July 2001 arXiv papers — page 10

Peter Spreij

In this paper we study various properties of finite stochastic systems or hidden Markov chains as they are alternatively called. We discuss their construction following different approaches and we also derive recursive filtering formulas for the different systems that we consider. The key tool is a simple lemma on conditional expectations.

Oleg I. Reinov

Among other things, it is shown that there exist Banach spaces $Z$ and $W$ such that $Z^{**}$ and $W$ have bases, and for every $p\in[1,2)$ there is an operator $T:W\to Z$ that is not $p$-nuclear but $T^{**}$ is $p$-nuclear.

Robert L. Bryant

The problem of immersing a simply connected surface with a prescribed shape operator is discussed. From classical and more recent work, it is known that, aside from some special degenerate cases, such as when the shape operator can be realized by a surface with one family of principal curves being geodesic, the space of such realizations is a convex set in a

Andrei Linde

Inflationary theory is already 20 years old, and it is impossible to describe all of its versions and implications in a short talk. I will concentrate on several subjects which I believe to be most important. First of all, I will give a brief review of the first versions of inflationary theory, from Starobinsky model to new inflation. Then I will describe ch

Donam Youm

We study static brane configurations in the bulk background of the topological black holes in asymptotically flat spacetime. We find that such configurations are possible even for flat black hole horizon, unlike the AdS black hole case. We construct the brane world model with an orbifold structure S^1/Z_2 in such bulk background. We also study massless bulk

Hong Liu, Jeremy Michelson

We give a detailed discussion of the disk amplitudes with one closed string insertion, which we used to construct the supergravity couplings of noncommutative D-branes to the RR potentials, given in hep-th/0104139. We prove the inclusion of Elliott's formula, the integer-valued modification of the noncommutative Chern character, to all orders in the gaug

J. S. Dowker

1.An expression for the smoothed counting function in terms of the fractional derivatives of the delta-function is presented. 2. The Neumann-Dirichlet (ND) boundary problem is introduced via some elementary examples based on a functorial relation between the ND, DD, NN and periodic boundary conditions.

P. Kennedy

The two-component approach to the one-dimensional Dirac equation is applied to the Woods-Saxon potential. The scattering and bound state solutions are derived and the conditions for a transmission resonance (when the transmission coefficient is unity) and supercriticality (when the particle bound state is at E=-m) are then derived. The square potential limit

Alex Buchel

The high energy thermodynamics of Little String Theory (LST) is known to be unstable. An unresolved question is whether the corresponding instability in LST holographic dual is of stringy or supergravity origin. We study UV thermodynamics of a large metric deformation of the LST dual realized (in the extremal case) by type IIB fivebranes wrapping a two-spher

J. Alexandre, K. Farakos, G. Koutsoumbas, N. E. Mavromatos

We consider magnetic catalysis in a field-theoretic system of (3+1)-dimensional Dirac fermions with anisotropic kinetic term. By placing the system in a strong external magnetic field, we examine magnetically-induced fermion mass generation. When the coupling anisotropy is strong, in which case the fermions effectively localize on the plane, we find a signif

Jian-Jun Yang

We check the $u$ and $d$ quark contributions to the spin content of the $Λ$ by means of the $q\toΛ$ fragmentation and find that the $u$ and $d$ quarks of the $Λ$ are likely positively polarized. The parton distributions in the $Λ$ are given by a successful statistical model which can reproduce and correlate a vast body of polarized and unpolarized structure

M. Campanelli, S. Navas-Concha, A. Rubbia

In this paper we stress the idea that new, more precise neutrino cross-sections measurements at low energies will be necessary to improve the results of future big neutrino detectors, which will be dominated by the contribution of the systematic errors. The use of a muon beam instead of the traditional pion beams is proposed. This choice allows the simultane

Isabella Masina

We review the problem of neutrino masses and mixings in the context of Grand Unified Theories. After a brief summary of the present experimental status of neutrino physics, we describe how the see-saw mechanism can automatically account for the large atmospheric mixing angle. We provide two specific examples where this possibility is realized by means of a f

Frithjof Karsch

After a brief introduction into basic aspects of the formulation of lattice regularized QCD at finite temperature and density we discuss our current understanding of the QCD phase diagram at finite temperature. We present results from lattice calculations that emphasize the deconfining as well as chiral symmetry restoring features of the QCD transition, and

L3 Collaboration

Using data collected with the L3 detector at LEP from 1992 to 1995 on the Z peak, we determine the branching fractions of the tau lepton into one, three and five charged particles to be: B(tau->(1-prong)) = 85.274 +- 0.105 +- 0.073 %, B(tau->(3-prong)) = 14.556 +- 0.105 +- 0.076 %, B(tau->(5-prong)) = 0.170 +- 0.022 +- 0.026 %. The first uncertainties are st

L3 Collaboration

Final results of the search for the Standard Model Higgs boson are presented for the data collected by the L3 detector at LEP at centre-of-mass energies up to about 209 GeV. These data are compared with the expectations of Standard Model processes for Higgs boson masses up to 120 GeV. A lower limit on the mass of the Standard Model Higgs boson of 112.0 GeV i

Vladimir Chekelian

Both components of the Standard Model, QCD and the electroweak sector, are tested in the H1 and ZEUS experiments at HERA. The inclusive ep single and double differential cross sections for neutral and charged current processes are measured in the range of four-momentum transfer squared, Q2, between 0.045 and 30000 GeV2, and Bjorken x between 10^{-6} and 0.65

K. Abe, The Belle Collaboration

Using a data sample of 21.3 fb$^{-1}$ collected by the Belle detector, three body charmless decays $B^+\to K^+ h^+ h^-$ have been studied. With no assumptions on the intermediate mechanisms, the following branching fractions have been measured for the first time $ {\cal{B}}(B^+\to K^+ π^- π^+) = (58.5\pm 7.1\pm 8.8)\times 10^{-6}$ and $ {\cal{B}}(B^+\to K^+

K. Abe, The Belle Collaboration

We report the first observation of the decay $B^+ \to χ_{c0} K^+$ using 21.3 fb$^{-1}$ of data collected by the Belle detector at the $Υ$(4S) resonance. The preliminary result for the branching fraction is ${\cal{B}}(B^+\to χ_{c0}K^+)=(8.0^{+2.7}_{-2.4}\pm 1.0\pm 1.1)\times 10^{-4}$ where the first error is statistical, the second is systematic, and the thir

B. Aubert, The BABAR Collaboration

We present a measurement of the decay amplitudes in B-->J/psi K^*(892) channels using 20.7 fb-1 of data collected at the Upsilon(4S) resonance with the BABAR detector at PEP-II. We measure a P-wave fraction R_perp = (16.0+/-3.2+/-1.4)% and a longitudinal polarization fraction (59.7+/-2.8+/-2.4)%. The measurement of a relative phase that is neither 0 nor pi,

K. Abe, The Belle Collaboration

We report the first observation of color-suppressed $\overline{B}^0\to D^0 π^0$ and $D^{(*)0} ω$ decays and evidence of $\overline{B}^0 \to D^{*0} π^0$ and $D^{(*)0} η$. The branching fractions are found to be ${\cal B} (\overline{B}^0\to D^0 π^0) = (2.9 ^{+0.4}_{-0.3} \pm 0.6) \times 10^{-4}$, ${\cal B} (\overline{B}^0 \to D^0 ω) = (1.7 ^{+0.5 +0.3}_{-0.4 -

A. Pravdova, V. Pravda

Boost-rotation symmetric vacuum spacetimes with spinning sources which correspond to gravitational field of uniformly accelerated spinning "particles" are studied. Regularity conditions and asymptotic properties are analyzed. News functions are derived by transforming the general spinning boost-rotation symmetric vacuum metric to Bondi-Sachs coordina

James A. Feigenbaum

We respond to Sornette and Johansen's criticisms of our findings regarding log-periodic precursors to financial crashes. Included in this paper are discussions of the Sornette-Johansen theoretical paradigm, traditional methods of identifying log-periodic precursors, the behavior of the first differences of a log-periodic price series, and the distributio

F. Schreck, L. Khaykovich, K. L. Corwin, G. Ferrari

We report the observation of co-existing Bose-Einstein condensate and Fermi gas in a magnetic trap. With a very small fraction of thermal atoms, the 7Li condensate is quasi-pure and in thermal contact with a 6Li Fermi gas. The lowest common temperature is 0.28 muK = 0.2(1) T_C = 0.2(1) T_F where T_C is the BEC critical temperature and T_F the Fermi temperatu

Jean-Louis Pichard

We review the random matrix theory describing elastic scattering through zero-dimensional ballistic cavities (having chaotic classical dynamics) and quasi-one dimensional disordered systems. In zero dimension, general symmetry considerations (flux conservation and time reversal symmetry) are only considered, while the combination law of scatterers put in ser

S. S. A. Razee, J. B. Staunton, L. Szunyogh, B. L. Gyorffy

On the basis of a first-principles electronic structure theory of finite temperature metallic magnetism in layered materials, we investigate the onset of magnetic order in thin (2-8 layers) fcc-Fe films on Cu(100) substrates. The nature of this ordering is altered when the systems are capped with copper. Indeed we find an oscillatory dependence of the Curie

R. A. Duine, H. T. C. Stoof

We present a variational solution of the Langevin field equation describing the nonequilibrium dynamics of a harmonically trapped Bose-Einstein condensate. If the thermal cloud remains in equilibrium at all times, we find that the equation of motions for the parameters in our variational ansatz are equivalent to the Langevin equations describing the motion o

Kai P. Schmidt, Christian Knetter, Götz S. Uhrig

The Raman response in the antiferromagnetic 2-leg S=1/2 Heisenberg ladder is calculated for various couplings by continuous unitary transformations. For leg couplings above 80% of the rung coupling a characteristic 2-peak structure occurs with a point of zero intensity within the continuum. Experimental data for CaV_2O_5 and La_yCa_(14-y)Cu_24O_41 are analyz

P. Vasek

Longitudinal and transverse voltages have been measured in zero external magnetic fields. In close vicinity of the superconducting transition nonzero transverse voltage has been observed while far away from Tc, both above and below no such voltage has been detected. The value of the transverse resistivity depends on the value of the transport current. Severa

Gerrit E. W. Bauer, Mauro S. Ferreira, Cees P. A. Wapenaar

A causality problem in the time-dependent scattering of classical waves from point scatterers is pointed out and analyzed. Based on an alternative model, the leading pole approximation of the exact scattering matrix of the square well potential, transparent expressions for the time and position dependent Green function in a disordered medium are derived.

J. D. Denlinger, G. -H. Gweon, J. W. Allen, A. D. Bianchi

Boron K-edge soft x-ray emission and absorption are used to address the fundamental question of whether divalent hexaborides are intrinsic semimetals or defect-doped bandgap insulators. These bulk sensitive measurements, complementary and consistent with surface-sensitive angle-resolved photoemission experiments, confirm the existence of a bulk band gap and

David K. Lubensky, David R. Nelson

We present an extensive theoretical investigation of the mechanical unzipping of double-stranded DNA under the influence of an applied force. In the limit of long polymers, there is a thermodynamic unzipping transition at a critical force value of order 10 pN, with different critical behavior for homopolymers and for random heteropolymers. We extend results

Anael Lemaitre

A microstructural theory of dense granular materials is presented, based on two main ideas. Firstly, that macroscopic shear results form activated local rearrangements at a mesoscopic scale. Secondly, that the update frequency of microscopic processes is determined by granular temperature. In a shear cell, the resulting constitutive equations account for Bag

Ar. Abanov, Andrey V. Chubukov, J. Schmalian

We present the full analysis of the normal state of the spin-fermion model near the antiferromagnetic instability in two dimensions. This model describes low-energy fermions interacting with their own collective spin fluctuations, which soften at the antiferromagnetic transition. We argue that in 2D, the system has two typical energies - an effective spin-fe

T. Fliessbach

We propose an effective Ginzburg-Landau energy functional for superfluid helium that is motivated by the ideal Bose gas model. The parameters of this phenomenological model are adjusted to known properties of the bulk system. The motivation and the field of applications of this model are quite similar to that of the Psi theory by Ginzburg and Sobyanin. The c

D. Marchesini, E. D'Onghia, G. Chincarini, C. Firmani

We present high spatial resolution Hαrotation curves of late-type dwarf and LSB galaxies. From our analysis we find good agreement between our Hαdata and the HI observations taken from the literature, concluding that the HI rotation curves for these galaxies suffer very little from beam smearing. A preliminary analysis of our data rules out the CDM model in

E. D'Onghia, G. Chincarini, C. Firmani, D. Marchesini

This work is focused on the preliminary results of the observations of Hαrotation curves for some of the late type dwarf and LSB galaxies carried out at the TNG telescope. In light of the observational data and of the N-body simulations we have performed recently, we discuss some of the implications on the nature of the DM particles and the formation of the

Scott Dodelson, Vijay K. Narayanan, Max Tegmark, Ryan Scranton

Early photometric data from the Sloan Digital Sky Survey (SDSS) contain angular positions for 1.5 million galaxies. In companion papers, the angular correlation function $w(θ)$ and 2D power spectrum $C_l$ of these galaxies are presented. Here we invert Limber's equation to extract the 3D power spectrum from the angular results. We accomplish this using a

Nahum Arav, Martijn de Kool, Kirk T. Korista

This is a companion paper to the manuscript entitled: ``HST STIS Observations Of PG 0946+301: The Highest Quality UV Spectrum of a BALQSO'' (Arav et al. 2001; accepted for publication in ApJ). Here we present photoionization-modeling results for ALL the ionic column density constraints found in these data, most of which we were unable to include in t

Nahum Arav, Martijn de Kool, Kirk T. Korista, D. Michael Crenshaw

We describe deep (40 orbits) HST/STIS observations of the BALQSO PG 0946+301 and make them available to the community. These observations are the major part of a multi-wavelength campaign on this object aimed at determining the ionization equilibrium and abundances (IEA) in broad absorption line (BAL) QSOs. We present simple template fits to the entire data

Henk Hoekstra, Howard K. C. Yee, Michael D. Gladders

We have measured the correlation between the lensing signal induced by (dark) matter and number counts of galaxies on scales ranging from 0.15-3.0 h_{50}^{-1} Mpc (which correspond to aperture radii of 1-15 arcminutes). This provides a direct probe of the scale dependence of the ratio of the classical bias parameter b and the galaxy-mass correlation coeffici

H. Li, R. V. E. Lovelace, J. M. Finn, S. A. Colgate

We study the evolution of a magnetic arcade that is anchored to an accretion disk and is sheared by the differential rotation of a Keplerian disk. By including an extremely low external plasma pressure at large distances, we obtain a sequence of axisymmetric magnetostatic equilibria and show that there is a fundamental difference between field lines that are

Gustavo E. Romero, M. M. Kaufman Bernado, Jorge A. Combi, Diego F. Torres

We present a study of the unidentified gamma-ray source 3EG J0542+2610. This source is spatially superposed to the supernova remnant G180.0-1.7, but its time variability makes unlikely a physical link. We have searched into the EGRET location error box for compact radio sources that could be the low energy counterpart of the gamma-ray source. Although 29 poi

G. Nelemans, E. P. J. van den Heuvel

The formation of low-mass X-ray binaries containing a rather massive (M >~ 7 \msun) black hole is problematic because in most recent stellar evolutionary calculations the immediate progenitors of these black holes (Wolf-Rayet stars) lose so much mass via their stellar wind that their final masses are well below the observed black hole masses. We discuss the

Shawn Snider, Carlos Allende Prieto, Ted von Hippel, Timothy C. Beers

We explore the application of artificial neural networks (ANNs) for the estimation of atmospheric parameters (Teff, logg, and [Fe/H]) for Galactic F- and G-type stars. The ANNs are fed with medium-resolution (~ 1-2 A) non flux-calibrated spectroscopic observations. From a sample of 279 stars with previous high-resolution determinations of metallicity, and a

Caroline E. J. M. L. J. Terquem

In low-mass disks, turbulent torques are probably the most important way of redistributing angular momentum. Here we present the theory of turbulent accretion disks. We show the molecular viscosity is far too small to account for the evolutionary timescale of disks, and we describe how turbulence may result in enhanced transport of (angular) momentum. We the

D. L. Block, R. Buta, I. Puerari, J. H. Knapen

The Hubble classification scheme of galaxies is based on blue-light appearance. Atlases reveal the rich variety of responses of the Population I component (the "mask") of gas and dust to the underlying, older, stellar population. However, the Population I component may only constitute 5 percent of the dynamical mass of the galaxy; furthermore, dusty

Jeremy Kepner

MatlabMPI is a Matlab implementation of the Message Passing Interface (MPI) standard and allows any Matlab program to exploit multiple processors. MatlabMPI currently implements the basic six functions that are the core of the MPI point-to-point communications standard. The key technical innovation of MatlabMPI is that it implements the widely used MPI ``loo

J. Greiner, G. Tovmassian, M. Orio, H. Lehmann

We report optical observations of the VY Scl star BZ Cam during its previous optical low state in 1999/2000. We find drastic variations in the line profiles. Narrow-band imaging observations show that its nebula extends farther than previously known and seems to be composed of two components. We determine the [OIII] line intensity of BZ Cam's nebula to 4

Jose A. Pons, Frederick M. Walter, James M. Lattimer, Maddapa Prakash

We discuss efforts to determine the mass, radius, and surface composition of the nearby compact object RX J185635-3754 from its multi-wavelength spectral energy distribution. We compute non-magnetized model atmospheres and emergent spectra for selected compositions and gravities, and discuss efforts to fit existing and new observational data from ROSAT, EUVE

Francoise Combes

The submillimeter and millimeter domains are privileged for the exploration of galaxies at high redshift, because of the negative K-correction: the peak of the dust emission at 60-100 microns is red-shifted in these domains. Already blind surveys in blank fields with today instrumentation have discovered in the continuum of the order of one object per square

P. Barmby, J. P. Huchra

Globular clusters at the distance of M31 have apparent angular sizes of a few arcseconds. While many M31 GCs have been detected and studied from ground-based images, the high spatial resolution of HST allows much more robust detection and characterization of star cluster properties. We present the results of a search of 157 HST/WFPC2 images of M31: we found

M. Buenerd

The results of the AMS01 experiment are reviewed. The proton flux measured below the geomagnetic cutoff is interpreted. Some Physics prospects for AMS02 on the International Space Station are outlined.

V. V. Sokolov

Unique data on $BVRI$ light curves of the optical transient (OT) of GRB 970508 obtained with the 6-m telescope have been interpreted in the framework of the idea of a straightforward link between supernovae (SNe) and long duration gamma-ray bursts (GRBs). The effect must be maximum in the $I_{c}$ band as for OT GRB 970228. The peak absolute ($M_{B}$) magnitu

Tadayui Takahashi, Shin Watanabe

Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and Gamma-ray detection. The high atomic number of the materials (Z_{Cd} =48, Z_{Te} =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (Eg ~ 1.5 eV) allows us to operate the detector at room t

D H Lumb, M Guainazzi, P Gondoin

We describe an XMM-Newton observation of the PKS0312-770 field, which facilitates the spectral analysis of serendipitous sources previously detected by CHANDRA. The combination of larger effective area and longer exposure duration allows a significant increase in detected photons, and a lower limit in source detection sensitivity. In particular the hard X-ra

Zakir F. Seidov

The very accurate analytical solutions are found to Lane-Emden equation of arbitrary index, n, using Picard type iteration scheme and rational Pade approximants. For n=2 the dimensionless polytropic "radius" and "mass" are 4.35287459595 and 2.4110450121, with the largest ever accuracy.

Biman Nath, Joseph Silk

We estimate the heating of the intergalactic medium due to shocks arising from structure formation. Heating of the gas outside the collapsed regions, with small overdensities (${n_b \over {\bar n_b}}\ll 200$) is considered here, with the aid of Zel'dovich approximation. We estimate the equation of state of this gas, relating the density with its temperat

Greg Madejski, Marek Sikora, Tsuneyoshi Kamae

The EGRET instrument onboard of CGRO detected a number of gamma-ray flares from blazars, and it is expected that GLAST, to be launched in 2006, should detect many more such flares. These flares should be preceded by X-ray precursors, and the MAXI All-Sky Monitor, to be deployed around the time of launch of GLAST, is likely to detect such precursors. This pap

Shay Zucker, Tsevi Mazeh

We analyzed the Hipparcos astrometric observations of 47 stars that were discovered to harbor giant planets and 14 stars with brown-dwarf secondary candidates. The Hipparcos measurements were used together with the corresponding stellar radial-velocity data to derive an astrometric orbit for each system. To find out the significance of the derived astrometri

Mirjam Cvetic, Gary Shiu, Angel M. Uranga

We construct N=1 supersymmetric four-dimensional orientifolds of type IIA on T^6/(Z_2 x Z_2) with D6-branes intersecting at angles. The use of D6-branes not fully aligned with the O6-planes in the model allows for a construction of many supersymmetric models with chiral matter, including those with the Standard Model and grand unified gauge groups. We perfor

Alain Riazuelo, Jean-Philippe Uzan

The framework for considering the astronomical and cosmological observations in the context of scalar-tensor quintessence in which the quintessence field also accounts for a time dependence of the gravitational constant is developed. The constraints arising from nucleosynthesis, the variation of the constant, and the post-Newtonian measurements are taken int

Zoltan Dezso, Albert-Laszlo Barabasi

The vanishing epidemic threshold for viruses spreading on scale-free networks indicate that traditional methods, aiming to decrease a virus' spreading rate cannot succeed in eradicating an epidemic. We demonstrate that policies that discriminate between the nodes, curing mostly the highly connected nodes, can restore a finite epidemic threshold and poten

Albert-Laszlo Barabasi, Erzsebet Ravasz, Tamas Vicsek

Scale-free networks are abundant in nature and society, describing such diverse systems as the world wide web, the web of human sexual contacts, or the chemical network of a cell. All models used to generate a scale-free topology are stochastic, that is they create networks in which the nodes appear to be randomly connected to each other. Here we propose a s

Justin R. David, Shiraz Minwalla, Carlos Nunez

We generalize the Jackiw-Rebbi-Hasenfratz-'t Hooft construction of fermions from bosons to demonstrate the fermionic nature of certain bound states involving SU(N) instantons in even spatial dimensions and SO(N) instantons in $8k+1$ spatial dimensions. We use this result to identify several fermionic excitations in various perturbatively bosonic string t

Charles Livingston

In knot concordance three genera arise naturally, g(K), g_4(K), and g_c(K): these are the classical genus, the 4-ball genus, and the concordance genus, defined to be the minimum genus among all knots concordant to K. Clearly 0 <= g_4(K) <= g_c(K) <= g(K). Casson and Nakanishi gave examples to show that g_4(K) need not equal g_c(K). We begin by reviewing and

Itai Benjamini, Harry Kesten, Yuval Peres, Oded Schramm

The uniform spanning forest (USF) in Z^d is the weak limit of random, uniformly chosen, spanning trees in [-n,n]^d. Pemantle proved that the USF consists a.s. of a single tree if and only if d <= 4. We prove that any two components of the USF in Z^d are adjacent a.s. if 5 <= d <= 8, but not if d >= 9. More generally, let N(x,y) be the minimum number of edges

Chui-Ping Yang, Julio Gea-Banacloche

We show how an arbitrary qubit rotation can be teleported, albeit probabilistically, using 1 e-bit of entanglement and one classical bit. We use this to present a scheme for implementing quantum secret sharing. The scheme operates essentially by sending a &#34;secret&#34; rotated qubit of information to several users, who need to cooperate in order to recove

Kasper Peeters, Marija Zamaklar

In the limit of small velocities, the dynamics of half-BPS Yang-Mills-Higgs solitons can be described by the geodesic approximation. Recently, it has been shown that quarter-BPS states require the addition of a potential term to this approximation. We explain the logic behind this modification for a larger class of models and then analyse in detail the dynam

Amand Faessler, Th. Gutsche, M. A. Ivanov, J. G. Korner

We study the semileptonic decays of the lowest lying double heavy baryons using the relativistic three-quark model. We do not employ a heavy quark mass expansion but keep the masses of the heavy quarks and baryons finite. We calculate all relevant form factors and decay rates.

A. Zheludev, Z. Honda, Y. Chen, C. L. Broholm

Inelastic neutron scattering experiments on the Haldane-gap quantum antiferromagnet NDMAP are performed in magnetic fields below and above the critical field Hc at which the gap closes. Quasi-elastic neutron scattering is found for H>Hc indicating topological excitations in the high field phase.

James C. Lombardi, Jessica Sawyer Warren, Frederic A. Rasio, Alison Sills

Collisions of main sequence stars occur frequently in dense star clusters. In open and globular clusters, these collisions produce merger remnants that may be observed as blue stragglers. Detailed theoretical models of this process require lengthy hydrodynamic computations in three dimensions. However, a less computationally expensive approach, which we pres

Ramesh Narayan, Michael R. Garcia, Jeffrey E. McClintock

We discuss new observations of X-ray novae which provide strong evidence that black holes have event horizons. Optical observations of 13 X-ray novae indicate that these binary stars contain collapsed objects too heavy to be stable neutron stars. The objects have been identified as black hole candidates. X-ray observations of several of these X-ray novae in

Hitoshi Nishino, Subhash Rajpoot

We present a superspace formulation of N=1 eleven-dimensional supergravity with no manifest local Lorentz covariance, which we call teleparallel superspace. This formulation will be of great importance, when we deal with other supergravity theories in dimensions higher than eleven dimensions, or a possible formulation of noncommutative supergravity. As an il

Poonam Mehta, Sukanta Dutta, Ashok Goyal

The accurate prediction of neutrino beam produced in muon decays and the absence of opposite helicity contamination for a particular neutrino flavour makes a future neutrino factory (NF) based on a muon storage ring (MSR), the ideal place to look for the lepton flavour violating (LFV) effects. In this paper, we address the contribution of mediating LFV lepto

Stefano Bellucci, Anton Galajinsky

We give a Lagrangian and display all local symmetries for N=4 topological string by Berkovits, Vafa and Siegel, the latter previously known in the superconformal gauge. Leading to a small N=4 superconformal algebra and exhibiting the manifest Lorentz invariance the model is proposed to be a framework for restoring the manifest Lorentz invariance in N=2 strin

I. I. Kogan, A. Nichols

We show that the SU(2)_0 WZNW model has a hidden OSp(2|2)_{-2} symmetry. Both these theories are known to have logarithms in their correlation functions. We also show that, like OSp(2|2)_{-2}, the logarithmic structure present in the SU(2)_0 model is due to the underlying c=-2 sector. We also demonstrate that the quantum Hamiltonian reduction of SU(2)_0 lead

Claudio A. Scrucca, Marco Serone

We construct a general class of chiral four-dimensional string models with Scherk--Schwarz supersymmetry breaking, involving freely acting orbifolds. The basic ingredient is to combine an ordinary supersymmetry-preserving Z_N projection with a supersymmetry-breaking projection Z_M' acting freely on a subspace of the internal manifold. A crucial condition is

A. R. Berdoz, TRIUMF E497 Collaboration

The parity-violating longitudinal analyzing power, Az, has been measured in pp elastic scattering at an incident proton energy of 221 MeV. The result obtained is Az =(0.84 +/- 0.29 (stat.) +/- 0.17 (syst.)) x 10^{-7}. This experiment is unique in that it selects a single parity violating transition amplitude, 3P2-1D2, and consequently directly constrains the

Sergei Nechaev, Raphael Voituriez

The stable profile of the boundary of a plant&#39;s leaf fluctuating in the direction transversal to the leaf&#39;s surface is described in the framework of a model called a &#34;surface à godets&#34;. It is shown that the information on the profile is encoded in the Jacobian of a conformal mapping (the coefficient of deformation) corresponding to an isometr

V. Radhakrishnan, A. A. Deshpande

The recent identification of the perpendicular mode of radio polarization as the primary one in the Vela pulsar by Lai et al. (2001) is interpreted in terms of the maser mechanism proposed by Luo & Melrose (1995). We suggest that such a mechanism may also be operative for the parallel mode which opens up the possibility of accounting for all types of polariz

Mason A. Porter, Richard L. Liboff

Quantum billiards provide an excellent forum for the analysis of quantum chaos. Toward this end, we consider quantum billiards with time-varying surfaces, which provide an important example of quantum chaos that does not require the semiclassical ($\hbar \longrightarrow 0$) or high quantum-number limits. We analyze vibrating quantum billiards using the frame

P. Bozek

We study a generalized ladder resummation in the superfluid phase of the nuclear matter. The approach is based on a conserving generalization of the usual T-matrix approximation including also anomalous self-energies and propagators. The approximation here discussed is a generalization of the usual mean-field BCS approach and of the in medium T-matrix approx

Rudy Wijnands, Jon M. Miller, Craig Markwardt, Walter H. G. Lewin

After more than a decade of actively accreting at about a tenth of the Eddington critical mass accretion rate, the neutron-star X-ray transient KS 1731-260 returned to quiescence in early 2001. We present a Chandra/ACIS-S observation taken several months after this transition. We detected the source at an unabsorbed flux of ~2 x 10^{-13} erg/cm^2/s (0.5-10 k

M. Bonamente, R. Lieu, J. P. D. Mittaz

The soft X-ray excess emission in the southern cluster Sersic 159-03 represents hiterto the strongest effect of its kind. Emission in the ~0.2-0.4 keV passband is detected far in excess of the expected contribution from the hot phase of the intra-cluster medium, and extends to the X-ray signal limit of the cluster. Our analysis of ROSAT PSPC observations rev

Bertrand Patureau-Mirand

The theory of Vassiliev invariants deals with many modules of diagrams on which the algebra Lambda defined by Pierre Vogel acts. By specifying a quadratic simple Lie superalgebra, one obtains a character on Lambda. We show the coherence of these characters by building a map of graded algebras beetwen Lambda and a quotient of a ring of polynomials in three va

P. S. Corasaniti, E. J. Copeland

Quintessence has been introduced as an alternative to the cosmological constant scenario to account for the current acceleration of the universe. This new dark energy component allows values of the equation of state parameter $w_{Q}^0\geq-1$, and in principle measurements of cosmological distances to Type Ia supernovae can be used to distinguish between thes

S. L. A. de Queiroz, M. Bahiana

We consider a single-interface model for the description of Barkhausen noise in soft ferromagnetic materials. Previously, the model had been used only in the adiabatic regime of infinitely slow field ramping. We introduce finite driving rates and analyze the scaling of event sizes and durations for different regimes of the driving rate. Coexistence of interm

M. V. Milosevic, S. V. Yampolskii, F. M. Peeters

The vortex states in a thin mesoscopic disk are investigated within the phenomenological Ginzburg-Landau theory in the presence of different &#39;&#39;model&#39;&#39; magnetic field profiles with zero average field which may result from a ferromagnetic disk or circulating currents in a loop near the superconductor. We calculated the dependences of both the g

H. Navelet, R. Peschanski

We find a consistency between two different approaches of hard diffraction, namely the QCD dipole model and the Soft Colour Interaction approach. A theoretical interpretation in terms of S-Matrix and perturbative QCD properties in the small $x_{Bj}$ regime is proposed.

L. B. Lucy

Transition probabilities governing the interaction of energy packets and matter are derived that allow Monte Carlo NLTE transfer codes to be constructed without simplifying the treatment of line formation. These probabilities are such that the Monte Carlo calculation asymptotically recovers the local emissivity of a gas in statistical equilibrium. Numerical

Bert van Es, Peter Spreij, Harry van Zanten

We consider two kinds of stochastic volatility models. Both kinds of models contain a stationary volatility process, the density of which, at a fixed instant in time, we aim to estimate. We discuss discrete time models where for instance a log price process is modeled as the product of a volatility process and i.i.d. noise. We also consider samples of certai

F. Loeser, J. Sebag

We construct a theory of motivic integration for smooth rigid varieties. As an application new invariants of degenerations are obtained.

Shlomo Dado, Arnon Dar, A. De Rujula

We severely criticize the consuetudinary analysis of the afterglows of gamma-ray bursts (GRBs) in the conical-ejection fireball scenarios. We argue that, instead, recent observations imply that the long-duration GRBs and their afterglows are produced by highly relativistic jets of cannonballs (CBs) emitted in supernova explosions. The CBs are heated by their

Christof Gattringer, Meinulf Goeckeler, P. E. L. Rakow, Stefan Schaefer

We study localization and chirality properties of eigenvectors of the lattice Dirac operator. In particular we focus on the dependence of our observables on the size of the corresponding eigenvalue, which allows us to study the transition of a near-zero mode into a bulk mode. We analyze ensembles of quenched SU(3) configurations using a Dirac operator which

Benedict W. Ritchie, Peter A. Thomas

We present the results of high-resolution AP3M+SPH simulations of merging clusters of galaxies. We find that the compression and shocking of the core gas during a merger can lead to large increases in bolometric X-ray luminosities and emission-weighted temperatures of clusters. Cooling flows are completely disrupted during equal-mass mergers, with the mass d

L. Bogacz, Z. Burda, C. Petersen, B. Petersson

We implement fermions on dynamical random triangulation and determine numerically the spectrum of the Dirac-Wilson operator D for the system of Majorana fermions coupled to two-dimensional Euclidean quantum gravity. We study the dependence of the spectrum of the operator (epsilon D) on the hopping parameter. We find that the distributions of the lowest eigen

Vladimir F. Golovko

The description of the narrowing effect at high pressures is demonstrated on the example of CO2-He absorption for Q-, P-, and R-branches and for the head of the R-branch. The problem is focused on the physical meaning of this phenomenon that should be associated with the angular and translation momentum transfer to matter from the photon absorbed. The effect

D. M. Wei, T. Lu

Sharp breaks have been observed in the afterglow light curves of several GRBs; this is generally explained by the jet model. However, there are still some uncertainties concerning this interpretation due to the unclear hydrodynamics of jet sideways expansion. Here we propose an alternative explanation to these observed breaks. If we assume that the multiwave

S. Mishima

We calculate branching ratios for pure penguin decay modes, $B\to ϕK$ decays using perturbative QCD approach. Our results of branching ratios are consistent with the experimental data and larger than those obtained from the naive factorization assumption and the QCD-improved factorization approach. This is due to a dynamical penguin enhancement in perturbati