June 2001 arXiv papers — page 3

N. E. Bonesteel, D. Stepanenko, D. P. DiVincenzo

We show how to eliminate the first-order effects of the spin-orbit interaction in the performance of a two-qubit quantum gate. Our procedure involves tailoring the time dependence of the coupling between neighboring spins. We derive an effective Hamiltonian which permits a systematic analysis of this tailoring. Time-symmetric pulsing of the coupling automati

L. A. Caron, H. Jirari, H. Kröger, X. Q. Luo

We address the problem of quantum chaos: Is there a rigorous, physically meaningful definition of chaos in quantum physics? Can the tools of classical chaos theory, like Lyapunov exponents, Poincaré sections etc. be carried over to quantum systems? Can quantitative predictions be made? We show that the recently proposed quantum action is well suited to answe

J. M. Cervero, A. Rodriguez-Gonzalez

In this Paper we present an approach to Quantum Mechanical Canonical Transformations. Our main result is that Time Dependent Quantum Canonical Transformations can always be cast in the form of Squeezing Operators. We revise the main properties of these operators in regard to its Lie group properties, how two of them can be combined to yield another operator

Mark P Davidson

It is shown using numerical simulation that classical charged tachyons have several features normally thought to be unique to quantum mechanics. Spin-like self-orbiting helical motions are shown to exist at discrete values for the velocity of the tachyon in Feynman-Wheeler electrodynamics and in normal causal electrodynamics more complex closed orbits also a

Hartmut Klauck

We investigate the power of interaction in two player quantum communication protocols. Our main result is a rounds-communication hierarchy for the pointer jumping function $f_k$. We show that $f_k$ needs quantum communication $Ω(n)$ if Bob starts the communication and the number of rounds is limited to $k$ (for any constant $k$). Trivially, if Alice starts,

Tom Chang, Cheng-chin Wu, Vassilis Angelopoulos

Observations indicate that the magnetotail convection is turbulent and bi-modal, consisting of fast bursty bulk flows (BBF) and a nearly stagnant background. We demonstrate that this observed phenomenon may be understood in terms of the intermittent interactions, dynamic mergings and preferential accelerations of coherent magnetic structures under the influe

P. Arun, Naveen Gaur

The simple pendulum is one of the first experiments that students of higher physics do. There are certain precautions which the students are asked to take while performing the experiment. In this note we will try to explain as to why these precautions are taken up and what will happen if we relax them.

Elise Lorenceau, David Quere, Jean-Yves Ollitrault, Christophe Clanet

We report gravity oscillations of a liquid column partially immersed in a bath of liquid. We stress in particular some peculiarities of this system, namely (i) the fact that the mass of this oscillator constantly changes with time; (ii) the singular character of the beginning of the rise, for which the mass of the oscillator is zero; (iii) the sources of dis

Dipankar Chattarji, Chiranjib Sur

We consider the process of double photoionization (DPI) in a rare gas atom as a two-step process, namely (i) photoionization in an inner shell followed by (ii) the emission of an Auger electron from an outer shell. An angular correlation function for the two emitted electrons is defined by analogy with the theory of angular correlation in nuclear physics. An

B. G. Sidharth

We point out that in the non commutativity and breakdown of conventional spacetime at micro scales lies the seed to the unification of gravitation and electromagnetism.

L. Frappat, A. Sciarrino, P. Sorba

mRNA editing of sequences of many species is analyzed. The nature of the inserted nucleotides and the position of the insertion sites, once fixed the edited peptide chain, are explained by introducing a minimum principle in the framework of the crystal basis model of the genetic code introduced by the authors.

Claus O. Wilke, Christoph Adami

We investigate the relationship between the average fitness decay due to single mutations and the strength of epistatic interactions in genetic sequences. We observe that epistatic interactions between mutations are correlated to the average fitness decay, both in RNA secondary structure prediction as well as in digital organisms replicating in silico. This

S. V. Artemov, M. A. Belov, Yu. N. Koblik, G. A. Radyuk

Mutual dependencies of mass and orbital moment increase for rotating bodies of various configurations (a string with uniform mass distribution, a string with squared mass distribution or a sphere with uniform mass distribution, double system of point masses) are considered in quasiclassical approximation. Results are used for analysis of meson, baryon resona

Cheuk-Yin Wong, E. S. Swanson, T. Barnes

Many of the hadron-hadron cross sections required for the study of the dynamics of matter produced in relativistic heavy-ion collisions can be calculated using the quark-interchange model. Here we evaluate the low-energy dissociation cross sections of $J/ψ$, $ψ'$, $χ$, $Υ$, and $Υ'$ in collision with $π$, $ρ$, and $K$, which are important for the int

A. Capella, D. Sousa

Hadron multiplicities in nucleus--nucleus interactions are calculated in the Dual Parton Model and its dependence on the number of collisions and the number of participants is analyzed. Shadowing corrections are calculated as a function of impact parameter and the multiplicity per participant as a funtion of centrality is found to be in agreement with experi

C. A. Bertulani, P. F. Bortignon, V. Yu. Ponomarev, V. V. Voronov

In a recent Letter [1] an overall agreement with the experimental data for the excitation of the single and double giant dipole resonances in relativistic heavy ion collision in 136Xe and 208Pb nuclei has been reported. We point out that this agreement is achieved by a wrong calculation of the DGDR excitation mechanism. We also argue that the agreement with

A. Rabhi, P. Schuck, R. Bennaceur, G. Chanfray

It is shown that the Self-Consistent RPA (SCRPA) approach allows in a very natural way to restore symmetries, spontaneously broken on the mean field level. This is achieved via the introduction of a second Lagrange multiplier which constrains the variance of the symmetry operator to zero. This important feature of SCRPA, here pointed out for the first time,

A. Pogrebkov

Quantization procedure of the Gardner-Zakharov-Faddeev and Magri brackets by means of the fermionic representation for the KdV field is considered. It is shown that in both cases the corresponding Hamiltonians are given as sums of two well defined operators. Each of them is bilinear and diagonal with respect to either fermion, or boson (current) creation-ann

M. Hnatič, J. Honkonen, M. Jurcisin

Interplay of kinematic and magnetic forcing in a model of a conducting fluid with randomly driven magnetohydrodynamic equations has been studied in space dimensions $d\ge 2$ by means of the renormalization group. A perturbative expansion scheme, parameters of which are the deviation of the spatial dimension from two and the deviation of the exponent of the p

Palle E. T. Jorgensen, Steen Pedersen

Let $ Ω\subset R^d $ have finite positive Lebesgue measure, and let $ \mathcal{L}^{2}(Ω) $ be the corresponding Hilbert space of $ \mathcal{L}^{2} $-functions on $ Ω$. We shall consider the exponential functions $ e_λ $ on $ Ω$ given by $ e_λ(x)=e^{i2πλx} $. If these functions form an orthogonal basis for $ \mathcal{L}^{2}(Ω) $, when $ λ$ ranges over some su

Thomas Kerler

The goal of this paper is to find a close to isomorphic presentation of 3-manifolds in terms of Hopf algebraic expressions. To this end we define and compare three different braided tensor categories that arise naturally in the study of Hopf algebras and 3-dimensional topology. The first is the category \Cob of connected surfaces with one boundary component

Robert Brooks, Eran Makover

In this paper, we address the following question: What does a typical compact Riemann surface of large genus look like geometrically? We do so by constructing compact Riemann surfaces from oriented 3-regular graphs. The set for such Riemann surfaces is dense in the space of all compact Riemann surfaces, namely Belyi surfaces. And in this construction we can

Robin Hartshorne

We give some experimental data of Gorenstein liaison, working with points in ${\mathbb P}^3$ and curves in ${\mathbb P}^4$, to see how far the familiar situation of liaison, biliaison, and Rao modules of curves in ${\mathbb P}^3$ will extend to subvarieties of codimension 3 in higher ${\mathbb P}^4$.

Mohamed Saidi

In this paper we study the semi-stable reduction of Galois covers of degree p above semi-stable curves over a complete discrete valuation ring of inequal characteristics (0,p). We are also able to describe the Galois action on these covers in terms of some geometric and combinatorial datas in characteristic p endowed with the action of the Galois group of th

Mohamed Saidi

In this paper we prove an explicit formula which compares the dimensions of the spaces of vanishing cycles in a Galois cover of degree p between formal germ of curves over a complete discrete valuation ring of inequal characteristics (0,p). This formula can be easily generalised to the case of a Galois cover with group which is nilpotent or which has a norma

Olivier Penacchio

We propose a generalization of the notion of ${\bf R}$-split mixed Hodge structure by defining a ${\bf R}$-splitting level for mixed Hodge structures. This is a discrete invariant taking values in positive integers and equal to 0 for ${\bf R}$-split mixed Hodge structures. We describe some properties of this invariant for classical operations on these struct

David Kazhdan, Alexander Polishchuk

A theorem of Waldspurger states that the Fourier transform of a stable distribution on the Lie algebra of a simply-connected semisimple group $G$ over a p-adic field, is again stable. We generalize this theorem to representations whose generic stabilizer subgroup is connected and reductive (assuming that $G$ is simple). In this more general situation the Fou

Yurii A. Neretin

Consider an infinite tree. A hierarchomorphism (spheromorphism) is a homeomorphism of the absolute which can be extended to the tree except a finite subtree. Examples of groups of hierarchomorphisms: groups of locally analitic diffeomorphisms of $p$-adic line; also Richard Thompson groups. The groups of hierarchomorphisms have some properties similar to the

Paolo Salvatore, Nathalie Wahl

The framed n-discs operad fD_n is studied as semidirect product of SO(n) and the little n-discs operad. Our equivariant recognition principle says that a grouplike space acted on by fD_n is equivalent to the n-fold loop space on a SO(n)-space. Examples of fD_2-spaces are nerves of ribbon braided monoidal categories. We compute the rational homology of fD_n.

Vyjayanthi Chari

We define an action of the braid group of a simple Lie algebra on the space of imaginary roots in the corresponding quantum affine algebra. We then use this action to determine an explicit condition for a tensor product of arbitrary irreducible finite--dimensional representations is cyclic. This allows us to determine the set of points at which the correspon

Leonid Polterovich, Jean-Claude Sikorav

It follows from a general theorem of Bonk and Eremenko that closed plane curves which are contractible in the complement to the integral lattice satisfy a linear isoperimetric inequality. We give an alternative proof of this fact. Our approach is based on a non-standard combinatorial isoperimetric inequality which requires a refinement of the small cancellat

Pavol Severa

Using a basic idea of Sullivan's rational homotopy theory, one can see a Lie groupoid as the fundamental groupoid of its Lie algebroid. This paper studies analogues of Lie algebroids with non-trivial higher homotopy. Using various homotopy classes one can obtain e.g. central extensions of loop groups, or one can integrate a Lie biagebroid to a double sym

S. A. Apikyan, C. J. Efthimiou

We study the Toda field theory with finite Lie algebras using an extension of the Goulian-Li technique. In this way, we show that, after integrating over the zero mode in the correlation functions of the exponential fields, the resulting correlation function resembles that of a free theory. Furthermore, it is shown that for some ratios of the charges of the

Valentina Riva

Critical systems are described by conformal field theories, whose dynamics can be exactly solved in two dimensions. In the presence of a boundary, with the so-called method of images it is possible to study the surface critical behaviour of these systems, and the conformal boundary conditions can be related to the bulk operator content of the theory. After a

Tetsuya Shiromizu, Daisuke Ida, Hirotaka Ochiai, Takashi Torii

We examine the stability of ${\rm AdS}_p \times {\rm S}^n \times {\rm S}^{q-n}$. The initial data constructed by De Wolfe et al \cite{Gary} has been carefully analyised and we have confirmed that there is no lower bound for the total mass for $q< 9$. The effective action on ${\rm AdS}_p$ has been derived for dilatonic compactification of the system to descri

Chiang-Mei Chen, T. Harko, M. K. Mak

We consider the dynamics of a viscous cosmological fluid in the generalized Randall-Sundrum model for an isotropic brane. To describe the dissipative effects we use the Israel-Hiscock-Stewart full causal thermodynamic theory. In the limiting case of a stiff cosmological fluid with pressure equal to the energy density, the general solution of the field equati

Hitoshi Ito

The commutation relations of the composite fields are studied in the 3, 2 and 1 space dimensions. It is shown that the field of an atom consisting of a nucleus and an electron fields satisfies, in the space-like asymptotic limit, the canonical commutation relations within the sub-Fock-space of the atom. The composite anyon fields are shown to satisfy the pro

U. Baur, M. Buice, L. H. Orr

We consider photon radiation in tbar-t events at the upgraded Fermilab Tevatron and the CERN Large Hadron Collider (LHC) as a tool to measure the electric charge of the top quark. We analyze the contributions of tbar-t-gamma production and radiative top quark decays to p-p, pbar-p -> gamma l^+/- nu bbar-b jj, assuming that both b-quarks are tagged. With 20~f

Jiao-Lin Xu

From the Dirac sea concept, the BCC model infers that the quarks u and d constitute a body center cubic quark lattice in the vacuum; when a quark $q^*$ is excited from the vacuum, the nearest primitive cell u&#39; and d&#39; is accompanying excited by the quark $q^*$. Using the energy band theory, the model deduces the quantum numbers (I, S, C, b, and Q) and

Fabio L. Braghin

A time dependent variational approach is considered to derive the equations of movement for the $λϕ^4$ model. The temporal evolution of the model is performed numerically in the frame of the Gaussian approximation in a lattice of 1+1 dimensions given non homogeneous initial conditions (like bubbles) for the classical and quantum parts of the field which expa

Jane H. MacGibbon, Ubi F. Wichoski, Bryan R. Webber

Previous work on the neutrino spectra from high energy sources has not included the tau neutrinos directly produced by the decays in the source. Here we consider the tau neutrino component and discuss how its inclusion modifies the expected neutrino spectra. We discuss implications for interpreting any observed tau neutrino component in TeV - UHE events as e

Thomas G. Rizzo

In the Universal Extra Dimensions model of Appelquist, Cheng and Dobrescu, all of the Standard Model fields are placed in the bulk and thus have Kaluza-Klein(KK) excitations. These KK states can only be pair produced at colliders due to the tree-level conservation of KK number, with the lightest of them being stable and possibly having a mass as low as $\sim

S. Fajfer, S. Prelovsek, P. Singer

We study the nine possible rare charm meson decays D->Pl^+l^- (P=pi,K,eta,eta&#39;) using the Heavy Meson Chiral Lagrangians and find them to be dominated by the long distance contributions. The decay D^+ -> pi^+l^+l^- with the branching ratio 1*10^(-6) is expected to have the best chances for an early experimental discovery. The short distance contribution

M. Antonelli, S. Moretti

We review the progress made at LEP in the quest for new particles.

E. Fischbach, D. E. Krause, V. M. Mostepanenko, M. Novello

Models in which the gravitational and gauge interactions are unified at ~1 TeV lead to the possibility that large extra dimensions would produce Yukawa-type corrections to the Newtonian gravitational law at small distances. In some models with n = 3 extra dimensions, deviations from Newtonian gravity would occur at separations ~5 nm, a distance scale accessi

K. J. Eskola, K. Kajantie, K. Tuominen

Atomic number ($A$) and energy ($\roots$) scaling exponents of multiplicity and transverse energy in heavy ion collisions are analytically derived in the perturbative QCD + saturation model. The exponents depend on the small-$x$ behaviour of gluon distribution functions at an $x$-dependent scale. The relation between initial state and final state saturation

Kenneth Lane

I discuss vacuum alignment and CP violation in technicolor theories of electroweak and flavor symmetry breaking. I review the surprising appearance of rational phase solutions in the technifermion sector and propose a new solution of the strong CP problem of quarks. I then discuss the sources of weak CP violation, in both the CKM matrix and the suppressed ex

Jae Sik Lee

We study the phenomenological implications of the Higgs sector CP violation at a photon collider. In our model, the CP violation is radiatively induced by the non-trivial CP phases of the third-generation scalar-quark sector in the MSSM. We re-evaluate the $s$-channel resonance production cross sections and the polarization asymmetries of the neutral Higgs b

Amol S. Dighe

We explore the earth matter effects on the energy spectra of neutrinos from a supernova. We show that the observations of the energy spectra of $ν_e$ and $\barν_e$ from a galactic supernova may enable us to identify the solar neutrino solution, to determine the sign of $Δm^2_{32}$, and to probe the mixing matrix element $|U_{e3}|^2$ to values as low as $10^{

Changhao Jin

The sum rule for charmless inclusive semileptonic B-meson decays allows a theoretically clean and experimentally efficient determination of |V_{ub}|. The leading twist contribution to the sum rule is known in QCD. We compute higher twist corrections to the sum rule using the heavy quark effective theory.

B. I. Ermolaev, M. Greco, S. I. Troyan

Talk given at 9th Workshop DIS 2001, Bologna, April,27 -May,1, 2001.

Christian W. Bauer, Cheng-Wei Chiang, Sean Fleming, Adam K. Leibovich

At the upper endpoint of the photon energy spectrum in Upsilon -> X gamma, the standard NRQCD power counting breaks down and the OPE gives rise to color-octet structure functions. Furthermore, in this kinematic regime large Sudakov logarithms appear in the octet Wilson coefficients. The endpoint spectrum can be treated consistently within the framework of a

R. -D. Heuer, D. J. Miller, F. Richard, P. M. Zerwas

The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider

Claudio Coriano&#39;

We describe the N=1 supersymmetric evolution of the parton distributions with coupled gluinos and scalar quarks (Exact Supersymmetric Altarelli Parisi or ESAP). Superymmetric distributions are generated radiatively and studied as a function of both a matching scale (the match is to an intermediate AP evolution), parameterized by a scalar quark mass, and a fi

2 Collaboration, O. Rind

The Muon (g-2) Experiment (E821) at Brookhaven National Laboratory (BNL) has measured the anomalous magnetic moment of the positive muon to an unprecedented precision of 1.3 parts per million. The result, a_{μ^+} = (g-2)/2 = 11 659 202(14)(6) X 10^{-10}, is based on data recorded in 1999 and is in good agreement with previous measurements. Upcoming analysis

The KLOE collaboration, presented by Achim Denig

We report on the measurement of the hadronic cross section below 1GeV at the electron-positron-collider DAPHNE, using the multiple purpose detector KLOE. The radiative return, which is due to initial state radiation (e+ e- \to gamma + hadrons), allows us to obtain the cross section for variable center-of-mass-energies of the hadronic system from the 2m_pi th

Pushpalatha C. Bhat

During the coming decade, high energy physics experiments at the Fermilab Tevatron and around the globe will use very sophisticated equipment to record unprecedented amounts of data in the hope of making major discoveries that may unravel some of Nature&#39;s deepest mysteries. The discovery of the Higgs boson and signals of new physics may be around the cor

J. A. Crittenden

We consider the contribution to our understanding of vacuum-exchange processes to be made by investigations at the proposed electron-proton collider THERA. Recent results have highlighted the value of such studies for testing quantum chromodynamical descriptions of both long-range and short-range strong interactions. Stringent quantitative constraints have b

Alberto De Min

In the last five years, the operation of the LEP accelerator has provided the HEP community with a unique opportunity to search for physics beyond the standard model at the typical energy scale of $~200$ GeV. Although most of the data analysis has been focused on the traditional sectors of Higgs and gravity-mediated SUSY physics, a considerable effort has be

Pushpalatha C. Bhat

In the next decade, high energy physicists will use very sophisticated equipment to record unprecedented amounts of data in the hope of making major advances in our understanding of particle phenomena. Some of the signals of new physics will be small, and the use of advanced analysis techniques will be crucial for optimizing signal to noise ratio. I will dis

Andrey Neronov

We study the localization of fermions on a brane embedded in a space-time with $AdS_n \times M^k$ geometry. Quantum numbers of localized fermions are associated with their rotation momenta around the brane. Fermions with different quantum numbers have different higher-dimensional profiles. Fermion masses and mixings, which are proportional to the overlap of

H. -J. Schmidt, U. Semmelmann

We consider strings with the Nambu action as extremal surfaces in a given space-time, thus, we ignore their back reaction. Especially, we look for strings sharing one symmetry with the underlying space-time. If this is a non-null symmetry, the problem of determining the motion of the string can be dimensionally reduced. We get exact solutions for the followi

Petros Maniatis, T. J. Giuli, Mary Baker

In this paper we describe how to build a trusted reliable distributed service across administrative domains in a peer-to-peer network. The application we use to motivate our work is a public key time stamping service called Prokopius. The service provides a secure, verifiable but distributable stable archive that maintains time stamped snapshots of public ke

Simeon Warner

In this article I outline the ideas behind the Open Archives Initiative metadata harvesting protocol (OAIMH), and attempt to clarify some common misconceptions. I then consider how the OAIMH protocol can be used to expose and harvest metadata. Perl code examples are given as practical illustration.

Raj P. Gopalan, Tariq Nuruddin, Yudho Giri Sucahyo

The need for Knowledge and Data Discovery Management Systems (KDDMS) that support ad hoc data mining queries has been long recognized. A significant amount of research has gone into building tightly coupled systems that integrate association rule mining with database systems. In this paper, we describe a seamless integration scheme for database queries and a

Dirk K. Morr, Alexander V. Balatsky

We study the electronic structure near impurities in the one-dimensional chains of YBa$_2$Cu$_3$O$_{6+x}$. Assuming chain superconductivity below $T_c$ due to a proximity coupling, we show that only a magnetic impurity induces resonance states in the local density of states. Its spatial structure reflects the particle-hole nature of chain superconductivity a

Weinan E, Zhongyi Huang

A new class of matching condition between the atomistic and continuum regions is presented for the multi-scale modeling of crystals. They ensure the accurate passage of large scale information between the atomistic and continuum regions and at the same time minimize the reflection of phonons at the interface. These matching conditions can be made adaptive if

Saul L. Ginzburg, Mark A. Pustovoit

In a simple system with periodic symmetric potential, the phase model under effect of strong multiplicative noise or periodic square wave, we found a giant response, in the form of directed flux, to an ultrasmall dc signal. The resulting flux demonstrates a bell-shaped dependence on multiplicative noise correlation time and occurs even in the case of large (

Subhadip Raychaudhuri, Yonathan Shapir, Shaul Mukamel

The center-bound excitonic diffusion on dendrimers subjected to several types of non-homogeneous funneling potentials, is considered. We first study the mean-first passage time (MFPT) for diffusion in a linear potential with different types of correlated and uncorrelated random perturbations. Increasing the funneling force, there is a transition from a phase

N. Shah, A. J. Millis

We present a theory of the interplane conductivity of bilayer high temperature superconductors, focusing on the effect of quantal and thermal fluctuations on the oscillator strengths of the superfluid stiffness and the bilayer plasmon. We find that the opening of the superconducting gap and establishment of superconducting phase coherence each lead to redist

D. C. Cabra, G. L. Rossini

We study the breaking of parity symmetry in the 2+1 Gross-Neveu model at finite temperature with chemical potential $μ$, in the presence of an external magnetic field. We find that the requirement of gauge invariance, which is considered mandatory in the presence of gauge fields, breaks parity at any finite temperature and provides for dynamical mass generat

J. Lorenzana, C. Castellani, C. Di Castro

The theory of first order density-driven phase transitions with frustration due to the long range Coulomb (LRC) interaction develop on paper I of this series is applied to the following physical systems: i) the low density electron gas ii) electronic phase separation in the low density three dimensional $t-J$ model iii) in the manganites near the charge orde

I. Grote, E. Koerding, F. Wegner

An effective Hartree-Fock-Bogoliubov-type interaction is calculated for the Hubbard-model in second order in the coupling by means of flow-equations. A stability analysis is performed in order to obtain the transition into various possible phases. We find, that the second order contribution weakens the tendency for the antiferromagnetic transition. Apart fro

Andrzej Eilmes, Rudolf A. Roemer, Michael Schreiber

We study the influence of many-particle interactions on a metal-insulator transition. We consider the two-interacting-particle problem for onsite interacting particles on a one-dimensional quasiperiodic chain, the so-called Aubry-André model. We show numerically by the decimation method and finite-size scaling that the interaction does not modify the critica

I. Peschel, L. Turban, Ferenc Igloi

We study two-dimensional systems with boundary curves described by power laws. Using conformal mappings we obtain the correlations at the bulk critical point. Three different classes of behaviour are found and explained by scaling arguments which also apply to higher dimensions. For an Ising system of parabolic shape the behaviour of the order at the tip is

B. J. Baelus, F. M. Peeters

The influence of the geometry of a thin superconducting sample on the penetration of the magnetic field lines and the arrangement of vortices are investigated theoretically. We compare superconducting disks, squares and triangles with the same surface area having nonzero thickness. The coupled nonlinear Ginzburg-Landau equations are solved self-consistently

A. C. Hewson

We illustrate the renormalized perturbation expansion method by applying it to a single impurity Anderson model. Previously, we have shown that this approach gives the {\it exact} leading order results for the specific heat, spin and charge susceptibilities and leading order temperature dependence of the resistivity for this model in the Fermi-liquid regime,

K. Held, A. K. McMahan, R. T. Scalettar

The merger of density-functional theory in the local density approximation (LDA) and many-body dynamical mean field theory (DMFT) allows for an ab initio calculation of Ce including the inherent 4f electronic correlations. We solve the DMFT equations by the quantum Monte Carlo (QMC) technique and calculate the Ce energy, spectrum, and double occupancy as a f

L. Turban

The statistics of nested spiral self-avoiding loops, which is closely related to the partition of integers into decreasing parts, is studied on the square and triangular lattices.

L. Turban

Using conformal invariance, we show that the non-universal exponent eta_0 associated with the decay of correlations along a defect line of modified bonds in the square-lattice Ising model is related to the amplitude A_0=xi_n/n of the correlation length ξ_n(K_c) at the bulk critical coupling K_c, on a strip with width n, periodic boundary conditions and two e

Wonkee Kim, Jian-Xin Zhu, J. P. Carbotte, C. S. Ting

The microscopic origin of the pseudogap state which exists in the underdoped cuprates remains unknown. The $c$-axis properties in the pseudogap regime are particularly anomalous. We use a recently proposed model of a $d$-density wave which leads to staggered currents and the doubling of the unit cell to investigate the $c$-axis kinetic energy and the optical

D. Braak, N. Andrei

In a recent paper (cond-mat/0009279), Fabricius and McCoy studied the spectrum of the spin 1/2 XXZ-model at Delta = (q+q^{-1})/2 and q^{2N}=1 for integer N >1. They found a certain pattern of degeneracies and linked it to the sl(2)-loop symmetry present in the commensurable spin sector (N divides S^z). We show that the degeneracies are due to zero-energy, tr

M. N. Kiselev, K. Kikoin, R. Oppermann

Interplay between Kondo effect and trends to antiferromagnetic and spin glass ordering in perfect and disordered bipartite Kondo lattices is considered. Ginzburg-Landau equation is derived from the microscopic effective action written in three mode representation (Kondo screening, antiferromagnetic correlations and spin liquid correlations). The problem of l

Zhenyu Li, Jinlong Yang, J. G. Hou, Qingshi Zhu

We report self-consistent {\it ab initio} calculations of structural and electronic properties for the B- and Mg-terminated MgB$_{2}$ (0001) surfaces. We employ ultra-soft pseudopotentials and plane wave basis sets within the generalized gradient approximation. The surface relaxations are found to be small for both B- and Mg-terminated surfaces. For the B-te

C. A. Perroni, G. De Filippis, V. Cataudella, G. Iadonisi

Within a recently proposed variational approach it has been shown that, in $La_{1-x}A_xMnO_3$ perovskites with $0<x<0.5$, near the metal-insulator transition, the combined effect of the magnetic and electron-phonon interactions pushes the system toward a regime of two coexisting phases: a low electron density one made by itinerant large polarons forming ferr

Nicolas Combe, Pablo Jensen, Jean-Louis Barrat

We investigate the equilibrium properties of arrays of coherent strained islands in heteroepitaxial thin films of bidimensional materials. The model we use takes into account only three essential ingredients : surface energies, elastic energies of the film and of the substrate and interaction energies between islands via the substrate. Using numerical simula

G. De Filippis, V. Cataudella, G. Iadonisi, V. Marigliano Ramaglia

The influence of next-nearest neighbor electron hopping, $t^{\prime}$, on the polaron and bipolaron formation in a square Hubbard-Holstein model is investigated within a variational approach. The results for electron-phonon and electron-electron correlation functions show that a negative value of $t^{\prime}$ induces a strong anisotropy in the lattice distor

P. Bordet, M. Mezouar, M. Nunez-Regueiro, M. Monteverde

We report measurements on MgB2 up to ~40GPa. Increasing pressure yields a monotonous decrease of the lattice parameters and of the c/a ratio, but no structural transition down to parameters smaller than those of AlB2. The transition superconducting temperature also decreases with temperature in a sample dependent way. The results are explained by an increase

Atsushi Nakasu, Keisuke Totsuka, Yasumasa Hasegawa, Kiyomi Okamoto

The effect of the four-spin cyclic exchange interaction at each plaquette in the $S=1/2$ two-leg spin ladder is investigated at T=0, especially focusing on the field-induced gap. The strong rung coupling approximation suggests that it yields a plateau at half of the saturation moment ($m=1/2$) in the magnetization curve, which corresponds to a field-induced

H. Rosner, R. Weht, M. D. Johannes, W. E. Pickett

An unusual quasi-two-dimensional heavy band mass van Hove singularity (vHs) lies very near the Fermi energy in MgCNi3, recently reported to superconduct at 8.5 K. This compound is strongly exchange enhanced and is unstable to ferromagnetism upon hole doping with 12% Mg --> Na or Li. The 1/4-depleted fcc (frustrated) Ni sublattice and lack of Fermi surface ne

N. Shah, A. J. Millis

We use a recently proposed model of the interplane conductivity of high temperature superconductors to investigate the `scattering rate sum-rule&#39; introduced by Basov and co-workers. We present a new derivation of the sum-rule. The quantal and thermal fluctuations of the order parameter which have been argued to produce the observed pseudogap behavior are

P. D. Johnson, T. Valla, A. Fedorov, Z. Yusof

High-resolution photoemission is used to study the electronic structure of the cuprate superconductor, Bi2212, as a function of hole doping and temperature. A kink observed in the band dispersion in the nodal direction in the superconducting state is associated with coupling to a resonant mode observed in neutron scattering. From the measured real part of th

A. Lobel, A. K. Dupree

Four spatially resolved near-UV raster scans across the chromospheric disk of alpha Ori, obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, reveal mean chromospheric infall from 1998 January to 1998 April, which reversed to upflow in deeper layers between 1998 September and 1999 March. In 1998 September we detect systematic

A. Lobel

We have developed a new formalism to compute the thermodynamic coefficient Gamma1 in the theory of stellar and atmospheric stability. We generalize the classical derivation of the first adiabatic index, which is based on the assumption of thermal ionization and equilibrium between gas and radiation temperature, towards an expression which incorporates photo-

V. Junkkarinen, R. D. Cohen, T. A. Barlow, F. Hamann

In the analysis of broad absorption line (BAL) quasar spectra, Keck HIRES spectra are a useful complement to lower resolution HST and ground based spectra. The HIRES spectra provide accurate parameters for narrow, intervening type absorption systems including Lyman limit systems and a direct measurement of the smoothness of BAL features. The smoothness of th

Hector Aceves

By means of N-body simulations we study the global dynamics of triplets of galaxies, considering initial conditions starting from `maximum expansion&#39; and in virial equilibrium. Unlike previous studies we treat galaxies self-consistently. We do not consider the influence of a primordial common halo of dark matter. Our results indicate that a low number of

F. Crawford, R. N. Manchester, V. M. Kaspi

We report on radio polarimetry observations for nine southern pulsars. Six of the nine in the sample are young, with characteristic ages under 100 kyr and high spin-down luminosities. All six show a significant degree of linear polarization. We also confirm a previously noticed trend in which the degree of linear polarization increases with spin-down luminos

B. J. Philhour, B. G. Keating, P. A. R. Ade, R. S. Bhatia

We describe the development of a bolometric receiver designed to measure the arcminute-scale polarization of the cosmic microwave background (CMB). The Polatron will be mounted at the Cassegrain focus of the 5.5 m telescope at the Owens Valley Radio Observatory (OVRO). The receiver will measure both the Q and U Stokes parameters over a 20% pass-band centered

Christian Theis

The formation of globular clusters is still an unsolved problem. Though most scenarios assume a massive molecular cloud as the progenitor, it is unclear, how the cloud is transformed into a star cluster. Here a scheme of supernova (SN) induced cluster formation is investigated. In this scenario the expanding SN shell accumulates the mass of the cloud. This i

R. L. Ingraham, L. A. Cummings

We show that a new force, which appeared in a five-dimensional generalization of general relativity, implies precisely the flat circular velocity curves of luminous matter observed in the outer parts of spiral galaxies. A cosmological solution for the new force (not the galactic solution treated in this paper) might explain the cosmic negative, or repulsive,