June 2001 arXiv papers — page 13

Mirjam Cvetic, G. W. Gibbons, H. Lu, C. N. Pope

We review the construction of regular p-brane solutions of M-theory and string theory with less than maximal supersymmetry whose transverse spaces have metrics with special holonomy, and where additional fluxes allow brane resolutions via transgression terms. We focus on the properties of resolved M2-branes and fractional D2-branes, whose transverse spaces a

Arkady Vainshtein

We consider chiral condensates in SU(2) gauge theory with broken N=2 supersymmetry and one fundamental flavor in the matter sector. Matter and gaugino condensates are determined by integrating out the adjoint field. The only nonperturbative input is the Affleck-Dine-Seiberg one-instanton superpotential. The results are consistent with those obtained by the `

R. Brustein, S. P. de Alwis

The region of moduli space of string theories which is most likely to describe the "real world" is where the string coupling is about unity and the volume of extra compact dimensions is about the same size as the string volume. Here we map the landscape of this "central" region in a model-independent way, assuming only that the string couplin

A. Smailagic, E. Spallucci

We have developed dualization of ordinary and ``Stueckelberg compensated'' massive phase for the Kalb-Ramond theory. The compensated phase allows to study the interplay between spin jumping and duality. We show that spin jumping is caused by mass, while gauge symmetry is not necessary for this effect to take place.

Yuri A. Rylov

A new quantization scheme (WL-scheme), using world lines as objects of quantization, is proposed. Applying to nonlinear scalar field, the WL -scheme is investigated and compared with the conventional PA-scheme of quantization. In the PA-scheme objects of quantization are particles and antiparticles, which are fragments of the total physical object -- world l

S. Bellucci, V. Faraoni

Attention has been recently called upon the fact that the weak and null energy conditions and the second law of thermodynamics are violated in wormhole solutions of Einstein's theory with classical, nonminimally coupled, scalar fields as material source. It is shown that the discussion is only meaningful when ambiguities in the definitions of stress-ener

Masa-aki Taniguchi, Shozo Uehara, Satoshi Yamada, Koichi Yamawaki

We develop a systematic DLCQ perturbation theory and show that DLCQ S-matrix does not have a covariant continuum limit for processes with $p^+=0$ exchange. This implies that the role of the zero mode is more subtle than ever considered in DLCQ and hence must be treated with great care also in non-perturbative approach. We also make a brief comment on DLCQ in

M. Cvetic, G. W. Gibbons, James T. Liu, H. Lu

Recently, a new example of a complete non-compact Ricci-flat metric of G_2 holonomy was constructed, which has an asymptotically locally conical structure at infinity with a circular direction whose radius stabilises. In this paper we find a regular harmonic 3-form in this metric, which we then use in order to obtain an explicit solution for a fractional D2-

N. Sanchez

We present a minimal model for the Universe evolution fully extracted from effective String Theory. This model is by its construction close to the standard cosmological evolution, and it is driven selfconsistently by the evolution of the string equation of state itself. The inflationary String Driven stage is able to reach enough inflation, describing a Big

Petr Zavada

The alternative to the standard formulation of the quark-parton model is proposed. Our relativistically covariant approach is based on the solution of the master equations relating the structure and distribution functions, which consistently takes into account the intrinsic quark motion. It is suggested, that the intrinsic quark motion can substantially redu

A. Bacchetta

The transversity distribution can be measured at leading-twist in single-particle inclusive DIS, where it appears in connection with chiral-odd fragmentation functions. Among these functions, we focus on the time-reversal odd ones. They occur in fragmentation to unpolarized hadrons or polarized spin-one hadrons. Using a simple model, we show how these functi

I. Hinchliffe, P. Richardson

We briefly review the SUGRA, GMSB and AMSB supersymmetry breaking models. We then discuss the phenomenological differences between them and consequent characteristic experimental signatures. This is followed by a review of the discovery potential for supersymmetry at the Tevatron, LHC and a future e+e- linear collider.

A. Gokalp, O. Yilmaz

We study the radiative decay $ϕ\toπ^{0}π^{0}γ$ within the framework of a phenomenological approach in which the contributions of $σ$-meson, $ρ$-meson and $f_0$-meson are considered. We analyze the interference effects between different contributions and utilizing the experimental branching ratio for this decay we estimate the coupling constant $g_{ϕσγ}$.

John Pinney

An indirect CP-violation neutrino factory experiment is studied, including simul taneous correlations of errors of the six oscillation parameters and a matter ef fect normalisation parameter, C. It is found that for larger values of $θ_{13}$ ($3^\circ$), an uncertainty on the matter effect of the order 5% means t hat the optimal baseline for measurement of $

A. K. Chaudhuri

We have investigated the phase transition and disoriented chiral condensate domain formation in linear sigma model. Solving the Langevin equation for the linear $σ$ model, we have shown that for zero mass pions the fields undergo phase transition above a certain temperature ($T_c$). For finite mass pions, there is no phase transition. It was also shown that

S. Pislak, R. Appel, G. S. Atoyan, B. Bassalleck

A sample of 400000 events from the decay K+->pi+pi-e+nu(e)(K(e4)) has been collected in experiment E865 at the Brookhaven AGS. The analysis of these data yields new measurements of the K(e4) branching ratio (4.11+-0.01+-0.11)*10**(-5)), the s-wave pi-pi scattering length a00=0.228+-0.012+-0.003, and the form factors F, G, and H of the hadronic current and th

Levan Babukhadia

We report a new measurement of the pseudorapidity (eta) and transverse- energy (Et) dependence of the inclusive jet production cross section in pbar p collisions at sqrt(s)=1.8 TeV using 95 pb**-1 of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d^2sigma/(dEt deta) is presented up to |eta|=3, significantly exten

D. Blaschke, V. Pervushin, D. Proskurin, S. Vinitsky

The cosmological creation of primordial vector bosons and fermions is described in the Standard Model of strong and electro-weak interactions given in a space-time with the relative standard of measurement of geometric intervals. Using the reparametrization - invariant perturbation theory and the holomorphic representation of quantized fields we derive equat

William McCune

MACE is a program that searches for finite models of first-order statements. The statement to be modeled is first translated to clauses, then to relational clauses; finally for the given domain size, the ground instances are constructed. A Davis-Putnam-Loveland-Logeman procedure decides the propositional problem, and any models found are translated to first-

André Grosse, Joerg Rothe, Gerd Wechsung

We prove that computing a single pair of vertices that are mapped onto each other by an isomorphism $ϕ$ between two isomorphic graphs is as hard as computing $ϕ$ itself. This result optimally improves upon a result of Gál et al. We establish a similar, albeit slightly weaker, result about computing complete Hamiltonian cycles of a graph from partial Hamilton

G. Sakkis, I. Androutsopoulos, G. Paliouras, V. Karkaletsis

We evaluate empirically a scheme for combining classifiers, known as stacked generalization, in the context of anti-spam filtering, a novel cost-sensitive application of text categorization. Unsolicited commercial e-mail, or "spam", floods mailboxes, causing frustration, wasting bandwidth, and exposing minors to unsuitable content. Using a public cor

Kenji Tsutsui, Didier Poilblanc, Sylvain Capponi

Charge current static and dynamical correlations are computed by exact diagonalisation methods on a 2-leg t-t'-J ladder which exhibits a sharp transition between a Luther-Emery (LE) phase of hole pairs and a phase with deconfined holes. In the LE phase, we find short-range low-energy incommensurate current fluctuations which are intrinsically connected t

H. Kitaguchi, H. Kumakura, K. Togano

The influence of mechanical strain on the critical current (Ic) is investigated for MgB2/stainless steel (SUS316) superconducting tapes. The tapes are fabricated by using 'powder in tube' method and deformation process without any heat treatment. The tensile axial strain along tape length is successfully induced to the sample by using a U-shape holde

Joel E. Moore, Xiao-Gang Wen

A general description of weak and strong tunneling fixed points is developed in the chiral-Luttinger-liquid model of quantum Hall edge states. Tunneling fixed points are a subset of `termination' fixed points, which describe boundary conditions on a multicomponent edge. The requirement of unitary time evolution at the boundary gives a nontrivial consiste

Stefan Wessel, Stephan Haas

We study the evolution of the dynamical spin structure factor in a spin-1 antiferromagnetic Heisenberg chain which is randomly doped with spin-1/2 moments. Using stochastic series expansion Quantum Monte Carlo simulations combined with the Maximum Entropy method, we monitor the crossover from the spin-1 chain, dominated by a single resonance at the Haldane e

E. S. Caixeiro, E. V. L. de Mello

We apply a method based on a BCS-type approach to the extended Hubbard model to deal with the YBa_2Cu_3O_{7-δ} superconductor family under pressure. The parameters of the tight-binding band are taken from experiments, and the coupling strength U and V are estimated from the zero pressure phase diagram Tc X n_h, where n_h is the hole content and Tc the critic

I. Ispolatov, E. G. D. Cohen

Collapse, or a gravitational-like phase transition is studied in a microcanonical ensemble of particles with an attractive $1/r^α$ potential. A mean field continuous integral equation is used to determine a saddle-point density profile that extremizes the entropy functional. For all $0<α<3$, a critical energy is determined below which the entropy of the syst

S. Picozzi, G. Profeta, A. Continenza, S. Massidda

First-principles full-potential linearized augmented plane wave (FLAPW) calculations are performed to clarify the role of the interface geometry on piezoelectric fields and on potential line-ups at the [0001]-wurtzite and [111]-zincblende GaN/Al junctions. The electric fields (polarity and magnitude) are found to be strongly affected by atomic relaxations in

Xiaoguang Wang, Shaohua Pan, Guozhen Yang

By using antitrace map method, we investigate the light transmission for a generalized Fibonacci multilayers. Analytical results are obtained for transmission coefficients in some special cases. We find that the transmission coefficients possess two-cycle property or six-cycle property. The cycle properties of the trace and antitrace are also obtained.

X. Batlle, B. J. Hattink, A. Labarta, B. J. Jonsson-Akerman

We demonstrate that at the usual 1E-7 torr range of base pressures in the sputtering chamber, X-ray photoelectron spectroscopy shows the existence of a thin AlOx layer at the Nb/Al interface in both Nb/Al-AlOx/Pb tunnel junctions and Nb/Al bilayers. This is due to the time elapsed between the deposition of the Nb and Al bottom layers, even at times as short

D. T. N. de Lang, L. A. Ponomarenko, A. de Visser, C. Possanzini

We study the quantum critical behavior of the plateau-insulator (PI) transition in a low mobility InGaAs/InP heterostructure. By reversing the direction of the magnetic field (B) we find an averaged Hall resistance ρ_xy which remains quantized at the plateau value h/e^2 throughout the PI transition. We extract a critical exponent κ&#39;= 0.57 +/- 0.02 for th

S. Kutter, E. M. Terentjev

Polymer entanglements lead to complicated topological constraints and interactions between neighbouring chains in a dense solution or melt. Entanglements can be treated in a mean field approach, within the famous reptation model, since they effectively confine each individual chain in a tube-like geometry. In polymer networks, due to crosslinks preventing th

Albert Biedermann, Rupert Tscheliessnig, Michael Schmid, Peter Varga

We report bcc-like crystal structures in 2-4 ML Fe films grown on fcc Cu(100) using scanning tunneling microscopy. The local bcc structure provides a straightforward explanation for their frequently reported outstanding magnetic properties, i.e., ferromagnetic ordering in all layers with a Curie temperature above 300 K. The non-pseudomorphic structure, which

J. Reijniers, F. M. Peeters, A. Matulis

The quasi-bound and scattered states in a 2DEG subjected to a circular symmetric steplike magnetic profile with zero average magnetic field are studied. We calculate the effect of a random distribution of such identical profiles on the transport properties of a 2DEG. We show that a nonzero Hall resistance can be obtained, although $<B_{z} >=0$, and that in s

Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida, Manfred Sigrist

We investigate the vortex structure in chiral p-wave superconductors by the Bogoliubov-de Gennes theory on a tight-binding model. We calculate the spatial structure of the pair potential and electronic state around a vortex, including the anisotropy of the Fermi surface and superconducting gap structure. The differences of the vortex structure between $\sin

J. F. Fontanari, P. F. Stadler

Stability and diversity are two key properties that living entities share with spin glasses, where they are manifested through the breaking of the phase space into many valleys or local minima connected by saddle points. The topology of the phase space can be conveniently condensed into a tree structure, akin to the biological phylogenetic trees, whose tips

Satya N. Majumdar, Deepak Dhar

We study the persistence in a class of continuous stochastic processes that are stationary only under integer shifts of time. We show that under certain conditions, the persistence of such a continuous process reduces to the persistence of a corresponding discrete sequence obtained from the measurement of the process only at integer times. We then construct

P. C. Haljan, I. Coddington, P. Engels, E. A. Cornell

We have developed an evaporative cooling technique that accelerates the circulation of an ultra-cold $^{87}$Rb gas, confined in a static harmonic potential. As a normal gas is evaporatively spun up and cooled below quantum degeneracy, it is found to nucleate vorticity in a Bose-Einstein condensate. Measurements of the condensate&#39;s aspect ratio and surfac

Kay Joerg Wiese

In these lecture notes, we give an overview about non-local field-theories and their application to polymerized membranes, i.e. membranes with a fixed internal connectivity. The main technical tool is the multi-local operator product expansion (MOPE), generalizing ideas from local field theories to the multi-local situation.

J. E. Hirsch

The theory of hole superconductivity proposes that MgB_2, and the high Tc cuprates, and the &#39;conventional superconductors&#39;, and all other superconductors, are driven by the same physical mechanism, which is not the electron-phonon interaction. That mechanism, hole undressing, evidence supporting it, and predictions for MgB_2, are briefly reviewed.

Massimo Marengo, Margarita Karovska, Giovanni G. Fazio, Joseph L. Hora

This paper presents results from high-angular resolution mid-IR imaging of the Mira AB circumbinary environment using the MIRAC3 camera at the NASA Infrared Telescope Facility (IRTF). We resolved the dusty circumstellar envelope at 9.8, 11.7 and 18 micron around Mira A (o Ceti), and measured the size of the extended emission. Strong deviations from spherical

Andrew S. Fruchter, Julian H. Krolik, James E. Rhoads

We show that if all gamma-ray bursts emit X-rays in a way similar to those observed by BeppoSax, much of the extinction along the line of sight in the host galaxy of the burst can be destroyed. Two mechanisms are principally responsible for dust destruction: grain heating and grain charging. The latter, which can lead to electrostatic stresses greater than t

Eduardo Telles

Stellar Clusters are identified in images and in the spectra of these star forming dwarf galaxies. These Stellar Clusters have properties similar to those observed in other violent star forming galaxies and may the elementary entities of a starburst.

P. Jean, J. Knödlseder, P. von Ballmoos, J. Gómez-Gomar

The radioactive isotope $^{22}$Na is one of the primary tracer isotopes that may potentially be detectable by gamma-ray spectroscopy. This isotope is predicted to be produced in ONe nova explosions, yet no detection of its 1.275 MeV gamma-ray signature has been reported so far. In particular, 6 years of COMPTEL observations of the galactic bulge, a region th

M. F. Bietenholz, D. A. Frail, J. J. Hester

We present three high resolution radio images of the Crab nebula, taken in 1998.6, 1998.8 and 2000.1 with the VLA. These are the best radio images of the Crab to date. We show that, near the pulsar, there are significant changes between our three observing epochs. These changes have an elliptical geometry very similar to that of the optical wisps. One radio

Christopher D. Matzner, Jonathan C. Tan, Christopher F. McKee

Supernova (SN) 1998bw and gamma-ray burst (GRB) 980425 offer the first direct evidence that supernovae are the progenitors of some GRBs. However, this burst was unusually dim, smooth and soft compared to other bursts with known afterglows. Whether it should be considered a prototype for cosmological GRBs depends largely on whether the supernova explosion and

A. I. Terlevich, N. Caldwell, R. G. Bower

We present a new photometric catalogue of the Coma galaxy cluster in the Johnson U- and V- bands. We cover an area of 3360arcmin2 of sky, to a depth of V=20 mag in a 13 arcsec diameter aperture, and produce magnitudes for ~1400 extended objects in metric apertures from 8.8 to 26arcsec diameters. The mean internal RMS scatter in the photometry is 0.014 mag in

Marco Lombardi, Giuseppe Bertin

We have re-examined the classical problem of the macroscopic equation of state for a hydrostatic isothermal self-gravitating gas cloud bounded by an external medium at constant pressure. We have obtained analytical conditions for its equilibrium and stability without imposing any specific shape and symmetry to the cloud density distribution. The equilibrium

R. A. Koopmann, J. D. P. Kenney, J. Young

Narrow-band Halpha and broadband R images and radial profiles are presented for 63 bright spiral galaxies in the Virgo Cluster. The sample is complete for Sb-Scd galaxies with B magnitude less than 12 and inclination less than 75 degrees. Isophotal radii, disk scalelengths, concentration parameters, and integrated fluxes are derived for the sample galaxies.

M. F. Bietenholz, N. E. Kassim, K. W. Weiler

We present new observations of the plerionic supernova remnant 3C58 with the VLA at 74 and 327 MHz. In addition, we re-reduced earlier observations at 1.4 and 4.9 GHz taken in 1973 and 1984. Comparing these various images, we find that: 1. the remnant has a flat and relatively uniform spectral index distribution, 2. any expansion of the remnant with time is

R. F. Coker

An attempt is made to reconcile the large wind-loss rates of stars in the Galactic Centre (GC) with the predicted low accretion rate for Sgr A*, the putative blackhole at the heart of the Milky Way. It is found that, independent of the details of the accretion, the bound but unaccreted gas has been accumulating in the potential well of Sgr A* for <1000 yrs a

Ralf Klessen

Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass from the surrounding cloud material. Molecular cloud regions without turbulent driving sources, or where turbulence is driven on large scales, exhibit rapid and efficient star formation in a clustered mode, whereas interstellar turbulence that ca

Charles B. Leffert

In previous papers, predictions of the new &#34;Spatial Condensation (SC-)&#34; cosmological model were presented on the (1) foundations, (2) new source of gravity, and (3) large-scale structure. In this paper predictions will include new physical features that are due mostly to the postulated geometry of our closed 3-D universe. Knowledge of the past univer

Justin Oelgoetz, Anil K. Pradhan

It is shown that the dielectronic satellites (DES) dominate X-ray spectral formation in the 6.7 keV K-alpha complex of Fe XXV at temperatures below that of maximum abundance in collisional ionization equilibrium T_m. Owing to their extreme temperature sensitivity the DES are excellent spectral diagnostics for T < T_m in photoionized, colllisional, or hybrid

J. Robert Buchler, Zoltan Kollath, Robert Cadmus

The light curves (time series of the radiated energy) of most large amplitude, pulsating stars such as the well known Cepheid stars are regular. However, a smaller group of variable stars that are located next to them in the Hertzsprung- Russell diagram undergoes irregular light variations and exhibits irregular radial velocities as well. The mechanism behin

Seb Oliver

We discuss some of the practical considerations that need to be made in the design of extra-galactic field surveys using FIRST. We investigate the various limitations that confusion noise imposes on possible FIRST surveys and the benefits of super resolution or decconvolution techniques. We consider the possible sizes and depths of survey fields in order to

Seb Oliver

I discuss some of the main extra-galactic field surveys which have been undertaken by the Infrared Space Observatory (ISO). I review the findings from the source counts analysies and then examine some of the more recent detailed investigations into the explicit nature of the populations that make up these source counts.

M. Loewenstein, R. F. Mushotzky, L. Angelini, K. A. Arnaud

Elliptical galaxy nuclei are the sites of the largest black holes known, but typically show little or no nuclear activity. We investigate this extreme quiescence using Chandra X-ray Observatory observations of the giant elliptical galaxies NGC 1399, NGC 4472, and NGC 4636. The unique Chandra imaging power enables us to place upper limits of 7.3, 15 and 28 X

G. Lodato, G. Bertin

The long wavelength emission of protostellar objects is commonly attributed to a disk of gas and dust around the central protostar. In the first stages of disk accretion or in the case of high mass protostars, the disk mass is likely to be sufficiently large, so that the disk self-gravity may have an impact on the dynamics and the emission properties of the

L. J. Kewley, M. A. Dopita, R. S. Sutherland, C. A. Heisler

We have modeled a large sample of infrared starburst galaxies using both the PEGASE v2.0 and STARBURST99 codes to generate the spectral energy distribution of the young star clusters. PEGASE utilizes the Padova group tracks while STARBURST99 uses the Geneva group tracks, allowing comparison between the two. We used our MAPPINGS III code to compute photoioniz

H. Krüger, E. Grün, M. Landgraf, S. Dermott

The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse ($ i = 79^{\circ}$, perihelion distance 1.3 AU, aphelion distance 5.4 AU). Between January 1996 and December 1999 the spacecraft was beyond 3 AU from the Sun and crossed the ecliptic plane at aphelion in May 1998. In this four-year period 218 dust impacts were recorded with the dust dete

Licia Verde, Zoltan Haiman, David N. Spergel

An extensive sample of galaxy clusters will be available in the coming years, detected through their Sunyaev-Zeldovich effect (SZE). We use a semi-analytic model to study the scientific yield of combining SZE data with X-ray and optical follow-up observations. If clusters at a given redshift z_o can be identified with virialized, spherical halos, they popula

A. Y. Potekhin, D. G. Yakovlev

The thermal structure of neutron stars with magnetized envelopes is studied using modern physics input. The relation between the internal (T_i) and local surface temperatures is calculated and fitted by analytic expressions for magnetic field strengths B from 0 to 10^{16} G and arbitrary inclination of the field lines to the surface. The luminosity of a neut

Dipankar Bhattacharya

Temporal behaviour of GRB afterglow light curve is derived for the case where the electron energy distribution is relatively flat, with the power-law index p lying between 1.0 and 2.0. It is shown that the expected behaviour will be the same as that for p>2.0 if the upper cutoff in the electron energy distribution evolves in direct proportion to the bulk Lor

Neil J. Cornish

The random superposition of many weak sources will produce a stochastic background of gravitational waves that may dominate the response of the LISA (Laser Interferometer Space Antenna) gravitational wave observatory. Unless something can be done to distinguish between a stochastic background and detector noise, the two will combine to form an effective nois

Sudarshan Fernando, Murat Gunaydin, Seiji Takemae

We study the positive energy unitary representations of 2N extended superconformal algebras OSp(8*|2N) in six dimensions. These representations can be formulated in a particle basis or a supercoherent state basis, which are labeled by the superspace coordinates in d=6. We show that the supercoherent states that form the bases of positive energy representatio

V. Barger, D. Marfatia, K. Whisnant

We perform a model-independent analysis of solar neutrino flux rates including the recent charged-current measurement at the Sudbury Neutrino Observatory (SNO). We derive a universal sum rule involving SNO and SuperKamiokande rates, and show that the SNO neutral-current measurement can not fix the fraction of solar $ν_e$ oscillating to sterile neutrinos. The

R. Korus, St. Mrowczynski, M. Rybczynski, Z. Wlodarczyk

The event-by-event p_T-fluctuations due to the temperature variation are considered. The so-called Phi-measure is computed and shown to be a linear function of the temperature variance. The fluctuations of temperature naturally explain the data on Phi(p_T) in proton-proton and central Pb-Pb collisions but independent measurements of the temperature fluctuati

Egor Babaev

In this paper we derive a dual presentation of free energy functional for spin-triplet superconductors in terms of gauge-invariant variables. The resulting equivalent model in ferromagnetic phase has a form of a version of the Faddeev model. This allows one in particular to conclude that spin-triplet superconductors allow formation of stable finite-length cl

H. Orland, A. Zee

We formulate the RNA folding problem as an $N\times N$ matrix field theory. This matrix formalism allows us to give a systematic classification of the terms in the partition function according to their topological character. The theory is set up in such a way that the limit $N\to \infty$ yields the so-called secondary structure (Hartree theory). Tertiary str

Benjamin Grinstein

We average the decay width of a heavy meson in the t&#39; Hooft model over the heavy quark mass M with a smooth weight function. The averaging has support over a few resonance spacings. We use the previously determined heavy meson decay width which differs from the free quark width by a 1/M correction. In contrast, we find that the averaged meson and quark w

M. Battaglia, A. De Roeck, J. Ellis, F. Gianotti

We propose a new set of supersymmetric benchmark scenarios, taking into account the constraints from LEP, b to s gamma, g_mu - 2 and cosmology. We work in the context of the constrained MSSM (CMSSM) with universal soft supersymetry-breaking masses and assume that R parity is conserved. We propose benchmark points that exemplify the different generic possibil

HERMES Collaboration, A. Airapetian

The beam-spin asymmetry in hard electroproduction of photons has been measured for the first time. The data have been accumulated by the HERMES experiment at DESY using the HERA 27.6 GeV longitudinally polarized positron beam and an unpolarized hydrogen gas target. The asymmetry in the azimuthal distribution of the produced photons in the angle phi relative

P. Postorino, A. Congeduti, P. Dore, A. Nucara

Raman and infrared absorption spectra of Mg(1-x)Al(x)B(2) have been collected for 0<x<0.5 in the spectral range of optical phonons. The x-dependence of the peak frequency, the width and the intensity of the observed Raman lines has been carefully analized. A peculiar x-dependence of the optical modes is pointed out for two different Al doping ranges. In part

F. Bigazzi, A. L. Cotrone, A. Zaffaroni

We present string duals of four dimensional N=2 pure SU(N) SYM theory. The theory is obtained as the low energy limit of D5-branes wrapped on non-trivial two-cycles. Using seven dimensional gauged supergravity and uplifting the result to ten dimensions, we obtain solutions corresponding to various points of the N=2 moduli space. The more symmetric solution m

Manfred Herbst, Alexander Kling, Maximilian Kreuzer

We define a non-commutative product for arbitrary gauge and B-field backgrounds in terms of correlation functions of open strings. While off-shell correlations are, of course, not conformally invariant, it turns out that, at least to first derivative order, our product has the trace property and is associative up to surface terms if the background fields are

J. P. Hague, N. d&#39;Ambrumenil

We investigate the applicability of Migdal--Eliashberg (ME) theory by revisiting Migdal&#39;s analysis within the dynamical mean-field theory framework. First, we compute spectral functions, the quasi-particle weight, the self energy, renormalised phonon frequency and resistivity curves of the half-filled Holstein model. We demonstrate how ME theory has a ph

Itzhak Bars

It is shown that Witten's star product in string field theory, defined as the overlap of half strings, is equivalent to the Moyal star product involving the relativistic phase space of even string modes. The string field A(x[\sigma]) can be rewritten as a phase space field of the even modes $x_{2n},x_{0}, p_{2n}$ where $x_{2n}$ are the positions of the even

SNO Collaboration

Solar neutrinos from the decay of $^8$B have been detected at the Sudbury Neutrino Observatory (SNO) via the charged current (CC) reaction on deuterium and by the elastic scattering (ES) of electrons. The CC reaction is sensitive exclusively to nu_e&#39;s, while the ES reaction also has a small sensitivity to nu_mu&#39;s and nu_tau&#39;s. The flux of nu_e&#3

Athanasios Dedes, Herbi Dreiner, Peter Richardson

The NuTeV Collaboration has observed an excess in their di-muon channel, possibly corresponding to a long-lived neutral particle with only weak interactions and which decays to muon pairs. We show that this can {\it not} be explained by pair production of neutralinos in the target followed by their decay far downstream in the detector via a $LLE$ R-parity vi

A. Freitas, D. J. Miller, P. M. Zerwas

Non-zero width and Coulomb rescattering effects are analyzed for the pair production of smuons and selectrons near the thresholds in e+ e- and e- e- collisions, respectively. The excitation curves are predicted in a gauge-invariant form. Energy cuts are designed to reduce irreducible supersymmetric backgrounds.

K. S. McFarland, A. C. Melissinos, N. V. Mikheev, W. W. Repko

Motivated by the evidence for a finite neutrino mass we examine anew the interaction of neutrinos in a magnetic field. We present the rate for radiative scattering for both massless and massive neutrinos in the standard model and give the corresponding numerical estimates. We also consider the effects arising from a possible neutrino magnetic moment.

Krastan Blagoev, Fred Cooper, John Dawson, Bogdan Mihaila

In this paper we discuss a Schwinger-Dyson [SD] approach for determining the time evolution of the unequal time correlation functions of a non-equilibrium classical field theory, where the classical system is described by an initial density matrix at time $t=0$. We focus on $λϕ^4$ field theory in 1+1 space time dimensions where we can perform exact numerical

S. James Gates

We establish a theorem about non-trivial 11D supergravity fluctuations that are conformally related to flat superspace geometry. Under the assumption that a theory of conformal 11D supergravity exists, similar in form to that of previously constructed theories in lower dimensions, this theorem demands the appearance of non-vanishing dimension 1/2 torsion ten

Michael M. Fogler

A long-standing problem of the low-energy dynamics of a disordered XY spin chain is re-examined. The case of a rigid chain is studied where the quantum effects can be treated quasiclassically. It is shown that as the frequency decreases, the relevant excitations change from localized spin waves to two-level systems to soliton-antisoliton pairs. The linear-re

Anjan Kundu

Exact quantum integrability is established for a class of multi-chain electron models with correlated hopping and spin models with interchain interactions, by constructing the related Lax operators and R-matrices through twisting and gauge transformations. Exact solution of the eigenvalue problem for commuting conserved quantities of such systems is achieved

Gottfried Curio, Albrecht Klemm, Boris Kors, Dieter Lust

In this paper we consider heterotic compactifications on K3 x T2 as well as type II compactifications on K3-fibred Calabi-Yau spaces with certain fluxes for the gauge and RR field strengths F and H turned on. By providing an identification of corresponding fluxes we show that the well-known N=2 heterotic/type II string-string duality still holds for a subset

J. M. B. Noronha, D. J. Toms

This paper has been withdrawn by the authors due to substantial changes.

M. D. Scadron, P. Zenczykowski

We show that melting the quark mass, the scalar $σ$ mass and the quark condensate leads uniquely to the quark-level SU(2) linear $σ$ model field theory. Upon thermalization, the chiral phase transition curve requires $T_c =2f^{CL}_π\approx 180 MeV$ when $μ= 0$, while the critical chemical potential is $μ_c =m_q\approx 325 MeV$. Transition to the superconduct

P. Dahan, V. Fleurov, K. Kikoin, I. D. Vagner

A theory of magnetic impurities in a 2D electron gas quantized by a strong magnetic field is formulated in terms of Friedel-Anderson theory of resonance impurity scattering. It is shown that this scattering results in an appearance of bound Landau states with zero angular moment between the Landau subbands. The resonance scattering is spin selective, and it

Jan-e Alam, Pradip Roy, Sourav Sarkar, Bikash Sinha

We estimate the photon and dilepton emission rates from hot hadronic matter with in-medium spectral shift and broadening of vector mesons. It is observed that both the WA98 photon data and CERES/NA45 dilepton data can be well reproduced with similar initial conditions. The freeze-out condition has been constrained by the transverse mass spectra of pions and

Stefano Zapperi, Alessandro Magni, Gianfranco Durin

The hysteresis properties of ferromagnetic materials at low field are described by the Rayleigh law. We analyze the problem in light of modern statistical mechanics models of hysteresis. In particular, we compute the demagnetization curve and derive the Rayleigh parameters a and b in the random-field Ising model and in a model of domain wall depinning. In th

Lorenzo Dante, Gianfranco Durin, Alessandro Magni, Stefano Zapperi

We analyze low field hysteresis close to the demagnetized state in disordered ferromagnets using the zero temperature random-field Ising model. We solve the demagnetization process exactly in one dimension and derive the Rayleigh law of hysteresis. The initial susceptibility a and the hysteretic coefficient b display a peak as a function of the disorder widt

R. Mélin, D. Feinberg

We derive a microscopic transport theory of multiterminal hybrid structures in which a superconductor is connected to several spin-polarized electrodes. We discuss the non-perturbative physics of extended contacts, and show that it can be well represented by averaging out the phase of the electronic wave function. The maximal conductance of a two-channel con

Masamichi Ishihara

Parametric resonance in soft modes at the critical temperature ($T_{c}$) in high energy heavy ion collisions is studied in the case when the temperature ($T$) of the system is almost constant for a long time. By deviding the fields into three parts, zero mode (condensate), soft modes and hard modes and assuming that the hard modes are in thermal equilibrium,

Riccardo Barbieri, Lawrence J. Hall, Yasunori Nomura

A new viewpoint for the gauge hierarchy problem is proposed: compactification at a large scale, 1/R, leads to a low energy effective theory with supersymmetry softly broken at a much lower scale, α/R. The hierarchy is induced by an extremely small angle αwhich appears in the orbifold compactification boundary conditions. The same orbifold boundary conditions

Qiang-Hua Wang

The response to a local strong non-magnetic impurity in the pseudogap phase is examined in two distinctly different scenarios: phase-fluctuation (PF) of pairing field and d-density-wave (DDW) order. In the PF scenario, the resonance state is generally double-peaked near the Fermi level, and is abruptly broadened by vortex fluctuations slightly above the tran

Marco Fiorentino, Jay E. Sharping, Prem Kumar, Dmitry Levandovsky

A new scheme for generating amplitude squeezed light by means of soliton self-phase modulation is experimentally demonstrated. By injecting 180-fs pulses into an equivalent Mach-Zehnder fiber interferometer, a maximum noise reduction of $4.4 \pm 0.3$ dB is obtained ($6.3 \pm 0.6$ dB when corrected for losses). The dependence of noise reduction on the interfe

F. Herbut

Continuing the study of mixed-state entanglement in terms of opposite-subsystem observables the measurement of one of which amounts to the same as that of the other (so-called twins), begun in a recent article, so-called strong twin events, which imply biorthogonal mixing of states, are defined and studied. It is shown that for each mixed state there exists

Rainer Steinwandt, Dominik Janzing, Thomas Beth

We consider the problem of detecting whether an attacker measures the amount of traffic sent over a communication channel-possibly without extracting information about the transmitted data. A basic approach for designing a quantum protocol for detecting a perpetual traffic analysis of this kind is described.