October 2000 arXiv papers — page 14

Reuven Cohen, Keren Erez, Daniel ben-Avraham, Shlomo Havlin

We study the tolerance of random networks to intentional attack, whereby a fraction p of the most connected sites is removed. We focus on scale-free networks, having connectivity distribution of P(k)~k^(-a) (where k is the site connectivity), and use percolation theory to study analytically and numerically the critical fraction p_c needed for the disintegrat

Amand Faessler, C. Fuchs, M. I. Krivoruchenko, B. V. Martemyanov

The dilepton production in elementary ${pp\to e^{+}e^{-}X}$ reactions at BEVALAC energies $T_{lab}=1÷5$ GeV is investigated. The calculations include direct ${e^{+}e^{-}}$ decays of the vector mesons $ρ^{0}$, $ω$, and $ϕ$, Dalitz decays of the $π^{0}$-, $η$-, $% ρ$-, $ω$-, and $ϕ$-mesons, and of the baryon resonances $% Δ(1232),N(1520),$ $... $ . The subthre

Hoang Ngoc Long, Le Phuoc Trung

The parity violation in cesium atom is analysed in the framework of the models based on the SU(3)_C X SU(3)_L X U(1)_N gauge group. It is shown that in the minimal version, the main contribution to a deviation of weak charge ΔQ_W due to direct Z' exchange is negative. New data on parity violation in the cesium atom seems not favour to the minimal version

A. Bottino, F. Donato, N. Fornengo, S. Scopel

We discuss to which extent the present experiments of direct search for WIMPs, when interpreted in terms of relic neutralinos, probe interesting regions of the supersymmetric parameter space, which are also being progressively explored at accelerators. Our analysis is performed in a number of different supersymmetric schemes. We derive the relevant neutralin

Daniel Boese, Walter Hofstetter, Herbert Schoeller

Using renormalization group techniques, we study spectral and transport properties of a spinless interacting quantum dot consisting of two levels coupled to metallic reservoirs. For strong Coulomb repulsion $U$ and an applied Aharonov-Bohm phase $ϕ$, we find a large direct tunnel splitting $|Δ|\sim (Γ/π)|\cos(ϕ/2)|\ln(U/ω_c)$ between the levels of the order

Ansgar Denner, Stefano Pozzorini

We present results for the complete one-loop electroweak logarithmic corrections for general processes at high energies and fixed angles. Our results are applicable to arbitrary matrix elements that are not mass-suppressed. We give explicit results for 4-fermion processes and gauge-boson-pair production in electron-positron annihilation.

M. Hennrich, T. Legero, A. Kuhn, G. Rempe

We report on the first observation of stimulated Raman scattering from a Lambda-type three-level atom, where the stimulation is realized by the vacuum field of a high-finesse optical cavity. The scheme produces one intracavity photon by means of an adiabatic passage technique based on a counter-intuitive interaction sequence between pump laser and cavity fie

Corneliu Sochichiu

We show that the algebra of functions on noncommutative space allows two different representations. One is describing the genuine noncommutative space, while another one can be rewritten in commutative form by a redefinition of generators.

Takeo Moroi, Tomo Takahashi

We study constraints on the natural inflation model from the cosmic microwave background radiation (CMBR). Inflaton ϕfor the natural inflation has a potential of the form V=Λ^4[1-\cos(ϕ/\sqrt{2}f_ϕ)], which is parametrized by two parameters f_ϕand Λ. Various cosmological quantities, like the primordial curvature perturbation and the CMBR anisotropy, are dete

Long Li, Bing-song Zou, Guang-lie Li

The experimental isoscalar $ππ\toππ$ S-wave amplitude squared below 1.75 GeV is characterized by a very broad structure $f_0(400-1200)$ with two narrow dips due to its destructive interference with the $f_0(980)$ and $f_0(1500)$. The $f_0(1370)$ and $f_0(1710)$ do not show up clearly in the $ππ\toππ$ S-wave amplitude due to their weak coupling to $ππ$. This

Weihong Zheng, C. J. Hamer, R. R. P. Singh, Simon Trebst

We use recently developed strong-coupling expansion methods to study the two-particle spectra for the frustrated alternating Heisenberg model, consisting of an alternating nearest neighbor antiferromagnetic exchange and a uniform second neighbor antiferromagnetic exchange. Starting from the limit of weakly coupled dimers, we develop high order series expansi

G. S. Agarwal, Anil K. Patnaik

We show that radiative coupling between two multilevel atoms having near-degenerate states can produce new interference effects in spontaneous emission. We explicitly demonstrate this possibility by considering two identical V systems each having a pair of transition dipole matrix elements which are orthogonal to each other. We discuss in detail the origin o

K. Kowalski, J. Rembielinski

It is demonstrated that in contrast to the well-known case with a quantum particle moving freely in a real line, the wave packets corresponding to the coherent states for a free quantum particle on a circle do not spread but develop periodically in time. The discontinuous changes during the course of time in the phase representing the position of a particle

Samuel J. Lomonaco

This paper is a written version of a one hour lecture given on Lov Grover's database search algorithm. Table Of Contents 1 ... Problem Definition 2 ... The quantum mechanical perspective 3 ... Properties of the inversion I_|psi> 4 ... The method in Lov's "madness" 5 ... Summary of Grover's algorithm 6 ... An example of Grover's algori

Horace P. Yuen

Bit commitment involves the submission of evidence from one party to another so that the evidence can be used to confirm a later revealed bit value by the first party, while the second party cannot determine the bit value from the evidence alone. It is widely believed that secure quantum bit commitment is impossible due to quantum entanglement cheating, whic

R. Schiavilla

Our current understanding of the structure of nuclei with up to A=8, including energy spectra, electromagnetic form factors, and capture reactions, is critically reviewed within the context of a realistic approach to nuclear dynamics based on two- and three-nucleon interactions and associated electromagnetic currents.

R. Schiavilla

Our current understanding of the structure of nuclei with up to A=8, including energy spectra, electromagnetic form factors, and weak transitions, is reviewed within the context of a realistic approach to nuclear dynamics based on two- and three- nucleon interactions and associated electro-weak currents. Low-energy radiative and weak capture reactions of ast

A. I. L'vov

The GDH sum rule is discussed for the Delta(1232) resonance. It is shown that apart from ordinary excitations to higher-energy states, the sum rule contains a large negative contribution due to de-excitation into the nucleon state. Therefore, a fulfillment of the sum rule assumes a strong coupling of Delta^+ and Delta^0 to resonances of spin 5/2 and higher.

M. I. Levchuk, A. I. L'vov

Differential cross section of deuteron Compton scattering has been calculated using the Bonn NN-potential, a consistent set of meson-exchange currents and seagulls, and lowest- and higher-order electromagnetic polarizabilities of the nucleon. Estimates of the polarizabilities of the neutron are obtained from recent experimental data.

A. Funk, H. V. von Geramb

Solutions SP00, SM00 and FA00 of nucleon-nucleon (NN) phase shift analyzes by Arndt et al. are used in optical model studies. The partial waves, single channels J.leq.7 and coupled channels J.leq.6, are scrutinized. The radial probability distributions and losses of flux are used to identify the known Delta and N* resonances as well as anticipated other stru

H. V. von Geramb, A. Funk, A. Faltenbacher

Several boson exchange potentials, describing the NN interaction $T_\ell\le 300$ MeV with high quality, are extended in their range of applicability as NN optical models with complex local or separable potentials in r-space or as complex boundary condition models. We determine in this work the separable potential strengths or boundary conditions on the backg

M. de Gosson, B. Dragovich, A. Khrennikov

We investigate various properties of p-adic differential equations which have as a solution an analytic function of the form $F_k (x) = \sum_{n\geq 0} n! P_k (n) x^n$, where $P_k (n) = n^k + C_{k-1} n^{k-1} + ...+ C_0$ is a polynomial in n with $C_i\in Z$ (in a more general case $C_i\in Q$ or $C_i\in C_p$). For some special classes of $P_k (n)$, as well as f

A. D. Popova

We present n-dimensional vortex-ring-like and potential-like solutions with unusual properties related to some elliptical differential equations with compact sources. Solutions have almost 3- or 2-dimensional behaviour in the spaces with arbitrary (large) odd and even dimensions, respectively.

A. N. Leznov, P. A. Marquez Aguilar, S. Mansurova

Spherically symmetrical reductions of self-dual Yang-Mills and Einstein-Plebanski equations are constructed at the same manner. As in the first case we come back to known before solutions (under such kind of reduction but in some different form) if in the second one we obtain unknown before equation describing the spherically symmetrical configurations of Pl

Rhodes Peele, Pantelimon Stanica

If L, respectively R are matrices with entries binom{i-1,j-1}, respectively binom{i-1,n-j}, it is known that L^2 = I (mod 2), respectively R^3 = I (mod 2), where I is the identity matrix of dimension n > 1 (see P10735-May 1999 issue of the American Mathematical Monthly). We generalize it for any prime p, and give a beautiful connection to Fibonacci numbers.

Mutsuo Oka, Duc Tai Pho

We show that the fundamental group of the complement of any irreducible tame torus sextics in $\bf P^2$ is isomorphic to $\bf Z_2*\bf Z_3$ except one class. The exceptional class has the configuration of the singularities $\{C_{3,9},3A_2\}$ and the fundamental group is bigger than $\bf Z_2*\bf Z_3$. In fact, the Alexander polynomial is given by $(t^2-t+1)^2$

Masahiko Miyamoto

We extend the modular invariance property of the trace functions of vertex operator algebra on the set of irreducible modules (Zhu's theory) to the case of trace functions of intertwining operators.

Andreas Nilsson, Jan Snellman

In the article "Non-commutative Grobner bases for commutative algebras", Eisenbud-Peeva-Sturmfels proved a number of results regarding Grobner bases and initial ideals of those ideals in the free associative algebra which contain the commutator ideal. We prove similar results for ideals which contains the anti-commutator ideal (the defining ideal of

Micha Berkooz

The six-dimensional (2,0) field theory admits a generalized ``noncommutative'' deformation associated with turning on a large null 3-form field strength. This theory is studied using its discrete light-cone formulation as quantum mechanics on a blow-up of the ADHM moduli space. We show how to interpret the ADHM manifold as configurations of open memb

R. Acharya, P. Narayana Swamy

We establish that in Quantum Chromodynamics (QCD) at zero temperature, SU_(L+R)(N_F) exhibits the vector mode conjectured by Georgi and SU_(L-R)(N_F)is realized in either the Nambu-Goldstone mode or else the axial-vector charge is also screened from view at infinity. The Wigner-Weyl mode is ruled out unless the beta function in QCD develops an infrared stabl

Yves Brihaye, Betti Hartmann, D. H. Tchrakian

Three dimensional SO(3) gauged Skyrme models characterised by specific potentials imposing special asymptotic values on the chiral field are considered. These models are shown to support finite energy solutions with nonvanishing magnetic and electrix flux, whose energies are bounded from below by two distinct charges - the magnetic (monopole) charge and a no

E. Bergshoeff, M. de Roo, A. Sevrin

We define an iterative procedure to obtain a non-abelian generalization of the Born-Infeld action. This construction is made possible by the use of the severe restrictions imposed by kappa-symmetry. We have calculated all bosonic terms in the action up to terms quartic in the Yang-Mills field strength and all fermion bilinear terms up to terms cubic in the f

Yu. M. Zinoviev

The main object of the proposed theory is not a pseudometric, but a symmetric affine connection on the Minkowski space. The coefficients of this connection have one upper and two lower indices. These coefficients are symmetric with respect to the permutation of the lower indices. We identify the convolution of the connection coefficients with the vector - po

Patrick Dorey, Clare Dunning, Roberto Tateo

We review a recently-discovered link between the functional relations approach to integrable quantum field theories and the properties of certain ordinary differential equations in the complex domain.

Takashi Hattori

In order to investigate the composite gauge field, we consider the compositeness condition (i.e. renormalization constant $Z_3=0$) in the general non-abelian gauge field theory. We calculate $Z_3$ at the next-to-leading order in $1/N_f$ expansion ($N_f$ is the number of fermion flavors), and obtain the expression to the gauge coupling constant through the co

Israel Quiros

Conformal symmetry is investigated within the context of axion-dilaton-modulus theory of gravity of Brans-Dicke-type. A distinction is made between general conformal symmetry and invariance under transformations of the physical units. The conformal degree of symmetry of the theory is studied when quantum fermion (lepton) modes with electromagnetic interactio

Ori J. Ganor

We propose a M(atrix) model for N=4 $SU(k)$ Super-Yang-Mills theory compactified on $T^4$. In this model it is possible to make $T^4$ noncommutative and it is easy to turn on all 6 components of the noncommutativity on $T^4$. The action of S-duality on the noncommutativity parameters is also manifest. The M(atrix)-model is given by the large $N$ limit of a $

Stephen L. Adler

This paper has been withdrawn, because the argument for generating Goldstone modes at a Lifshitz point is incorrect.

Stephen L. Adler

This paper has been withdrawn, because the argument for generation of Goldstone modes is incorrect.

Stacy McGaugh

The amplitude of the second peak in the angular power spectrum of the cosmic microwave background radiation is constrained to be small by recent experiments like Boomerang. This is surprising in the context of the LambdaCDM model, which predicted a large second peak. However, this result is expected if CDM does not exist. The observed shape of the power spec

Peter Arnold

I review the Bose-Einstein condensation phase transition of dilute gases of cold atoms, for particle theorists acquainted with methods of field theory at finite temperature. I then discuss how the dependence of the phase transition temperature on the interaction strength can be computed in the large N approximation.

D. Palle

We perform comparative analyses of quantum loop corrections to some observationally important two- and three-point Green functions within two distinct symmetry-breaking mechanisms. It appears that the existing high-energy data, neutrino experiments and present astrophysical and cosmological constraints strongly disfavour the Higgs mechanism, while the introd

E. de Rafael

I report on some recent work done in collaboration with Santi Peris and Boris Phily (hep-ph/0007338) where, using the Aleph data on vector and axial-vector spectral functions, we test simple duality properties of QCD in the large-Nc limit which emerge in the approximation of a {\it minimal hadronic ansatz} of a spectrum of narrow states. These duality proper

M. Beneke, V. M. Braun

Even for short-distance dominated observables the QCD perturbation expansion is never complete. The divergence of the expansion through infrared renormalons provides formal evidence of this fact. In this article we review how this apparent failure can be turned into a useful tool to investigate power corrections to hard processes in QCD.

Boris Kayser

We argue that the evidence for neutrino mass is quite compelling. This mass raises a number of questions, which we enumerate, about neutrinos. Then we focus on one of these questions---the issue of the possible neutrino mass spectra. In particular, we explain that one can have a four-neutrino spectrum which does not require significant sterile-neutrino invol

M. Beccaria, F. M. Renard, C. Verzegnassi

The production of a tt(bar) pair from lepton-antilepton annihilation is considered for values of the center of mass energy much larger than the top mass, typically of the few TeV size. In this regime a number of simplifications occurs that allows to derive the leading asymptotic terms of various observables using the same theoretical description that was use

Tuomas Multamaki

Collisions of non-topological solitons, Q-balls, are studied in the Minimal Supersymmetric Standard Model in two different cases: where supersymmetry has been broken by a gravitationally coupled hidden sector and by a gauge mediated mechanism at a lower energy scale. Q-ball collisions are studied numerically on a two dimensional lattice for a range of Q-ball

Markus Diehl

I briefly review the physics of skewed parton distributions. Special emphasis is put on the relevance of target polarization, and on the different roles of small and of intermediate x_B.

P. J. Mulders

Current fragmentation in semiinclusive deep inelastic leptoproduction offers, besides refinement of inclusive measurements such as flavor separation and access to the chiral-odd quark distribution functions $h_1^q(x) = δq(x)$, the possibility to investigate intrinsic transverse momentum of hadrons via azimuthal asymmetries.

E. Gotsman, E. Levin, M. Lublinsky, U. Maor

These notes are a summary of our efforts to answer the question in the title. Our answer is in the affirmative as: (i) HERA data indicate a large value of the gluon structure function; (ii) no contradictions with the asymptotic predictions of high density QCD have been observed; and (iii) the numerical estimates of our model give a natural description of the

Antonio Vairo

I review and discuss a selected sample of recent results in pNRQCD.

Amol S. Dighe, Anjan S. Joshipura

We show in a model independent manner that, if the magnitudes of Majorana masses of neutrinos are exactly equal at some high scale, the radiative corrections cannot reproduce the observed masses and mixing spectrum at the low scale, irrespective of the Majorana phases or the mixing angles at the high scale.

Tatsu Takeuchi, Oleg Lebedev, Will Loinaz

We constrain the size of R-parity violating couplings using precision electroweak data.

She-Sheng Xue

On the basis of previous work on chiral gauged fermions on a lattice, we discuss the lattice-regularization of the standard model by introducing two Weyl fields interacting with quarks and leptons. These interactions form massive bound states to gauge-invariantly decouple doublers at high energies and these bound states dissolve into their constituents at lo

L. Littenberg

The current status of the study of rare kaon decays is reviewed. Future prospects are discussed.

V. Savinov, CLEO Collaboration

We report on a search for a supersymmetric $\tilde{B}$ meson with mass between 3.5 and 4.5 GeV/$c^2$ using 4.52 ${\rm fb}^{-1}$ of integrated luminosity produced at $\sqrt{s}=10.52$ GeV, just below the $e^+e^-\to B\bar{B}$ threshold, and collected with the CLEO detector. We find no evidence for a light scalar bottom quark.

Hans-Ulrich Martyn

Recent progress on the study of power corrections applied to event shape variables in deep inelastic ep scattering is discussed.

NA52 collaboration, R. Arsenescu, H. P. Beck, K. Borer

The NA52 collaboration searches for a discontinuous behaviour of charged kaons produced in Pb+Pb collisions at 158 A GeV as a function of the impact parameter, which could reveal a hadron to quark-gluon plasma (QGP) phase transition. The K+ yield is found to grow proportional to the number of participating ('wounded') nucleons N, above N=100. Previou

Andreas Warburton

Using ~13.7 fb^{-1} of e^+e^- collision data recorded at near the Upsilon(4S) resonance by the CLEO II and CLEO II.V detector configurations on the Cornell Electron Storage Ring, we present the world's most precise measurements of the Sigma_c^0, Sigma_c^+, and Sigma_c^{++} charmed-baryon masses as well as the first measurements of the intrinsic widths of

P. M. Alsing, J. C. Evans, K. K. Nandi

We investigate the quantum mechanical wave equations for free particles of spin 0,1/2,1 in the background of an arbitrary static gravitational field in order to explicitly determine if the phase of the wavefunction is $S/\hbar = \int p_μ dx^μ / \hbar$, as is often quoted in the literature. We work in isotropic coordinates where the wave equations have a simp

Arkady L. Kholodenko

In the recent publication (Journal of Geometry and Physics,33(2000)23-102) we demonstrated that dynamics of 2+1 gravity can be described in terms of train tracks. Train tracks were introduced by Thurston in connection with description of dynamics of surface automorphisms. In this work we provide an example of utilization of general formalism developed earlie

A. Chamorro, S. S. Deshingkar, I. H. Dwivedi, P. S. Joshi

A piecewise Tolman-Bondi-Lemaitre (TBL) cell-model for the universe incorporating local collapsing and expanding inhomogeneities is presented here. The cell-model is made up of TBL underdense and overdense spherical regions surrounded by an intermediate region of TBL shells embedded in an expanding universe. The cell-model generalizes the Friedmann as well a

S. S. Xulu

The energy distribution in the Kerr-Newman space-time is computed using the Møller energy-momentum complex. This agrees with the Komar mass for this space-time obtained by Cohen and de Felice. These results support the Cooperstock hypothesis.

Miroslav Sukenik, Jozef Sima, Julius Vanko

The contribution provides the backround of the model of Expansive Nondecelerative Universe, rationalizes the introduction of Vaidya metrics allowing thus to localize and quantify gravitational energy. A unifying explanation of the fundamental physical interactions is accompanied by demonstration of some consequences and predictions relating to cosmological p

R. T. Clay, S. Mazumdar, D. K. Campbell

Previous work has demonstrated the existence of soliton defect states with charges +/- e/2 in the limits of zero and of infinite on-site Coulomb interactions in the one-dimensional (1D) quarter-filled band. For large but finite on-site Coulomb interaction, the low temperature 2k_F bond distortion that occurs within the 4k_F bond-distorted phase is accompanie

Robert Konik, Hubert Saleur, Andreas Ludwig

Recent experiments have probed quantum dots through transport measurements in the regime where they are described by a two lead Anderson model. In this paper we develop a new method to analytically compute for the first time the corresponding transport properties. This is done by using the exact solvability of the Anderson Hamiltonian, together with a genera

Zvonimir Dogic, Seth Fraden

We have prepared a homologous series of filamentous viruses with varying contour length using molecular cloning techniques. These viruses are monodisperse enough to form a stable smectic phase. Two systems are studied. The first system consists of viruses to which polymers are covalently attached to the virus surface. Through studies of the isotropic - chole

G. C. Barker, Anita Mehta

We investigate the spatial dependence of the density of vibrated granular beds, using simulations based on a hybrid Monte Carlo algorithm. We find that the initial consolidation is typically inhmogeneous, both in the presence of a constant shaking intensity and when the granular bed is submitted to `annealed shaking'. We also present a theoretical model

F. Cordero, A. Paolone, R. Cantelli, M. Ferretti

We compare the low frequency (~1 kHz) anelastic spectra of La_{2-x}Sr_xCuO_4 and La_{2-x}Ba_xCuO_4 at x = 0.03 and 0.06 in the temperature region where the freezing into the cluster spin-glass (CSG) phase occurs and is accompanied by an increase of the acoustic absorption. The dependence of the amplitude of the anelastic relaxation on doping is explained in

P. Grassberger, W. Nadler

We describe a general strategy for sampling configurations from a given (Gibbs-Boltzmann or other) distribution. It is {\it not} based on the Metropolis concept of establishing a Markov process whose stationary state is the wanted distribution. Instead, it builds weighted instances according to a biased distribution. If the bias is optimal, all weights are e

Hubert Temmen, Harald Pleiner, Mario Liu, Helmut R. Brand

In the limit of infinite yield time for stresses, the hydrodynamic equations for viscoelastic, Non-Newtonian liquids such as polymer melts must reduce to that for solids. This piece of information suffices to uniquely determine the nonlinear convective derivative, an ongoing point of contention in the rheology literature.

Taisei Kaizoji

We present an interacting-agent model of speculative activity explaining bubbles and crashes in stock markets. We describe stock markets through an infinite-range Ising model to formulate the tendency of traders getting influenced by the investment attitude of other traders. Bubbles and crashes are understood and described qualitatively and quantitatively in

Mario Liu

In a recent Letter, Luo, Du and Huang reported a novel convective instability driven by a force rarely studied before -- that exerted by an external magnetic field on a strongly magnetizable liquid. The associated physics is surprisingly rich and promises many more interesting results for the future. Unfortunately, the analysis starts from a misconception an

Mario Liu, Klaus Stierstadt

While the electromagnetic force is microscopically simply the Lorentz force, its macroscopic form is more complicated, and given by expressions such as the Maxwell stress tensor and the Kelvin force. Their derivation is fairly opaque, at times even confusing, and their range of validity all but a well kept secret. These circumstances unnecessarily reduce the

Yimin Jiang, Mario Liu

Comparing various microscopic theories of rotating superconductors to the conclusions of thermodynamic considerations, we traced their marked difference to the question of how some thermodynamic quantities (the electrostatic and chemical potentials) are related to more microscopic ones: The electron's the work function, mean-field potential and Fermi ene

Carmen J. Calzado, Jean-Paul Malrieu

Accurate ab initio calculations on embedded Cu_4O_{12} square clusters, fragments of the La_2CuO_4 lattice, confirm a value of the nearest neighbor antiferromagnetic coupling (J=124 meV) previously obtained from ab initio calculations on bicentric clusters and in good agreement with experiment. These calculations predict non negligible antiferromagnetic seco

Helen Gomonay, Vadim Loktev

The problem of the observable equilibrium domain structure in pure antiferromagnets (and other thermoelastics) is investigated with the use of continuous elasticity theory. It is shown that completely rigid surface produces the imaginary ``incompatibility elastic charges'' analogous to the surface magnetic charges in ferromagnets. Corresponding long-

Carmen J. Calzado, Jean-Paul Malrieu

A series of accurate ab initio calculations on Cu_pO-q finite clusters, properly embedded on the Madelung potential of the infinite lattice, have been performed in order to determine the local effective interactions in the CuO_2 planes of La_{2-x}Sr_xCuO_4 compounds. The values of the first-neighbor interactions, magnetic coupling (J_{NN}=125 meV) and hoppin

J. Barnas, J. Martinek, G. Michalek, B. R. Bulka

Electron tunneling in ferromagnetic single-electron transistors is considered theoretically in the sequential tunneling regime. A new formalism is developed, which operates in a two-dimensional space of states, instead of one-dimensiona space used in the spinless case. It is shown that spin fluctuations can be significantly larger than the charge fluctuation

A. Ciach, M. Tasinkevych

Effect of hydrophilicity of the confining walls on lamellar phases in oil-water-surfactant mixtures is studied in a slit geometry. In contrast to strongly hydrophilic or hydrophobic walls, which induce parallel orientation of lamellae, the lamellae can be oriented perpendicularly to the neutral walls when the material properties and the termodynamical state

Stefano Ciliberti, Guido Caldarelli, Paolo De Los Rios, Luciano Pietronero

We study the properties of the ``Rigid Laplacian'' operator, that is we consider solutions of the Laplacian equation in the presence of fixed truncation errors. The dynamics of convergence to the correct analytical solution displays the presence of a metastable set of numerical solutions, whose presence can be related to granularity. We provide some

D. V. Fil, S. I. Shevchenko

We present a method of finding approximate analytical solutions for the spectra and eigenvectors of collective modes in a two-dimensional system of interacting bosons subjected to a linear external potential or the potential of a special form $u(x,y)=μ-u \cosh^2 x/l$, where $μ$ is the chemical potential. The eigenvalue problem is solved analytically for an a

E. Korutcheva, V. Del Prete, J. -P. Nadal

We evaluate the mutual information between the input and the output of a two layer network in the case of a noisy and non-linear analogue channel. In the case where the non-linearity is small with respect to the variability in the noise, we derive an exact expression for the contribution to the mutual information given by the non-linear term in first order o

A. Ciach, V. Babin, M. Tasinkevych

Systems in which particles can self-assemble into mono- or bilayers can form variety of stable and metastable structures on a nanometer length scale. For this reason confinement has a particularly strong effect on such systems. We discuss in some detail effects of confinement on lamellar and cubic phases with double-diamond structure. Structural deformations

S. Ben-Tabou de-Leon, B. Laikhtman

The gas of interacting excitons in quantum wells is studied. We obtain the Hamiltonian of this gas by the projection of the electron-hole plasma Hamiltonian to exciton states and an expansion in a small density. Matrix elements of the exciton Hamiltonian are rather sensitive to the geometry of the heterostructure. The mean field approximation of the exciton

Parongama Sen

The phase transitions in the transverse field Ising model in a competing spatially modulated (periodic and oscillatory) longitudinal field are studied numerically. There is a multiphase point in absence of the transverse field where the degeneracy for a longitudinal field of wavelength $λ$ is $(\frac {1 + \sqrt{5}}{2})^{2N/λ}$ for a system with $N$ spins, an

B. Roessli, J. Schefer, G. Petrakovskii, B. Ouladdiaf

The magnetic ground-state of copper metaborate is investigated by means of elastic neutron scattering.The magnetic structure of CuB2O4 is incommensurate with respect to the chemical lattice at T=1.8K and undergoes a continuous phase transition to a non-collinear commensurate antiferromagnetic state which is realized at T=10K. Close to the phase transition hi

Marek Cieplak, Neal S. Holter, Amos Maritan, Jayanth R. Banavar

We present and implement a distance-based clustering of amino acids within the framework of a statistically derived interaction matrix and show that the resulting groups faithfully reproduce, for well-designed sequences, thermodynamic stability in and kinetic accessibility to the native state. A simple interpretation of the groups is obtained by eigenanalysi

Raffaele Cafiero

Inspired by the chemical etching processes, where experiments show that growth rates depending on the local environment might play a fundamental role in determining the properties of the etched surfaces, we study here a model for kinetic roughening which includes explicitly an anisotropic effect in the growth rules. Our model introduces a dependence of the g

Wenji Deng, P. M. Hui

Starting from a second-quantized Hamiltonian of many-particle systems, we derive the Gross-Pitaevskii (GP) equation in momentum space, which is suitable for studying the multi-wave mixing processes of coherent matter waves. The coupling equations are then applied to study ideal four-wave mixing (4WM), in which only four waves with definite wavevectors are in

E. M. Leitch, A. C. S. Readhead, T. J. Pearson, S. T. Myers

We report a measurement of anisotropy in the cosmic microwave background radiation (CMBR) on 7-22 arcminute scales. Observations of 36 fields near the North Celestial Pole (NCP) were made at 31.7 and 14.5 GHz, using the 5.5-meter and 40-meter telescopes at the Owens Valley Radio Observatory (OVRO) from 1993 to 1996. Multi-epoch VLA observations at 8.5 and 15

R. S. McGary, W. F. Brisken, A. S. Fruchter, W. M. Goss

The pulsar velocity distribution provides information about the binary history of pulsar progenitors as well as asymmetries of the supernova events in which pulsars are born. Studies of local pulsars present a biased view of this distribution, since they preferentially select low velocity pulsars that have remained near their birthplaces in the Galactic plan

James D. Neill, Jean P. Brodie, William W. Craig, Charles J. Hailey

We present an investigation of the dynamical state of the cluster A262. Existing optical line of sight velocities for select cluster galaxies have been augmented by new data obtained with the Automated Multi-Object Spectrograph at Lick Observatory. We find evidence for a virialized early-type population distinct from a late-type population infalling from the

Mark L. Houdashelt, Rosemary F. G. Wyse, Gerard Gilmore

We present deep Hubble Space Telescope optical imaging observations of two Galactic globular clusters, 47 Tuc and M15, using the Space Telescope Imaging Spectrograph (STIS) longpass (LP) filter and the Wide Field and Planetary Camera 2 (WFPC2) F606W and F814W filters. These globular clusters have very different metallicities ([Fe/H] = -0.7 dex for 47 Tuc, an

Gavin Ramsay, Tracey Poole, Keith Mason, France Cordova

We present XMM-Newton observations of the eclipsing, disc accreting, cataclysmic variable OY Car which were obtained as part of the performance verification phase of the mission. The star was observed 4 days after an outburst and then again 5 weeks later when it was in a quiescent state. There is a quasi-stable modulation of the X-rays at ~2240 sec, which is

Inma Dominguez, Peter Hoeflich, Oscar Straniero

At this moment, the use of SNIa for cosmology lies on the assumption that the SNe at high redshifts are equal to the local ones. However, some observations indicate a correlation between the light curve (LC) properties and the morphological type of the host galaxy. This could indicate a dependence with the age (mass/composition) of the underlying population.

J. N. Reeves, M. J. L. Turner, P. J. Bennie, K. A. Pounds

We present XMM-Newton observations of the high redshift z=3.104, radio-loud quasar PKS 0537-286. The EPIC CCD cameras provide the highest signal-to-noise spectrum of a high-z quasar to date. The EPIC observations show that PKS 0537-286 is extremely X-ray luminous (Lx=2x10^47 erg/s), with an unusually hard X-ray spectrum (Gamma=1.27+/-0.02). The flat power-la

Arjun Berera, Alan F. Heavens

We investigate to what extent future microwave background experiments might be able to detect a suppression of fluctuation power on large scales in flat and open universe models. Such suppression would arise if fluctuations are generated by causal processes, and a measurement of a small suppression scale would be problematic for inflation models, but consist

Inma Dominguez, Carlos Abia, Oscar Straniero, Alessandro Chieffi

We present theoretical evolutionary models for Z=0 stars in the mass range 4< M/Mo <8 from the pre-main sequence up to the AGB phase. Contrary to previous calculations we found that these stars develop normal thermal pulses and third dredge-up episodes. Special attention is devoted to analyze the chemical enrichment in the envelope due to the above mechanism

T. Tamura, J. S. Kaastra, J. R. Peterson, F. Paerels

The initial results from XMM-Newton observations of the rich cluster of galaxies Abell 1795 are presented. The spatially-resolved X-ray spectra taken by the European Photon Imaging Cameras (EPIC) show a temperature drop at a radius of $\sim 200$ kpc from the cluster center, indicating that the ICM is cooling. Both the EPIC and the Reflection Grating Spectrom