low energy absorbing column is significantly less than previously seen. Prominent O~vii and O~viii absorptio

Edward J. Shaya, Daniel M. Dowling, Douglas G. Currie, S. M. Faber

We present HST Planetary Camera V and I~band images of the central region of the peculiar giant elliptical galaxy NGC 1316. The inner profile is well fit by a nonisothermal core model with a core radius of 0.41&#34; +/- 0.02&#34; (34 pc). At an assumed distance of 16.9 Mpc, the deprojected luminosity density reaches $\sim 2.0 \times 10^3 L_{\sun}$ pc$^{-3}$.

G. A. Kriss, B. R. Espey, J. H. Krolik, Z. Tsvetanov

We observed the Seyfert 1 galaxy NGC 3516 twice during the flight of Astro-2 using the Hopkins Ultraviolet Telescope in March 1995. Simultaneous X-ray observations were performed with ASCA. Our far-ultraviolet spectra cover the spectral range 820-1840 A with a resolution of 2-4 A. No significant variations were found between the two observations. The total s

Vicent J. Martinez

A brief introduction is given to some aspects of the statistical description of the luminous matter distribution. I review the features of the redshift surveys that arise in the statistical analysis of the galaxy clustering. Special topics include intensity functions, correlation functions, correlation integrals, multifractals and multiscaling.

B. T. Draine

The optical and magnetic properties of dust grains are reviewed, as they relate to the problem of interstellar grain alignment. Grain geometry plays an important role in determining the optical properties, and scattering and absorption of starlight will produce radiative torques which may drive grains to suprathermal rates of rotation in interstellar clouds;

Karl Rakos, Thomas Maindl, James Schombert

This paper presents new and synthetic narrow band photometry of ellipticals, spirals, Seyferts and interacting galaxies in an attempt to identify the cause of the unusually high fraction of blue cluster galaxies in distant clusters (Butcher-Oemler effect). The properties and distribution of the low redshift sample specifically points to starbursts as the ori

Valeri A. Gritsenko, Viacheslav V. Nikulin

We find automorphic corrections for the Lorentzian Kac--Moody algebras with the simplest generalized Cartan matrices of rank 3: A_{1,0} = 2 0 -1 0 2 -2 -1 -2 2 and A_{1,I} = 2 -2 -1 -2 2 -1 -1 -1 2 For A_{1,0} this correction is given by the Igusa Sp_4(Z)-modular form χ_{35} of weight 35, and for A_{1,I} by a Siege modular form of weight 30 with respect to a

Daniel Altschuler, Laurent Freidel

At any order, the perturbative expansion of the expectation values of Wilson lines in Chern-Simons theory gives certain integral expressions. We show that they all lead to knot invariants. Moreover these are finite type invariants whose order coincides with the order in the perturbative expansion. Together they combine to give a universal Vassiliev invariant

James V. Steele, Hidenaga Yamagishi, Ismail Zahed

We analyze the dilepton and photon emission rates from a hadronic gas using chiral reduction formulas and a virial expansion. The emission rates are reduced to pertinent vacuum correlation functions, most of which can be assessed from experiment. Our results indicate that in the low mass region, the dilepton and photon rates are enhanced compared to most of

Min-Ho Lee, Hyeong-Chan Kim, Jae Kwan Kim

We calculate the entropy of a scalar field in a rotating black hole in 2 + 1 dimension. In the Hartle-Hawking state the entropy is proportional to the horizon area, but diverges linearly in $\sqrt{h}$, where $h$ is the radial cut-off. In WKB approximation the superradiant modes do not contribute to the entropy.

Richard Earl

The rational cohomology of the moduli space of rank two, odd degree stable bundles over a curve (of genus g > 1) has been studied intensely in recent years and in particular the invariant subring generated by Newstead&#39;s generators alpha, beta, gamma. Several authors have independently found a minimal complete set of relations for this subring. Their meth

I. Kuss, D. Schildknecht

In view of the forthcoming results on $W^{\pm}$ pair production at LEP~2, we emphasize that {\em direct empirical evidence} on non-trivial properties of the weak vector bosons can be obtained with relatively limited integrated luminosity. An integrated luminosity of $10\;\mathrm{pb}^{-1}$ at $\sqrt{s}=175$ GeV will be sufficient to provide direct experimenta

Wojciech Slominski, Jerzy Szwed

The QCD structure of the electron is defined and calculated. The leading order splitting functions are extracted, showing an important contribution from $γ$-$Z$ interference. Leading logarithmic QCD evolution equations are constructed and solved in the asymptotic region where log$^2$ behaviour of the parton densities is observed. Corrections to the naive evo

Marcus Hutter

Numerical and anaytical studies of the instanton liquid model have allowed the determination of many hadronic parameters during the last 13 years. Most part of this thesis is devoted to the extension of the analytical methods. The meson correlation (polarization) functions are calculated in the instanton liquid model including dynamical quark loops. The corr

Fernando Quevedo

The phenomenological aspects of string theory are briefly reviewed. Emphasis is given to the status of 4D string model building, effective Lagrangians, model independent results, supersymmetry breaking and duality symmetries.

Peter J. Kernan, Subir Sarkar

Contrary to a recent claim, the inferred primordial abundances of the light elements are quite consistent with the expectations from standard big bang nucleosynthesis when attention is restricted to direct observations rather than results from chemical evolution models. The number of light neutrino (or equivalent particle) species ($N_\nu$) can be as high as

Koichi Yamawaki

In the light of recent discovery of a very heavy top quark, we reexamine the top quark condensate model proposed by Miransky, Tanabashi and Yamawaki (MTY) and by Nambu. We first review the original MTY formulation based on the ladder Schwinger-Dyson equation and the Pagels-Stokar formula. It is particularly emphasized that the critical phenomenon gives a sim

Kanehisa Takasaki, Toshio Nakatsu

Seiberg-Witten solutions of four-dimensional supersymmetric gauge theories possess rich but involved integrable structures. The goal of this paper is to show that an isomonodromy problem provides a unified framework for understanding those various features of integrability. The Seiberg-Witten solution itself can be interpreted as a WKB limit of this isomonod

P. A. Baikov

Explicit formulas for the solutions of the recurrence relations for 3--loop vacuum integrals are suggested. This formulas can be used for direct calculations and demonstrate a high efficiency. They also produce a new type of recurrence relations over the space--time dimension.

Victor Enolskii, Mario Salerno

Lax representation in terms of $2\times 2$ matrices is constructed for a separable multiply--periodic system splitting on two tori. Hyperelliptic Kleinian functions and their reduction to elliptic functions are used.

Marek Czachor

The nonrelativistic singlet state average $\langle ψ|{\vec a}\cdot\vec σ\otimes {\vec b}\cdot\vec σ|ψ\rangle =-\vec a\cdot\vec b $ can be relativistically generalized if one defines spin {\it via\/} the relativistic center-of-mass operator. The relativistic correction is quadratic in $v/c$ and can be measured in Einstein-Podolsky-Rosen-Bohm-type experiments

Jan Sobczyk

Lie bialgebra structures on $e(2)$ are classified. For two Lie bialgebra structures which are not coboundaries (i.e. which are not determined by a classical $r$-matrix) we solve the cocycle condition, find the Lie-Poisson brackets and obtain quantum group relations. There is one to one correspondence between Lie bialgebra structures on $e(2)$ and possible qu

Jan Sobczyk

We present contraction prescription of the quantum groups: from $SU_q(2)$ to $E_κ(2)$. Our strategy is different then one chosen in ref. [P. Zaugg, J. Phys. A {\bf 28} (1995) 2589]. We provide explicite prescription for contraction of $a, b, c$ and $d$ generators of $SL_q(2)$ and arrive at $^*$ Hopf algebra $E_κ(2)$.

A. Molev

A simple proof of the higher Capelli identities is given.

Martin-Daniel Lacasse, Gary S. Grest, Dov Levine, T. G. Mason

We present a new model to describe the unusual elastic properties of compressed emulsions. The response of a single droplet under compression is investigated numerically for different Wigner-Seitz cells. The response is softer than harmonic, and depends on the coordination number of the droplet. Using these results, we propose a new effective inter-droplet p

Martin-Daniel Lacasse, Gary S. Grest, Dov Levine

We investigate the elastic properties of small droplets under compression. The compression of a bubble by two parallel plates is solved exactly and it is shown that a lowest-order expansion of the solution reduces to a form similar to that obtained by Morse and Witten. Other systems are studied numerically and results for configurations involving between 2 a

John E. McCarthy

A classical proof of Pisier&#39;s construction of a polynomially bounded operator not similar to a contraction is given.

R. P. Lano

The gravitational analogue of the electromagnetic Meissner effect is investigated. Starting from the post-Newtonian approximation to general relativity we arrive at gravitational London equations, predicting a gravitational Meissner effect. Applied to neutron stars we arrive at a London penetration depth of 12km, which is about the size of a neutron star.

I. N. Kondrashuk, A. V. Kotikov

It is found that the recently published first coefficient of nonzero $β$-function for the Chern-Simons term in the $1/N$ expansion of the $CP^{N-1}$ model is untrue numerically. The correct result is given. The main conclusions of Park&#39;s paper are not changed.

Konstantin Selivanov

The infrared behaviour of the $ϕ^3$-theory is discussed stressing analogies with the Witten-Seiberg story about $N=2$ $QCD$. Though the microscopic theory is apparently not integrable, the effective theory is shown to be integrable at classical level, and a general solution of it in terms of hypergeometric functions is obtained. An effective theory for the m

Katsushi Ito, Sung-Kil Yang

The Picard-Fuchs equations for $N=2$ supersymmetric $SU(N_{c})$ Yang-Mills theories with massless hypermultiplets are obtained for $N_{c}=2$ and $3$. For $SU(2)$ we derive the non-linear differential equations for the prepotentials and calculate full non-perturbative corrections to the effective gauge coupling constant in the weak and strong coupling regions

H. Grosse, C. Klimcik, P. Presnajder

A construction of supersymmetric field-theoretical models in non-commutative geometry is reviewed. The underlying superstructure of the models is encoded in $osp(2,2)$ superalgebra.

J. Bolz, P. Kroll

Current light-cone wave functions for the nucleon are unsatisfactory since they are in conflict with the data of the nucleon&#39;s Dirac form factor at large momentum transfer. Therefore, we attempt a determination of a new wave function respecting theoretical ideas on its parameterization and satisfying the following constraints: It should provide a soft Fe

Axel Saalfeld, Andreas Schafer

We present a Monte Carlo (MC) study of $W^{\pm}$ and $Z_{0}$ production of longitudinally polarized proton collisions at a center of mass (CMS) energy of $500\,{\rm GeV}$. All results were obtained with the SPHINX MC code. We consider two different types of polarized parton distributions with large and small gluon polarization. Various spin asymmetries are f

A. Le Yaouanc, L. Oliver, O. Pène, J. -C. Raynal

The heavy mass limit of quark models based on the Bakamjian-Thomas cons\-truction reveals remarkable features. In addition to previously demonstrated properties of covariance and Isgur-Wise scaling, exact duality, leading to the Bjorken-Isgur-Wise sum rule, is proven, for the first time to our knowledge in relativistic quark models. Inelastic as well as elas

Elvio Di Salvo

We show that the Gottfried and the Bjorken integrals have the same nonperturbative evolution, which is related to the gluon polarization in the proton.

M. Genovese, N. N. Nikolaev, B. G. Zakharov

We develop the pQCD description of diffraction excitation of heavy flavours in DIS and we derive the analytic formulas for the mass spectrum in leading log$m_f^{2}$. The result illustrates nicely non-factorization properties of the QCD pomeron. We predict a very steep rise of the charm content of diffraction dissociation of photons at small $x_{\Pom}$. We ev

K. C. Chou, Yue-Liang Wu

Assuming universality of Yukawa coupling of the superpotential and maximal spontaneous CP violation, fermion masses and mixing angles including that of neutrinos are studied in an SUSY SO(10)$\times Δ(48)\times$ U(1) model with small $\tan β$. The low energy parameters of the standard model are determined solely by the Clebsch factors of the symmetry group a

Michael H. Seymour

We calculate the mean number of subjets in quark and gluon jets in the final state of e^+e^- annihilation. Since `quark&#39; and `gluon&#39; jets are scheme-dependent objects, we stress the importance of using the same definition as in experimental analyses. We define the jets using the k_perp algorithm at a coarse scale y_1, and the subjets using a finer sc

A. Capella, B. Z. Kopeliovich

When a diquark does not fragment directly but breaks in such a way that only one of its quarks gets into the produced baryon, the latter is produced closer to mid rapidities. The relative size of this diquark breaking component increases quite fast with increasing energy. We show that at a given energy it also increases with the atomic mass number and with t

V. Bernard, N. Kaiser, Ulf-G. Meißner

We calculate the one--loop corrections to the Kroll--Ruderman low--energy theorems for charged pion photoproduction in the framework of heavy baryon chiral perturbation theory. We predict the threshold S--wave multipole $E_{0+}$ to be $E_{0+}^{\rm thr}(γp \to π^+ n) = ( 28.2 \pm 0.6 )\cdot 10^{-3}/M_π$ and $E_{0+}^{\rm thr} (γn \toπ^- p) = ( -32.7 \pm 0.6 )\

V. V. Anisovich, A. V. Sarantsev

K-matrix analysis of the $00^{++}$ wave is performed in the channels $ππ,~K\bar K,~ηη$ and $4π$ in the mass region up to 1550 MeV. The fit is based on the following data: $p\bar p ~(at~rest)\to π^0π^0π^0$, $π^0π^0η,~π^0ηη$ [1,2], $πN\to ππN$ [3,4], $πN\to K\bar K N$ [5] and the inelastic cross section of the $ππ$ interaction [6]. Simultaneous analysis of the

Cong-Feng Qiao, Chong Sheng Li, Kuang-Ta Chao

For top quark decays into heavy quark mesons $Υ$ and $\bar{B}_c^*$ , a complete calculation to the leading order both in QCD coupling constant $α_s$ and in $v$, the typical velocity of the heavy quarks inside the mesons, is performed. Relatons between the top quark mass and the decay branching ratios are studied. Comparion with the results which are obtained

Cong-feng Qiao, Han-Wen Huang, Kuang-Ta Chao

The reduced Bethe-Salpeter equation with scalar confinement and vector gluon exchange is applied to quark-antiquark bound states. The so called intrinsic flaw of Salpeter equation with static scalar confinement is investigated. The notorious problem of narrow level spacings is found to be remedied by taking into consideration the retardation effect of scalar

Kang Young Lee, Jae Kwan Kim

We test the parton model approach to inclusive $B \ra γX_s$ and $B \ra e \barν X_u$ processes by calculating a few moments of the distribution function. The $1/m_Q$ expansion of $b$-quark distribution function is discussed. We show that Peterson&#39;s fragmentation function is useful as the distribution function of $b$-quark but requires some improvements. B

Rodolfo Gambini, Jorge Pullin

We suggest how to interpret the action of the quantum Hamiltonian constraint of general relativity in the loop representation as a skein relation on the space of knots. Therefore, by considering knot polynomials that are compatible with that skein relation, one guarantees that all the quantum Einstein equations are solved. We give a particular example of suc

S. Massar, R. Parentani

We argue that the analysis of transients, of decoherence effects, or of any breaking of the exact boost invariance of the Ernst metric shows that uniformly accelerated black holes do emit an energy flux given by the Doppler-shifted Hawking radiation, in perfect {\it agreement} to what happens for accelerated particles.

G. Rudolph, T. Tok

A class of $ G $-invariant Einstein-Yang-Mills (EYM) systems with cosmological constant on homogeneous spaces $ G / H $, where $ G $ is a semisimple compact Lie group, is presented. These EYM--systems can be obtained in terms of dimensional reduction of pure gravity. If $ G / H $ is a symmetric space, the EYM--system on $ G / H $ provides a static solution o

H. Castella, X. Zotos

We study numerically the finite temperature and frequency mobility of a particle coupled by a local interaction to a system of spinless fermions in one dimension. We find that when the model is integrable (particle mass equal to the mass of fermions) the static mobility diverges. Further, an enhanced mobility is observed over a finite parameter range away fr

Sitangshu Bikas Santra, Stefan Schwarzer, Hans Herrmann

We perform a two-dimensional molecular-dynamics study of a model for sheared bidisperse granular systems under conditions of simple shear and Poiseuille flow. We propose a mechanism for particle-size segregation based on the observation that segregation occurs if the viscous length scale introduced by a liquid in the system is smaller than of the order of th

D. L. Shepelyansky

It is shown that two repulsing / attracting particles in a random potential can propagate coherently on a distance much larger than one-particle localization length without interaction. In dimension $d$ this leads to delocalization of pairs formed by two repulsing / attracting particles. The results of numerical simulations allow to understand some specific

Maya Paczuski, Stefan Boettcher

The propagator for the activity in a broad class of self-organized critical models obeys an imaginary-time Schrödinger equation with a nonlocal, history-dependent potential representing memory. Consequently, the probability for an avalanche to spread beyond a distance $r$ in time $t$ has an anomalous tail $\exp{[-C\,x^{1/(D-1)}]}$ for $x=r^D/t \gg 1$ and $D>

J. Ranninger, J. M. Robin

The normal state behaviour of the density of states of the electrons described by the BOSON - FERMION model for Bose-Einstein condensation driven superconductivity is characterized by the appearence of a pseudogap which developes into a true gap upon lowering the temperature and the superconducting critical temperature is approached. The consequences of this

David Iñiguez, Giorgio Parisi, Juan J. Ruiz-Lorenzo

We have carried out numerical simulations of the three-dimensional Ising spin glass model with first neighbour Gaussian couplings using three replicas for each sample of couplings. We have paid special attention to the measure of two types of Binder cumulant that can be constructed from the three possible overlaps between the replicas. We obtain new informat

K. Hallberg, X. Q. G. Wang, P. Horsch, A. Moreo

Using the density-matrix renormalization-group technique we study the long-wavelength properties of the spin S=3/2 nearest-neighbor Heisenberg chain. We obtain an accurate value for the spin velocity v=3.8+- 0.02, in agreement with experiment. Our results show conclusively that the model belongs to the same universality class as the S=1/2 Heisenberg chain, w

J. Jaklic, P. Prelovsek

Several thermodynamic quantities within the planar $t-J$ model are calculated using the $T>0$ Lanczos method on clusters of up to 26 sites. Hole density $c_h(μ,T)$ shows a non-Fermi liquid behavior as a function of $T$ and suggests a transition from small to large Fermi surface at $c_h\sim 0.15$. Specific heat reveals a maximum at the exchange energy-scale u

S. Krompiewski, F. Süss, U. Krey

First-principles calculations have been performed in order to determine effective exchange integrals between {\it strongly} and {\it weakly} exchange-coupled Co monolayers in certain modulated periodic $CoCu_2/CoCu_n$-type superlattices with three non-equivalent Co planes, which have not yet been studied hitherto. For $3\le n\le 6$ we find that the two non-e

J. Moreno, P. Coleman

Conventional approaches to thermal conductivity in itinerant systems neglect the contribution to thermal current due to interactions. We derive this contribution to the thermal current and show how it produces important corrections to the thermal conductivity in anisotropic superconductors. We discuss the possible relevance of these corrections for the inter

Ian Affleck, Bertrand I. Halperin

A recently proposed renormalization group approach to dimensional crossover in quasi-one-dimensional quantum antiferromagnets is improved and then shown to give identical results, in some cases, to those obtained earlier.

Rolf Schwitter, Norbert E. Fuchs

Deriving formal specifications from informal requirements is difficult since one has to take into account the disparate conceptual worlds of the application domain and of software development. To bridge the conceptual gap we propose controlled natural language as a textual view on formal specifications in logic. The specification language Attempto Controlled

Fritz Haake, Marek Kuś, Hans--Jürgen Sommers, Henning Schomerus

We consider the characteristic polynomials of random unitary matrices $U$ drawn from various circular ensembles. In particular, the statistics of the coefficients of these polynomials are studied. The variances of these ``secular coefficients&#39;&#39; are given explicitly for arbitrary dimension and continued analytically to arbitrary values of the level re

D. Friedli, H. Wozniak, M. Rieke, L. Martinet

We present detailed JHK surface photometry with ellipse fits of 13 galaxies selected from previous optical observations as likely candidates for having a secondary bar or a triaxial bulge within the primary bar. We have found 7 double-barred galaxies, 3 double-barred galaxies with an additional intermediate structure with twisted isophotes, and 3 galaxies wi

B. F. Roukema

Hot big bang cosmology says nothing about the topology of the Universe. A topology-independent algorithm is presented which is complementary to that of Lehoucq et al. 1996 and which searches for evidence of multi-connectedness using catalogues of astrophysically observed objects. The basis of this algorithm is simply to search for a quintuplet of quasars (ov

Dario Grasso, Edward W. Kolb

The magnetic moment of tau neutrinos in the MeV mass range may be large enough to modify the cosmological freeze-out calculation and determine the tau-neutrino relic density. In this paper we revisit such a possibility. We calculate the evolution and freeze-out of the tau neutrino number density as a function of its mass and magnetic moment. We then determin

G. Squires, D. M. Neumann, N. Kaiser, M. Arnaud

We report on the detection of dark matter in the cluster of galaxies Abell~2163 using the weak gravitational distortion of background galaxies, and an analysis of the cluster X-ray emission. We find that while the qualitative distributions of the cluster light and the dark matter are similar -- shallow and extended, with significant substructure -- the X-ray

R. N. Mohapatra, Vigdor L. Teplitz

The idea of the universe with a mirror sector having all particles and forces identical to those in the familiar sector has been proposed in the context of neutrino physics as well as superstring theories. Assuming that all the quark and charged lepton masses in the mirror universe are scaled by a common factor, $ζ$, as is required in one interpretation of t

Vicent J. Martinez, Maria Jesus Pons-Borderia

We introduce the unbiased way statisticians look at the 2--point correlation function and study its relation to multifractal analysis. We apply this method to a simulation of the distribution of galaxy clusters in order to check the dependence of the correlation dimension on the cluster richness.

M. Pohl

Here we review our current knowledge on diffuse gamma-rays from galactic halos. Estimates of the relative contribution of the various emission processes at low and high latitudes are compared to the data over 6 decades in energy. The observed spectral shape differs from what was expected, especially at ver low and very high energies. In the latter case, abov

G. Raffelt, D. Seckel, G. Sigl

In a nuclear medium, spin-dependent forces cause the nucleon spins to fluctuate with a rate $Γ_σ$. We have previously shown that as a consequence the effective axial-current neutrino-nucleon scattering cross section is reduced. Here, we calculate this reduction explicitly in the perturbative limit $Γ_σ\ll T$. By virtue of an exact sum rule of the spin-densit

S. Junqueira, F. Combes

We report the results of self-gravitating simulations of spiral galaxies, modeled by stellar and gaseous components, developed to investigate in particular the role of dissipation in the evolution of galaxy disks. The gas disk is simulated by the Beam-Scheme method, where it is considered as a self-gravitating fluid. The results suggest that the gravitationa

Oleg Y. Gnedin, Jeremiah P. Ostriker

We investigate the dynamical evolution of the Galactic Globular Cluster System in considerably greater detail than has been done hitherto, finding that destruction rates are significantly larger than given by previous estimates. More than half of the present clusters (52%-58% for the OC galactic model, and 75%-86% for the BSS model) will be destroyed in the

L. A. Balona, T. Böhm, B. H. Foing, K. K. Ghosh

We present data from high-dispersion echelle spectra and simultaneous $uvby$ photometry for $γ$~Doradus. These data were obtained from several sites during 1994 November as part of the MUSICOS-94 campaign. The star has two closely-spaced periods of about 0.75 d and is the brightest member of a new class of variable early F-type stars. A previously suspected

M. I. Ayzatsky

Analytical solution of precise equations that describe the rf-coupling of two cavities through a co-axial cylindrical hole are given for various limited cases. For their derivation we have used the method of solution of an infinite set of linear algebraic equations, based on its transformation into dual integral equations.

M. I. Ayzatsky

This work presents research results on a novel analytical model of electromagnetic systems coupling through small size holes. The key problem regarding coupling of two cavities through an aperture in separating screen of finite thickness without making assumption on smallness of any parameters is considered. We are the first to calculate on the base of rigor

M. I. Ayzatsky

This paper presents the results of studies in elaboration of a mathematical model of the cavity-chain slow wave structures. Considered is the problem of coupling of an infinitely long cylindrical cavity chain coupled through centerholes in the dividing walls of finite thickness without the assumption about smallness of any parameters. On the basis of a rigor

Tin-Lun Ho, V. B. Shenoy

The Bose-Einstein condensates of alkali atomic gases are spinor fields with local ``spin-gauge&#34; symmetry. This symmetry is manifested by a superfluid velocity ${\bf u}_{s}$ (or gauge field) generated by the Berry phase of the spin field. In ``static&#34; traps, ${\bf u}_{s}$ splits the degeneracy of the harmonic energy levels, breaks the inversion symmet

Sanghyeon Chang, Claudio Coriano, Alon E. Faraggi

Perturbative gauge coupling unification in realistic superstring models suggests the existence of additional heavy down-type quarks, beyond the minimal supersymmetric standard model. The mass scale of the heavy down-type quarks is constrained by requiring agreement between the measured low energy gauge parameters and the string-scale gauge coupling unificati

Melissa A. Lampert, John F. Dawson, Fred Cooper

We examine the non-equilibrium time evolution of the hadronic plasma produced in a relativistic heavy ion collision, assuming a spherical expansion into the vacuum. We study the $O(4)$ linear sigma model to leading order in a large-$N$ expansion. Starting at a temperature above the phase transition, the system expands and cools, finally settling into the bro

U. Heinz, B. Tomasik, U. A. Wiedemann, Y. -F. Wu

We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the two-particle correlation function for azimuthally symmetric expanding sources. We derive model-independent expressions for the YKP fit parameters and discuss their physical interpretation. We use them to evaluate the YKP fit parameters and their momentum dependence for a simple model for th

R. Pittau

In this paper, I study final state QCD radiative corrections to off-shell single top production via decaying $W$ at hadron collider energies. The tree level Breit-Wigner distribution of the produced top invariant mass is distorted by final state QCD radiation, while the peak position remains unchanged. The exact one loop QCD calculation and the narrow width