April 2001 arXiv papers — page 10

K. A. Kirkpatrick

Relative to a given factoring of the Hilbert space, the decomposition of an operator into a convex sum of products over sets of distinct 1-projectors, one set linearly independent, is unique.

Indranil Paul, Gabriel Kotliar

We use the coupled 2d-spin-3d-fermion model proposed by Rosch {\sl et. al.} (Phys. Rev. Lett. {\bf 79}, 159 (1997)) to study the thermoelectric behaviour of a heavy fermion compound when it is close to an antiferromagnetic quantum critical point. When the low energy spin fluctuations are quasi two dimensional, as has been observed in ${\rm YbRh}_2{\rm Si}_2$

Gopal-Krishna, Paul J. Wiita

We show that a model for radio source dynamics we had earlier proposed can readily reproduce the relationship between the radio power division separating the two Fanaroff-Riley classes of extragalactic radio sources and the optical luminosity of the host galaxy, as found by Owen and Ledlow (1994). In our scenario, when less powerful jets eventually slow down

Ulf Gran, Mikkel Nielsen

In this paper we make an SL(2,Z)-covariant generalisation of the noncommutative theories, NCYM and NCOS on the D3-brane, and NCOS on the D5-brane in type IIB. Usually, the noncommutative theories are obtained by studying perturbative F-string theory, and the parameters governing the noncommutative theories are given by the open string data. The S-duality of

F. J. Castro, M. N. Kuperman, M. Fuentes, H. S. Wio

In order to test theoretical predictions, we have studied the phenomenon of stochastic resonance in an electronic experimental system driven by white non Gaussian noise. In agreement with the theoretical predictions our main findings are: an enhancement of the sensibility of the system together with a remarkable widening of the response (robustness). This im

P. Marage

Talk given at the First Workshop on Forward Physics and Luminosity Determination at the LHC, Helsinki, Finland, November 2000. 12 pages, 9 figures

V. Baran, D. M. Brink, M. Colonna, M. Di Toro

We estimate the dipole radiation emitted in fusion processes. We show that a classical bremsstrahlung approach can account for both the preequilibrium and the thermal photon emission. We give an absolute evaluation of the pre-equilibrium component due to the charge asymmetry in the entrance channel and we study the energy and mass dependence in order to opti

Thomas Wellens, Marek Kus

We describe a purely algebraic method for finding the best separable approximation to a mixed state of a composite 2x2 quantum system, consisting of a decomposition of the state into a linear combination of a mixed separable part and a pure entangled one. We prove that, in a generic case, the weight of the pure part in the decomposition equals the concurrenc

Toni Mateos, Alex Moreno

We analyze the unitarity of a non-relativistic non-commutative scalar field theory. We show that electric backgrounds spoil unitarity while magnetic ones do not. Furthermore, unlike its relativistic counterparts, unitarity can not be restored (at least at the level of one-to-one scattering amplitude) by adding new states to the theory. This is a signal that

A. Kehagias, K. Tamvakis

We derive a new class of time-dependent solutions for the Randall-Sundrum model by patching together isometries broken by the brane. Solutions generated by generalized boosts along the fifth dimension are associated with localized gravity and lead to an effective Friedman equation on the brane with a scale factor exhibiting power law or exponential behaviour

D. S. Petrov, G. V. Shlyapnikov, J. T. M. Walraven

We find that in very elongated 3D trapped Bose gases, even at temperatures far below the BEC transition temperature Tc, the equilibrium state will be a 3D condensate with fluctuating phase (quasicondensate). At sufficiently low temperatures the phase fluctuations are suppressed and the quasicondensate turns into a true condensate. The presence of the phase f

J. Baker, M. Campanelli, C. Lousto

We present a detailed description of techniques developed to combine 3D numerical simulations and, subsequently, a single black hole close-limit approximation. This method has made it possible to compute the first complete waveforms covering the post-orbital dynamics of a binary black hole system with the numerical simulation covering the essential non-linea

V. A. Miransky, I. A. Shovkovy, L. C. R. Wijewardhana

The masses of the pseudo-Nambu-Goldstone bosons in the color superconducting phase of dense QCD with two light flavors are estimated by making use of the Cornwall-Jackiw-Tomboulis effective action. Parametrically, the masses of the doublet and antidoublet bosons are suppressed by a power of the coupling constant as compared to the value of the superconductin

R. P. Vasquez, C. U. Jung, J. Y. Kim, Min-Seok Park

The electron-doped infinite-layer superconductor Sr0.9La0.1CuO2 is studied with x-ray photoemission spectroscopy (XPS). A nonaqueous chemical etchant is shown to effectively remove contaminants and to yield surfaces from which signals intrinsic to the superconductor dominate. These data are compared to measurements from hole-doped La1.85Sr0.15CuO4, from undo

W. F. Kao

Stability analysis of the Bianchi type I universe in pure gravity theory is studied in details. We first derive the non-redundant field equation of the system by introducing the generalized Bianchi type I metric. This non-redundant equation reduces to the Friedmann equation in the isotropic limit. It is shown further that any unstable mode of the isotropic p

Jeroen Homan, Michiel van der Klis, Peter G. Jonker, Rudy Wijnands

We have analyzed ~600 ks of Rossi X-ray Timing Explorer data of the neutron star low-mass X-ray binary and Z source GX 17+2. A study was performed of the properties of the noise components and quasi-periodic oscillations (QPOs) as a function of the spectral properties, with the main goal to study the relation between the frequencies of the horizontal branch

H. Kamada, A. Nogga, W. Gloeckle, E. Hiyama

In the past, several efficient methods have been developed to solve the Schroedinger equation for four-nucleon bound states accurately. These are the Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis variational, the stochastic variational, the hyperspherical variational, the Green's function Monte Carlo, the no-core shell model and th

NuTeV Collaboration, T. Adams, A. Alton, S. Avvakumov

A search for long-lived neutral particles (N^0's) with masses above 2.2 GeV/c^2 that decay into at least one muon has been performed using an instrumented decay channel at the NuTeV experiment at Fermilab. Data were examined for particles decaying into the final states mu mu, mu e, and mu pi. Three mu mu events were observed over an expected Standard Mod

Nissim Kanekar, Tapasi Ghosh, Jayaram N Chengalur

We present sensitive Giant Metrewave Radio Telescope (GMRT) and high-resolution Arecibo HI 21-cm observations of the damped Lyman-$α$ absorber (DLA) at $z=0.2212$ towards OI 363. The spectra are in excellent agreement and yield a spin temperature $T_s = 890 \pm 160$ K, far higher than $T_s$ values measured in local spirals, but similar to values obtained in

N. O. Agasian

It is shown that the temperature derivatives of the anomalous and normal (quark massive term) contributions to the trace of the energy-momentum tensor in QCD are equal to each other in the low temperature region. The physical consequences of this relation are discussed.

Alexander A. Osipov, Brigitte Hiller

A method is described for the development of the one-loop effective action expansion as an asymptotic series in inverse powers of the fermion mass. The method is based on the Schwinger-DeWitt proper-time technique, which allows for loop particles with non-degenerate masses. The case with SU(2)xSU(2) as the symmetry group is considered. The obtained novel ser

J. Y. Xiang, D. N. Zheng, J. Q. Li, L. Li

The superconducting and structural properties of a series of Mg1-xAlxB2 samples have been investigated. X-ray diffraction results confirmed the existence of a structural transition associated with the significant change in inter-boron layer distance as reported previously by Slusky et al. Moreover,transmission-electron-microscopy observations revealed the ex

Raffaella Burioni, Davide Cassi, Alessandro Vezzani

Topological inhomogeneity gives rise to spectral anomalies that can induce Bose-Einstein Condensation (BEC) in low dimensional systems. These anomalies consist in energy regions composed of an infinite number of states with vanishing weight in the thermodynamic limit (hidden states). Here we present a rigorous result giving the most general conditions for BE

Ctirad Klimcik, Thomas Strobl

We observe that a term of the WZW-type can be added to the Lagrangian of the Poisson Sigma model in such a way that the algebra of the first class constraints remains closed. This leads to a natural generalization of the concept of Poisson geometry. The resulting "WZW-Poisson" manifold M is characterized by a bivector Pi and by a closed three-form H

Mohsen Alishahiha

We compute one-loop correction to the string field theory action of the tachyon for unstable D-branes in the framework of the boundary superstring field theory. We would expect that the one-loop correction comes from the partition function of the two-dimensional world-sheet theory on the annulus. The annulus correction suggests that the genus expansion is, s

M. Grousson, G. Tarjus, P. Viot

We have investigated by Monte-Carlo simulation the phase diagram of a three-dimensional Ising model with nearest-neighbor ferromagnetic interactions and small, but long-range (Coulombic) antiferromagnetic interactions. We have developed an efficient cluster algorithm and used different lattice sizes and geometries, which allows us to obtain the main characte

Yi Zhou, Hui Zhai, Rong Lü, Zhan Xu

Macroscopic quantum coherence of Bose gas in a double-well potential is studied based on SU(2)-coherent-state path-integral. The ground state and fluctuations around it can be obtained by this method. In this picture, one can obtain macroscopic quantum superposition states for attractive Bose gas. The coherent gap of degenerate ground states is obtained with

M. Krcmar, Z. Krecak, A. Ljubicic, M. Stipcevic

We describe a novel approach to the search for solar, near-monochromatic hadronic axions, the latter being suggested to be created in the solar core during M1 transitions between the first excited level of Li-7, at 478 keV, and the ground state. As a result of Doppler broadening, in principle these axions can be detected via resonant absorption by the same n

Tilo Eggeling, Karl Gerd H. Vollbrecht, Reinhard F. Werner, Michael M. Wolf

We show that all quantum states that do not have a positive partial transpose are distillable via channels, which preserve the positivity of the partial transpose. The question whether NPT bound entanglement exist is therefore closely related to the connection between the set of separable superoperators and PPT-preserving maps.

Mikhail Z. Iofa

We study string-loop corrections to magnetic black hole. Four-dimensional theory is obtained by compactification of the heterotic string theory on the manifold $K3\times T^2$ or on a suitable orbifold yielding N=1 supersymmetry in 6D. The resulting 4D theory has N=2 local supersymmetry. Prepotential of this theory receives only one-string-loop correction. Th

Dinesh Kumar Srivastava

The transverse momenta of hadrons in central nucleus-nucleus collisions are evaluated in a boost invariant hydrodynamics with transverse expansion. Quark gluon plasma is assumed to be formed in the initial state which expands and cools via a first order phase transition to a rich hadronic matter and ultimately undergoes a freeze-out. The average transverse m

Ralf Hofmann

A model for the quantum effective description of the vacuum structure of thermalized SU(3) Yang-Mills theory is proposed. The model is based on Abelian projection leading to a Ginzburg-Landau theory for the magnetic sector. The possibility of topologically non-trivial, effective monopole fields in the deconfining phase is explored. These fields are assumed t

Gady Frenkel, Moshe Schwartz

We consider a deformable body immersed in an incompressible liquid that is randomly stirred. Sticking to physical situations in which the body departs only slightly from its spherical shape, we calculate the diffusion constant of the body. We give explicitly the dependence of the diffusion constant on the velocity correlations in the liquid and on the size o

Torsten Sommer, Matthias Vojta, Klaus W. Becker

The two-layer square lattice quantum antiferromagnet with spins 1/2 shows a zero-field magnetic order-disorder transition at a critical ratio of the inter-plane to intra-plane couplings. Adding a uniform magnetic field tunes the system to canted antiferromagnetism and eventually to a fully polarized state; similar behavior occurs for ferromagnetic intra-plan

H. Athar, G. -L. Lin, J. -J. Tseng

The cross section for muon pair productions by electrons scattering over photons, $σ_{MPP}$, is calculated analytically in the leading order. It is pointed out that for the center-of-mass energy range, $s \geq 5 m^{2}_μ$, the cross section for $σ_{MPP}$ is less than $1 μ$b. The differential energy spectrum for either of the resulting muons is given for the p

N. J. Kim, H. W. Lee, Y. S. Myung, Gungwon Kang

We study the holographic principle in the brane cosmology. Especially we describe how to accommodate the 5D anti de Sitter Schwarzschild (AdSS$_5$) black hole in the Binetruy-Deffayet-Langlois (BDL) approach of brane cosmology. It is easy to make a connection between a mass $M$ of the AdSS$_5$ black hole and a conformal field theory (CFT)-radiation dominated

R. M. Serra, P. B. Ramos, N. G. de Almeida, W. D. Jose

We present a reliable scheme for engineering arbitrary motional ionic states through an adaptation of the projection synthesis technique for trapped-ion phenomena. Starting from a prepared coherent motional state, the Wigner function of the desired state is thus sculpted from a Gaussian distribution. The engineering process has also been developed to take in

Hai-Woong Lee

We present a setup for a direct, total teleportation of a single-particle entangled state. Our scheme consists of a parametric down-conversion source, which emits a pair of entangled photons, and a dual Bell measurement system with two beam splitters and two pairs of detectors. An entangled state shared by a pair of beams can be directly transferred to anoth

Xu-Bo Zou, Jaewan Kim, Hai-Woong Lee

We present an efficient scheme to generate two-mode SU(2) macroscopic quantum superposition (Schrödinger cat) states, entangled number states and entangled coherent states for the vibrational motion of an ion trapped in a two-dimensional harmonic potential well. We also show that the same scheme can be used to realize a Fredkin gate operation.

S. Danko Bosanac

Angular momentum is important concept in physics, and its phase space properties are important in various applications. In this work phase space analysis of the angular momentum is made from its classical definition, and by imposing uncertainty principle its quantum properties are obtained. It is shown that kinetic energy operator is derived, but it has diff

T. C. Ralph, W. J. Munro

Recently K. Banaszek, I. A. Walmsley, K. Wodkiewicz (quant-ph/0012097) commented on our Proposal for the Measurement of Bell-Type Correlations from Continuous Variables [T. C. Ralph, W. J. Munro, R. E. S. Polkinghorne, Phys. Rev. Lett. 85, 2035 (2000)]. Their comment is based on a blatant misreading and misunderstanding of our letter and as such is simply wr

I. M. Tsai, S. Y. Kuo

To build a general-purpose quantum computer, it is crucial for the quantum devices to implement classical boolean logic. A straightforward realization of quantum boolean logic is to use auxiliary qubits as intermediate storage. This inefficient implementation causes a large number of auxiliary qubits to be used. In this paper, we have derived a systematic wa

V. F. Elesin, A. I. Podlivaev, L. A. Openov

Stability of recently predicted cage-like carbon cluster C$_8$ (prismane) against its transformations to structures lying at lower energies is studied theoretically. The smallest energy barrier inhibiting prismane transformation is shown to be 0.44 eV, in qualitative agreement with the value of activation energy for prismane decay calculated by molecular dyn

D. L. Khokhlov

It is assumed the existence of the universal potential fluctuations valid for all scales in the universe which follow the fractal law $δ_U=(Δr/r)^2$. The value of the universal potential fluctuations is determined from the data on anisotropy of the cosmic microwave background on degree scales. It is suggested to test the existence of the universal potential

J. S. Pethkar, A. M. Selvam

Turbulence, namely, irregular fluctuations in space and time characterize fluid flows in general and atmospheric flows in particular.The irregular,i.e., nonlinear space-time fluctuations on all scales contribute to the unpredictable nature of both short-term weather and long-term climate.It is of importance to quantify the total pattern of fluctuations for p

C. A. Bertulani

The physics of peripheral collisions with relativistic heavy ions (PCRHI) is reviewed. One- and two-photon processes are discussed.

Alexey Ustinov, Boris Malomed

We report the first experimental observation of phase-locked motion of a topological soliton at a nonzero average velocity in a periodically modulated lossy medium, under the action of an ac force with no dc component [the effect was predicted by G. Filatrella, B.A. Malomed, and R.D. Parmentier, Phys. Lett. A 198, 43 (1995)]. The velocity is related by a res

Ayse Karasu, Ismet Yurdusen

We show that the Drinfeld-Sokolov system of equations has a nontrivial prolongation structure. The closure process for prolongation algebra gives rise to the sl(4,c) algebra which is used to derive the scattering problem for the system of equations under consideration. The nontrivial new Backlund transformations and some explicit solutions are given.

Stefan Heusler

The semiclassical origin of the logarithmic singularity at the Heisenberg time of the symplectic form factor is deduced by combining the result of M. Sieber and K. Richter for the first term of the loop-expansion in the orthogonal case with the contribution that arises due to the spin. We are able to make a quantitative statement about the topology of all no

R. P. Thomas

Simple examples are given of bundles on Calabi-Yau 3-folds satisfying 8 out of 9 conditions required for a realistic compactification of string theory to 4 dimensions.

Viktor Bekkert, Vyacheslav Futorny

We classify the derived tame Schur and infinitesimal Schur algebras and describe indecomposable objects in their derived categories.

Siman Wong

We apply Tate's conjecture on algebraic cycles to study the Néron-Severi groups of varieties fibered over a curve. This is inspired by the work of Rosen and Silverman, who carry out such an analysis to derive a formula for the rank of the group of sections of an elliptic surface. For a semistable fibered surface, under Tate's conjecture we derive a f

Nets Hawk Katz, Nataša Pavlović

We prove that for the Navier Stokes equation with dissipation $(-Δ)^α$, where $1<α<{5/4}$, and smooth initial data, the Hausdorff dimension of the singular set at time of first blow up is at most $5-4α$. This unifies two directions from which one might approach the Clay prize problem.

Istvan Juhász, Saharon Shelah, Lajos Soukup, Zoltan Szentmiklóssy

We introduce a general method of constructing locally compact scattered spaces from certain families of sets and then, with the help of this method, we prove that if kappa^{<kappa}=kappa then there is such a space of height kappa^+ with only kappa many isolated points. This implies that there is a locally compact scattered space of height omega_2 with omega_

R. P. Thomas

Via considerations of symplectic reduction, monodromy, mirror symmetry and Chern-Simons functionals, a conjecture is proposed on the existence of special Lagrangians in the hamiltonian deformation class of a given Lagrangian submanifold of a Calabi-Yau manifold. It involves a stability condition for graded Lagrangians, and can be proved for the simple case o

Uri Abraham, Saharon Shelah

Any model of ZFC + GCH has a generic extension (made with a poset of size aleph_2) in which the following hold: MA + 2^{aleph_0}= aleph_2+ there exists a Delta^2_1-well ordering of the reals. The proof consists in iterating posets designed to change at will the guessing properties of ladder systems on omega_1. Therefore, the study of such ladders is a main c

Rüdiger Göbel, Saharon Shelah

An abelian group is said to be aleph_1-free if all its countable subgroups are free. Our main result is: If R is a ring with R^+ free and |R|<lambda <= 2^{aleph_0}, then there exists an aleph_1-free abelian group G of cardinality lambda with End(G)=R . A corollary to this theorem is: Indecomposable aleph_1-free abelian groups of cardinality aleph_1 do exist.

Paul Hacking

We define a geometrically meaningful compactification of the moduli space of smooth plane curves, which can be calculated explicitly. The basic idea is to regard a plane curve D in P^2 as a pair (P^2,D) of a surface together with a divisor, and allow both the surface and the curve to degenerate. For plane curves of degree d at least 4, we obtain a compactifi

Matthew E. White

We show there is an upper bound on the diameter of a closed, hyperbolic 3-manifold in terms of the length of any presentation of its fundamental group.

Matthew E. White

We show that there is an upper bound on the injectivity radius of a hyperbolic 3-manifold in terms of the the number of generators of its fundamental group.

Dirk Tasche

For a linear combination of random variables, fix some confidence level and consider the quantile of the combination at this level. We are interested in the partial derivatives of the quantile with respect to the weights of the random variables in the combination. It turns out that under suitable conditions on the joint distribution of the random variables t

Baruch Solel

It is shown that every linear surjective isometry between two right, full, Hilbert C*-modules is a sum of two maps : a (bi-) module map (which is completely isometric and preserves the inner product) and a map that reverses the (bi-) module actions. Every such isometry can be extended to an isometry of the C* linking algebras.

Philippe Caldero

We study algebras on which the Berenstein-Zelevinsky conjecture is true. In particular, we prove that this conjecture is true &#34;up to localization&#34;.

J. L. F. Barbon, E. Rabinovici

We extend the study of the nature of the Hagedorn transition in NCOS systems in various dimensions. The canonical analysis results in a microscopic ionization picture of a bound state system in which the Hagedorn transition is postponed till irrelevancy. A microcanonical analysis leads to a limiting Hagedorn behaviour dominated by highly excited, long open s

Alfredo Iorio, Gaetano Lambiase, Giuseppe Vitiello

We show that a suitable deformation of the algebra $h_k(1)$ of the creation and annihilation operators for a complex scalar field, initially quantized in Minkowski space--time, induces the canonical quantization of the same field in a generic gravitational background. This discloses the physical meaning of the deformation parameter $q$ which turns out to be

Y. Brihaye, B. M. A. G Piette

We consider the Einstein-Yang-Mills-Higgs equations for an SU(3) gauge group in a spherically symmetric ansatz. Several properties of the gravitating monopole solutions are obtained an compared with their SU(2) counterpart.

M. R. Setare, R. Mansouri

The Casimir stress on two parallel plates in de Sitter background for massless scalar field satisfying Robin boundary conditions on the plates is calculated. The metric is written in conformally flat form to make maximum use of the Minkowski space calculations. Different cosmological constants are assumed for the space between and outside of the plates to ha

Bo Feng, Yang-Hui He, Nicolas Moeller

The operators K_n are generators of reparameterization symmetries of Witten&#39;s cubic open string field theory. One pertinent question is whether they can be utilised to generate deformations of the tachyon vacuum and thereby violate its uniqueness. We use level truncation to show that these transformations on the vacuum are in fact pure gauge transformati

Loyal Durand, Phuoc Ha, Gregory Jaczko

We analyze the structure of meson loop corrections to the O($m_s$) expressions for the baryon masses and magnetic moments in heavy-baryon chiral perturbation theory (HBChPT), and show in detail how the bulk of the corrections are absorbed into redefinitions of the unknown parameters of the O($m_s$) chiral expansion. To effect this analysis, we use the three-

M. B. Gay Ducati, M. V. T. Machado

We study the contribution of the truncated BFKL series to the electroproduction process showing that a reliable description is obtained taking into account two orders in perturbation theory. Using the recent F2 logarithmic slope data as a constraint to the adustable parameters, the inclusive structure function is described in a wide range of the small x HERA

M. J. Herrero, F. J. Yndurain

We remark that the precision of recent determinations of $α_s(M^2_Z)$ is such that one can get bounds on supersymmetric partner masses (squark and gluino) by requiring consistency of determinations of $α_s$ at &#34;low&#34; energies, where those particles do not contribute, and on the $Z$ peak. For approximately degenerate squarks and gluinos with mass $\wid

W. Buchmüller, M. Plümacher

Spectator processes which are in thermal equilibrium during the period of baryogenesis influence the final baryon asymmetry. We study this effect quantitatively for thermal leptogenesis where we find a suppression by a factor O(1).

Daijiro Suematsu

We propose a model for the mass matrices of quarks and leptons based on two Abelian flavor symmetries. One is assumed to be broken at a high energy region near the Planck scale. It is used for the Froggatt-Nielsen mechanism in both quark and charged lepton sectors. Another one remains unbroken to a multi-TeV region. The mixings among neutrinos and gauginos i

Masaaki Fujii, K. Hamaguchi, T. Yanagida

We briefly review the present status of Affleck-Dine baryo/leptogenesis scenarios in the minimal supersymmetric standard model (MSSM) in the context of the gravity-mediated SUSY breaking, and show that there is a serious cosmological problem in the Affleck-Dine mechanism. That is, the late decay of the associated large Q-balls leads to the over production of

ZEUS Collaboration

Multiplicity moments of charged particles in deep inelastic E+P scattering have been measured with the ZEUS detector at HERA using an integrated luminosity of 38.4 pb^{-1}$. The moments for Q^2 > 1000 GeV^2 were studied in the current region of the Breit frame. The evolution of the moments was investigated as a function of restricted regions in polar angle a

C Gundlach

The first British Gravity Meeting was held at the University of Southampton, UK, on 27/28 March. 47 10-minute plenary talks were given. Here are the abstracts in the order given. A brief conference report will also appear in Matters of Gravity.

F. Q. Potiguar, U. M. S. Costa

In this work assuming valid the equipartition theorem and using the normalized q-expectation value, we obtain, until first order approximation, the hydrodynamics equation for the generalized statistics. This equations are different from those obtained in the context of the Boltzmann-Gibbs statistics. This difference is that now appears two transport coeffici

Su-Chan Park, Jeong-Man Park, Doochul Kim

Two-point density-density correlation functions for the diffusive binary reaction system $A+A\to\emptyset$ are obtained in one dimension via Monte Carlo simulation. The long-time behavior of these correlation functions clearly deviates from that of a recent analytical prediction of Bares and Mobilia [Phys. Rev. Lett. {\bf 83}, 5214 (1999)]. An alternative ex

P. Buonsante, R. Burioni, D. Cassi

Complex molecules and mesoscopic structures are naturally described by general networks of elementary building blocks and tight-binding is one of the simplest quantum model suitable for studying the physical properties arising from the network topology. Despite the simplicity of the model, topological complexity can make the evaluation of the spectrum of the

G. A. Farias, R. N. Costa Filho, F. M. Peeters, Nelson Studart

Using the Feynman path-integral formalism we study the polaron effects in quantum wires above a liquid helium film. The electron interacts with two-dimensional (2D) surface phonons, i.e. ripplons, and is confined in one dimension (1D) by an harmonic potential. The obtained results are valid for arbitrary temperature ($T$), electron-phonon coupling strength (

A. E. Koshelev, I. Aranson

We investigate the dynamics of the Josephson vortex lattice in layered high-T$_{c}$ superconductors at high magnetic fields. Starting from coupled equations for superconducting phases and magnetic field we derive equations for the relative displacements [phase shifts] between the planar Josephson arrays in the layers. These equations reveal two families of s

D. Giller, B. Ya. Shapiro, I. Shapiro, A. Shaulov

The Landau-Khalatnikov time-dependent equation is applied to describe the crystallization process of the ordered vortex lattice in high temperature superconductors after a sudden application of a magnetic field. Dynamic coexistence of a stable ordered phase and an unstable disordered phase, with a sharp interface between them, is demonstrated. The transforma

Giovanni Bonanno, Fabrizio Lillo, Rosario N. Mantegna

We consider different levels of complexity which are observed in the empirical investigation of financial time series. We discuss recent empirical and theoretical work showing that statistical properties of financial time series are rather complex under several ways. Specifically, they are complex with respect to their (i) temporal and (ii) ensemble properti

Z. Yusof, B. O. Wells, T. Valla, A. V. Fedorov

We present results from the study of a highly overdoped (OD) Bi2212 with a $T_{c}=51$K using high resolution angle-resolved photoemission spectroscopy. The temperature dependent spectra near the ($π,0$) point show the presence of the sharp peak well above $T_{c}$. From the nodal direction, we make comparison of the self-energy with the optimally doped and un

L. Šamaj

We consider an asymmetric version of a two-dimensional Coulomb gas, made up of two species of pointlike particles with positive $+1$ and negative -1/Q $(Q = 1, 2, ...)$ charges; Q=1 corresponds to the symmetric two-component plasma and the limiting case $Q\to\infty$ is related to the one-component plasma. The system lives on the surface of a sphere, and it i

Fabrizio Lillo, Giovanni Bonanno, Rosario N. Mantegna

We investigate the recently introduced variety of a set of stock returns traded in a financial market. This investigation is done by considering daily and intraday time horizons in a 15-day time period centered at the August 31st, 1998 crash of the S&P500 index. All the stocks traded at the NYSE during that period are considered in the present analysis. We s

K. Schoenhammer

The acceleration theorem for Bloch electrons in a homogenous external field is usually presented using quasiclassical arguments. In quantum mechanical versions the Heisenberg equations of motion for an operator $\hat {\vec k}(t)$ are presented mostly without properly defining this operator. This leads to the surprising fact that the generally accepted versio

Gang Su, Masuo Suzuki

On the basis of gauge invariance, it is proven in an elementary and straightforward manner, but without invoking any {\it ad hoc} assumption, that the existence of off-diagonal long-range order in one-particle reduced density matrix in Bose liquids implies both the irrotational flow in a simply connected region and the quantization of circulation in a multip

Takeshi Mizushima, Tomoya Isoshima, Kazushige Machida

The vortex phase diagram in the external rotation frequency versus temperature is calculated for dilute Bose-Einstein condensed gases. It is determined within the Bogoliubov-Popov theory for a finite temperature where the condensate and non-condensate fractions are treated in an equal footing. The temperature dependences of various thermodynamic instability

Claudio Brangian, Walter Kob, Kurt Binder

We use Monte Carlo simulations to investigate the dynamical properties of the infinite range 10 states Potts glass. By analyzing the spin autocorrelation function for system sizes up to N=2560, we show that strong finite size effects are present around the predicted dynamical transition temperature. The autocorrelation function shows strong self-averaging at

C. S. Sundar, A. Bharathi, M. Premila, T. N. sairam

Infrared absorption measurements in the range of 125 to 700 cm^(-1) have been carried out as a function of temperature upto 5 K in MgB2. The absorption spectrum is characterised by a broad band centred at 485 cm^{-1}, with shoulders at 333 and 387 cm^{-1}. Studies on the temperature dependence of absorption, indicate that these modes initially harden with th

Shun-Qing Shen

In their Letter (Phys. Rev. Lett. 83, 5118 (1999)), den Brink, Khaliullin, and Khomskii proposed theoretically that the one-dimensional ferromagnetic zigzag chains in CE phase in half-doped manganites play an essential role in forming the orbital ordering, and, more surprisingly, the on-site Coulomb interaction U between electrons with different orbitals lea

Mi-Ock Mun, Young Sup Roh, Kibum Kim, Jae Hoon Kim

We have identifies the otical phonon modes of the superconducting infinite-layer compounds Sr$_{0.9}Ln_{0.1}$CuO$_2$ ($Ln$ = La, Gd, Sm; $T_c$ = 43 K for all) from their infrared reflectivity spectra obtained with a Fourier-transform infrared spectrometer on high-quality high-purity samples synthesized under high pressure. The La- and the Gd-doped compounds

C. D. Batista, J. Bonča, J. E. Gubernatis

We introduce a novel mechanism for the unusual itinerant ferromagnetism found in mixed valence systems like Ce(Rh$_{1-x}$Ru$_x$)$_3$B$_2$, La$_x$Ce$_{1-x}$Rh$_3$B$_2$, US, USe, and UTe. With it we can provide an explanation for the long-unexplained large value of $T_c$ ($\sim$ 100$^\circ$K) value and the maximum in the magnetization below $T_c$ found experim

J. Q. Li, L. Li, Y. Q. Zhou, Z. A. Ren

The structural properties of MgB2 superconductors have been analyzed by means of convergent-beam electron diffraction, high-resolution transmission-electron microscopy, and theoretical simulations. The MgB2 crystal has been identified to have a hexagonal structure with the space group of P6/mmm. Microstructural features of MgB6 materials depend evidently upo

Robert A. Wickham, An-Chang Shi

The phase behaviour of blends of ABC triblock and ac diblock copolymers is examined using self-consistent field theory. Several equilibrium lamellar structures are observed, depending on the volume fraction of the diblocks, phi_2, the monomer interactions, and the degrees of polymerization of the copolymers. For segregations just above the order-disorder tra

V. M. Pudalov, A. Punnoose, G. Brunthaler, A. Prinz

We report novel manifestation of the valley splitting for the two valley electron system in (100) Si-inversion layers at low carrier density. We found that valley splitting causes almost 100% modulation of the Shubnikov de Haas oscillations in very low magnetic fields, almost on the bound of the quantum interference peak of the negative magnetoresistance. Fr

E. Infeld, A. Senatorski

The changes observed in the topology of superfluid helium vortices have intrigued people for some time now [1]. These vortices either extend from wall to wall, however tangled they may be in between, or else can be roughly circular and freely move around the superfluid [1]. Some time ago, Richard Feynman postulated that two oppositely polarized line vortices

I. L. Menezes-Sobrinho

In this paper, a computational model in (2+1)-dimensions which simulates the rupture process of a fibrous material submitted to a constant force $F$, is analyzed. The roughness exponent $ζ$ at the boundary that separates two failure regimes, catastrophic and slowly shredding, is evaluated. In the catastrophic (dynamic) regime the initial strain creates a cra

Michael Loewenstein

Intracluster medium (ICM) abundances are higher than expected assuming enrichment by supernovae with progenitors belonging to the simple stellar population (SSP) observed in cluster galaxies, if stars formed with a standard initial mass function (IMF). Moreover, new results on ICM oxygen abundances imply that nucleosynthesis occurred with nonstandard yields.