July 2001 arXiv papers — page 15

I. de la Calle, J. L. Contreras, J. Cortina, V. Fonseca

Cherenkov radiation produced in Extensive Air Showers shows a net polarization. This article discusses its properties and physical origin, and proposes an arrangement of polarizers potentially useful for Imaging Atmospheric Cherenkov Telescopes.

R. Willingale, J. A. M. Bleeker, K. J. van der Heyden, J. S. Kaastra

A detailed X-ray spectral analysis of Cas A using a deep exposure from the EPIC-MOS cameras on-board XMM-Newton is presented. Spectral fitting was performed on a 15x15 grid of 20"x20" pixels using a two component non-equilibrium ionisation model (NEI) giving maps of ionisation age, temperature, interstellar column density, abundances and Doppler velo

J. Spyromilio, B. Leibundgut, R. Gilmozzi

Infrared spectra of two type II supernovae 6 months after explosion are presented. The spectra exhibit a strong similarity to the observations of SN 1987A and other type II SNe at comparable epochs. The continuum can be fitted with a cool black body and the hydrogen lines have emissivities that are approximately those of a Case B recombination spectrum. The

Gary A. Mamon, Quentin A. Parker, Dominique Proust

As a pilot survey for the forthcoming 6dF Galaxy Redshift Survey, spectroscopy of galaxies selected in J (1.2 mu) with the DENIS survey was performed at the UKST using the FLAIR II multi-object spectroscope. 69 galaxy redshifts (z's) were obtained in a high |b| field and an additional 12 z's in a low latitude (b=-17 deg), obscured field. This study i

D. Krajnovic, R. Bacon, M. Bureau, C. M. Carollo

Early results are reported from the SAURON survey of the kinematics and stellar populations of nearby cluster and field E, S0, and Sa galaxies. We present maps of the Hbeta and [OIII] emission-line distribution and kinematics for NGC 5813 and NGC 7742.

V. G. Gurzadyan, S. Rauzy, R. Triay

We describe a method for recovering of the substructure, internal dynamics and geometrical shapes of clusters of galaxies. Applying the method to the Virgo cluster, we, first, reveal the substructure of the central 4 arc degree field of the Virgo cluster by means of S-tree technique. The existence of three main subgroups of galaxies is revealed and their dyn

T. L. Wilson, D. Muders, C. Kramer, C. Henkel

Images of an 8 square minute region around the Orion KL source have been made in the J=7-6 (806 GHz) and J=4-3 (461 GHz) lines of CO with angular resolutions of 13" and 18". These data were taken employing on-the-fly mapping and position switching techniques. Our J=7-6 data set is the largest image of Orion with the highest sensitivity and resolution

Isabel Márquez, the DEGAS Consortium

The analysis of a sample of 30 isolated spiral galaxies with and without an AGN results in active and control galaxies having similar bulge and disk properties (since both samples are selected to match in morphological and bar classification, they have similar bar percentages). Secondary bars seem also to be indistinguishable. The central kinematics (both st

Tadashi Nakajima

Sensitivity limits of ground-based infrared interferometers using aperture synthesis are presented. The motivation of this analysis is to compare an interferometer composed of multiple large telescopes and a single giant telescope with adaptive optics. In deriving these limits, perfect wavefront correction by adaptive optics and perfect cophasing by fringe t

P. Amaro-Seoane, R. Spurzem

This is a starting point of future work on a more detailed study of early evolutionary phases of galactic nuclei. We put into port the study of the evolution of star accretion onto a supermassive gaseous object in the central region of an active galactic nucleus, which was previously addressed semi-analytically. For this purpose, we use a gaseous model of re

Chuan-Hung Chen, Yong-Yeon Keum, Hsiang-nan Li

We investigate exclusive nonleptonic $B$ meson decays $B\toϕK$ in perturbative QCD formalism. It is shown that the end-point (logarithmic and linear) singularities in decay amplitudes do not exist, after $k_T$ and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfacto

Prasanta Das, Uma Mahanta

In this paper we determine the contribution of a light stabilized radion to the weak isospin violating $ρ$ parameter by using an ultraviolet momentum cut off as the regulator. The LEP1 bound on $ρ^{new}$ is then used to derive constraints on the radion mass $\mphi$ and its vev $\vphi$. Finally by using the beta function of the higgs self coupling we have det

David Ruelle

Starting from a hyperbolic toral automorphism, we obtain, for a small volume preserving perturbation, an exact and rigorous second order perturbation expansion of the Lyapunov exponents.

Vladimir Voevodsky

In this paper we prove the 2-local part of the Beilinson-Lichtenbaum conjectures on tosion in motivic cohomology. In particular we prove the Milnor conjecture relating Milnor's K-theory and the Galois cohomology with Z/2-coefficients. This paper is a new version of the previously distributed preprint "The Milnor Conjecture".

Vladimir Voevodsky

In this paper we construct an analog of Steenrod operations in motivic cohomology and prove their basic properties including the Cartan formula, the Adem relations and the realtions to characteristic classes.

Vicente Cortes

A holomorphic representation formula for special parabolic hyperspheres is given.

John Son

We study string theory on singular Z_N quotients of AdS_3, corresponding to spaces with conical defects. The spectrum is computed using the orbifold procedure. It is shown that spectral flow may be used to generate the twisted sectors. We further compute the thermal partition function and show that it correctly reproduces the spectrum.

Ali Abbasabadi, Wayne W. Repko

We compute the one-loop helicity amplitudes for low-energy $νγ\toνγ$ scattering and its crossed channels in the standard model with massless neutrinos. In the center of mass, with $\sqrt{s} = 2ω\ll 2m_e$, the cross sections for these $2\to 2$ channels grow roughly as $ω^6$. The scattered photons in the elastic channel are circularly polarized and the net val

Gustavo C. Branco, Takuya Morozumi, B. M. Nobre, M. N. Rebelo

We discuss the possibility of relating the size and sign of the observed baryon asymmetry of the universe to CP violation observable at low energies, in a framework where the observed baryon asymmetry is produced by leptogenesis through the out of the equilibrium decay of heavy Majorana neutrinos. We identify the CP violating phases entering in leptogenesis

Piero Zucchelli

The evolution of neutrino physics demands new schemes to produce intense, collimated and pure neutrino beams. The current neutrino factory concept implies the production, collection, and storage of muons to produce beams of muon and electron neutrinos at equal intensities at the same time. Research and development addressing its feasibility are still going o

James Hammerton, Erik F. Tjong Kim Sang

Memory-based learning (MBL) has enjoyed considerable success in corpus-based natural language processing (NLP) tasks and is thus a reliable method of getting a high-level of performance when building corpus-based NLP systems. However there is a bottleneck in MBL whereby any novel testing item has to be compared against all the training items in memory base.

John Nerbonne, Anja Belz, Nicola Cancedda, Herve Dejean

This paper reports on the "Learning Computational Grammars" (LCG) project, a postdoc network devoted to studying the application of machine learning techniques to grammars suitable for computational use. We were interested in a more systematic survey to understand the relevance of many factors to the success of learning, esp. the availability of anno

Erik F. Tjong Kim Sang, Herve Dejean

We describe the CoNLL-2001 shared task: dividing text into clauses. We give background information on the data sets, present a general overview of the systems that have taken part in the shared task and briefly discuss their performance.

Alan McKane, Martin Tarlie

The decay of unstable states when several metastable states are available for occupation is investigated using path-integral techniques. Specifically, a method is described which allows the probabilities with which the metastable states are occupied to be calculated by finding optimal paths, and fluctuations about them, in the weak noise limit. The method is

J. T. Devreese

I discuss how a variatonal approach can be extended to systems of identical particles (in particular fermions) within the path-integral treatment. The applicability of the many-body variational principle for path integrals is illustrated for different model systems, and is shown to crucially depend on whether or not a model system possesses the proper symmet

G. P. Segre, N. Gedik, J. Orenstein, D. A. Bonn

We report measurements of the photoinduced change in reflectivity of an untwinned single crystal of YBa2Cu3O6.5 in the ortho II structure. The decay rate of the transient change in reflectivity is found to decrease rapidly with decreasing temperature and, below Tc, with decreasing laser intensity. We interpret the decay as a process of thermalization of anti

R. F. Klie, J. C. Idrobo, N. D. Browning

Here we describe the results of an atomic resolution study of the structure and composition of both the interior of the grains, and the grain boundaries in polycrystalline MgB2. We find that there is no oxygen within the bulk of the grains but significant oxygen enrichment at the grain boundaries. The majority of grain boundaries contain BOx phases smaller t

A. A. Zhukov, L. F. Cohen, A. Purnell, Y. Bugoslavsky

In this paper we present the results of measurements of the microwave surface impedance of a powder sample and two films of MgB$_2$. One film has $T_c=30$ K and is not textured, the other is partially c-axis orientated with $T_c=38$ K. These samples show different types of temperature dependence of the field penetration depth: linear for the powder sample, e

Philipp Podsiadlowski, Saul Rappaport, Eric Pfahl

We present the results of a systematic study of the evolution of low- and intermediate-mass X-ray binaries (LMXBs and IMXBs). Using a standard Henyey-type stellar-evolution code and a standard model for binary interactions, we have calculated 100 binary evolution sequences containing a neutron star and a normal-type companion star, where the initial mass of

Mingzhe Li, Wenbin Lin, Xinmin Zhang, Robert Brandenberger

We study the effects of gravitational back-reaction in models of Quintessence. The effective energy-momentum tensor with which cosmological fluctuations back-react on the background metric will in some cases lead to a termination of the phase of acceleration. The fluctuations we make use of are the perturbations in our present Universe. Their amplitude is no

A. Andre, L. -M. Duan, M. D. Lukin

We suggest a technique to induce effective, controllable interactions between atoms that is based on Raman scattering into an optical mode propagating with a slow group velocity. The resulting excitation corresponds to the creation of spin-flipped atomic pairs in a way that is analogous to correlated photon emission in optical parametric amplification. The t

Hui Yin, Bulbul Chakraborty

A simple, non-disordered spin model has been studied in an effort to understand the origin of the precipitous slowing down of dynamics observed in supercooled liquids approaching the glass transition. A combination of Monte Carlo simulations and exact calculations indicates that this model exhibits an entropy vanishing transition accompanied by a rapid diver

Denis Bernard, Andre LeClair

We analyze in detail the renormalization group flows which follow from the recently proposed all orders beta functions for the Chalker-Coddington network model. The flows in the physical regime reach a true singularity after a finite scale transformation. Other flows are regular and we identify the asymptotic directions. One direction is in the same universa

D. N. Aristov, A. Luther

We study the sine-Gordon (SG) model at finite densities of the topological charge and small SG interaction constant, related to the one-dimensional Hubbard model near half-filling. Using the modified WKB approach, we find that the spectrum of the Gaussian fluctuations around the classical solution reproduces the results of the Bethe ansatz studies. The modif

Per Osland, Geir Vigdel

We obtain bounds for the neutrino masses by combining atmospheric and solar neutrino data with the phenomenology of neutrinoless double beta decay where hypothetical values of |< m>| are envisaged from future 0νββ-experiments. Different solutions for the solar neutrino data are considered. For the Large-Mixing-Angle solution, a bound |< m>| \leq 0.01 eV woul

Indranil Mitra, Shibaji Roy

We generalize the non-threshold bound state in type IIB supergravity of the form (NS5, D5, D3) constructed by the present authors (in hep-th/0011236) to non-zero asymptotic value of the axion $(χ_0$). We identify the decoupling limits corresponding to both the open D3-brane theory and open D5-brane theory for this supergravity solution as expected. However,

M. Bastero-Gil, L. Mersini

The SN1a data, although inconclusive, when combined with other observations makes a strong case that our universe is presently dominated by dark energy. We investigate the possibility that large distance modifications of the curvature of the universe would perhaps offer an alternative explanation of the observation. Our calculations indicate that a universe

T. Hosokawa, S. Mineshige, T. Kawaguchi, K. Yoshikawa

Cosmological evolution of the QSO luminosity functions (LFs) at NIR/optical/X-ray bands for 1.3 < z < 3.5 is investigated based on the realistic QSO spectra. The accretion-disk theory predicts that although QSO luminosities only depend on mass-accretion rate, \Mdot, QSO spectra have a dependence on black-hole mass, M_{BH}, as well. The smaller M_{BH} is and/

Tomas Tyc, Barry C. Sanders

We develop the theory of continuous-variable quantum secret sharing and propose its interferometric realization using passive and active optical elements. In the ideal case of infinite squeezing, a fidelity ${\cal F}$ of unity can be achieved with respect to reconstructing the quantum secret. We quantify the reduction in fidelity for the (2,3) threshold sche

B. Blankleider, J. Gegelia

The doublet channel neutron-deuteron scattering amplitude is calculated in leading order effective field theory (EFT). It is shown that this amplitude does not depend on a constant contact interaction three-body force. Satisfactory agreement with available data is obtained when only two-body forces are included.

Paolo Giuliani

We review the main properties of shell models for magnetohydrodynamic (MHD) turbulence. After a brief account on shell models with nearest neighbour interactions, the paper focuses on the most recent results concerning dynamical properties and intermittency of a model which is a generalization to MHD of the Gledzer-Yamada-Okhitani (GOY) model for hydrodynami

Indranil Biswas, Tomas L. Gomez

Let X be a smooth projective complex curve, and let M be the moduli space of stable Higgs bundles on X (with genus g>1), with rank n and fixed determinant ξ, with n and deg(ξ) coprime. Let X&#39; and ξ&#39; be another such curve and line bundle, and M&#39; the corresponding moduli space. We prove that if M and M&#39; are isomorphic as algebraic varieties, th

A. K. Sanyal, B. Modak

The form of the coupling of the scalar field with gravity and the potential have been found by applying Noether theorem to two dimensional minisuperspaces in induced gravity model. It has been observed that though the forms thus obtained are consistent with all the equations $£_{X}L=0$, yet they do not satisfy the field equations for $k=\pm 1$, in Robertson-

P. Horsch, G. Khaliullin

We analyse the dynamical density fluctuation spectra for cuprates starting from the $t-J$ model in a slave-boson 1/N representation. The results obtained are consistent with diagonalization studies and show novel low-energy structure on the energy scale $J+δt$ due to the correlated motion of holes in a RVB spin liquid. The low-energy response implies an anom

M. N. Popova, A. B. Sushkov, S. A. Klimin, E. P. Chukalina

We report high resolution polarized infrared studies of the quarter-filled spin ladder compound alpha&#39;-NaV_2O_5 as a function of temperature (5K <= T <= 300K). Numerous new modes were detected below the temperature T_c=34K of the phase transition into a charge ordered nonmagnetic state accompanied by a lattice dimerization. We analyse the Brillouin zone

Maria de Sousa Vieira

We introduce two sandpile models which show the same behavior of real sandpiles, that is, an almost self-organized critical behavior for small systems and the dominance of large avalanches as the system size increases. The systems become fully self-organized critical, with the critical exponents of the Bak, Tang and Wiesenfeld model, as the system parameters

A. Turiel, N. Parga

We present a formalism that leads very naturally to a hierarchical description of the different contrast structures in images, providing precise definitions of sharp edges and other texture components. Within this formalism, we achieve a decomposition of pixels of the image in sets, the fractal components of the image, such that each set only contains points

A. Turiel, G. Mato, N. Parga, J. -P. Nadal

We show that the statistics of an edge type variable in natural images exhibits self-similarity properties which resemble those of local energy dissipation in turbulent flows. Our results show that extended self-similarity remarkably holds for the statistics of the local edge variance, and that the very same models can be used to predict all the associated e

D. R. C. Dominguez, M. Maravall, A. Turiel, J. C. Ciria

The mutual information of a single-layer perceptron with $N$ Gaussian inputs and $P$ deterministic binary outputs is studied by numerical simulations. The relevant parameters of the problem are the ratio between the number of output and input units, $α= P/N$, and those describing the two-point correlations between inputs. The main motivation of this work ref

Thomas J. Loredo, Don Q. Lamb

We present a Bayesian analysis of the energies and arrival times of the neutrinos from supernova SN 1987A detected by the Kamiokande II, IMB, and Baksan detectors, and find strong evidence for two components in the neutrino signal: a long time scale component from thermal Kelvin-Helmholtz cooling of the nascent neutron star, and a brief (~< 1 s), softer comp

M. A. Malkov, P. H. Diamond, T. W. Jones

The linear theory of shock acceleration predicts the maximum particle energy to be limited only by the acceleration time and the size of the shock. We study the combined effect of acceleration nonlinearity (shock modification by accelerated particles, that must be present in strong astrophysical shocks) and propagation of Alfven waves that are responsible fo

B. J. Carter, D. G. Fabricant, M. J. Geller, M. J. Kurtz

The 15R-North galaxy redshift survey is a uniform spectroscopic survey (S/N $\sim $10) covering the range 3650---7400Åfor 3149 galaxies with median redshift 0.05. The sample is 90% complete to $R=15.4$. The median slit covering fraction is 24% of the galaxy, apparently sufficient to minimize the effects of aperture bias on the EW(H$α$). Forty-nine percent of

Ewa Szuszkiewicz, John C. Miller

We are carrying out a programme of non-linear time-dependent numerical calculations to study the evolution of the thermal instability driven by radiation pressure in transonic accretion discs around black holes. In our previous studies we first investigated the original version of the slim-disc model with low viscosity (parameter alpha = 0.001) for a stellar

A. A. Lagutin, K. I. Osadchiy, D. V. Strelnikov

We have made a new calculation of the cosmic ray electron spectrum using an anomalous diffusion model to describe the propagation of electrons in the Galaxy. The parameters defining the anomalous diffusion have been recently determined from the study of nuclei propagation. The predicted electron spectrum is in a good agreement with the measurements. The sour

A. A. Lagutin, V. V. Makarov, A. G. Tyumentsev

We consider the propagation of galactic cosmic rays in the fractal interstellar medium. Steady state solution of the fractional diffusion equation, describing cosmic ray propagation, is found. We show that the exponent of the steady state spectrum turns out to be equal to the exponent of the cosmic ray spectrum above the &#34;knee&#34;, that is approximately

S. J. Wallace

Considering two spinless particles, a simple, approximate boost rule is derived that is sufficient to keep the mass invariant and to relate interactions, vertex functions, wave functions and t-matrices of the instant two-body problem in an arbitrary frame to those in the c.m. frame. The boost generator ${\bf K}$ that is used provides a solution to the Poinca

N. K. Tran, O. Pfister

Following the lead of Cochrane, Milburn, and Munro [Phys. Rev. A {\bf 62}, 062307 (2000)], we investigate theoretically quantum teleportation by means of the number-sum and phase-difference variables. We study Fock-state entanglement generated by a beam splitter and show that two-mode Fock-state inputs can be entangled by a beam splitter into close approxima

G. T. Bodwin, D. K. Sinclair, S. Kim

We calculate the long-distance matrix elements for the decays of the Upsilon (eta_b) and chi_b (h_b) states in lattice QCD with two flavors of light dynamical quarks. We relate the lattice matrix elements to their continuum counterparts through one-loop order in perturbation theory. In the case of the leading S-wave matrix element, we compare our result with

R. Jin, J. He, S. McCall, C. S. Alexander

We report the observation of superconductivity in high-quality Cd$_2$Re$_2$O$_7$ single crystals with room-temperature pyrochlore structure. Resistivity and ac susceptibility measurements establish an onset transition temperature T$_c^{onset}$ = 1.47 K with transition width $Δ$T$_c$ = 0.25 K. In applied magnetic field, the resistive transition shows a type-I

Christos Charmousis

We find and study solutions to the Einstein equations in D dimensions coupled to a scalar field source with a Liouville potential under the assumption of D-2 planar symmetry. The general static or time-dependent solutions are found yielding three classes of SO(D-2) symmetric spacetimes. In D=4 homogeneous and isotropic subsets of these solutions yield planar

Michael Seevinck, Jos Uffink

We point out a loophole problem in some recent experimental claims to produce three-particle entanglement. The problem consists in the question whether mixtures of two-particle entangled states might suffice to explain the experimental data. In an attempt to close this loophole, we review two sufficient conditions that distinguish between N-particle states i

Bo-Qiang Ma, Ivan Schmidt, Jacques Soffer, Jian-Jun Yang

We consider the inclusive production of longitudinally polarized baryons in ${\vec p}p$ collisions at RHIC-BNL, with one longitudinally polarized proton. We study the spin transfer between the initial proton and the produced baryon as a function of its rapidity and we elucidate its sensitivity to the quark helicity distributions of the proton and to the pola

Andre&#39;de Gouvea, Gian Francesco Giudice, Alessandro Strumia, Kazuhiro Tobe

Standard Model singlet neutrinos propagating in extra dimensions induce small Dirac neutrino masses. While it seems rather unlikely that their Kaluza-Klein excitations directly participate in the observed neutrino oscillations, their virtual exchange may lead to detectable signatures in future neutrino experiments and in rare charged lepton processes. We sho

M. Botta Cantcheff

It is often claimed [PST1] that the (Hodge type) duality operation is defined only in even dimensional spacetimes and that self-duality is further restricted to twice-odd dimensional spacetime theories. The purpose of this paper is to extend the notion of both duality symmetry as well as self-duality. By considering tensorial doublets, we introduce a novel w

Malte Henkel, Michel Pleimling, Claude Godreche, Jean-Marc Luck

In a variety of systems which exhibit aging, the two-time response function scales as $R(t,s)\approx s^{-1-a} f(t/s)$. We argue that dynamical scaling can be extended towards conformal invariance, obtaining thus the explicit form of the scaling function $f$. This quantitative prediction is confirmed in several spin systems, both for $T<T_c$ (phase ordering)

J. Burgy, M. Mayr, V. Martin-Mayor, A. Moreo

The influence of quenched disorder on the competition between ordered states separated by a first-order transition is investigated. A phase diagram with features resembling quantum-critical behavior is observed, even using classical models. The low-temperature paramagnetic regime consists of coexisting ordered clusters, with randomly oriented order parameter

A. Hoefer, J. Gluza, F. Jegerlehner

The complete one-loop QED initial state, final state and initial--final state interference corrections to the process e+e- -> pi+pi- are presented. Analytic formulae are given for the virtual and for the real photon corrections. The total cross section, the pion angular distribution and the pi+pi- invariant mass distribution are investigated in the regime of

Helen A. Bridgman, Karim A. Malik, David Wands

We study cosmological perturbations in a brane-world scenario where the matter fields live on a four-dimensional brane and gravity propagates in the five-dimensional bulk. We present the equations of motion in an arbitrary gauge for metric perturbations in the bulk and matter perturbations on the brane. Gauge-invariant perturbations are then constructed corr

Sadhan K. Adhikari

Quantized vortex states of weakly interacting Bose-Einstein condensate of atoms with attractive interatomic interaction in an axially symmetric harmonic oscillator trap are investigated using the numerical solution of the time-dependent Gross-Pitaevskii (GP) equation obtained by the semi-implicit Crank-Nicholson method. Collapse of the condensate is studied

Philippos Papadopoulos, Carlos F. Sopuerta

The formulation of the initial value problem for the Einstein equations is at the heart of obtaining interesting new solutions using numerical relativity and still very much under theoretical and applied scrutiny. We develop a specialised background geometry approach, for systems where there is non-trivial a priori knowledge about the spacetime under study.

Bergfinnur Durhuus, Thordur Jonsson, Ryszard Nest

We establish existence and stabilty results for solitons in noncommutative scalar field theories in even space dimension $2d$. In particular, for any finite rank spectral projection $P$ of the number operator ${\mathcal N}$ of the $d$-dimensional harmonic oscillator and sufficiently large noncommutativity parameter $θ$ we prove the existence of a rotationall

F. T. Brandt, Ashok Das, J. Frenkel

We study the parity breaking effective action in 2+1 dimensions, generated, at finite temperature, by massive fermions interacting with a non-Abelian gauge background. We explicitly calculate, in the static limit, parity violating amplitudes up to the seven point function, which allows us to determine the corresponding effective actions. We derive the exact

A. B. Lahanas, D. V. Nanopoulos, V. C. Spanos

In the framework of the Constrained Minimal Supersymmetric Standard Model (CMSSM) we discuss the impact of the recent experimental information, especially from E821 Brookhaven experiment on $g_μ-2$ along with the light Higgs boson mass bound from LEP, to the Dark Matter direct searches. Imposing these experimental bounds, the maximum value of the spin-indepe

M. Maltoni, T. Schwetz, J. W. F. Valle

Using the most recent atmospheric neutrino data, as well as short-baseline, long-baseline and tritium $β$-decay data we show that the joint interpretation of the LSND, solar and atmospheric neutrino anomalies in (3+1) sterile neutrino schemes is severely disfavored, in contrast to the theoretically favored (2+2) schemes.

Milan M. Cirkovic

The intriguing suggestion of Tegmark (1996) that the universe--contrary to all our experiences and expectations--contains only a small amount of information due to an extremely high degree of internal symmetry is critically examined. It is shown that there are several physical processes, notably Hawking evaporation of black holes and non-zero decoherence tim

Riccardo Barbieri, Giacomo Cacciapaglia, Alessandro Romito

In a recently proposed extension of the Standard Model with a compact extra dimension of size R we compute the leading corrections, of relative order (m_t R)^2, to the Branching Ratio B -> X_s gamma. For 1/R = 370 \pm 80 GeV, the branching ratio is increased in a significant way relative to the SM, although not al level of being inconsistent with present mea

Benoit Gremaud

The validity of semiclassical expansions in the power of $\hbar$ for the quantum Green&#39;s function have been extensively tested for billiards systems, but in the case of chaotic dynamics with smooth potential, even if formula are existing, a quantitative comparison is still missing. In this paper, extending the theory developed by Gaspard et al., Adv. Che

V. Villar, R. Mélin, C. Paulsen, J. Souletie

We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y$_2$BaNi$_{1-x}$Zn$_x$O$_5$. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional because antiferromagnetism coexists with random dimers. We present new susceptibility experiments a

T. Christodoulakis, E. Korfiatis, G. O. Papadopoulos

An invariant description of Bianchi Homogeneous (B.H.) 3-spaces is presented, by considering the action of the Automorphism Group on the configuration space of the real, symmetric, positive definite, $3\times 3$ matrices. Thus, the gauge degrees of freedom are removed and the remaining (gauge invariant) degrees, are the --up to 3-- curvature invariants. An a

Vijay Balasubramanian, Micha Berkooz, Asad Naqvi, Matthew J. Strassler

Giant gravitons in AdS_5 x S^5, and its orbifolds, have a dual field theory representation as states created by chiral primary operators. We argue that these operators are not single-trace operators in the conformal field theory, but rather are determinants and subdeterminants of scalar fields; the stringy exclusion principle applies to these operators. Evid

S. Sirca

The recent experimental program with the out-of-plane spectrometer system (OOPS) at MIT-Bates encompassed an extensive set of $\mathrm{d}(\vec\mathrm{e},\mathrm{e}&#39;\mathrm{p})$ measurements, investigations of the $\mathrm{N}\toΔ$ transition using $\mathrm{p}(\vec\mathrm{e},\mathrm{e}&#39;\mathrm{p})π^0$ and $\mathrm{p}(\vec\mathrm{e},\mathrm{e}&#39;π^+)\

Antonio Dobado, Maria J. Herrero, David Temes

In this paper we study the Yukawa Higgs-quark-quark interactions that are generated from radiative corrections of squarks and gluinos, in the Minimal Supersymmetric Standard Model. We compute the corrections to the effective action for Higgs and quark fields that are produced by explicit integration, in the path integral formalism, of all the squarks and glu

Shigeki Onoda, Masatoshi Imada

Thermodynamic and dynamical properties of filling-control metal-insulator transition (MIT) in the Hubbard model are studied by the operator projection method, especially in two dimensions. This is a non-perturbative analytic approach to many-body systems. The present theory incorporates the Mott-Hubbard, Brinkman-Rice and Slater pictures of the MIT into a un

S. Burdin, D. R. Grempel, A. Georges

We study the competition between the Kondo effect and frustrating exchange interactions in a Kondo-lattice model within a large-${\cal N}$ dynamical mean-field theory. We find a T=0 phase transition between a heavy Fermi-liquid and a spin-liquid for a critical value of the exchange $J_c = T_{K}^0$, the single-impurity Kondo temperature. Close to the critical

Mauro Mobilia, Pierre-Antoine Bares

We solve an one-dimensional stochastic model of interacting particles on a chain. Particles can have branching and coagulation reactions, they can also appear on an empty site and disappear spontaneously. This model which can be viewed as an epidemic model and/or as a generalization of the {\it voter} model, is treated analytically beyond the {\it convention

Kentaro Nomura, Daijiro Yoshioka

Transitions from a paired quantum Hall state to another quantum Hall state in bilayer systems are discussed in the framework of the edge theory. Starting from the edge theory for the Haldane-Rezayi state, it is shown that the charging effect of a bilayer system which breaks the SU(2) symmetry of the pseudo-spin shifts the central charge and the conformal dim

Takao Suyama

We give an interpretation of the non-supersymmetric heterotic theories as the supersymmetric heterotic theories on Melvin background with Wilson lines. The coincidence of the partition functions are shown for most of the non-supersymmetric theories. We also discuss the tachyonic instability in terms of the non-trivial background fields. The behavior in the s

A. S. Shteinberg, V. A. Shcherbakov, Z. A. Munir

Theoretical analysis and experimental results on the combustion in the Ni-Al layered system are presented. Combustion wave temperature and velocity were measured and microstructural and compositional determinations were made. The latter were made on products of complete combustion and on quenched samples using metallographic and electron microprobe analyses.

Eric R. Weeks, D. A. Weitz

We use confocal microscopy to study the motions of particles in concentrated colloidal systems. Near the glass transition, diffusive motion is inhibited, as particles spend time trapped in transient ``cages&#39;&#39; formed by neighboring particles. We measure the cage sizes and lifetimes, which respectively shrink and grow as the glass transition approaches

F. Lizzi, R. J. Szabo, A. Zampini

A detailed description of the infinite-dimensional Lie algebra of star-gauge transformations in noncommutative Yang-Mills theory is presented. Various descriptions of this algebra are given in terms of inner automorphisms of the underlying deformed algebra of functions on spacetime, of deformed symplectic diffeomorphisms, of the infinite unitary Lie algebra,

Andrei N. Soklakov, Ruediger Schack

We show that the coarse-grained quantum baker&#39;s map exhibits a linear entropy increase at an asymptotic rate given by the Kolmogorov-Sinai entropy of the classical chaotic baker&#39;s map. The starting point of our analysis is a symbolic representation of the map on a string of $N$ qubits, i.e., an $N$-bit register of a quantum computer. To coarse-grain

Milan M. Cirkovic, Suzana Cveticanin

The recent operationalization of the famous Newcomb&#39;s game by Schmidt (1998) offers an interesting and thought-provoking look at the plausibility of backward causation in a Newtonian universe. Hereby we investigate two details of the Schmidt&#39;s scenario which may, at least in principle, invalidate his conclusion in two different domains: one dealing w

A. C. Hayes, Luca Zanini

In the last decade, the scattering of polarized neutrons on compound nucleus resonances proved to be a powerful experimental technique for probing nuclear parity violation. Longitudinal analyzing powers in neutron transmission measurements on p-wave resonances in nuclei such as $^{139}$La and $^{232}$Th were found to be as large as 10%. Here we examine the p

S. Q. Zhang, J. Meng, S. -G. Zhou, J. Y. Zeng

Based on the systematic investigation of the data available for $A \geq 40$, a $Z^{1/3}$ dependence for the nuclear charge radii is shown to be superior to the generally accepted $A^{1/3}$ law. A delicate scattering of data around $R_c/Z^{1/3}$ is infered as owing to the isospin effect and a linear dependence of $R_c/Z^{1/3}$ on $N/Z$ (or $(N-Z)/2$) is found

J. Meng, S. -G. Zhou, I. Tanihata

The ground state properties including radii, density distribution and one neutron separation energy for C, N, O and F isotopes up to the neutron drip line are systematically studied by the fully self-consistent microscopic Relativistic Continuum Hartree-Bogoliubov (RCHB) theory. With the proton density distribution thus obtained, the charge-changing cross se

Robert D. Deegan, Paul J. Petersan, M. Marder, Harry L. Swinney

We have found an oscillating instability of fast-running cracks in thin rubber sheets. A well-defined transition from straight to oscillating cracks occurs as the amount of biaxial strain increases. Measurements of the amplitude and wavelength of the oscillation near the onset of this instability indicate that the instability is a Hopf bifurcation.

Adam Rennie

We prove a noncompact Serre-Swan theorem characterising modules which are sections of vector bundles not necessarily trivial at infinity. We then identify the endomorphism algebras of the resulting modules. The endomorphism results continue to hold for the generalisation of these modules to noncommutative, nonunital algebras. Finally, we apply these results

Harald Grosse, Karl-Georg Schlesinger

We study a noncommutative deformation of the commutative Hopf algebra of rooted trees which was shown by Connes and Kreimer to be related to the mathematical structure of renormalization in quantum field theories. The requirement of the existence of an antipode for the noncommutative deformation leads to a natural extension of the algebra. Noncommutative def

Pere Ara, Gert K. Pedersen, Francesc Perera

We prove a new extension result for $QB-$rings that allows us to examine extensions of rings where the ideal is purely infinite and simple. We then use this result to explore various constructions that provide new examples of $QB-$rings. More concretely, we show that a surjective pullback of two $QB-$rings is usually again a $QB-$ring. Specializing to the ca

Steven B. Bradlow, Oscar Garcia-Prada, Peter B. Gothen

We count the connected components in the moduli space of PU(p,q)-representations of the fundamental group for a closed oriented surface. The components are labelled by pairs of integers which arise as topological invariants of the flat bundles associated to the representations. Our results show that for each allowed value of these invariants, which are bound