March 2002 arXiv papers — page 23

Alex Samorodnitsky

We investigate universal bounds on spherical codes and spherical designs that could be obtained using Delsarte's linear programming methods. We give a lower estimate for the LP upper bound on codes, and an upper estimate for the LP lower bound on designs. Specifically, when the distance of the code is fixed and the dimension goes to infinity, the LP uppe

A. Zinger

We give a practical formula for counting irreducible nodal genus-three plane curves that a fixed generic complex structure on the normalization. As an intermediate step, we enumerate rational plane curves that have a $(3,4)$-cusp.

Nikita Sidorov

In [17] the author and A. Vershik have shown that for $\be=\frac12(1+\sqrt5)$ and the alphabet $\{0,1\}$ the infinite Bernoulli convolution ($=$ the Erdös measure) has a property similar to the Lebesgue measure. Namely, it is quasi-invariant of type $\mathrm{II}_1$ under the $\be$-shift, and the natural extension of the $\be$-shift provided with the measure

M. I. Ostrovskii

We consider real spaces only. Definition. An operator $T:X\to Y$ between Banach spaces $X$ and $Y$ is called a Hahn-Banach operator if for every isometric embedding of the space $X$ into a Banach space $Z$ there exists a norm-preserving extension $\tilde T$ of $T$ to $Z$. A geometric property of Hahn-Banach operators of finite rank acting between finite-dime

Janusz Grabowski, Katarzyna Grabowska

Results describing Lie ideals and maximal finite-codimensional Lie subalgebras of the Lie algebras associated with Lie algebroids with non-singular anchor maps are presented. It is also proved that every isomorphism of such Lie algebras induces a diffeomorphism of base manifolds respecting the generalized foliations defined by the anchor maps.

Gero Fendler

Let (G,S) be a Coxeter group. We construct a continuation, to the open unit disc, of the unitary representations associated to the positive definite functions g -> r^l(g). (Here 0<r<1, and l denotes the length function with respect to the generating set S.) The constructed representations are uniformly bounded and we prove that this implies the weak amenabil

Claudia Pinzari, John E. Roberts

The notion of left (resp. right) regular object of a tensor C*-category equipped with a faithful tensor functor into the category of Hilbert spaces is introduced. If such a category has a left (resp. right) regular object, it can be interpreted as a category of corepresentations (resp. representations) of some multiplicative unitary. A regular object is an o

Charles P. Boyer, Krzysztof Galicki

We prove that for every integer k>1 there is a simply connected rational homology 5-sphere $\scriptstyle{M^5_k}$ with spin such that $\scriptstyle{H_2(M^5_k,\bbz)}$ has order $\scriptstyle{k^2},$ and $\scriptstyle{M^5_k}$ admits a Riemannian metric of positive Ricci curvature. Moreover, if the prime number decomposition of $\scriptstyle{k}$ has the form $\sc

Christopher D. Sogge

The purpose of this paper is to give a simple proof of sharp $L^\infty$ estimates for the eigenfunctions of the Dirichlet Laplacian on smooth compact Riemannian manifolds $(M,g)$ of dimension $n\ge 2$ with boundary $\partial M$ and then to use these estimates to prove new estimates for Bochner Riesz means in this setting. Our eigenfunction estimates involve

Andrey Yu. Dubin

I put forward the low-energy confining asymptote of the solution $<W_{C}>$ (valid for large macroscopic contours C of the size $>>1/Λ_{QCD}$) to the large N Loop equation in the D=4 U(N) Yang-Mills theory with the asymptotic freedom in the ultraviolet domain. Adapting the multiscale decomposition characteristic of the Wilsonean renormgroup, the proposed Ansa

Richard Corrado, Murat Gunaydin, Nicholas P. Warner, Marco Zagermann

We examine orbifolds of the IIB string via gauged supergravity. For the gravity duals of the A_{n-1} quiver gauge theories, we extract the massless degrees of freedom and assemble them into multiplets of N=4 gauged supergravity in five dimensions. We examine the embedding of the gauge group into the isometry group of the scalar manifold, as well as the symme

S. Groot Nibbelink, H. P. Nilles, M. Olechowski

We study models compactified on S^1/Z_2 with bulk and brane matter fields charged under U(1) gauge symmetry. We calculate the FI-terms and show by minimizing the resulting potential that supersymmetry or gauge symmetry is spontaneously broken if the sum of the charges does not vanish. Even if this sum vanishes, there could be an instability as a consequence

V. B. Bezerra, E. M. F. Curado, M. A. Rego-Monteiro

We analyze some consequences of two possible interpretations of the action of the ladder operators emerging from generalized Heisenberg algebras in the framework of the second quantized formalism. Within the first interpretation we construct a quantum field theory that creates at any space-time point particles described by a q-deformed Heisenberg algebra and

M. C. Diamantini, C. A. Trugenberger

We show that the high-temperature behaviour of the recently proposed confining strings reproduces exactly the correct large-N QCD result, for a large class of truncations of the long-range interaction between surface elements.

A. Niégawa

Two forms are available for the fermion propagator at finite temperature and density. It is shown that, when one deals with a diquark-condensation-operator inserted Green function in hot and dense QCD, the standard form of the quark propagator does not work. On the other hand, another form of the quark propagator does work.

G. Sardanashvily

The deformation star product of smooth functions on the momentum phase space of covariant (polysymplectic) Hamiltonian field theory is introduced.

Eunsang Kim

In this article, we study how the Grothendieck group of coherent sheaves can be used to describe D-branes. We show how global bound state construction in topological $K$-theory can be adapted to our context, showing that D-branes wrapping a subvariety are holomorphically classified by a relative $K$-group. By taking the duality between the relative $K$-group

T. Banks

We point out consequences of the assumption that supersymmetry breaking is of cosmological origin.

Guang-jiong Ni

Einstein&#39;s theory of special relativity(SR) and the principle of causality imply that the speed of any moving object can not exceed that of light in a vacuum($c$).However,there were many attempts in literature discussing the particle moving with speed $u>c$(called as superluminal particle or tachyon)either in the scheme of SR or beyond it.These theories

Yu. A. Simonov

Nonperturbative spin-dependent forces of quarks in a baryon are calculated directly from the QCD Lagrangian in the framework of the Field Correlator Method both for heavy and light quarks. Resulting forces contain terms of 5 different structures, only one being known before in asymptotic form. Perturbative terms obtained by the same method are standard and h

V. N. Baier, V. M. Strakhovenko

Various positron distributions are obtained using an approach developed earlier for the description of electron-photon showers in axially aligned single crystals. Based on these distributions, characteristics of the positron yield measured in recent experiments are calculated. Theoretical estimations display a rather good agreement with experimental results

Silas R. Beane, Martin J. Savage

Properties of the proton and the neutron are explored in partially-quenched chiral perturbation theory with two non-degenerate light flavors. Masses, magnetic moments, matrix elements of isovector twist-2 operators and axial-vector currents are computed at the one-loop level in the chiral expansion.

Garry Ludwig

Fayos and Sopuerta have recently set up a formalism for studying vacuum spacetimes with an isometry, a formalism that is centred around the bivector corresponding to the Killing vector and that adapts the tetrad to the bivector. Steele has generalized their approach to include the homothetic case. Here, we generalize this formalism to arbitrary spacetimes an

S. Dain

I describe the construction of a large class of asymptotically flat initial data with non-vanishing mass and angular momentum for which the metric and the extrinsic curvature have asymptotic expansions at space-like infinity in terms of powers of a radial coordinate. I emphasize the motivations and the main ideas behind the proofs.

Edward K. Porter

The prior knowledge of the gravitational waveform from compact binary systems makes matched filtering an attractive detection strategy. This detection method involves the filtering of the detector output with a set of theoretical waveforms or templates. One of the most important factors in this strategy is knowing how many templates are needed in order to re

Ozay Gurtug, Mustafa Halilsoy

It was believed that when gravitational, electromagnetic and scalar waves interact, a spacelike curvature singularity or Cauchy horizon develops because of mutual focusing. We show with an exact solution that the collision of Einstein-Maxwell-Scalar fields, in contrast to previous studies, predicts singularities on null surfaces and that this is a transition

Sawa Manoff

Basic notions of continuous media mechanics are introduced for spaces with affine connections and metrics. The physical interpretation of the notion of relative velocity is discussed. The notions of deformation velocity tensor, shear velocity, rotation (vortex) velocity, and expansion velocity are introduced. Different types of flows are considered. PACS num

O. S. Matlin, E. Lusk, W. McCune

We describe our experiences in using SPIN to verify parts of the Multi Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of processes connected by Unix network sockets. MPD is dynamic: processes and connections among them are created and destroyed as MPD is initialized, runs user processes, recovers from faults, and ter

Joseph O&#39;Rourke

The concept of pointed pseudo-triangulations is defined and a few of its applications described.

A. A. Louis, P. G. Bolhuis, E. J. Meijer, J. P. Hansen

The depletion interactions between two colloidal plates or between two colloidal spheres, induced by interacting polymers in a good solvent, are calculated theoretically and by computer simulations. A simple analytical theory is shown to be quantitatively accurate for case of two plates. A related depletion potential is derived for two spheres; it also agree

Kwon Park

We present a theory of Kondo effect caused by an induced magnetic moment near non-magnetic impurities such as Zn and Li in the cuprate superconductors. Based on the co-existence of charge order and superconductivity, a natural description of the induced moment and the resulting Kondo effect is obtained in the framework of bond-operator theory of microscopic

O. P. Vajk, P. K. Mang, M. Greven, P. M. Gehring

The study of randomness in low-dimensional quantum antiferromagnets is at the forefront of research in the field of strongly correlated electron systems, yet there have been relatively few experimental model systems. Complementary neutron scattering and numerical experiments demonstrate that the spin-diluted Heisenberg antiferromagnet La2Cu(1-z)(Zn,Mg)zO4 is

V. R. Misko, V. M. Fomin, J. T. Devreese, V. V. Moshchalkov

A thermodynamically stable vortex-antivortex pattern has been revealed in mesoscopic type I superconducting triangles, contrary to type II superconductors where similar patterns are unstable. The stable vortex-antivortex &#34;molecule&#34; appears due to the interplay between two factors: a repulsive vortex-antivortex interaction in type I superconductors an

A. Calzolari, R. Di Felice, E. Molinari, A. Garbesi

We present a first-principle investigation of quadruple helix nanowires, consisting of stacked planar hydrogen-bonded guanine tetramers. Our results show that long wires form and are stable in potassium-rich conditions. We present their electronic bandstructure and discuss the interpretation in terms of effective wide-bandgap semiconductors. The microscopic

V. I. Belyavsky, Yu. V. Kopaev

The pairing of charge carriers with large pair momentum is considered in connection with high-temperature superconductivity of cuprate compounds. The possibility of pairing arises due to some essential features of quasi-two-dimensional electronic structure of cuprates: (i) The Fermi contour with strong nesting features; (ii) The presence of extended saddle p

W. P. Ferreira, G. A. Farias, H. A. Carmona, F. M. Peeters

The ground state of a classical two-dimensional (2D) system with finite number of charged particles, trapped by two positive impurities charges localized at a distance (zo) from the 2D plane and separated from each other by a distance xp are obtained. The impurities are allowed to carry more than one positive charge. This classical system can form a 2D-like

F. Evers, A. Mildenberger, A. D. Mirlin

Statistical properties of critical wave functions at the spin quantum Hall transition are studied both numerically and analytically (via mapping onto the classical percolation). It is shown that the index $η$ characterizing the decay of wave function correlations is equal to 1/4, at variance with the $r^{-1/2}$ decay of the diffusion propagator. The multifra

A. Kaminski, S. Rosenkranz, H. M. Fretwell, J. C. Campuzano

When matter undergoes a phase transition from one state to another, usually a change in symmetry is observed, as some of the symmetries exhibited are said to be spontaneously broken. The superconducting phase transition in the underdoped high-Tc superconductors is rather unusual, in that it is not a mean-field transition as other superconducting transitions

F. Marchesoni, M. Borromeo

A linear defect, viz. an elastic string, diffusing on a planar substrate traversed by a travelling wave experiences a drag known as Stokes&#39; drift. In the limit of an infinitely long string, such a mechanism is shown to be characterized by a sharp threshold that depends on the wave parameters, the string damping constant and the substrate temperature. Mor

M. Borromeo, F. Marchesoni, G. Costantini

The rectification efficiency of an underdamped ratchet operated in the adiabatic regime increases according to a scaling current-amplitude curve as the damping constant approaches a critical threshold; below threshold the rectified signal becomes extremely irregular and eventually its time average drops to zero. Periodic (locked) and diffusive (fully chaotic

T. V. Ignatova, G. A. Zvyagina, I. G. Kolobov, E. A. Masalitin

The sound velocity is measured in polycrystalline MgB2 synthesized from the elements, and the bulk modulus and the Debye temperature are calculated. The conversion of an elastic wave into electromagnetic radiation is investigated in the mixed state.The dynamic parameters of the vortex lattice are estimated. This paper was published in Low Temp. Rhys., 2002,

Dennis Bonatsos, D. Lenis, P. P. Raychev, P. A. Terziev

The analytic properties of Nilsson&#39;s Modified Oscillator (MO), which was first introduced in nuclear structure, and of the recently introduced, based on quantum algebraic techniques, 3-dimensional q-deformed harmonic oscillator (3-dim q-HO) with Uq(3) > SOq(3) symmetry, which is known to reproduce correctly in terms of only one parameter the magic number

C. U. Jung, J. Y. Kim, P. Chowdhury, Kijoon H. P. Kim

We synthesized hexagonal-disc-shaped MgB2 single crystals under high-pressure conditions and analyzed the microstructure and pinning properties. The lattice constants and the Laue pattern of the crystals from X-ray micro-diffraction showed the crystal symmetry of MgB2. A thorough crystallographic mapping within a single crystal showed that the edge and c-axi

C. A. Perroni, V. Cataudella, G. De Filippis, G. Iadonisi

Employing a variational approach that takes into account electron-phonon and magnetic interactions in $La_{1-x}A_xMnO_3$ perovskites with $0<x<0.5$, the effects of the magnetic field and the oxygen isotope substitution on the phase diagram, the electron-phonon correlation function and the infrared absorption at $x=0.3$ are studied. The lattice displacements

R. Brusetti, P. Haen, J. Marcus

We revisited the problem of the stability of the superconducting state in RbxWO3 and identified the main causes of the contradictory data previously published. We have shown that the ordering of the Rb vacancies in the nonstoichiometric compounds have a major detrimental effect on the superconducting temperature Tc.The order-disorder transition is first orde

V. K. Dugaev, V. I. Litvinov, J. Barnas, M. Vieira

We propose a new mechanism of indirect exchange interaction, which can be responsible for the ferromagnetic ordering in Mn-doped semiconductors (like GaMnAs) at low carrier concentration. The mechanism is based on the interplay of the hybridization of band states (conduction or valence) with localized impurity (donor or acceptor) states and the direct exchan

N. Barisic, R. Gaal, I. Kezsmarki, G. Mihaly

We have measured the thermoelectric power (S) of high purity single-walled carbon nanotube mats as a function of temperature at various hydrostatic pressures up to 2.0 GPa. The thermoelectric power is positive, and it increases in a monotonic way with increasing temperature for all pressures. The low temperature (T < 40 K) linear thermoelectric power is pres

V. I. Anisimov, M. A. Korotin, I. A. Nekrasov, Z. V. Pchelkina

Using the structural data of the La2CuO4 compound both in the low temperature tetragonal phase and in the isotropic phase we have derived an effective t-J model with hoppings t and superexchange interactions J extended up to fourth and second neareast neighbors respectively. By numerically studying this hamiltonian we have then reproduced the main experiment

A. D. Drozdov, J. deC. Christiansen

Observations are reported on isotactic polypropylene (i) in a series of tensile tests with a constant strain rate on specimens annealed for 24 h at various temperatures in the range from 110 to 150 C and (ii) in two series of creep tests in the sub-yield region of deformation on samples not subjected to thermal treatment and on specimens annealed at 140 C. A

C. Tejedor, L. Martin-Moreno

Transport through a quantum dot (QD) in the Kondo regime shows alternating regions of high and low conductance when both an external magnetic field and the gate potential controlling the depth of the QD potential are varied. We present a theoretical analysis of this chessboard aspect of the magneto-conductance. An effective Kondo Hamiltonian is obtained by m

H. L. Suo, C. Beneduce, X. D. Su, R. Flukiger

Multifilamentary MgB2/Fe wires and tapes with high transport critical current densities have been fabricated using a straightforward powder-in-tube (PIT) process. After annealing, we measured transport jc values up to 1.1 * 105 A/cm2 at 4.2 K and in a field of 2 T in a MgB2/Fe square wire with 7 filaments fabricated by two-axial rolling, and up to 5 * 104 A/

K. Komori, K. Kawagishi, Y. Takano, H. Fujii

The paper reports the first successful fabrication of MgB2 superconducting tape using a flexible metallic substrate as well as its strong pinning force, which was verified by direct measurement of transport critical current density. The tape was prepared by depositing MgB2 film on a Hastelloy tape buffered with an YSZ layer. The Jc of the tape exceeds 105A/c

L. A. Falkovsky

Using the Boltzmann equation for electrons in metals, we show that the optical phonons soften and have a dispersion due to screening in agreement with the results reported recently [M. Reizer, Phys. Rev. B {\bf 61}, 40 (2000)]. Additional phonon damping and frequency shift arise when the electron--phonon interaction is properly included.

Yoshihiko Takano, Takeshi Hatano, Akira Ishii, Akihiro Fukuyo

An intrinsic Josephson junction has been successfully fabricated without any micro-fabrication technique. Two Bi2212 whiskers were crossed with one another and joined by post-annealing. The inter-whisker electrical transport properties were measured by the four-probe method. The temperature dependence of resistance exhibited metallic behavior above TC. The r

Yue Yu, Shijie Yang

We construct a generalized Laughlin-liquid wave function and a variational electron solid wave function when the magnetic field is tilted. The energy of the liquid state is evaluated by Monte Carlo methods while the energy of the solid state is calculated by the optimization. Comparing these two energies for a given tilted angle $θ$, it is seen that the crit

G. F. Reiter, J. Mayers, P. Platzman

Neutron Compton Scattering measurements presented here of the momentum distribution of hydrogen in $KH_2PO_4$ (KDP) just above and well below the ferroelectric transition temperature show clearly that the proton is coherent over both sites in the in the high temperature phase, a result that invalidates the commonly accepted order-disorder picture of the tran

Seiki Komiya, Yoichi Ando, X. F. Sun, A. N. Lavrov

Both the in-plane and the out-of-plane resistivities (ρ_{ab} and ρ_{c}) are measured in high-quality La_{2-x}Sr_{x}CuO_{4} (LSCO) single crystals in the lightly- to moderately-doped region, x = 0.01 to 0.10, and the resistivity anisotropy is determined. In all the samples studied, the anisotropy ratio ρ_{c}/ρ_{ab} quickly increases with decreasing temperatur

Yoichi Ando, J. Takeya, Yasushi Abe, X. F. Sun

Since the nature of pairing interactions is manifested in the superconducting gap symmetry, the exact gap structure, particularly any deviation from the simple d_{x^2-y^2} symmetry, would help elucidating the pairing mechanism in high-T_c cuprates. Anisotropic heat transport measurement in Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} (Bi-2212) reveals that the quasiparticle

P. Punyindu Chatraphorn, S. Das Sarma

We study, using noise reduction techniques, layer by layer epitaxial growth in limited mobility solid-on-solid nonequilibrium surface growth models, which have been introduced in the context of kinetic surface roughening in ideal molecular beam epitaxy. Multiple hit noise reduction and long surface diffusion length lead to qualitatively similar layer by laye

M. Hayashi, H. Ebisawa

Effects of inhomogeneous doping on the high-$T_c$ cuprate superconductors are studied within the framework of the t-J model. Especially, the boundary between two non-superconducting regions with doping rates much higher and lower than the optimal one is examined. It is found that, although there is no superconductivity in the bulk, a superconducting region a

M. K. Kostov, M. W. Cole, G. D. Mahan, C. Carraro

We evaluate the cohesive energies E$_b$ of four systems in which particles move on a cylindrical surface, at fixed distance R from the axis. We find quite nonuniversal dependences of E$_b$ on R. For the Coulomb binding problem, E$_b$ is a monotonically decreasing function of R. For three problems involving Lennard-Jones interactions, the behavior is nonmonot

Harding E. Smith

From the earliest extragalactic infrared studies AGN have shown themselves to be strong infrared sources and IR surveys have revealed new populations of AGN. I briefly review current motivations for AGN surveys in the infrared and results from previous IR surveys. The Luminous Infrared Galaxies, which in some cases house dust-enshrouded AGN, submillimeter su

Esther M. Hu, Lennox L. Cowie, Richard G. McMahon, Peter Capak

We report the discovery of a redshift z=6.56 galaxy lying behind the cluster Abell 370. The object HCM 6A was found in a narrowband imaging survey using a 118 Angstrom bandpass filter centered at 9152 Ang in the LRIS camera on the 10 m Keck II Telescope. Candidate Lyman alpha emitters were identified by the equivalent width of the emission and the absence of

T. Lery, R. N. Henriksen, J. D. Fiege, T. P. Ray

Powerful, highly collimated jets, surrounded by bipolar molecular outflows, are commonly observed near Young Stellar Objects (YSOs). In the usual theoretical picture of star formation, a jet is ejected from a magnetized accretion disk, with a molecular outflow being driven either by the jet or by a wider wind coming from the disk. Here, we propose an alterna

Ralf Quast, Robert Baade, Dieter Reimers

New high-resolution high signal-to-noise spectra of the $z=1.15$ damped Lyman $α$ (DLA) system toward the quasi-stellar object HE 0515-4414 reveal absorption lines of the multiplets 2 and 3 in \ion{C}{i}. The resonance lines are seen in two components with total column densities of $\log N=13.79\pm0.01$ and $\log N=13.36\pm0.01$, respectively. The comparisio

Ronald J. Allen

Young stars in the disks of galaxies produce HI from their parent H2 clouds by photodissociation. This paper describes the observational evidence for and the morphology of such HI. Simple estimates of the amount of dissociated gas lead to the startling conclusion that much, and perhaps even all, of the HI in galaxy disks can be produced in this way.

M. P. Redman, J. Meaburn, A. J. Holloway

The narrow optical filaments (`strings&#39; or `spikes&#39;) emerging from the Homunculus of Eta Carinae are modelled as resulting from the passage of ballistic `bullets&#39; of material through the dense circumstellar environment. In this explanation, the string is the decelerating flow of ablated gas from the bullet. An archive HST image and new forbidden

J-F. Olive, K. Hurley, J-P. Dezalay, J-L. Atteia

After a long period of quiescence, the soft gamma repeater SGR1900+14 was suddenly reactivated on April 2001. On July 2, 2001, a bright flare emitted by this source triggerred the WXM and FREGATE instruments onboard the HETE-2 satellite. Unlike typical short (0.1 s) and spiky SGRs recurrent bursts, this event features a 4.1 s long main peak, with a sharp ris

J-F. Olive, J-P. Dezalay, J-L. Atteia, C. Barraud

We present the first results of the in-flight validation of the spectral response of the FREGATE X/gamma detectors on-board the HETE-2 satellite. This validation uses the Crab pulsar and nebula as reference spectra.

Marco Beltrame, Ennio Poretti

We report on the discovery of the second case of a galactic Cepheid, ASAS112843-5925.7=HD 304373, pulsating in the the first (1O) and second (2O) radial overtones. The ratio between the periods (0.8058), the short value of the 1O period (0.922405 d) and the shape of the 1O light curve makes HD 304373 very similar to the 1O/2O Cepheids in the Magellanic Cloud

V. Castellani, M. Cignoni, S. Degl&#39;Innocenti, S. Petroni

We make use of a previous well tested Galactic model, but describing the observational behavior of the various stellar components in terms of suitable assumptions on their evolutionary status. In this way we are able to predict the expected distribution of Galactic White Dwarfs (WDs), with results which appear in {\em rather good} agreement with recent estim

M. A. Huang

The Alpha Magnetic Spectrometer (AMS) is a detector designed to search for antimatter in the cosmic rays. The physics results from the test flight in June 1998 are analyzed and published. This paper reviews the results in the five published papers of the AMS collaboration, updates the current understanding of two puzzles, albedo $e^+/e^-$ and albedo $^3$He,

Jean-Luc Vergely, Joachim Koeppen, Daniel Egret, Olivier Bienayme

An inverse method is developed to determine the star formation history, the age-metallicity relation, and the IMF slope from a colour-magnitude diagram. The method is applied to the Hipparcos HR diagram. We found that the thin disk of our Galaxy shows a peak of stellar formation 1.6 Gyr ago. The stars close to the Sun have a solar metallicity and a mean IMF

M. Hoshino, N. Shimada

We study the suprathermal electron acceleration mechanism in a perpendicular magnetosonic shock wave in a high Mach number regime by using a particle-in-cell simulation. We find that shock surfing/surftron acceleration producing the suprathermal electrons occurs in the shock transition region where a series of large amplitude electrostatic solitary waves (ES

Jonathan C. Tan, Christopher F. McKee

We model the formation of high-mass stars, specifying the accretion rate in terms of the instantaneous and final mass of the star, the ambient pressure of the star-forming region and the form of polytropic pressure support of the pre-stellar gas core. The high pressures typical of Galactic regions of massive star formation allow a 100 solar mass star to form

Christopher F. McKee, Jonathan C. Tan

Massive stars (with mass m_* > 8 solar masses) are fundamental to the evolution of galaxies, because they produce heavy elements, inject energy into the interstellar medium, and possibly regulate the star formation rate. The individual star formation time, t_*f, determines the accretion rate of the star; the value of the former quantity is currently uncertai

K. Ebisawa, A. Bamba, H. Kaneda, Y. Maeda

Using the Chandra ACIS-I instruments, we have carried out the deepest X-ray observation on a typical Galactic plane region at l 28.5 deg, where no discrete X-ray sources have been known previously. We have detected, as well as strong diffuse emission, 275 new point X-ray sources (4 sigma confidence) within two partially overlapping fields (~250 arcmin^2 in t

G. Lugones, J. E. Horvath

(abridged) We construct quark-diquark equations of state using the quark mass density-dependent formalism. A region inside a $2-D$ parameter space in which this matter is absolutely stable is identified. Motivated by the reported compactness of some neutron star candidates we present stellar sequences and show that the quark-diquark EOSs allow a very compact

S. C. Chapman, I. Smail, R. J. Ivison, G. Helou

We present Keck spectroscopy and UKIRT near-IR imaging observations of two 170micron-selected sources from the ISO-FIRBACK survey which have faint counterparts in the optical, and r-K~5. Both sources were expected to lie at z>1 based on their far-infrared, submillimeter and radio fluxes, assuming a similar spectral energy distribution to the local ultra-lumi

A. Kinkhabwala, M. Sako, E. Behar, S. M. Kahn

We present high-resolution soft-X-ray spectra of the prototypical Seyfert 2 galaxy, NGC 1068, taken with XMM-Newton RGS and Chandra LETGS. Its rich emission-line spectrum is dominated by recombination in a warm plasma (bright, narrow radiative recombination continua provide the ``smoking gun&#39;&#39;), which is photoionized by the inferred nuclear power-law

Darryl D. Holm, Martin F. Staley

We study exchange of stability in the dynamics of solitary wave solutions under changes in the nonlinear balance in a 1+1 evolutionary partial differential equation related both to shallow water waves and to turbulence. We find that solutions of the equation $ m_t + um_x +b u_xm = \nu m_{xx} $ with $m = u - \alpha^2 u_{xx}$ for fluid velocity $u(x,t)$ change

Paul M. N. Feehan, Thomas G. Leness

We prove an analogue of the Kotschick-Morgan conjecture in the context of SO(3) monopoles, obtaining a formula relating the Donaldson and Seiberg-Witten invariants of smooth four-manifolds using the SO(3)-monopole cobordism. The main technical difficulty in the SO(3)-monopole program relating the Seiberg-Witten and Donaldson invariants has been to compute in

Nevin N. Weinberg, Marc Kamionkowski

We calculate the abundance of dark-matter concentrations that are sufficiently overdense to produce a detectable weak-gravitational-lensing signal. Most of these overdensities are virialized halos containing identifiable X-ray and/or optical clusters. However, a significant fraction are nonvirialized overdensities still in the process of gravitational collap

F. J. Sanchez-Salcedo, E. Vazquez-Semadeni, A. Gazol

(Abridged) We discuss the nonlinear development of the isobaric mode of thermal instability (TI) in the context of the atomic interstellar medium (ISM), in order to assess the ability of TI to establish a well-segregated multi-phase structure in the turbulent ISM. The key parameter is the ratio of the cooling time to the dynamical crossing time $η$. The isob

R. Barbieri, R. Contino, P. Creminelli, R. Rattazzi

We study the consistency of orbifold field theories and clarify to what extent the condition of having an anomaly-free spectrum of zero-modes is sufficient to guarantee it. Preservation of gauge invariance at the quantum level is possible, although at the price, in general, of introducing operators that break the 5d local parity. These operators are, however

Csaba Csaki, Joshua Erlich, John Terning

We consider the two-brane Randall-Sundrum (RS) model with bulk gauge fields. We carefully match the bulk theory to a 4D low-energy effective Lagrangian. In addition to the four-fermion operators induced by KK exchange we find that large negative S and T parameters are induced in the effective theory. This is a tree-level effect and is a consequence of the sh

Saul Barshay, Georg Kreyerhoff

The possibility exists that cosmic-ray neutrinos with energies of $\sim 10^{20}$ eV interact in the atmosphere with a cross section at the millibarn level, giving rise to some of the highest-energy air showers. In a specific dynamical model which can give rise to such a cross section, we show that there can be a small effect upon the extraction of the effect

Rogerio de Sousa, S. Das Sarma

We theoretically consider coherence times for spins in two quantum computer architectures, where the qubit is the spin of an electron bound to a P donor impurity in Si or within a GaAs quantum dot. We show that low temperature decoherence is dominated by spin-spin interactions, through spectral diffusion and dipolar flip-flop mechanisms. These contributions

S. G. Sharapov, V. P. Gusynin, H. Beck

The temperature and field dependence of the superfluid density $ρ_s$ in the vortex state of a d-wave superconductor are calculated using a microscopic model in the quasiclassical approximation. We show that at temperatures below T^{*} \varpropto \sqrt{H}$, the linear T dependence of rho_s crosses over to a T^2 dependence differently from the behavior of the

S. Cacciatori, A. H. Chamseddine, D. Klemm, L. Martucci

We deform two-dimensional topological gravity by making use of its gauge theory formulation. The obtained noncommutative gravity model is shown to be invariant under a class of transformations that reduce to standard diffeomorphisms once the noncommutativity parameter is set to zero. Some solutions of the deformed model, like fuzzy AdS_2, are obtained. Furth

A. Falkowski, C. Grojean, S. Pokorski

We present a class of four-dimensional models, with a non-supersymmetric spectrum, in which the radiative corrections to the Higgs mass are not sensitive, at least at one-loop, to the UV completion of the theory. At one loop, Yukawa interactions of the top quark contribute to a finite and negative Higgs squared mass which triggers the electroweak symmetry br

Michael Salem, Tanmay Vachaspati

Stability and instability bands in classical mechanics are well-studied in connection with systems such as described by the Mathieu equation. We examine whether such band structure can arise in classical field theory in the context of an embedded kink in 1+1 dimensions. The static embedded kink is unstable to perturbations but we show that if the kink is dyn

A. Houghton, S. Lee, J. B. Marston

We show that the Wiedemann-Franz law, which holds for Landau Fermi liquids, breaks down in a large-n treatment of the t-J model. The calculated ratio of the in-plane thermal and electrical conductivities agrees quantitatively with experiments on the normal state of the electron-doped Pr_{2-x}Ce_xCuO_4 (x = 0.15) cuprate superconductor. The violation of the W

A. Broncano, O. Mena

In view of their physics goals, future neutrino factories from muon decay aim at an overall flux precision of ${\cal O}(1%)$ or better. We analytically study the QED radiative corrections to the neutrino differential distributions from muon decay. Kinematic uncertainties due to the divergence of the muon beam are considered as well. The resulting corrections

Jeremy S. Heyl, Nir J. Shaviv

The thermal emission of strongly magnetized neutron-star atmospheres is thought to be highly polarized. However, because of the different orientations of the magnetic field over the surface of the neutron star (NS), it is commonly assumed that the net observed polarization will be significantly reduced as the polarization from different regions will cancel e

John Atwell Moody

This paper gives a general nonsingularity condition for a blowup along an ideal, related to Gaussian curvature.

Janos Polonyi

The effective action for the current and density is shown to satisfy an evolution equation, the functional generalization of Callan-Symanzik equation. The solution describes the dependence of the one-particle irreducible vertex functions on the strength of the quenched disorder and the annealed Coulomb interaction. The result is non-perturbative, no small pa

M. Fischer, S. Groote, J. G. Körner, M. C. Mauser

We calculate the radiative corrections to the unpolarized and the four polarized spectrum and rate functions in the leptonic decay of a polarized $ μ$ into a polarized electron. The new feature of our calculation is that we keep the mass of the final state electron finite which is mandatory if one wants to investigate the threshold region of the decay. Analy

A. P. Bakulev, S. V. Mikhailov

Recent data of lattice measurements of the gauge-invariant nonlocal scalar quark condensates are analyzed to extract the short--distance correlation length, 1/λ_q, and to construct an admissible Ansatz for the condensate behaviour in a coordinate space. The correlation length values for both the quenched and full-QCD cases appear in a good agreement with the

Jaroslav Dittrich, Jan Kriz

We investigate the discrete spectrum of the Hamiltonian describing a quantum particle living in the two-dimensional curved strip. We impose the Dirichlet and Neumann boundary conditions on opposite sides of the strip. The existence of the discrete eigenvalue below the essential spectrum threshold depends on the sign of the total bending angle for the asympto