February 1997 arXiv papers — page 5

A. Lorek, W. Weich, J. Wess

A noncommutative *-algebra that generalizes the canonical commutation relations and that is covariant under the quantum groups SOq(3) or SOq(1,3) is introduced. The generating elements of this algebra are hermitean and can be identified with coordinates, momenta and angular momenta. In addition a unitary scaling operator is part of the algebra.

Ioan Kosztin, Byron Faber, Klaus Schulten

A self-contained and tutorial presentation of the diffusion Monte Carlo method for determining the ground state energy and wave function of quantum systems is provided. First, the theoretical basis of the method is derived and then a numerical algorithm is formulated. The algorithm is applied to determine the ground state of the harmonic oscillator, the Mors

Reha V. Cakmur, David A. Egolf, Brendan B. Plapp, Eberhard Bodenschatz

For Rayleigh-Benard convection in a square cell with a fluid of Prandtl number one, we report experimental results on the transition between a stationary pattern of ideal straight rolls (ISR) and the spatiotemporal chaotic state of spiral defect chaos (SDC). In contrast to experiments in circular geometries, we found ISR states below a particular value of th

A. B. Balantekin, C. A. Bertulani, M. S. Hussein

We study the effect of vacuum polarization in nuclear reactions of astrophysical interest. This effect has the opposite sign compared to the screening by the atomic electrons. It is shown that vacuum polarization further increases the longstanding differences between the experimental data of astrophysical nuclear reactions at very low energies and the theore

P. E. Knowles, A. Adamczak, J. M. Bailey, G. A. Beer

Muon catalyzed fusion in deuterium has traditionally been studied in gaseous and liquid targets. The TRIUMF solid-hydrogen-layer target system has been used to study the fusion reaction rates in the solid phase of D_2 at a target temperature of 3 K. Products of two distinct branches of the reaction were observed; neutrons by a liquid organic scintillator, an

Alejandro Adem

We use buildings and group extensions to compute lower bounds on the top Betti numbers for the cohomology of the level p congruence subgroups of SL(3,Z) and Sp(4,Z).

Christos A. Athanasiadis, Svante Linusson

The Shi arrangement ${\mathcal S}_n$ is the arrangement of affine hyperplanes in ${\mathbb R}^n$ of the form $x_i - x_j = 0$ or $1$, for $1 \leq i < j \leq n$. It dissects ${\mathbb R}^n$ into $(n+1)^{n-1}$ regions, as was first proved by Shi. We give a simple bijective proof of this result. Our bijection generalizes easily to any subarrangement of ${\mathca

Charles Miller, Michael Shapiro

The arguments of Cannon, Floyd, Grayson and Thurston showing that solve geometry groups are not almost convex also show that solvable Baumslag-Solitar groups are not almost convex.

A. Herrera, O. Kechkin

The Kähler formulation of 5-dimensional Einstein-Kalb-Ramond (EKR) theory admitting two commuting Killing vectors is presented. Three different Kramer-Neugebauer-like maps are established for the 2-dimensional case. A class of solutions constructed on the double Ernst one is obtained. It is shown that the double Kerr solution corresponds to a EKR dipole conf

Ivan G. Avramidi, Giampiero Esposito

A key problem in the attempt to quantize the gravitational field is the choice of boundary conditions. These are mixed, in that spatial and normal components of metric perturbations obey different sets of boundary conditions. In the covariant quantization scheme this leads to a boundary operator involving both normal and tangential derivatives of metric pert

C. Bagnuls, C. Bervillier

We shortly illustrate how the field-theoretic approach to critical phenomena takes place in the more complete Wilson theory of renormalization and qualitatively discuss its domain of validity. By the way, we suggest that the differential renormalization functions (like the beta-function) of the perturbative scalar theory in four dimensions should be Borel su

Yu. A. Sitenko

We consider an analogue of the Aharonov-Bohm effect in quantum field theory: the fermionic vacuum attains nontrivial quantum numbers in the background of a magnetic vortex even in the case when the spatial region of nonvanishing external field strength is excluded. The dependence of the vacuum quantum numbers on the value of the vortex flux and the choice of

E. T. Tomboulis

We investigate 4-dim gauge theories and gravitational theories with nonpolynomial actions containing an infinite series in covariant derivatives of the fields representing the expansion of a transcendental entire function. A class of entire functions is explicitly constructed such that: (i) the theory is perturbatively superrenormalizable; (ii) no (gauge-inv

Stephen L. Adler

We show that our recent SU(4) generalized ``rishon&#39;&#39; composite model for quarks and leptons, augmented either by the hypothesis of breaking of color SU(3) to ``glow&#39;&#39; SO(3), or by the hypothesis of incomplete color neutralization in very hard processes, leads to an interpretation of the HERA positron-jet events as the production by color gluo

Chris Barnes, Neil Turok

We investigate the observable consequences of creating cosmic texture by breaking a global SU(3) symmetry, rather than the SU(2) case which is generally studied. To this end, we study the nonlinear sigma model for a totally broken SU(3) symmetry, and develop a technique for numerically solving the classical field equations. This technique is applied in a cos

Frithjof Karsch, Andras Patkos, Peter Petreczky

A new perturbative scheme is proposed for the evaluation of the free energy density of field theories at finite temperature. The screened loop expansion takes into account exactly the phenomenon of screening in thermal propagators. The approach is tested in the N-component scalar field theory at 2-loop level and also at 3-loop in the large N limit. The pertu

Matthias Neubert

We review the theory and phenomenology of heavy-quark symmetry, exclusive weak decays of B mesons, inclusive decay rates and lifetimes of b hadrons.

Stefan Groote

This talk presents details of the calculation of two-loop corrections to heavy baryon currents containing one heavy quark in leading order of the $1/m_Q$-expansion, i.e. in the limit of Heavy Quark Symmetry (HQS). The calculations lead to the determination of the anomalous dimension of these currents. I also discuss problems with different $γ_5$-schemes and

A. Hebecker

Recently, a semiclassical approach to diffraction has been proposed, which treats the proton as a classical colour field. The present paper demonstrates that this approach is consistent with the concept of diffractive parton distributions. The diffractive quark and gluon distributions are expressed through integrals of non-Abelian eikonal factors in the fund

M. A. Reyes

Results are presented of the spin-parity analysis on a sample of centrally produced mesons in the reaction (p p -> p_{slow} K_s K_s p_{fast}) with 800 GeV protons on liquid hydrogen. The spin-parity analysis in the mass region between threshold and 1.58 GeV/c^2 shows that the (K_s K_s) system is produced mainly in S-wave. The f_0(1500) is clearly observed in

Francois Goy

The transmission time of an electromagnetic signal in the vicinity of the earth is calculated to c-2 and contains an orbital Sagnac term. On earth, the synchronisation of the Barycentric Coordinate Time (TCB) can be realised by atomic clocks, but not the one of Geocentric Coordinate Time (TCG). The principle of equivalence is discussed.

Ulf S. Nilsson, C. Uggla

Einstein&#39;s field equations for stationary Bianchi type II models with a perfect fluid source are investigated. The field equations are rewritten as a system of autonomous first order differential equations. Dimensionless variables are subsequently introduced for which the reduced phase space is compact. The system is then studied qualitatively using the

Sukanta Bose, Leonard Parker, Yoav Peleg

In this work, we extend the analysis of Brown and York to find the quasilocal energy in a spherical box in the Schwarzschild spacetime. Quasilocal energy is the value of the Hamiltonian that generates unit magnitude proper-time translations on the box orthogonal to the spatial hypersurfaces foliating the Schwarzschild spacetime. We call this Hamiltonian the

J. J. Palacios, H. A. Fertig

We present a theoretical study of the $I-V$ tunneling characteristic between two parallel two-dimensional electron gases in a perpendicular magnetic field when both are near filling factor $ν=1$. Finite-size calculations of the single-layer spectral functions in the spherical geometry and analytical expressions for the disk geometry in the thermodynamic limi

David Pines

I describe recent theoretical and experimental progress in understanding the physical properties of the two dimensional nearly antiferromagnetic Fermi liquids (NAFL&#39;s) found in the normal state of the cuprate superconductors. In such NAFL&#39;s, the magnetic interaction between planar quasiparticles is strong and peaked at or near the commensurate wave v

T. P. Devereaux, A. P. Kampf

A theory for electronic Raman scattering in the cuprate superconductors is presented with a specific emphasis on the polarization dependence of the spectra which can infer the symmetry of the energy gap. Signatures of the effects of disorder on the low frequency and low temperature behavior of the Raman spectra for different symmetry channels provide detaile

G. Hackenbroich, W. D. Heiss, H. A. Weidenmueller

We extend the theory of Coulomb blockade oscillations to quantum dots which are deformed by the confining potential. We show that shape deformations can generate sequences of conductance resonances which carry the same internal wavefunction. This fact may cause strong correlations of neighboring conductance peaks. We demonstrate the relevance of our results

O. Schapiro, P. J. Kuntz, K. Möhring, P. A. Hervieux

We discuss the role and the treatment of polarization effects in many-body systems of charged conducting clusters and apply this to the statistical fragmentation of Na-clusters. We see a first order microcanonical phase transition in the fragmentation of $Na^{Z+}_{70}$ for Z=0 to 8. We can distinguish two fragmentation phases, namely evaporation of large par

K. Harigaya

Nonlinear optical properties of extracted higher fullerenes - C70, C76, C78, and C84 - are theoretically investigated. Magnitudes of off-resonant third-harmonic-generation are calculated by the intermediate exciton theory. We find that optical nonlinearities of higher fullerenes are a few times larger than those of C60. The magnitudes of nonlinearity tend to

Dimitar D. Sasselov

Gravitational microlensing is not achromatic when the star being microlensed is resolved by the lens. We show how narrow-band photometry and moderate- to high-resolution spectroscopy can be used to reconstruct the stellar surface intensity distribution of a microlensed star. Such microlens imaging can provide a unique opportunity to study the surfaces of nor

C. M. Gutierrez, S. Hancock, R. D. Davies, R. Rebolo

We present observations at 10 and 15 GHz taken with the Tenerife experiments in a band of the sky at Dec.=+35 degrees. These experiments are sensitive to multipoles in the range l=10-30. The sensitivity per beam is 56 and 20 microK for the 10 and the 15 GHz data, respectively. After subtraction of the prediction of known radio-sources, the analysis of the da

J. P. Gardner, R. M. Sharples, C. S. Frenk, B. E. Carrasco

We present the first determination of the near-infrared K-band luminosity function of field galaxies from a wide field K-selected redshift survey. The best fit Schechter function parameters are $M^* = -23.12 +5log(h)$, $α= -0.91$, and $ϕ^* = 1.66 \times 10^{-2} h^3 ~ Mpc^{-3}$. We estimate that systematics are no more than 0.1 mag in $M^*$ and 0.1 in $α$, wh

Martine Mouchet, Jean-Marc Bonnet-Bidaud, Nicolai Somov, Tania Somova

We present the results of fast temporal optical spectroscopy and photometry of the AM Her type system BY Cam obtained in February 1990 and March 1991. Emission line profiles show a complex structure and are strongly variable. The radial velocity studies of a sharp component detected in Balmer lines in March confirms the non-synchronism of the system. Differe

C. Megan Urry

The multiwavelength spectra of blazars appear to be dominated by nonthermal emission from a relativistic jet oriented close to the line of sight. The recent detection of many blazars at gamma-ray energies strongly supports this scenario. High quality multiwavelength monitoring data for the brightest one or two blazars suggest the optical through X-ray contin

Klaus J&#34;ager, Klaus J. Fricke, Jochen Heidt

We outline our recently started program to investigate the galaxy environment of QSOs, in particular of radio-quiet objects at intermediate redshifts.

Misao Sasaki, Takahiro Tanaka, Yoshihiro Yakushige

We calculate the spectrum of large angle cosmic microwave background (CMB) anisotropies due to quantum fluctuations of the gravitational wave modes in one-bubble open inflation models. We find the bubble-wall fluctuation modes, which had been thought to exist discretely in previous analyses, are actually contained in the continuous spectrum of gravitational

Myeong-Gu Park, J. Richard Gott

In a flat, k=0 cosmology with galaxies that approximate singular isothermal spheres, gravitational lens image separations should be uncorrelated with source redshift. But in an open k=-1 cosmology such gravitational lens image separations become smaller with increasing source redshift. The observed separations do become smaller with increasing source redshif

Erik M. Gregersen, Neal J. Evans, Shudong Zhou, Minho Choi

We have observed 23 Class 0 sources in the HCO+ J=4-3 and 3-2 lines. The mean bolometric temperature of the 16 sources with well-determined values is 44 K and the mean luminosity is 5.7 L_sun, excluding two sources of considerably higher luminosity. Nine sources, including three sources previously suggested to be collapsing, have the correct (blue) spectral

Alberto Alzati, Marina Bertolini, Gian Mario Besana

In Butler, J.Differential Geom. 39 (1):1--34,1994, the author gives a sufficient condition for a line bundle associated with a divisor D to be normally generated on $X=P(E)$ where E is a vector bundle over a smooth curve C. A line bundle which is ample and normally generated is automatically very ample. Therefore the condition found in Butler&#39;s work, tog

K. Martins, D. Blaschke

We investigate a scenario where conditions for Mott dissociation of charmonium are fulfilled locally in ultrarelativistic heavy ion collisions at the short time scales before hadronization and study possible consequences to be drawn from observation of ``anomalous&#39;&#39; thresholds in the J/ψsuppression pattern. We suggest that for a compilation of experi

Wayne Hu, Martin White

A total angular momentum representation simplifies the radiation transport problem for temperature and polarization anisotropy in the CMB. Scattering terms couple only the quadrupole moments of the distributions and each moment corresponds directly to the observable angular pattern on the sky. We develop and employ these techniques to study the general prope

Antonio H. Castro Neto

We study the problem of phase coherence in doped striped cuprates. We assume the stripes to form a network of one-dimensional Luttinger liquids which are dominated by superconducting fluctuations and pinned by impurities. The problem of phase coherence is discussed. We study the dynamics of the superconducting phase using a model of resistively shunted junct

H. Nunokawa, J. T. Peltoniemi, A. Rossi, J. W. F. Valle

We discuss the effects of resonant $ν_e \to ν_s$ and $\barν_e \to \barν_s$ ($ν_s$ is a sterile neutrino) conversions in the dense medium of a supernova. In particular, we assume the sterile neutrino $ν_s$ to be in the hot dark matter few eV mass range. The implications of such a scenario for the supernova shock re-heating, the detected $\barν_e$ signal from

Brian Lee, Carl Akerlof, David Band, Scott Barthelmy

The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) has searched for contemporaneous optical counterparts to gamma ray bursts (GRBs) using an automated rapidly slewing wide field of view optical telescope at Lawrence Livermore National Laboratory. The telescope was triggered in real time by the Burst And Transient Source Experiment (BATSE) data tele

Frank Wilczek

In the first part of the talk, I give a low-resolution overview of the current state of particle physics - the triumph of the Standard Model and its discontents. I review and re-endorse the remarkably direct and (to me) compelling argument that existing data, properly interpreted, point toward a unified theory of fundamental particle interactions and toward

H. Niggemann, A. Klümper, J. Zittartz

Optimum ground states are constructed in two dimensions by using so called vertex state models. These models are graphical generalizations of the well-known matrix product ground states for spin chains. On the hexagonal lattice we obtain a one-parametric set of ground states for a five-dimensional manifold of S=3/2 Hamiltonians. Correlation functions within

T. A. Ivanova

Infinite-dimensional algebras of hidden symmetries of the self-dual Yang-Mills equations are considered. A current-type algebra of symmetries and an affine extension of conformal symmetries introduced recently are discussed using the twistor picture. It is shown that the extended conformal symmetries of the self-dual Yang-Mills equations have a simple descri

V. A. Saleev

In the framework of the perturbative QCD and the diquark model of baryons we have obtained the fragmentation functions for heavy quark that split into polarized Lambda_b baryons. We predict the longitudinal polarization asymmetry for the prompt Lambda_b produced in electron-positron annihilation at the Z resonance and estimate the spin-1/2 and spin-3/2 beaut

Daniel L. Miller

Free electron approximation for electron states in poly($p$-phenylene vinylene) and other conjugated systems is developed. It provides simple and clear analytical expressions for energies of electron states and for wave functions. The results are in quantitative agreement with experiments. Our model does not contain fitting parameters. We present two example

Y. Saito, K. Takemura, D. Uglov

Recently Varagnolo and Vasserot established that the q-deformed Fock spaces due to Hayashi, and Kashiwara, Miwa and Stern, admit actions of the quantum toroidal algebra $U_q(sl_n,tor)$ (n > 2) with the level (0,1). In the present article we propose a more detailed proof of this fact then the one given by Varagnolo and Vasserot. The proof is based on certain

F. Hasenbalg, D. Abriola, J. I. Collar, D. E. Di Gregorio

We report on new estimates of the modulation expected in semiconductor detectors due to eclipsing of dark matter particles in the Earth. We reevaluate the theoretical modulation significances and discuss the differences found with previous calculations. We find that a significantly larger statistics than previously estimated is needed to achieve the same lev

Ana Achucarro, Julian Borrill, Andrew R Liddle

We present a toy model for the investigation of the formation of semilocal strings, where a planar symmetry is employed to reduce the system to two dimensions. We approximate the symmetry breaking using an extension of the Vachaspati-Vilenkin algorithm, where we throw down random phases for the scalar fields and then find the gauge field configuration which

R. Casalbuoni

In this paper we consider the problem of quantizing theories defined over configuration spaces described by non-commuting parameters. If one tries to do that by generalizing the path-integral formalism, the first problem one has to deal with is the definition of integral over these generalized configuration spaces. This is the problem we state and solve in t

A. N. Gorban, Yu. I. Shokin, V. I. Verbitskii

One of shortcomings of stepwise interval methods is the following. The intervals determining the solution of a system are often expanded in the course of time irrespective of the method and step used (the {\em Moore effect}). We introduce the notion of general {\em interval spaces} and study the infinitesimal Moore effect (IME) in these spaces. We obtain the

Rong-Gen Cai, Y. S. Myung

The black hole solutions in the higher dimensional Brans-Dicke-Maxwell theory are investigated. We find that the presence of the nontrivial scalar field depends on the spacetime dimensions (D). When D=4, the solution corresponds to the Reissner-Nordström black hole with a constant scalar field. In higher dimensions (D>4), one finds the charged black hole sol

S. Kumano

1. Introduction 2. Possible violation of the Gottfried sum rule 2.1 Gottfried sum rule 2.2 Early experimental results 2.3 NMC finding and recent progress 2.4 Small $x$ contribution 2.5 Nuclear correction: shadowing in the deuteron 2.6 Parametrization of antiquark distributions 3 Expectations in perturbative QCD 3.1 Operator product expansion 3.2 Perturbative

Takayuki Matsuki, Toshiyuki Morii

Operating just once with the naive Foldy-Wouthuysen-Tani transformation on the relativistic Fermi-Yang equation for $Q\bar q$ bound states described by the semi-relativistic Hamiltonian which includes Coulomb-like as well as confining scalar potentials, we have calculated heavy meson mass spectra of D and B together with higher spin states. Based on the form

Won Young Hwang, In Gyu Koh, Yeong Deok Han

We discuss the unambiguous measurement of quantum nonorthogonal states in connection with the quantum cryptography. We show that checking a ratio of null one to signal is essential in detecting a certain kind of eavesdropping in the case of two nonorthogonal states quantum cryptography. We prove that it is not needed in the case of the four states quantum cr

I. I. Mazin, D. J. Singh

The magnetic properties of (Ca,Sr)RuO_3 and Sr_2YRuO_6 are studied within the context of band structure based Stoner theory. LSDA calculations without recourse to strong correlation effects yield the correct magnetic behavior and order in all cases. Insulating character of Sr_2YRuO_6 is reproduced. The different magnetic states of SrRuO_3 and CaRuO_3 are sho

M. Zaldarriaga, D. Spergel, U. Seljak

We use a high-accuracy computational code to investigate the precision with which cosmological parameters could be reconstructed by future cosmic microwave background (CMB) experiments, in particular the two satellite missions MAP and Planck Surveyor (COBRAS/SAMBA). We identify several parameter combinations that could be determined with a few percent accura

I. G. Korepanov

This paper adds two observations to the work solv-int/9701016 where some eigenstates for a model based on tetrahedron equation have been constructed. The first observation is that there exists a more &#34;algebraic&#34; construction of one-particle states, resembling the 1+1-dimensional algebraic Bethe ansatz. The second observation is that the strings intro

W. M. Itano, C. Monroe, D. M. Meekhof, D. Leibfried

Experiments are described in which a single, harmonically bound, beryllium ion in a Paul trap is put into Fock, thermal, coherent, squeezed, and Schroedinger cat states. Experimental determinations of the density matrix and the Wigner function are described. A simple calculation of the decoherence of a superposition of coherent states due to an external elec

Ioan Kosztin, Klaus Schulten

The boundary integral method for calculating the stationary states of a quantum particle in nano-devices and quantum billiards is presented in detail at an elementary level. According to the method, wave functions inside the domain of the device or billiard are expressed in terms of line integrals of the wave function and its normal derivative along the doma

Sang Pyo Kim

We propose a mean-field approach to the Duffing oscillator to construct perturbatively the bounded operators that generate the quantum states, and to define a non-Gaussian density operator.

Pavlos Protopapas, Abraham Klein

Core-particle coupling models are made viable by assuming that core properties such as matrix elements of multipole and pairing operators and excitation spectra are known independently. From the completeness relation, it is seen, however, that these quantities are themselves algebraic functions of the calculated core-particle amplitudes. For the deformed rar

J. Skalski, S. Mizutori, W. Nazarewicz

Shapes and high-spin properties of nuclei from the neutron-rich (N>56) zirconium region are calculated using the Nilsson-Strutinsky method with the cranked Woods-Saxon average potential and monopole pairing residual interaction. The shape coexistence effects and the competition between rotationally-aligned 1h11/2 neutron and 1g9/2 proton bands is discussed.

Myung Ki Cheoun, Shin Nan Yang, Bong Soo Han, Il-Tong Cheon

Sum of the time component of $Σ$ term and the induced pseudo scalar term in axial current is shown to be the t-channel pion pole in Born terms for pion electroproduction near threshold. We also show that this $Σ$ term represents the charged pseudo scalar quark density matrix elements in nucleon and manifests itself in the $L_0^+$ amplitude on this reaction.

B. Schroer

We extend the &#39;&#39;modular localization&#39;&#39; principle from free to interacting theories and test its power for the special class of d=1+1 factorizing models.

Vincenzo Marotta

W_k structure underlying the tensverse realization of SU(2) at level k is analyzed. Extension of the equivalence existing between covariant and light-cone gauge realization of affine Kac-Moody algebra to W_k algebras is given. Higher spin generators related to parafermions are extracted from the operator product algebra of the generators and are showed to be

Rong-Gen Cai

By investigating the critical behavior appearing at the extremal limit of the non-dilatonic, black p-branes in (d+p) dimensions, we find that some critical exponents related to the critical point obey the scaling laws. From the scaling laws we obtain that the effective spatial dimension of the non-dilatonic black holes and black strings is one, and is p for

I. L. Buchbinder, V. D. Pershin, G. B. Toder

A method of constructing a canonical gauge invariant quantum formulation for a non-gauge classical theory depending on a set of parameters is advanced and then applied to the theory of closed bosonic string interacting with massive background fields. It is shown that within the proposed formulation the correct linear equations of motion for background fields

Th. Wilke, S. P. Klevansky

The Coulomb gauge model of QCD is studied with the introduction of a confining potential into the scalar part of the vector potential. Using a Green function formalism, we derive the self-energy for this model, which has both scalar and vector parts, $Σ^S(p)$ and $Σ^V(p)$. A rotation of these variables leads to the so-called gap and energy equations. We then

P. S. Joshi

We review here some recent developments on the issue of final fate of gravitational collapse within the framework of Einstein theory of gravity. The structure of collapsed object is discussed in terms of either a black hole or a singularity having causal connection with outside universe. Implications for cosmic censorship are discussed.

Sunil Nair

In this paper we prove geometric residue theorems for bundle maps over a compact manifold. The theory developed associates residues to the singularity submanifolds of the map for any invariant polynomial. The theory is then applied to a variety of settings: smooth maps between equidimensional manifolds, CR-singularities, finite singularities and singularitie

L. Coffey, D. Lacy, K. Kouznetsov, A. Erner

ARPES measurements on HiTc superconductors such as BiSrCaCuO reveal a quasiparticle peak, a broad background and a dip. The background may originate from inelastic spin fluctuation emission. Calculations of the spectral weight are presented incorporating these inelastic processes. Superconducting correlations have been included in the magnetic susceptibility

Stephen W. Pierson, Oriol T. Valls, Zlatko Tesanovic, Michael A. Lindemann

We study the applicability of magnetization and specific heat equations derived from a lowest-Landau-level (LLL) calculation, to the high-temperature superconducting (HTSC) materials of the YBa$_2$Cu$_3$O$_{7-δ}$ (YBCO) family. We find that significant information about these materials can be obtained from this analysis, even though the three-dimensional LLL

A. Gabrielli, R. Cafiero, M. Marsili, L. Pietronero

We introduce a general theoretical scheme for a class of phenomena characterized by an extremal dynamics and quenched disorder. The approach is based on a transformation of the quenched dynamics into a stochastic one with cognitive memory and on other concepts which permit a mathematical characterization of the self-organized nature of the avalanche type dyn

A. Moskalenko, Yu. A. Kuznetsov, K. A. Dawson

We study the phase transitions of a random copolymer chain with quenched disorder. We apply a replica variational approach based on a Gaussian trial Hamiltonian in terms of the correlation functions of monomer Fourier coordinates. This allows us to study collapse, phase separation and freezing transitions within the same mean field theory. The effective free

R. Cafiero, A. Gabrielli, M. Marsili, L. Pietronero

We analyze the combined effect of a Laplacian field and quenched disorder for the generation of fractal structures with a study, both numerical and theoretical, of the quenched dielectric breakdown model (QDBM). The growth dynamics is shown to evolve from the avalanches of invasion percolation (IP) to the smooth growth of Laplacian fractals, i. e. diffusion

M. H. Pedersen, J. J. Rodriguez-Nunez, H. Beck, T. Schneider

A self-consistent set of equations for the one-electron self-energy in the ladder approximation is derived for the attractive Hubbard model in the superconducting state. The equations provide an extension of a T-matrix formalism recently used to study the effect of electron correlations on normal-state properties. An approximation to the set of equations is

Henk W. J. Blöte, Erik Luijten

We solve the long-standing discrepancy between Monte Carlo results and the renormalization prediction for the Binder cumulant of the five-dimensional Ising model. Our conclusions are based on accurate Monte Carlo data for systems with linear sizes up to L=22. A detailed analysis of the corrections to scaling allows the extrapolation of these results to L=\in

J. C. Chaves, I. I. Satija

Motivated by the existence of metal-insulator transition in one-dimensional non-interacting fermions in quasiperiodic and pseudorandom potentials, we studied interacting spinless fermion models using exact many-body Lanczos diagonalization techniques. Our main focus was to understand the effect of the fermion-fermion interaction on the transport properties o

E. V. Tsiper, P. D. Wang, J. L. Merz, A. L. Efros

Selectively excited photoluminescence (SPL) of an array of self-organized In$_{0.5}$Ga$_{0.5}$As quantum dots has been measured in a magnetic field up to 11T. Anomalous magnetic field sensitivity of the SPL spectra has been observed under conditions for which the regular photoluminescence spectra is insensitive to the magnetic field due to large inhomogeneou

Ferenc Pazmandi, Gergely T. Zimanyi

We introduce a new renormalization group theory to examine the quantum phase transitions upon exiting the insulating phase of a disordered, strongly interacting boson system. For weak disorder we find a direct transition from this Mott insulator to the Superfluid phase. In d > 4 a finite region around the particle-hole symmetric point supports this direct tr

Abdullah Kurtulus Yorulmaz

All natural language processing systems (such as parsers, generators, taggers) need to have access to a lexicon about the words in the language. This thesis presents a lexicon architecture for natural language processing in Turkish. Given a query form consisting of a surface form and other features acting as restrictions, the lexicon produces feature structu

Harvey B. Richer, Gregory G. Fahlman, Rodrigo A. Ibata, Carlton Pryor

Using WFPC2 on the Hubble Space Telescope, we have isolated a sample of 258 white dwarfs (WDs) in the Galactic globular cluster M4. Fields at three radial distances from the cluster center were observed and sizeable WD populations were found in all three. The location of these WDs in the color-magnitude diagram, their mean mass of 0.51($ \pm 0.03$)M$_{\odot}

Lam Hui, Nickolay Y. Gnedin, Yu Zhang

Absorption lines in the Lyman-alpha forest can be thought of as peaks in neutral hydrogen density along lines of sight. The column density distribution (the number density of absorption lines as a function of column density) is then a statistic of density peaks, which contains information about the underlying power spectrum. In particular, we show that the s

Scott Dodelson, William H. Kinney, Edward W. Kolb

Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus for observations of CMB anisotropies at the accuracy of planned satellite missions to reject currently po

Pedro G. Ferreira

We propose a set of new statistics which can be extracted out of the angular distribution of the Fourier transform of the temperature anisotropies in the small field limit. They quantify generic non-Gaussian structure and complement the power spectrum in characterizing the sampled distribution function of a data set (contribution to the 18th Texas Symposium

Y. Ultchin, O. Regev, C. Bertout

Assuming a diamagnetic interaction between a stellar-spot originated localized magnetic field and gas blobs in the accretion disk around a T- Tauri star, we show the possibility of ejection of such blobs out of the disk plane. Choosing the interaction radius and the magnetic field parameters in a suitable way gives rise to closed orbits for the ejected blobs

Sarbani Basu, J. Christensen-Dalsgaard

Inversions to determine the squared isothermal sound speed and density within the Sun often use the helium abundance Y as the second parameter. This requires the explicit use of the equation of state (EOS), thus potentially leading to systematic errors in the results if the equations of state of the reference model and the Sun are not the same. We demonstrat

S. Andreon, E. Davoust, P. Poulain

We present the results of an isophotal shape analysis of galaxies in the Coma and Perseus clusters. These data, together with those of two previous papers, provide two complete samples of galaxies with reliable Hubble types in rich clusters: 1) all galaxies brighter than m_b = 16.5 falling within one degree (=2.3 Mpc) from the center of the Coma cluster (187

D. Ruffolo

We examine effects on the charge states of energetic ions associated with gradual solar flares due to shock heating and stripping at high ion velocities. Recent measurements of the mean charges of various elements after the flares of 1992 Oct 30 and 1992 Nov 2 allow one to place limits on the product of the electron density times the acceleration or coronal

Zong-Hong Zhu, Xiang-Ping Wu

We present an alternative but intuitive method of obtaining the true or intrinsic quasar luminosity function through the observed one in the framework of gravitational lensing. Such a so-called inversion of the magnification bias can be straightforwardly performed by means of the Mellin transformation instead of other complex methods. Application of our appr

Daniel E. Reichart, P. Meszaros

Two models of the gamma ray burst population, one with a standard candle luminosity and one with a power law luminosity distribution, are chi^2-fitted to the union of two data sets: the differential number versus peak flux distribution of BATSE&#39;s long duration bursts, and the time dilation and energy shifting versus peak flux information of pulse duratio

Kei Tokita, Ayumu Yasutomi

Introducing the effect of extinction into the so-called replicator equations in mathematical biology, we construct a general model of ecosystems. The present model shows mass extinction by its own extinction dynamics when the system initially has a large number of species ( diversity). The extinction dynamics shows several significant features such as a powe

Moshe Rozali

We demonstrate the emergence of the U-duality group in compactification of Matrix theory on a 4-torus. The discussion involves non-trivial effects in strongly coupled 4+1 dimensional gauge theory, and highlights some interesting phenomena in the Matrix theory description of compactified M-theory.

B. Z. Kopeliovich

Nuclear suppression of charmonium production in proton-nucleus interactions is poorly understood, what restrains our attempts to single out unusual effects in heavy ion collisions. We develop a phenomenological approach, based on the light-cone dynamics of charmonium production, which has much in common with deep-inelastic scattering and Drell-Yan lepton pai

Robert D. Pisarski, T. L. Trueman, Michel H. G. Tytgat

At zero temperature, in the chiral limit the amplitude for pi0 to decay into two photons is directly related to the coefficient of the axial anomaly. At any nonzero temperature, this direct relationship is lost: while the coefficient of the axial anomaly is independent of temperature, in a thermal bath the anomalous Ward identities do not uniquely constrain

Ann E. Nelson, David Wright

We construct explicit examples with a horizontal, ``anomalous&#39;&#39; $U(1)$ gauge group, which, in a supersymmetric extension of the standard model, reproduce qualitative features of the fermion spectrum and CKM matrix, and suppress FCNC and proton decay rates without the imposition of global symmetries. We review the motivation for such ``more&#39;&#39;