July 2002 arXiv papers — page 25

H. Boschi-Filho, Nelson R. F. Braga

We find a one to one mapping between low energy string dilaton states in AdS bulk and high energy glueball states on the corresponding boundary. This holographic mapping leads to a relation between bulk and boundary scattering amplitudes. From this relation and the dilaton action we find the appropriate momentum scaling for high energy QCD amplitudes at fixe

R. Kuchimanchi, R. N. Mohapatra

Freedom from global anomalies in the presence of a local SU(2)_H horizontal symmetry under which right handed charged leptons transform nontrivially requires that there be at least two right handed neutrinos with masses of order of the horizontal symmetry breaking scale. If a third right handed neutrino is introduced to satisfy quark lepton symmetry, it is u

G. M. Bruun

We examine a dilute two-component atomic Fermi gas trapped in a harmonic potential in the superfluid phase. For experimentally realistic parameters, the trapping potential is shown to have crucial influence on various properties of the gas. Using an effective hamiltonian, analytical results for the critical temperature, the temperature dependence of the supe

Xiao-Ming Xu, Cheuk-Yin Wong, T. Barnes

We study $J/ψ$ suppression in Pb+Pb collisions at CERN-SPS energies in hadronic matter with energy- and temperature-dependent charmonium dissociation cross sections calculated in the quark-interchange model of Barnes and Swanson. We find that the variation of J/$ψ$ survival probability from peripheral to central collisions can be explained as induced by hadr

Karsten Kruse, Frank Julicher

A phenomenological description for active bundles of polar filaments is presented. The activity of the bundle results from crosslinks, that induce relative displacements between the aligned filaments. Our generic description is based on momentum conservation within the bundle. By specifying the internal forces, a simple minimal model for the bundle dynamics

Sean Sather-Wagstaff

Let (R,m) be a regular local ring with prime ideals p and q such that p+q is m-primary and dim(R/p)+dim(R/q)=dim(R). It has been conjectured by Kurano and Roberts that p^{(n)} \cap q \subseteq m^{n+1} for all positive integers n. We discuss this conjecture and related conjectures. In particular, we prove that this conjecture holds for all regular local rings

Boaz Tsaban

A permutation P on {1,..,N} is a_fast_forward_permutation_ if for each m the computational complexity of evaluating P^m(x)$ is small independently of m and x. Naor and Reingold constructed fast forward pseudorandom cycluses and involutions. By studying the evolution of permutation graphs, we prove that the number of queries needed to distinguish a random cyc

F. C. Cooper, V. M. Nakariakov, D. Tsiklauri

Kink modes of solar coronal structures, perturbing the loop in the direction along the line-of-sight (LOS), can be observed as emission intensity disturbances propagating along the loop provided the angle between the LOS and the structure is not ninety degrees. The effect is based upon the change of the column depth of the loop (along the LOS) by the wave. T

A. C. Aguiar Pinto, M. T. Thomaz

We study a two-level model coupled to the electromagnetic vacuum and to an external classic electric field with fixed frequency. The amplitude of the external electric field is supposed to vary very slow in time. Garrison and Wright [{\it Phys. Lett.} {\bf A128} (1988) 177] used the non-hermitian Hamiltonian approach to study the adiabatic limit of this mode

G. Asti, M. Ghidini, R. Pellicelli, M. Solzi

The activated torsion oscillation magnetometer exploits the mechanical resonance of a cantilever beam, driven by the torque exerted on the sample by an ac field applied perpendicularly to the film plane. We describe a model for the cantilever dynamics which leads to the calculation of the cantilever dynamic profile and allows the mechanical sensitivity of th

Kazumi Okuyama

We consider the radial quantization of N=4 super Yang-Mills (SYM) in 4 dimensions, i.e., N=4 SYM on a cylinder R times S^3. We construct the generators of superconformal symmetry in the case of U(N) gauge group, generalizing the earlier work by Nicolai et al. for U(1) gauge group. We study how these generators contract to the symmetry of pp-wave when they ac

Frank Ferrari

Fractional charges, and in particular the spectral asymmetry eta of certain Dirac operators, can appear in the central charge of supersymmetric field theories. This yields unexpected analyticity constraints on eta from which classic results can be recovered in an elegant way. The method could also be applied in the context of string theory.

Luc Blanchet

We apply standard post-Newtonian methods in general relativity to locate the innermost circular orbit (ICO) of irrotational and corotational binary black-hole systems. We find that the post-Newtonian series converges well when the two masses are comparable. We argue that the result for the ICO which is predicted by the third post-Newtonian (3PN) approximatio

Miyuki Nishikawa

In this paper, we discuss the self-consistency condition for the spherical symmetric Klein-Gordon equation, and then discuss a natural possibility that gravity and weak coupling constants g_G and g_W may be defined after g_{EM}. In this point of view, gravity and the weak force are subsidiary derived from electricity. Particularly, SU(2)_L * U(1) unification

Soumitra SenGupta, Saurabh Sur

In this work we show that the Universe evolving in a spacetime with torsion (originated from a second rank antisymmetric Kalb-Ramond field) and dilaton is free from any big bang singularity and can have acceleration during the evolution. Both the matter and radiation dominated era have been considered and the role of the dilaton to explain the decelerating p

John Schliemann, Alexander V. Khaetskii, Daniel Loss

We study the time evolution of a single spin coupled inhomogeneously to a spin environment. Such a system is realized by a single electron spin bound in a semiconductor nanostructure and interacting with surrounding nuclear spins. We find striking dependencies on the type of the initial state of the nuclear spin system. Simple product states show a profoundl

J. M. Cordes, T. J. W. Lazio

We present a new model for the Galactic distribution of free electrons. It (a) describes the distribution of the free electrons responsible for pulsar dispersion measures and thus can be used for estimating the distances to pulsars; (b) describes large-scale variations in the strength of fluctuations in electron density that underly interstellar scattering;

Marc Mezard, Riccardo Zecchina

We study the problem of satisfiability of randomly chosen clauses, each with K Boolean variables. Using the cavity method at zero temperature, we find the phase diagram for the K=3 case. We show the existence of an intermediate phase in the satisfiable region, where the proliferation of metastable states is at the origin of the slowdown of search algorithms.

M. Yakiyama, Y. Hasegawa

We study the dynamical spin susceptibility $χ({\bf q},ω)$ for spin-triplet superconductivity. We show that a large peak at $ω= 2 Δ$ appears in $\textrm{Im} χ_{zz}({\mathbf{Q}}, ω)$, where $z$ is the direction of the $\mathbf{d}$ vector for triplet pairing, if Fermi surface has a nested part with the nesting vector $\mathbf{Q}$ and the order parameter is $+Δ$

Philipp Podsiadlowski, Saul Rappaport, Zhanwen Han

We present the results of a systematic study of the formation and evolution of binaries containing black holes and normal-star companions with a wide range of masses. We first reexamine the standard formation scenario for close black-hole binaries, where the spiral-in of the companion in the envelope of a massive star causes the ejection of the envelope. We

S. Gheorghiu-Svirschevski

We outline an approach that streamlines considerably the construction and analysis of well-behaved nonlinear quantum dynamics, with completely positive extensions to entangled systems. A few notes are added on the issue of quantum measurements under a nonlinear dynamics.

T. B. Pittman, J. D. Franson

We have performed a proof-of-principle experiment in which qubits encoded in the polarization states of single-photons from a parametric down-conversion source were coherently stored and read-out from a quantum memory device. The memory device utilized a simple free-space storage loop, providing a cyclical read-out that could be synchronized with the cycle t

A. Iorio, G. Lambiase, G. Vitiello

The quantum deformation of the Hopf algebra describes the skeleton of quantum field theory, namely its characterizing feature consisting in the existence of infinitely many unitarily inequivalent representations of the canonical commutation relations. From this we derive the thermal properties of quantum field theory, with the entropy playing the role of the

P. Milman, H. Ollivier, J. M. Raimond

We propose an implementation of an universal quantum cloning machine [UQCM, Hillery and Buzek, Phys. Rev. A {\bf 56}, 3446 (1997)] in a Cavity Quantum Electrodynamics (CQED) experiment. This UQCM acts on the electronic states of atoms that interact with the electromagnetic field of a high $Q$ cavity. We discuss here the specific case of the $1 \to 2$ cloning

Peng Xue, Guang-Can Guo

We propose an experimentally feasible scheme to generate nonmaximal entanglement between two atomic ensembles. The degree of entanglement is readily tunable. The scheme involves laser manipulation of atomic ensembles, adjustable quarter- and half-wave plates, beam splitter, polarizing beam splitters, and single-photon detectors, and well fits the status of t

V. Hnizdo

The reply of de la Torre, Daleo and Garcia-Mata [Eur. J. Phys. 23 (2002) L15-L16] to a criticism of their `demythologizing' analysis of the clock-in-the-box debate between Einstein and Bohr is commented on.

S. Gheorghiu-Svirschevski

We argue that usual quantum statics and the dynamical equivalence of mixed quantum states to {\it probabilistic mixtures}suffice to guarantee a linear evolution law, which necessarily complies with the no-signaling condition. Alternatively, there are nonlinear dynamical extensions that treat mixed states as {\it elementary mixtures} and evolve {\it every}pur

A. I. Artemyev, Yu. V. Rostovtsev, S. Trendafilov, K. Kapale

We propose a two-magnet design of a drift region for a free-electron laser without inversion (FELWI). By performing direct calculations of the phase shifts for electrons passing the drift region, we prove that the small-signal gain integrated over the detuning is positive and is inversely proportional to the energy spread of the ``hot'' electron beam

Michael C. Wittmann, Richard N. Steinberg, Edward F. Redish

Student learning of sound waves can be helped through the creation of group-learning classroom materials whose development and design rely on explicit investigations into student understanding. We describe reasoning in terms of sets of resources, i.e. grouped building blocks of thinking that are commonly used in many different settings. Students in our unive

V. Smiricinschi

The main problem in liquid porosimetry, which prevents to see the pore sizes smaller than 2 microns in diameter, is direct gas diffusion flow through a micro-porous membrane. This diffusion causes bubbles formation below the membrane and that spoils extrusion (intrusion) data, as one cannot distinguish the volume of extrusion (intrusion) liquid from the volu

Michael C. Wittmann, Richard N. Steinberg, Edward F. Redish

Students are taught several models of conductivity, both at the introductory and the advanced level. From early macroscopic models of current flow in circuits, through the discussion of microscopic particle descriptions of electrons flowing in an atomic lattice, to the development of microscopic non-localized band diagram descriptions in advanced physics cou

I. M. Savukov, W. R. Johnson, H. G. Berry

Ab-initio theory is developed for energies of J=1 particle-hole states of neutral neon and for oscillator strengths of transitions from such states to the J=0 ground state. Hole energies of low-Z neonlike ions are evaluated.

Calvin W. Johnson, Ionel Stetcu, J. P. Draayer

Deformation is fundamental to understanding nuclear structure. We compare two ways to efficiently realize deformation for many-fermion wavefunctions, the leading SU(3) irrep and the angular-momentum projected Hartree-Fock state. In the absence of single-particle spin-orbit splitting the two are nearly identical. With realistic forces, however, the difference

B. Tatischeff

Using mainly $\vec{p}$ p $\to$ p ${π^+}X$ and $\vec{p}$ p $\to$ p$_{f}$~p$_{s}$ X reactions, narrow baryonic structures were observed in the mass range 950$\le$ M $\le$ 1800 MeV.

Alex Veksler, Yair Zarmi

A Lax pair consisting of the Forsyth-Hopf-Cole transformation and a linear differential (in time) - difference (in continuous space) equation generates the whole hierarchy of the Burgers equation and admits exact moving front solutions. This model mimics finite-distance spatial correlations or nearest neighbor interactions in a physical situation

Elizabeth Gasparim

The two applications are: 1. sometimes instanton numbers stratify moduli of bundles better than Chern numbers. 2. sometimes instanton numbers distinguish singularities better than the classical numerical invariants.

Lionel Richard

We study Hochschild homology and cohomology for some polynomial algebras mixing both ``classical'' relations ($XY-YX=1$) and ``quantum'' relations ($XY=łYX$). More specifically, we prove that the algebra of differential operators on any quantum affine space (quantum Weyl algebra) have the same Hochschild homology, and satisfy the same duality

Siegfried Echterhoff, Dana P. Williams

We examine the structure of central twisted transformation group \cs-algebras $C_{0}(X)\rtimes_{\id,u}G$, and apply our results to the group \cs-algebras of central group extensions. Our methods require that we study Moore's cohomology group $H^{2}\bigl(G,C(X,\T)\bigr)$, and, in particular, we prove an inflation result for pointwise trivial cocyles which

Brian Forbes

For a particular toric variety, I explore to what extent the SYZ conjecture applied to the orbits of the torus action gives the mirror manifold, in the sense of Batyrev's mirror construction using reflexive polytopes.

Yaron Ostrover

We compare Hofer's geometries on two spaces associated with a closed symplectic manifold M. The first space is the group of Hamiltonian diffeomorphisms. The second space L consists of all Lagrangian submanifolds of $M \times M$ which are exact Lagrangian isotopic to the diagonal. We show that in the case of a closed symplectic manifold with $π_2(M) = 0$,

Peter Schauenburg

Let H be a finite-dimensional quasibialgebra. We show that H is a quasi-Hopf algebra if and only if the category of its finite-dimensional left modules is rigid if and only if a structure theorem for Hopf modules over H holds. We also show that a dual structure theorem for Hopf modules over a coquasibialgebra H holds if and only if the category of finite-dim

Saurya Das

We show that the Bekenstein-Hawking entropy associated with any black hole undergoes logarithmic corrections when small thermodynamic fluctuations around equilibrium are taken into account. Thus, the corrected expression for black hole entropy is given by $S= A/4 - k \ln(A)$, where $A$ is the horizon area and $k$ is a constant which depends on the specific b

Aninda Sinha

The supersymmetry constraints on the $\hat{G}^{4}\lamda^{16}$ term in the effective action of type IIB superstring theory are studied in order to determine the dependence of its coefficient on the complex scalar field, $τ$. The resulting expression is consistent with the $SL(2,{\Bbb Z})$ invariant conjectures in the literature.

Kentaro Hori

Recently, mirror symmetry is derived as T-duality applied to gauge systems that flow to non-linear sigma models. We present some of its applications to study quantum geometry involving D-branes. In particular, we show that one can employ D-branes wrapped on torus fibers to reproduce the mirror duality itself, realizing the program of Strominger-Yau-Zaslow in

O. A. Battistel, G. Dallabona

A very general calculational strategy is applied to the evaluation of the divergent physical amplitudes which are typical of perturbative calculations. With this approach in the final results all the intrinsic arbitrariness of the calculations due to the divergent character is still present. We show that by using the symmetry properties as a guide to search

Thomas G. Rizzo

We discuss how mixing between the Standard Model Higgs boson, $h$, and the radion of the Randall-Sundrum model can lead to significant shifts in the expected properties of the Higgs boson. In particular we show that the total and partial decay widths of the Higgs, as well as the $h\to gg$ branching fraction, can be substantially altered from their SM expecta

M. Baker, R. Steinke

We show how an effective field theory of long distance QCD, describing a dual superconductor, can be expressed as an effective string theory of superconducting vortices. We use the semiclassical expansion of this effective string theory about a classical rotating string solution in any spacetime dimension D to obtain the semiclassical meson energy spectrum.

Romuald A. Janik

Recently, string theory on some specific curved backgroud spacetime geometries has been conjectured to be equivalent to certain gauge theories (AdS/CFT correspondence). This correspondence may be used to investigate the non-perturbative regime of gauge theories. I describe its application to the study of soft scattering amplitudes in a confining gauge theory

S. G. Rubin, H. Kröger, G. Melkonian

We investigate an influence of virtual particles on the classical motion of a system in Minkowski and Euclidean spaces. Our results indicate that fluctuations of fields different from the main field decelerate significantly its motion at high energies. The formalism described here is applicable to the majority of inflationary models. We show also that the qu

Robert Fleischer

A review of CP violation in the $B$ system and strategies to determine the unitarity triangle of the CKM matrix is given. We begin with an introduction to the description of CP violation in the Standard Model of electroweak interactions, and discuss the basic features of the theoretical framework to deal with non-leptonic B decays, which play the main role i

F. Bissey, J. R. Cudell, J. Cugnon, M. Jaminon

The pion structure function is investigated in a simple model, where pion and constituent quark fields are coupled through the simplest pseudoscalar coupling. The imaginary part of the forward gamma* pi-> gamma* pi scattering amplitude is evaluated and related to the structure functions. It is shown that the introduction of non-perturbative effects, linked t

S. Atashbar Tehrani, Ali N. Khorramian

We calculated the polarized parton distributions in leading order approximation in QCD from valon model. Polarized structure function of the nucleon are analyzed in the polarized valon model in which a nucleon is assumed to be a bound state of three polarized valence quark cluster(valons). It is shown that the results of the model calculation agree rather we

Joerg Eilers Bodo Geyer

We show that the twist decomposition of non-local scalar off-cone QCD-operators, which in $x-$space is infinite, after Fourier transformation with the singular functions $1/(x^2 - {\text{i}} ε)^λ$ for $λ= 1$ and 2 terminates at leading and sub-leading twist, respectively. Therefore, only a finite number of twists contribute to the target mass corrections of

V. A. Korotkov, W. -D. Nowak

A simple way to extract the Generalized Parton Distribution H(xi,xi,t) at small t from the single beam-spin asymmetry in Deeply Virtual Compton Scattering is proposed. Projections are given for future measurements at the HERMES experiment upgraded with a recoil detector.

Dan Pirjol

In the Standard Model, the photon emitted in b->sγdecays is predicted to be left-handed polarized. We discuss the types of New Physics which can produce a deviation from this prediction, focusing on the Minimal Supersymmetric Standard Model. A new method is proposed for testing these predictions, which makes use of angular correlations in exclusive B -> Kππγ

F. Schrempp, A. Utermann

We pursue the intriguing possibility that larger-size instantons build up diffractive scattering, with the marked instanton-size scale $<ρ> \approx 0.5$ fm being reflected in the conspicuous ``geometrization&#39;&#39; of soft QCD. As an explicit illustration, the known instanton contribution to DIS is transformed into the intuitive colour dipole picture. Wit

The OPAL collaboration, G. Abbiendi

A search is performed for production of short-lived particles in e+e- -> XY, with X -> gamma gamma and Y -> ffbar, for scalar X and scalar or vector Y. Model-independent limits in the range of 25-60 femtobarns are presented on sigma (e+e- -> XY) x B(X -> ffbar) for centre-of-mass energies in the range 205-207 GeV. The data from all LEP centre-of-mass energie

Martin Bojowald, Franz Hinterleitner

A free massless scalar field is coupled to homogeneous and isotropic loop quantum cosmology. The coupled model is investigated in the vicinity of the classical singularity, where discreteness is essential and where the quantum model is non-singular, as well as in the regime of large volumes, where it displays the expected semiclassical features. The particul

Enore Guadagnini

The helicity modification of light polarization which is induced by the gravitational deflection from a classical heavy rotating body, like a star or a planet, is considered. The expression of the helicity asymmetry is derived; this asymmetry signals the gravitationally induced spin transfer from the rotating body to the scattered photons.

C. Cayrol, S. Doutre, M. -C. Lagasquie-Schiex, J. Mengin

Dung&#39;s abstract framework for argumentation enables a study of the interactions between arguments based solely on an ``attack&#39;&#39; binary relation on the set of arguments. Various ways to solve conflicts between contradictory pieces of information have been proposed in the context of argumentation, nonmonotonic reasoning or logic programming, and ca

Paul E. Dunne

Much work on argument systems has focussed on preferred extensions which define the maximal collectively defensible subsets. Identification and enumeration of these subsets is (under the usual assumptions) computationally demanding. We consider approaches to deciding if a subset S is a preferred extension which query a representations encoding all such exten

Babak H. Seradjeh, Igor F. Herbut

We study the effects of the leading irrelevant perturbations on chiral symmetry breaking in the effective $QED_3$ theory of d-wave superconductor-insulator transition in underdoped cuprates. For weak symmetry breaking, the effect of a perturbation on energies of various insulating states can be classified according to its engineering dimension in the maximal

Wei Zhang, Alexander O. Govorov, Sergio E. Ulloa

We study the coherent dynamics of a Holstein polaron in strong electric fields. A detailed analytical and numerical analysis shows that even for small hopping constant and weak electron-phonon interaction, polaron states can become delocalized if a resonance condition develops between the original Wannier-Stark states and the phonon modes, yielding both tunn

V. A. Vdovenkov

Temperature-dependent thermoelectric power (TEP) in semiconductor crystals and crystal structures containing an electron-vibrational centers (EVC) was investigated in this article. The TEP contain narrow pius at Debye temperatures for different phonons. In thin epitaxial layers on substrates such pius exist at Debye temperatures of substrates phonons. These

Manuel Rodriguez Gonzalez, Rolando Bonal Caceres

The fundamental application of the ultrasonic pulse velocity method (UPV) in the study of concrete, consist in the analysis and estimation of the mechanical properties (compressive strength). The precission of the estimation may be dependent on the incidence of various factors, one of which is the water content acquired by the sample of concrete. In [Etsuzo]

V. A. Vdovenkov

Oscillations of atomic nuclei in crystals are considered in this paper. It is shown that elastic nuclei oscillations relatively electron envelops (inherent, I-oscillations) and waves of such oscillations can exist in crystals at adiabatic condition. The types and energy quantums of I-oscillations for different atoms are determined. In this connection the adi

C. Fusco, A. Fasolino, P. Gallo, A. Petri

We study by Monte Carlo simulation the compaction dynamics of hard dimers in 2D under the action of gravity, subjected to vertical and horizontal shaking, considering also the case in which a friction force acts for horizontal displacements of the dimers. These forces are modeled by introducing effective probabilities for all kinds of moves of the particles.

Giuseppe Benfatto, Alessandro Giuliani, Vieri Mastropietro

We prove the convergence of the perturbative expansion, based on Renormalization Group, of the two point Schwinger function of a system of weakly interacting fermions in d=2, with symmetric Fermi surface and up to exponentially small temperatures, close to the expected onset of superconductivity

G. Manoj, Mustansir Barma

We study phase separation in a system of hard-core particles driven by a fluctuating two-dimensional self-affine potential landscape which evolves through Kardar-Parisi-Zhang (KPZ) dynamics. We find that particles tend to cluster together on a length scale which grows in time. The final phase-separated steady state is characterized by an unusual cusp singula

René Mikkelsen, Martin van Hecke, Tomas Bohr

We study the transition from laminar to chaotic behavior in deterministic chaotic coupled map lattices and in an extension of the stochastic Domany--Kinzel cellular automaton [DK]. For the deterministic coupled map lattices we find evidence that ``solitons&#39;&#39; can change the {\em nature} of the transition: for short soliton lifetimes it is of second or

Ronald Dickman, Daniel ben-Avraham

We study a version of compact directed percolation (CDP) in one dimension in which occupation of a site for the first time requires that a &#34;mine&#34; or antiparticle be eliminated. This process is analogous to the variant of directed percolation with a long-time memory, proposed by Grassberger, Chate and Rousseau [Phys. Rev. E 55, 2488 (1997)] in order t

J. Lorenzana, G. Seibold

We perform a systematic slave-boson mean-field analysis of the three-band model for cuprates with first-principle parameters. Contrary to widespread believe based on earlier mean-field computations low doping stripes have a linear density close to 1/2 added hole per lattice constant. We find a dimensional crossover from 1D to 2D at doping $\sim 0.1$ followed

E. G. Timoshenko, Yu. A. Kuznetsov

A version of the Gaussian self-consistent (GSC) method, which avoids the use of the Edwards&#39; virial expansion, is presented. Instead, the mean energy is evaluated directly via a convolution of the attractive part of the pair-wise non-bonded potential with the Gaussian trial radial distribution function. The hard sphere repulsion is taken into account via

Zbigniew Koza

We model a processive linear molecular motor as a particle diffusing in a one-dimensional periodic lattice with arbitrary transition rates between its sites. We present a relatively simple proof of a theorem which states that the ratio of the drift velocity V to the diffusion coefficient D has the upper bound 2N/d, where N is the number of nodes in an elemen

Y. Yilmaz, A. Erzan, O. Pekcan

A nano-second scale in situ probe reveals that a bulk linear polymer undergoes a sharp phase transition as a function of the degree of conversion, as it nears the glass transition. The scaling behaviour is in the same universality class as percolation. The exponents γand βare found to be 1.7 \pm .1 and 0.41\pm 0.01 in agreement with the best percolation resu

Mark Srednicki

We reconsider the question of the spectral statistics of the k-body random-interaction model, investigated recently by Benet, Rupp, and Weidenmueller, who concluded that the spectral statistics are Poissonian. The binary-correlation method that these authors used involves formal manipulations of divergent series. We argue that Borel summation does not suffic

Yury M. Zinoviev

We suggest the new definition of the magnetization. For the two - dimensional Ising model with the free boundary conditions we calculate this magnetization.

E. V. Sampathkumaran, H. Bitterlich, K. K. Iyer, W. Löser

The magnetic behavior of single-crystal Ho$_2$PdSi$_3$, crystallizing in an AlB$_2$-derived hexagonal structure, is investigated by magnetic susceptibility ($χ$) and electrical resistivity ($ρ$) measurements along two directions. There is no dramatic anisotropy in the high temperature Curie-Weiss parameter or in the $ρ$ and isothermal magnetization data, tho

Aleksandra Nowicka, Artur Duda, Miroslaw R. Dudek

We construct a model of speciation from evolution in an ecosystem consisting of a limited amount of energy recources. The species posses genetic information, which is inherited according to the rules of the Penna model of genetic evolution. The increase in number of the individuals of each species depends on the quality of their genotypes and the available e

V. P. Plakhty, S. V. Maleyev, S. V. Gavrilov, F. Bourdarot

In the external field slightly inclined to the $x$- or y-axis of the frustrated tetragonal atiferromagnet Pr2CuO4, a transition is discovered from the phase with orthogonal antiferromagnetic spin subsystems along [1,0,0] and [0,1,0] to the phase with the collinear spins. This phase is shown to be due to the pseudodipolar interaction, and transforms into the

Markus Greiner, Olaf Mandel, Theodor W. Haensch, Immanuel Bloch

At the heart of a Bose-Einstein condensate lies its description as a single giant matter wave. Such a Bose-Einstein condensate represents the most &#34;classical&#34; form of a matter wave, just as an optical laser emits the most classical form of an electromagnetic wave. Beneath this giant matter wave, however, the discrete atoms represent a crucial granula

K. Sasaki

Conditions for intra and inter layer Coulomb interactions in multi-walled carbon nanotubes are derived from stability of capacitance excitations. It is pointed out, supposing the stability conditions are not satisfied, that the system has unstable modes which correspond to a charge transfer between layers or charge density oscillation in each layer depending

O. Cepas, T. Ziman

Anisotropic spin-spin interactions of Dzyaloshinsky and Moriya symmetry are generally considered weak, as they depend on the spin-orbit couplings. In spin systems with gapped ground states they can, however, have rather strong effects. We will discuss recent results related to the results of neutron scattering and ESR for $\rm SrCu_2(BO_3)_2$. Inclusion of t

Daniel L. Miller

This is a three step work: i) we explain why quantum point contacts are similar to ballistic quantum dots; ii) we introduce the virtual Kondo state in both systems; iii-1st) this state explains 0.7 structure in point contacts; iii-2nd) formation of the local moment on this state is described by the nearly symmetric Anderson model, we solve it for finite size

Martin van Hecke

Much of the nontrivial dynamics of the one dimensional Complex Ginzburg-Landau Equation (CGLE) is dominated by propagating structures that are characterized by local ``twists&#39;&#39; of the phase-field. I give a brief overview of the most important properties of these various structures, formulate a number of experimental challenges and address the questio

L. Acedo, A. Santos, A. V. Bobylev

Uniform shear flow is a paradigmatic example of a nonequilibrium fluid state exhibiting non-Newtonian behavior. It is characterized by uniform density and temperature and a linear velocity profile $U_x(y)=a y$, where $a$ is the constant shear rate. In the case of a rarefied gas, all the relevant physical information is represented by the one-particle velocit

Martin White

We present the mass functions for different mass estimators for a range of cosmological models. We pay particular attention to how universal the mass function is, and how it depends on the cosmology, halo identification and mass estimator chosen. We investigate quantitatively how well we can relate observed masses to theoretical mass functions.

F. Krennrich, I. H. Bond, S. M. Bradbury, J. H. Buckley

The detection of spectral variability of the gamma-ray blazar Mrk 421 at TeV energies is reported. Observations with the Whipple Observatory 10m gamma-ray telescope taken in 2000/2001 revealed exceptionally strong and long-lasting flaring activity. Flaring levels of 0.4 to 13 times that of the Crab Nebula flux provided sufficient statistics for a detailed st

John J. Bialek, August E. Evrard, Joseph J. Mohr

We present a simulated cluster of galaxies, modeled with a pre-heated intracluster medium, that exhibits X-ray features similar to the `cold fronts&#39; seen in Chandra observations. Mock observations at a particular epoch show factor two discontinuities in X-ray temperature and factor four in surface brightness on a spatial scale <= 100 kpc. Analysis of the

L. O. Kerber, B. X. Santiago, R. Castro, D. Valls-Gabaud

We present the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC. The data were obtained with HST/WFPC2 in the F555W (~V) and F814W (~I) filters, reaching m_555 ~ 25. We discuss and apply a method of correcting the CMD for sampling incompleteness and field star contamination. Efficient use of the CMD data was made

Robin H. D. Corbet, Koji Mukai

A pulse timing orbit has been obtained for the X-ray binary XTE J1855-026 using observations made with the Proportional Counter Array on board the Rossi X-ray Timing Explorer. The mass function obtained of ~16Mo together with the detection of an extended near-total eclipse confirm that the primary star is a supergiant as predicted. The orbital eccentricity i

Christopher J. Miller, Robert C. Nichol, Xuelei Chen

We examine power spectra from the Abell/ACO rich cluster survey and the 2dF Galaxy Redshift Survey (2dfGRS) for observational evidence of features produced by the baryons. A non-negligible baryon fraction produces relatively sharp oscillatory features at specific wavenumbers in the matter power spectrum. However, the mere existence of baryons will also produ

D. K. Strickland, T. M. Heckman, E. J. M. Colbert, C. G. Hoopes

In this contribution we present a few selected examples of how the latest generation of space-based instrumentation -- NASA&#39;s Chandra X-ray Observatory and the Far-Ultraviolet Spectroscopic Explorer (FUSE) -- are finally answering old questions about the influence of massive star feedback on the warm and hot phases of the ISM and IGM. In particular, we d

N. M. Nagar, H. Falcke, A. S. Wilson, J. S. Ulvestad

(abbreviated): This paper presents the results of a high resolution radio imaging survey of all known (96) low-luminosity active galactic nuclei (LLAGNs) at D<19Mpc. We find that almost half of all LINERs and low-luminosity Seyferts have flat-spectrum radio cores when observed at 150mas resolution. Higher (2mas) resolution observations of a flux-limited subs

M. L. Lister, K. I. Kellermann, I. I. Pauliny-Toth

We discuss the morphology and kinematics of five gigahertz-peaked spectrum (GPS) sources that have been observed with the VLBA. We find a wide range of observed properties including core-jet structure, superluminal motion, variability, extended structure, and polarization, all of which appear to deviate from commonly-accepted GPS paradigms (e.g., O&#39;Dea 1

C. P. Burgess

Although quintessence models have attractive cosmological features, they face two major difficulties. First, it has not yet been possible to find one which convincingly realizes the goal of explaining present-day cosmic acceleration generically using only attractor solutions. Second, quintessence has proven difficult to obtain within realistic microscopic th

S. Anton, A. Thean, A. Pedlar, I. W. A. Browne

Multi-frequency observations of Mrk 348 are presented consisting of 2 epochs of MERLIN data at 5 GHz, ISOPHOT data at 170, 90, 60 and 25 micron, NOT images at U, B, R and I bands and data at 1350 micron from the archive for SCUBA. The new optical images reveal a disrupted arm that ends towards the eastern companion of Mrk 348, consistent with the hypothesis

B. Santiago, L. Kerber, R. Castro, R. de Grijs

Evidence for a second main-sequence turn-off in a deep colour-magnitude diagram of NGC 1868 is presented. The data were obtained with HST/WFPC2 and reach down to m_{555} ~ 25. Besides the usual t ~ 0.8 Gyr turn-off found in previous analyses, another possible turn-off is seen at m_{555} ~ 21 (M_V ~ 2.5), which is consistent with an age of t ~ 3 Gyrs. This CM

S. L. Skinner, S. A. Zhekov, M. Guedel, W. Schmutz

We present new X-ray and radio observations of the WR star EZ CMa (HD 50896) obtained with XMM-Newton and the VLA. This WN4 star shows optical/UV variability at a period of 3.76 d whose cause is unknown. VLA flux measurements at five frequencies show the radio spectral energy distribution is well-described by a power law with spectral index +0.69 (+-0.05), a

Jorick S. Vink, Alex de Koter

We present radiation-driven wind models for Luminous Blue Variables (LBVs) and predict their mass-loss rates. We study the effects of lower masses and modified abundances in comparison to the normal OB supergiants, and we find that the main difference in mass loss is due to the lower masses of LBVs. In addition, we find that the increase in helium abundance