April 2000 arXiv papers — page 15

Peter Constantin

We present rigorous bounds for the average heat transport in Boussinesq Rayleigh-Benard convection.

Peter Constantin

We present an infinite dimensional family of of exact solutions of the incompressible three-dimensional Euler equations. These solutions, proposed by Gibbon and Ohkitani, have infinite kinetic energy and blow up in finite time.

Novikov S. P

This work is the direct continuation of the author's note published in Russian Math Surveys 52 (1997), no 6. Discrete Schrodinger operators on graphs and higher dimensional simplicial complexes are considered. A vector-valued symplectic form on the space of solutions is consructed. This form, "Symplectic Wronskian", takes value in the group of 1-

Sergey P. Novikov

Hystory of topology is discussed uncluding the Golden Age Period (1950-1970), the Period of Decay (1970-1980) and the Period of Recovery in 80s and 90s based on the ideas borrowed from physics community. In the second part recent result of the present author, A.Malcev, I Dynnikov and A.Zorich concerning new observable topological phenomena in normal metals a

S. P. Novikov, A. S. Schwarz

Discrete Lagrangian Systems on graphs are considered. Vector-valued closed differential 2-form on the space of solutions is constructed. This form takes values in the first homology group of the graph. This construction generalizes the Symplectic Wronskian for the linear self-adjoint operators on graphs found in 1997 by the first author and used for the need

Richard L. Hall

Non-relativistic potential models are considered of the pure power V(r)=sgn(q) r^q and logarithmic V(r)=ln(r) types. It is shown that, from the spectral viewpoint, these potentials are actually in a single family. The log spectra can be obtained from the power spectra by the limit q --> 0 taken in a smooth representation P(n,l,q) for the eigenvalues E(n,l,q)

Erik N. Tjotta

We formulate a generalization of Givental-Kim's quantum hyperplane principle. This is applied to compute the quantum cohomology of a Calabi-Yau 3-fold defined as the rank 4 locus of a general skew-symmetric 7x7 matrix with coeffisients in P^6. The computation verifies the mirror symmetry predictions of Rødland in math.AG/9801092.

Robert L. Bryant

I discuss geometry and normal forms for pseudo-Riemannian metrics with parallel spinor fields in some interesting dimensions. I also discuss the interaction of these conditions for parallel spinor fields with the condition that the Ricci tensor vanish (which, for pseudo-Riemannian manifolds, is not an automatic consequence of the existence of a nontrivial pa

Karl Petersen

A very short and direct proof along the lines of the Kamae-Katznelson-Weiss approach.

Gentiana Danila

We compute the dimensions of spaces of sections of all powers of the Donaldson determinant bundle on the moduli space of rank 2 semi-stable sheaves on the projective plane, with zero first Chern class, and second Chern class equal to 3 or 4. We prove Le Potier's strange duality conjecture in some cases.

R. Ibanez, M. de Leon, B. Lopez, J. C. Marrero

In this paper we introduce cohomology and homology theories for Nambu-Poisson manifolds. Also we study the relation between the existence of a duality for these theories and the vanishing of a particular Nambu-Poisson cohomology class, the modular class. The case of a regular Nambu-Poisson structure and some singular examples are discussed.

I. Petras

This paper deals with fractional-order controllers. We outline mathematical description of fractional controllers and methods of their synthesis and application. Synthesis method is a modified root locus method for fractional-order systems and fractional-order controllers. In the next section we describe how to apply the fractional controller on control syst

Willem Veys

Let X be a nonsingular algebraic variety in characteristic zero. To an effective divisor on X Kontsevich has associated a certain 'motivic integral', living in a completion of the Grothendieck ring of algebraic varieties. He used this invariant to show that birational Calabi-Yau varieties have the same Hodge numbers. Then Denef and Loeser introduced

G. Arcioni, J. L. F. Barbon, Joaquim Gomis, M. A. Vazquez-Mozo

We show that thermal noncommutative field theories admit a version of `channel duality' reminiscent of open/closed string duality, where non-planar thermal loops can be replaced by an infinite tower of tree-level exchanges of effective fields. These effective fields resemble closed strings in three aspects: their mass spectrum is that of closed-string wi

C. R. Hagen

It is shown that the recent criticism of Brevik et al. (hep-th/0004041) is in error.

Werner Krauth, Matthias Staudacher

We apply numerical and analytic techniques to the study of Yang-Mills integrals with orthogonal, symplectic and exceptional gauge symmetries. The main focus is on the supersymmetric integrals, which correspond essentially to the bulk part of the Witten index for susy quantum mechanical gauge theory. We evaluate these integrals for D=4 and group rank up to th

Dan N. Vollick

It has recently been proposed that our universe is a three-brane embedded in a higher dimensional spacetime. Here I show that black holes on the brane, black strings intersecting the brane, and gravitational waves propagating in the bulk induce an effective energy-momentum tensor on the brane that contains negative energy densities.

D. Black, A. H. Fariborz, S. Nasri, J. Schechter

We propose a simple Ansatz for the three generation neutrino mass matrix $M_ν$ which is motivated from an SO(10) grand unified theory. The Ansatz can be combined with information from neutrino oscillation experiments and bounds on neutrinoless double beta decay to determine the neutrino masses themselves and to reconstruct, with some assumptions, the matrix

Zoltan Kunszt

Lectures given at the International School of Subnuclear Physics: 37th Course: Basics and Highlights of Fundamental Physics, Erice, Italy, 29 Aug - 7 Sep 1999.

E. Waxman

Ultra-high-energy, >10^19 eV, cosmic-ray and high energy, ~10^14 eV, neutrino production in GRBs is discussed in the light of recent GRB and cosmic-ray observations. Emphasis is put on model predictions that can be tested with operating and planned cosmic-ray and neutrino detectors, and on the prospects of testing for neutrino properties.

Kiwoon Choi, Eung Jin Chun, Kyuwan Hwang

We analyze the electron and neutron electric dipole moments induced by R-parity violating interactions in supersymmetric models. It is pointed out that dominant contributions can come from one-loop diagrams involving both the bilinear and trilinear R-parity odd couplings, leading to somewhat severe constraints on the products of those couplings.

CAPRICE Collaboration

A new measurement of the momentum spectra of both positive and negative muons as function of atmospheric depth was made by the balloon-borne experiment CAPRICE94. The data were collected during ground runs in Lynn Lake on the 19-20th of July 1994 and during the balloon flight on the 8-9th of August 1994. We present results that cover the momentum intervals 0

O. Yavas, A. K. Ciftci, S. Sultansoy

New facilities for particle and nuclear physics research, which will be available due to constructing the TESLA linear electron-positron collider tangentially to the HERA proton ring, are discussed.

Alfonso F. Agnew, Tevian Dray

We propose a mode-sum formalism for the quantization of the scalar field based on distributional modes, which are naturally associated with a slight modification of the standard plane-wave modes. We show that this formalism leads to the standard Rindler temperature result, and that these modes can be canonically defined on any Cauchy surface.

D. Pal, B. Basu

From topological viewpoint we have analysed the role of Berry phase in spin pairing mechanism of high $T_c$ superconducting state.

Charles Buhler, Seiji Yunoki, Adriana Moreo

The effect of adding non-magnetic impurities (NMI), such as Zn or Li, to high-Tc cuprates is studied applying Monte Carlo techniques to a spin-fermion model. It is observed that adding Li is qualitatively similar to doping with equal percentages of Sr and Zn. The mobile holes (MH) are trapped by the NMI and the system remains insulating and commensurate with

C. C. Tsuei, J. R. Kirtley

Phase-sensitive tests of pairing symmetry have provided strong evidence for predominantly d-wave pairing symmetry in both hole- and electron-doped high-Tc cuprate superconductors. Temperature dependent measurements in YBCO indicate that the d-wave pairing dominates, with little if any imaginary component, at all temperatures from 0.5K through Tc. In this art

Stefano Sanvito, Nicola A. Hill

In this paper we investigate theoretically the ground state NiAs-type structure of MnAs and we compare the magnetic and structural properties with an hypothetical zincblende structure. A zincblende structure can be obtained, in principle, from the diluted magnetic semiconductor Ga$_{1-x}$Mn$_x$As in the limit $x=1$. Using density functional calculations with

Belita Koiller, Mark O. Robbins

We study the morphology of magnetic domain growth in disordered three dimensional magnets. The disordered magnetic material is described within the random-field Ising model with a Gaussian distribution of local fields with width $Δ$. Growth is driven by a uniform applied magnetic field, whose value is kept equal to the critical value $H_c(Δ)$ for the onset o

Shu-Chiuan Chang, Robert Shrock

In this paper we present exact calculations of the partition function $Z$ of the $q$-state Potts model and its generalization to real $q$, for arbitrary temperature on $n$-vertex strip graphs, of width $L_y=2$ and arbitrary length, of the triangular lattice with free, cyclic, and Möbius longitudinal boundary conditions. These partition functions are equivale

V. N. Smolyaninova, Amlan Biswas, X. Zhang, K. H. Kim

We report low temperature specific heat measurements of Pr$_{1-x}$Ca$_{x}$MnO$_{3}$ ($0.3\leq x \leq 0.5$) and La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ with and without applied magnetic field. An excess specific heat, $C^{\prime}(T)$, of non-magnetic origin associated with charge ordering is found for all the samples. A magnetic field sufficient to induce the transitio

Wolfgang Breymann, Shoaleh Ghashghaie, Peter Talkner

A time series model for the FX dynamics is presented which takes into account structural peculiarities of the market, namely its heterogeneity and an information flow from long to short time horizons. The model emerges from an analogy between FX dynamics and hydrodynamic turbulence. The heterogeneity of the market is modeled in form of a multiplicative casca

Amandine Aftalion, Etienne Sandier, Sylvia Serfaty

We study the Ginzburg-Landau energy of superconductors with a term $a_\ep$ modelling the pinning of vortices by impurities in the limit of a large Ginzburg-Landau parameter $κ=1/\ep$. The function $a_\ep$ is oscillating between 1/2 and 1 with a scale which may tend to 0 as $κ$ tends to infinity. Our aim is to understand that in the large $κ$ limit, stable co

A. J. F. de Souza, U. M. S. Costa, M. L. Lyra

We investigate the critical relaxational dynamics of the S=1/2 Heisenberg ferromagnet on a simple cubic lattice within the Handscomb prescription on which it is a diagrammatic series expansion of the partition function that is computed by means of a Monte Carlo procedure. Using a phenomenological renormalization group analysis of graph quantities related to

M. F. Laguna, D. Dominguez, C. A. Balseiro

In this paper we analyze the structure, phase transitions and some transport properties of the vortex system when the external magnetic field lies parallel to the planes in layered superconductors. We show that experimental results for resistivity are qualitatively consistent with numerical simulations that describe the melting of a commensurate rotated latt

Bodo Huckestein, Michael Backhaus

Recent developments in the scaling theory of the integer quantum Hall effect are discussed. In particular, the influence of electron-electron interactions on the critical behavior are studied. It is further argued that recent experiments on the disappearance of the quantum Hall effect at low magnetic fields support rather than disprove the scaling theory, wh

Amandine Aftalion, Norman Dancer

In this paper, we study the Ginzburg-Landau equations for a two dimensional domain which has small size. We prove that if the domain is small, then the solution has no zero, that is no vortex. More precisely, we show that the order parameter $Ψ$ is almost constant. Additionnally, we obtain that if the domain is a disc of small radius, then any non normal sol

Enrique Canessa

We apply the concepts of multifractal physics to financial time series in order to characterize the onset of crash for the Standard & Poor's 500 stock index x(t). It is found that within the framework of multifractality, the "analogous" specific heat of the S&P500 discrete price index displays a shoulder to the right of the main peak for low valu

Ugo Bastolla, Peter Grassberger

We study a heteropolymer model with random contact interactions introduced some time ago as a simplified model for proteins. The model consists of self-avoiding walks on the simple cubic lattice, with contact interactions between nearest neighbor pairs. For each pair, the interaction energy is an independent Gaussian variable with mean value $B$ and variance

M. Warner, E. M. Terentjev, R. B. Meyer, Y. Mao

A mechanical strain field applied to a monodomain cholesteric elastomer will unwind the helical director distribution. There is an analogy with the classical problem of an electric field applied to a cholesteric liquid crystal, but with important differences. Frank elasticity is of minor importance unless the gel is very weak. The interplay is between direct

M. Latkovic, A. Bjelis, V. Dananic

We propose the Landau model for lock-in phase transitions in uniaxially modulated improper ferroelectric incommensurate-commensurate systems of class I. It includes Umklapp terms of third and fourth order and secondary order parameter representing the local polarization. The corresponding phase diagram has the structure of harmless staircase, with the allowe

P. König, T. Schmidt, R. J. Haug

We present spin-resolved measurements of the local density of states in Si doped GaAs. Both spin components exhibit strong mesoscopic fluctuations. In the magnetic quantum limit, the main features of the spin-up and spin-down components of the local density of states are found to be identical apart from Zeeman splitting. Based on this observation, we introdu

Sagar A. Pandit, R. E. Amritkar

We present the analytical and numerical results of a random walk on the family of small-world graphs. The average access time shows a crossover from the regular to random behavior with increasing distance from the starting point of the random walk. We introduce an {\em independent step approximation}, which enables us to obtain analytic results for the avera

A. Diaz-Ortiz, J. M. Sanchez

Phase equilibrium in confined Ising antiferromagnets was studied as a function of the coupling (v) and a magnetic field (h) at the surfaces, in the presence of an external field H. The ground state properties were calculated exactly for symmetric boundary conditions and nearest-neighbor interactions, and a full zero-temperature phase diagram in the plane v-h

K. Sasaki, M. Hotta

We analyze systematically composable composite entropy of two Tsallis subsystems with different q indices. H-theorem and thermal balance relation are commented.

T. Toutain, A. G. Kosovichev

We suggest a solution to an important problem of observational helioseismology of the separation of lines of solar acoustic (p) modes of low angular degree in oscillation power spectra by constructing optimal masks for Doppler images of the Sun. Accurate measurements of oscillation frequencies of low-degree modes are essential for the determination of the st

R. F. Elsner, J. J. Kolodziejczak, S. L. O'Dell, D. A. Swartz

NASA's Chandra X-ray Observatory includes a Flight Contamination Monitor (FCM), a system of 16 radioactive calibration sources mounted to the inside of the Observatory's forward contamination cover. The purpose of the FCM is to verify the ground-to-orbit transfer of the Chandra flux scale, through comparison of data acquired during the ground calibra

Asantha Cooray, Wayne Hu

Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters which govern them. The non-linear evolution of large scale structure produces a non-Gaussian signal which is potentially observable in galaxy shear data. We study the three-point statistics of the convergence, specifically the bisp

Daniel Muller, Reuven Opher

We study the orbits in the MOND theory within a dwarf galaxy of mass Md at a distance of ~100kpc from a neighboring galaxy of mass Mg, such as ours. It is assumed that a second mass m<<Md is gravitationally bound to Md by a previously calculated potential for the MOND theory. This potential is obtained for a free falling mass Md in a constant external gravit

Daniel A. Dale, Juan M. Uson

We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes ce

Thomas M. Brown, Randy A. Kimble, Henry C. Ferguson, Jonathan P. Gardner

Far-UV observations in and near the Hubble Deep Fields demonstrate that the Space Telescope Imaging Spectrograph (STIS) can potentially obtain unique and precise measurements of the diffuse far-ultraviolet background. Although STIS is not the ideal instrument for such measurements, high-resolution images allow Galactic and extragalactic objects to be masked

D. Raimann, E. Bica, T. Storchi-Bergmann, J. Melnick

We study the stellar population of galaxies with active star formation, determining ages of the stellar components by means of spectral population synthesis of their absorption spectra. The data consist of optical spectra of 185 nearby ($z \leq 0.075$) emission line galaxies. They are mostly HII galaxies, but we also include some Starbursts and Seyfert 2s, f

Claudia Maraston, Daniel Thomas

Comparing models of Simple Stellar Populations (SSP) with observed line strengths generally provides a tool to break the age-metallicity degeneracy in elliptical galaxies. Due to the wide range of Balmer line strengths observed, ellipticals have been interpreted to exhibit an appreciable scatter in age. In this paper, we analyze Composite Stellar Population

Peter B. Stetson

Stars appearing in CCD images obtained over 224 nights during the course of 69 observing runs have been calibrated to the Johnson/Kron-Cousins BVRI photometric system defined by the equatorial standards of Landolt (1992, AJ, 104, 340). More than 15,000 stars suitable for use as photometric standards have been identified, where &#34;suitable&#34; means that t

G. C. Perola, G. Matt, F. Fiore, P. Grandi

BeppoSAX observations of the Seyfert galaxies Mrk 509 and MCG+8-11-11 are presented. Earlier evidence of a soft excess in Mrk 509 is confirmed. This excess is found to be better represented by a power law than by a black body: with a photon slope of 2.5, its extrapolation matches the flux recorded in the far UV. An ASCA observation, which appeared to exclude

M. Brüggen, H. C. Spruit

Inhomogeneities in wave propagation conditions near and below the solar surface have been detected by means of time-distance helioseismology. Here we calculate the effect of temperature inhomogeneities on the travel times of sound waves. A temperature increase, e.g. in active regions, not only increases the sound speed but also lengthens the path along which

Takahiro Sumi, Mareki Honma

We propose a new method to constrain the location of microlensing objects using EAGLE (Extremely Amplified Gravitational LEnsing) events. We have estimated the rate of EAGLE events by taking the finite-source effect in to account. We found that the EAGLE event rate for using a 1-m class telescope w hose limiting magnitude is $V \sim 21$ is the same as or hig

Rekhesh Mohan, K. S. Dwarakanath, G. Srinivasan, Jayaram N. Chengalur

We have made HI 21cm-line absorption measurements using the GMRT towards 15 directions in the Galaxy which are known to have high random velocity clouds as seen in the optical absorption lines of CaII and NaI. For the first time, in 6 out of these 15 directions we detect HI absorption features corresponding to the high random velocity optical absorption line

C. Armendariz-Picon, V. Mukhanov, Paul J. Steinhardt

Increasing evidence suggests that most of the energy density of the universe consists of a dark energy component with negative pressure, a ``cosmological constant&#34; that causes the cosmic expansion to accelerate. In this paper, we address the puzzle of why this component comes to dominate the universe only recently rather than at some much earlier epoch.

Brad M. S. Hansen

A popular interpretation of recent microlensing studies of the line of sight towards the Large Magellanic Cloud invokes a population of old white dwarf stars in the Galactic halo. Below I review the basic properties of old white dwarf stars and the ongoing efforts to detect this population directly.

Stefan Gottloeber, Anatoly Klypin, Andrey Kravtsov

According to the hierarchical scenario, galaxies form via merging and accretion of small objects. Using N-body simulations, we study the frequency of merging events in the history of the halos. We find that at z<~2 the merging rate of the overall halo population can be described by a simple power law (1+z)^3. The main emphasis of the paper is on the effects

R. R. Sefako, O. C. de Jager, D. J. Van der Walt, H. Winkler

The detection of unpulsed TeV emission from PSR B1706-44 raised the question if this VHE emission results from inverse Compton scattering of multi-TeV electrons on the CMBR and other soft photon fields. This hints at the existence of an unseen synchrotron nebula, which is larger than the observed 1 arcminute compact X-ray nebula. In a search for synchrotron

Krzysztof Pilch, Nicholas P. Warner

We show that there is a non-trivial relationship between the dilaton of IIB supergravity, and the coset of scalar fields in five-dimensional, gauged N=8 supergravity. This has important consequences for the running of the gauge coupling in massive perturbations of the AdS/CFT correspondence. We conjecture an exact analytic expression for the ten-dimensional

A. Nogga, H. Kamada, W. Gloeckle

We present new calculations of the $α$-particle which are based on the most modern nucleon-nucleon interactions alone and combined with the Tucson-Melbourne or the Urbana IX three-nucleon interaction. Results for the binding energies and some properties of the wavefunction are given. On that phenomenological level little room is left for the action of a poss

Shinji Mukohyama

Gravitational perturbations of anti-deSitter spacetime play important roles in AdS/CFT correspondence and the brane world scenario. In this paper, we develop a gauge-invariant formalism of gravitational perturbations of maximally symmetric spacetimes including anti-deSitter spacetime. Existence of scalar-type master variables is shown and the corresponding m

Tarek Ibrahim, Pran Nath

The effects of large CP violating phases arising from the soft SUSY breaking parameters on the proton lifetime are investigated in supersymmetric grand unified models. It is found that the CP violating phases can reduce as well as enhance the proton lifetime depending on the part of the parameter space one is in. Modifications of the proton lifetime by as mu

D. E. Segall, Sohrab Ismail-Beigi, T. A. Arias

We initiate the development of a theory of the elasticity of nanoscale objects based upon new physical concepts which remain properly defined on the nanoscale. This theory provides a powerful way of understanding nanoscale elasticity in terms of local group contributions and gives insight into the breakdown of standard continuum relations. We also give two a

S. Kharchev, D. Lebedev

The recurrent relations between the eigenfunctions for $GL(N,\RR)$ and $GL(N-1,\RR)$ quantum Toda chains is derived. As a corollary, the Mellin-Barnes integral representation for the eigenfunctions of a quantum open Toda chain is constructed for the $N$-particle case.

A. Chattopadhyay, A. J. Millis, S. Das Sarma

We present the T=0 phase diagram of the double-exchange model (ferromagnetic Kondo lattice model) for all values of the carrier concentration $n$ and Hund&#39;s couplng $J$, within dynamical mean field theory. We find that depending on the values of $n$ and $J$, the ground state is either a ferromagnet, a commensurate antiferromagnet or some other incommensu

Geza Odor

Numerical simulations and cluster mean-field approximations with coherent anomaly extrapolation show that the critical line of the 1d annihilation fission process is separated into two regions. In both the small and high diffusion cases the critical behavior is different from the well known universality classes of non-equilibrium phase transitions to absorbi

Alexander R. Its, Craig A. Tracy, Harold Widom

This paper, a continuation of math.CO/9909169, connects the analysis of the length of the longest weakly increasing subsequence of inhomogeneous random words to a Riemann-Hilbert problem and an associated system of integrable PDEs. In particular, we show that the Poissonization of the distribution function of this length can be identified as the Jimbo-Miwa-U

P. V. Pobylitsa, M. V. Polyakov

We derive new positivity bounds on spin-dependent parton distributions in multicolored QCD. They are stronger than Soffer inequality. We check that the new inequalities are stable under one-loop DGLAP evolution to higher normalization points.

Hans Fangohr, Andrew R. Price, Simon J. Cox, Peter A. J. de Groot

A number of problems arise when long-range forces, such as those governed by Bessel functions, are used in particle-particle simulations. If a simple cut-off for the interaction is used, the system may find an equilibrium configuration at zero temperature that is not a regular lattice yet has an energy lower than the theoretically predicted minimum for the p

D. S. Gorbunov, V. A. Ilyin

In some supersymmetric extensions of the Standard Model fairly light superpartner of t-quark is predicted, which may form bound states ({\it stoponiums}) under certain conditions. We study prospects of search for stoponium at the future Photon Linear Collider. It is found that this machine could be the best machine for discovery and study of these resonances

I. Antoniadis, K. Benakli, M. Quiros

We propose a way to generate the electroweak symmetry breaking radiatively in non-supersymmetric type I models with string scale in the TeV region. By identifying the Higgs field with a tree-level massless open string state, we find that a negative squared mass term can be generated at one loop. It is finite, computable and typically a loop factor smaller th

N. Destainville, R. Mosseri, F. bailly

Some combinatorial properties of fixed boundary rhombus random tilings with octagonal symmetry are studied. A geometrical analysis of their configuration space is given as well as a description in terms of discrete dynamical systems, thus generalizing previous results on the more restricted class of codimension-one tilings. In particular this method gives ac

Anupam Mazumdar, Jing Wang

We demonstrate that there exists an inflationary solution on the positive tension brane in the Randall-Sundrum scenario. Inflation is driven by a slow-rolling scalar field on the brane and is achieved within the perturbative limit of the radion field. We find that inflation on the positive tension brane results in a slight increase in the separation between

C. Sochichiu

Description of the spectrum of fluctuations around a commutative vacuum solution, as well as around a solution with degenerate commutator in IIB matrix model is given in terms of supersymmetric Yang-Mills (YM) model. We construct explicitly the map from Hermitian matrices to YM fields and study the dependence of the spectrum and respective YM model on the sy

Parviz Haggi-Mani, Ulf Lindstrom, Maxim Zabzine

We discuss the non-linear sigma model representing a NSR open string in a curved background with non-zero $B_{μν}$-field. With this coupling the theory is not automatically supersymmetric, due to boundary contributions. When B=0 supersymmetry is ensured by the conditions that follow as the boundary contribution to the field equations. We show that inclusion

J. Bijtebier

We perform a 3D reduction of the two-fermion Bethe-Salpeter equation, by series expansion around a positive-energy instantaneous approximation of the Bethe-Salpeter kernel, followed by another series expansion at the 3D level in order to get a manifestly hermitian 3D potential. It turns out that this potential does not depend on the choice of the starting ap

Anthony Hams, Hans De Raedt

A theoretical analysis is given of the equation of motion method, due to Alben et al., to compute the eigenvalue distribution (density of states) of very large matrices. The salient feature of this method is that for matrices of the kind encountered in quantum physics the memory and CPU requirements of this method scale linearly with the dimension of the mat

C. Monthus, T. Garel, H. Orland

We consider two different problems involving the localization of a single polymer chain: (i) a periodic $AB$ copolymer at a selective fluid-fluid interface, with the upper (resp. lower) fluid attracting $A$ (resp. $B$) monomers (ii) a homopolymer chain attracted to a hard wall (wetting). Self avoidance is neglected in both models, which enables us to study t

B. L. Hazelzet, M. R. Wegewijs, T. H. Stoof, Yu. V. Nazarov

We propose a new mode of operation of an electron pump consisting of two weakly coupled quantum dots connected to reservoirs. An electron can be transferred within the device at zero bias voltage when it is subjected to electromagnetic radiation, thereby exciting the double dot. The excited state can decay by transferring charge from one lead and to the othe

Pablo I. Hurtado, Miguel A. Munoz

We report on some extensive analysis of a recently proposed model [A. Lipowski Phys. Rev. E {\bf 60}, 6255 (1999)] with infinitely many absorbing states. By performing extensive Monte Carlo simulations we have determined critical exponents and show strong evidence that this model is not in the directed percolation universality class. The conjecture that this

Mark J. Hadley

It is shown that models of elementary particles in classical general relativity (geons) will naturally have the transformation properties of a spinor if the spacetime manifold is not time orientable. From a purely pragmatic interpretation of quantum theory this explains why spinor fields are needed to represent particles. The models are based entirely on cla

Sz. Borsanyi, A. Patkos, J. Polonyi, Zs. Szep

Thermalisation of configurations with initial white noise power spectrum is studied in numerical simulations of a classical one-component $Φ^4$ theory in 2+1 dimensions, coupled to a small amplitude homogenous external field. The study is performed for energy densities corresponding to the broken symmetry phase of the system in equilibrium. The effective equ

A. Beige, D. Braun, B. Tregenna, P. L. Knight

We propose a new approach to the implementation of quantum gates in which decoherence during the gate operations is strongly reduced. This is achieved by making use of an environment induced quantum Zeno effect that confines the dynamics effectively to a decoherence-free subspace.

H. C. Rosu, P. Espinoza

We apply the Ermakov-Lewis procedure to the one-parameter damped modes \tilde{y} recently introduced by Rosu and Reyes, which are related to the common Newtonian free damping modes y by the general Riccati solution [H.C. Rosu and M. Reyes, Phys. Rev. E 57, 4850 (1998), physics/9707019]. In particular, we calculate and plot the angle quantities of this approa

Shu-Chiuan Chang, Robert Shrock

We present exact calculations of the zero-temperature partition function (chromatic polynomial) $P$ for the $q$-state Potts antiferromagnet on triangular lattice strips of arbitrarily great length $L_x$ vertices and of width $L_y=3$ vertices and, in the $L_x \to \infty$ limit, the exponent of the ground-state entropy, $W=e^{S_0/k_B}$. The strips considered,

Bilha Segev, Peter W. Milonni, James F. Babb, Raymond Y. Chiao

Causal &#34;superluminal&#34; effects have recently been observed and discussed in various contexts. The question arises whether such effects could be observed with extremely weak pulses, and what would prevent the observation of an &#34;optical tachyon.&#34; Aharonov, Reznik, and Stern (ARS) [Phys. Rev. Lett., vol. 81, 2190 (1998)] have argued that quantum

Adrian Alscher, Hermann Grabert

We reply to a comment on `Semiclassical dynamics of a spin-1/2 in an arbitrary magnetic field&#39;.

Benjamin Schumacher, Michael D. Westmoreland

We review the properties of the quantum relative entropy function and discuss its application to problems of classical and quantum information transfer and to quantum data compression. We then outline further uses of relative entropy to quantify quantum entanglement and analyze its manipulation.

C. Grupen

Photons are exponentially attenuated in matter producing high doses close to the surface. Therefore they are not well suited for the treatment of deep seated tumours. Charged particles, in contrast, exhibit a sharp increase of ionisation density close to the end of their range, the so-called Bragg-peak. The depth of the Bragg-peak can be adjusted by varying

B. Prinari

Potentials of the heat conduction operator constructed by means of 2 binary Backlund transformations are studied in detail. Corresponding Darboux transformations of the Jost solutions are introduced. We show that these solutions obey modified integral equations and present their analyticity properties.

L. L. Bonilla, C. J. Perez-Vicente, F. Ritort, J. Soler

We analyze mean-field models of synchronization of phase oscillators with singular couplings and subject to external random forces. They are related to the Kuramoto-Sakaguchi model. Their probability densities satisfy local partial differential equations similar to the Porous Medium, Burgers and extended Burgers equations depending on the degree of singulari

Indranil Biswas, Christophe Mourougane

We prove that the $L^2$ metric on the direct image of an adjoint positive line bundle by a locally trivial submersion between projective manifolds is Nakano positive, under the assumption that the typical fiber has zero first Betti number. As a consequence, we get that the symmetric powers of an ample vector bundle tensorized by its determinant are Nakano po

Matias Grana

This is a contribution to the classification program of pointed Hopf algebras. We give a generalization of the quantum Serre relations and propose a generalization of the Frobenius-Lusztig kernels in order to compute Nichols algebras of diagonal group type. With this, we classify Nichols algebras B(V) with dimension < 32 or with dimension p^3, p a prime numb

Andrea Giacobbe

We extend the famous convexity theorem of Atiyah, Guillemin and Sternberg to the case of non-Hamiltonian actions. We show that the image of a generalized momentum map is a bounded polytope times a vector space. We prove that this picture is stable for small perturbations of the symplectic form. We also observe that an n-dimensional torus symplectic action on

R. Hansen, M. Piacquadio

This paper contains a comparative study of two families of simple curves drawn in the plane. On the one hand, we have the fractal curves on the unit interval, with self-similar structure, which have associated a Hausdorff dimension. On the other hand, we have the opposite: a class of locally rectifiable unbounded curves, which have another &#34;fractional di

P. Constantin

We present a local existence result for the three dimensional incompressible Euler equations. The solution is constructed using a formulation of the equations as an active vector system in Eulerian coordinates. The formulation employs the inverse of the Lagrangian path map (the &#34;back-to-labels&#34; map) and its Eulerian gradient. We express sufficient co