July 2001 arXiv papers — page 3

D. J. Dean, T. Papenbrock

We study precursors of thermal phase transitions in finite systems of interacting Bose gases. For weakly repulsive interactions there is a phase transition to the one-vortex state. The distribution of zeros of the partition function indicates that this transition is first order, and the precursors of the phase transition are already displayed in systems of a

D. J. Singh, I. I. Mazin

It has been long suspected that spin fluctuations in the weak itinerant ferromagnet ZrZn2 may lead to a triplet superconductivity in this material. Here we point out another possibility, a spatially inhomogeneous singlet superconducting state (a Fulde-Ferrell-Larkin-Ovchinnikov state). We report detailed electronic structure calculations, as well as calculat

V. Podzorov, B. G. Kim, V. Kiryukhin, M. E. Gershenson

In this paper, we report polarized optical microscopy and electrical transport studies of manganese oxides that reveal that the charge ordering transition in these compounds exhibits typical signatures of a martensitic transformation. We demonstrate that specific electronic properties of charge-ordered manganites stem from a combination of martensitic accomm

Konstantin Klemm, Victor M. Eguiluz

In the context of growing networks, we introduce a simple dynamical model that unifies the generic features of real networks: scale-free distribution of degree and the small world effect. While the average shortest path length increases logartihmically as in random networks, the clustering coefficient assumes a large value independent of system size. We deri

Konstantin Klemm, Victor M. Eguiluz

We propose a model for growing networks based on a finite memory of the nodes. The model shows stylized features of real-world networks: power law distribution of degree, linear preferential attachment of new links and a negative correlation between the age of a node and its link attachment rate. Notably, the degree distribution is conserved even though only

D. A. Dikin, S. Jung, V. Chandrasekhar

Using a new second derivative technique and thermometers which enable us to determine the local electron temperature in a mesoscopic metallic sample, we have obtained quantitative measurements of the low temperature field and temperature dependent thermopower of Andreev interferometers. As in previous experiments, the thermopower is found to oscillate as a f

B. G. Giraud, A. Touzeau

Neural nets are known to be universal approximators. In particular, formal neurons implementing wavelets have been shown to build nets able to approximate any multidimensional task. Such very specialized formal neurons may be, however, difficult to obtain biologically and/or industrially. In this paper we relax the constraint of a strict ``Fourier analysis&#

A C C Coolen, J A F Heimel

We solve the dynamics of the on-line minority game, with general types of decision noise, using generating functional techniques a la De Dominicis and the temporal regularization procedure of Bedeaux et al. The result is a macroscopic dynamical theory in the form of closed equations for correlation- and response functions defined via an effective continuous-

N. S. Averkiev, L. E. Golub

Spin relaxation in-plane anisotropy is predicted for heterostructures based on zinc-blende semiconductors. It is shown that it manifests itself especially brightly if the two spin relaxation mechanisms (D'yakonov-Perel' and Rashba) are comparable in efficiency. It is demonstrated that for the quantum well grown along the [0 0 1] direction, the main a

P. Allegrini, P. Grigolini, P. Hamilton, L. Palatella

We study the long-range correlations of heartbeat fluctuations with the method of diffusion entropy. We show that this method of analysis yields a scaling parameter $δ$ that apparently conflicts with the direct evaluation of the distribution of times of sojourn in states with a given heartbeat frequency. The strength of the memory responsible for this discre

Leticia F. Cugliandolo

We review an scenario for the non-equilibrium dynamics of glassy systems that has been motivated by the exact solution of simple models. This approach allows one to set on firmer grounds well-known phenomenological theories. The old ideas of entropy crisis, fictive temperatures, free-volume... have clear definitions within these models. Aging effects in the

Marco Airoldi

Fat tails in financial time series and increase of stocks cross-correlations in high volatility periods are puzzling facts that ask for new paradigms. Both points are of key importance in fundamental research as well as in Risk Management (where extreme losses play a key role). In this paper we present a new model for an ensemble of stocks that aims to encom

M. Rusanen, I. T. Koponen, T. Ala-Nissila

We study the meandering instability during growth of an isolated nanostructure, a crystalline cone, consisting of concentric circular steps. The onset of the instability is studied analytically within the framework of the standard Burton-Cabrera-Frank model, which is applied to describe step flow growth in circular geometry. We derive the correction to the m

Yshai Avishai, Yigal Meir

Using heuristic arguments and numerical simulations it is argued that the critical exponent $ν$ describing the localization length divergence at the quantum Hall transition is modified in the presence of spin-orbit scattering with short range correlations. The exponent is very close to $ν=4/3$, the percolation correlation length exponent, the prediction of a

K. Xia, P. J. Kelly, G. E. W. Bauer, A. Brataas

Recent theories of spin-current-induced magnetization reversal are formulated in terms of a spin-mixing conductance $G^{mix}$. We evaluate $G^{mix}$ from first-principles for a number of (dis)ordered interfaces between magnetic and non-magnetic materials. In multi-terminal devices, the magnetization direction of a one side of a tunnel junction or a ferromagn

Keiichirou Kikuchi, Hiroshi Imamura, Saburo Takahashi, Sadamichi Maekawa

The Andreev reflection of narrow ferromagnet/superconductor point contacts is theoretically studied. We show that the conductance quantization depends on whether the contact region is superconducting or ferromagnetic as well as on the strength of the exchange field in the ferromagnet. The Andreev reflection of the ferromagnetic contact is more suppressed tha

Valeria Del Prete, Alessandro Treves

In a previous report we have evaluated analytically the mutual information between the firing rates of N independent units and a set of multi-dimensional continuous+discrete stimuli, for a finite population size and in the limit of large noise. Here, we extend the analysis to the case of two interconnected populations, where input units activate output ones

A. Albrecht, C. P. Burgess, F. Ravndal, C. Skordis

We examine the late-time (nucleosynthesis and later) cosmological implications of brane-world scenarios having large (millimeter sized) extra dimensions. In particular, recent proposals for understanding why the extra dimensions are so large in these models indicate that moduli like the radion appear (to four-dimensional observers) to be extremely light, wit

William D. Watson

Theoretical research on extragalactic masers (and hence this review) is almost entirely directed toward 22 GHz water masers in circumnuclear disks with the focus being the near ideal masing disk at the nucleus of the galaxy NGC4258. The discussion here is organized around (1) the excitation and conditions for the masers, (2) the spatial and spectral appearan

Steven Furlanetto, Abraham Loeb

We propose to use gravitational wakes as a direct observational probe of the collisional nature of the dark matter. We calculate analytically the structure of a wake generated by the motion of a galaxy in the core of an X-ray cluster for dark matter in the highly-collisional and collisionless limits. We show that the difference between these limits can be re

L. Maraschi, F. Tavecchio

The broad band sensitivity and flexibility of the BeppoSAX satellite have allowed unprecedented studies of the X-ray emission from blazars. Here we focus on recent results on the SEDs of a group of blazars with emission lines, allowing to estimate both the luminosity in the jet and the luminosity of the accretion disk. Implications for the origin of the powe

Laura Maraschi

Advances in the capabilities of X-ray, gamma-ray and TeV telescopes have brought new information on the physics of relativistic jets, which are responsible for the blazar "phenomenon". In particular the broad band sensitivity of the BeppoSAX satellite, extending up to 100 KeV has allowed unprecedented studies of their hard X-ray spectra. I summarize

Dibyendu Nandy

We have developed a hybrid model of the solar dynamo on the lines of the Babcock-Leighton idea that the poloidal field is generated at the surface of the Sun from the decay of active regions. In this model magnetic buoyancy is handled with a realistic recipe - wherein toroidal flux is made to erupt from the overshoot layer wherever it exceeds a specified cri

Paola Marigo, Leo Girardi

In this paper we emphasize the close connection between the chemical and spectrophotometric evolution of stellar systems: Chemical yields from stars correspond to a precise fraction of their emitted light. We translate this concept quantitatively. Starting from simple stellar populations, we derive useful analytical relations to calculate the stellar fuel co

S. Recchi, F. Matteucci, A. D'Ercole

In this paper we present some results of numerical simulations concerning the development of galactic winds in starburst galaxies. In particular, we focus on a galaxy similar to IZw18, the most metal-poor galaxy locally known. We compute the chemio-dynamical evolution of this galaxy, considering the energetic input and the chemical yields originating from Su

Jelte de Jong, Penny D. Sackett, Konrad Kuijken, Robert Uglesich

One of the possible astrophysical solutions to the galactic dark matter problem is the presence of a significant amount of ``dark'' compact objects (MACHOs) in galactic dark matter halos. MEGA (Microlensing Exploration of the Galaxy and Andromeda) tries to find proof for or against the presence of compact objects in the halo of the Andromeda galaxy (

Curtis J. Saxton, Ralph S. Sutherland, Geoffrey V. Bicknell

We model the northern middle radio lobe of Centaurus A (NGC 5128) as a buoyant bubble of plasma deposited by an intermittently active jet. The extent of the rise of the bubble and its morphology imply that the ratio of its density to that of the surrounding ISM is less than 10^{-2}, consistent with our knowledge of extragalactic jets and minimal entrainment

Amy J. Mioduszewski, Vikram V. Dwarkadas, Lewis Ball

We present calculations of the radio emission from supernovae based on high-resolution simulations of the hydrodynamics and radiation transfer, using simple energy density relations which link the properties of the radiating electrons and the magnetic field to the hydrodynamics. As a specific example we model the emission from SN1993J, which cannot be adequa

Robert K. Soberman, Maurice Dubin

A comet-like, but magnitudes smaller, extremely low albedo interstellar meteoroid population of fragile aggregates with solar type composition, measured in space and terrestrially, is most probably the universal dark matter. Although non-baryonic particles cannot be excluded, only "Big Bang" cosmology predicts an appreciable fraction of such alternat

Edward L. Wright, Benjamin D. Johnson

Stellar fluxes from the 2MASS catalog are used to remove the contribution due to Galactic stars from the intensity measured by DIRBE in 13 regions in the North and South Galactic polar caps. Allowing for a constant calibration factor between the DIRBE 3.5 micron intensity and the 2MASS 2.2 micron fluxes gives very small pixel to pixel scatter. After subtract

Adan Cabello

A proof of Bell's theorem without inequalities valid for both inequivalent classes of three-qubit entangled states under local operations assisted by classical communication, namely Greenberger-Horne-Zeilinger (GHZ) and W, is described. This proof leads to a Bell inequality that allows more conclusive tests of Bell's theorem for three-qubit systems.

T. M. Cormier, A. I. Pavlinov, M. V. Rykov, V. L. Rykov

The procedure for the STAR Barrel Electromagnetic Calorimeter (BEMC) absolute calibrations, using penetrating charged particle hits (MIP-hits) from physics events at RHIC, is presented. Its systematic and statistical errors are evaluated. It is shown that, using this technique, the equalization and transfer of the absolute scale from the test beam can be don

Chuanwei Zhang

We propose a scheme for preparing arbitrary two photons polarization entangled mixed states via controlled location decoherence. The scheme uses only linear optical devices and single-mode optical fibers, and may be feasible in experiment within current optical technology.

Adam S. Sikora

Mazur, Kapranov, Reznikov, and others developed ``Arithmetic Topology,'' a theory describing some surprising analogies between 3-dimensional topology and number theory, which can be summarized by saying that knots are like prime numbers. We extend their work by proving several formulas concerning branched coverings of 3-manifolds and extensions of nu

Alexei A. Starobinsky, Shinji Tsujikawa, Jun'ichi Yokoyama

We study cosmological perturbations generated from quantum fluctuations in multi-field inflationary scenarios in generalized Einstein theories, taking both adiabatic and isocurvature modes into account. In the slow-roll approximation, explicit closed-form long-wave solutions for field and metric perturbations are obtained by the analysis in the Einstein fram

D. A. Garanin, E. M. Chudnovsky

We compute the width and shape of the EPR and tunneling resonances due to dislocations in Mn-12 acetate crystals. Uncorrelated dislocations produce the Gaussian shape of resonances while dislocations bound in pairs produce the Lorentzian shape. We stress that the uniaxial spin Hamiltonian together with crystal defects can explain the totality of experimental

Saharon Shelah, Lutz Strüngmann

Given an aleph_1-free abelian group G we characterize the class C_G of all torsion abelian groups T satisfying Ext(G,T)=0 assuming the continuum hypothesis CH. Moreover, in Godel's constructable universe we prove that this characterizes C_G for arbitrary torsion-free abelian G. It follows that there exist some ugly aleph_1-free abelian groups.

Saharon Shelah

Under some cardinal arithmetic assumptions, we prove that every stationary subset of lambda of a right cofinality has the weak diamond. This is a strong negation of uniformization. We then deal with a weaker version of the weak diamond- colouring restrictions. We then deal with semi- saturated (normal) filters.

Franz--Viktor Kuhlmann, Salma Kuhlmann, Saharon Shelah

We generalize the main result of math.RA/9608214 concerning the convex embeddings of a chain Gamma in a lexicographic power Delta^Gamma. For a fixed nonempty chain Delta, we derive necessary and sufficient conditions for the existence of nonempty solutions Gamma to each of the lexicographic functional equations (Delta^Gamma)^{<=0} simeq Gamma, (Delta^Gamma)

Anders Skovsted Buch

We give a direct geometric proof of the quantum Monk&#39;s formula which relies only on classical Schubert calculus.

H. B. Nielsen, S. Pallua, P. Prester

The consequences of certain simple assumptions like smoothness of ground state properties and vanishing of the vacuum energy (at least perturbatively) are explored. It would be interesting from the point of view of building realistic theories to obtain these properties without supersymmetry. Here we show, however, at least in some quantum mechanical models,

J. Gutowski, G. Papadopoulos

We investigate the dynamics of a pair of (4+1)-dimensional black holes in the moduli approximation and with fixed angular momentum. We find that spinning black holes at small separations are described by the de Alfaro, Fubini and Furlan model. For more than two black holes, we find an explicit expression for the three-body interactions in the moduli metric b

A. Konechny, A. Schwarz

This review paper is a continuation of hep-th/0012145 and it deals primarily with noncommutative ${\mathbb R}^{d}$ spaces. We start with a discussion of various algebras of smooth functions on noncommutative ${\mathbb R}^{d}$ that have different asymptotic behavior at infinity. We pay particular attention to the differences arising when working with nonunita

Ulf Gran

We have developed a Mathematica package capable of performing gamma-matrix algebra in arbitrary (integer) dimensions. As an application we can compute Fierz transformations.

Ken-Ichi Tezuka

Spacetime non-commutativity appears in string theory. In this paper, the non-commutativity in string theory is reviewed. At first we review that a Dp-brane is equivalent to a configuration of infinitely many D($p-2$)-branes. If we consider the worldvolume as that of the Dp-brane, coordinates of the Dp-brane is commutative. On the other hand if we deal with t

A. A. Pivovarov

The nonleading corrections in the inverse mass of the heavy charmed quark to the effective local ΔS=2 Lagrangian of K^0-anti K^0 mixing are calculated within the standard model.

Ruo Peng Wang

I show that there exist twelve independent Dirac equations for spin 1/2 fermions. The Dirac fields that satisfy these equations can be grouped into six pairs according to the way they transform under continuous space-time transformations. These six pairs of Dirac equations correspond to the three quark generations and the three lepton generations. The charge

J. McDonald

Preliminary results for the neutrino-nucleon differential cross section from the NuTeV experiment are presented. The extraction of the differential cross section from NuTeV is discussed and the structure functions $F_2$ and $ΔxF_3$ are presented. Comparisons are made with CCFR results.

A. Lopatenko

The most exciting challenge for CRIS is to create a service for research information which should be wide-spread, distributed and actual like Google, but at the same time structured, trusted, with a complex search and navigation similar to today CRIS application. The core technology for such a &#34;new&#34; CRIS is the semantic web technology to integrate da

Amnon Aharony

The multicritical point at which both a 3-component and a 2-component order parameters order simultaneously in 3 dimensions is shown to have the critical behavior of the decoupled fixed point, with separate n=3 and n=2 behavior. This contradicts both the extrapolation of the epsilon-expansion at leading order, which yields the biconical point, and recent Mon

T. C. Kobayashi, K. Hanazono, N. Tateiwa, K. Amaya

The electrical resistivity measurements in the magnetic field are carried out on the pressure-induced superconductor UGe$_2$. The superconductivity is observed from 1.06 to 1.44 GPa. The upper critical field of $H_{C2}$ is anisotropic where $H_{C2}(T)$ exhibits positive curvature for $H//b$ and $c$-axis. The characteristic enhancement of $H_{C2}$ is reconfir

P. Mazzotta, J. S. Kaastra, F. B. Paerels, C. Ferrigno

We report on the deep Chandra observation of central r=200kpc region of the cluster of galaxies MKW3s which was previously identified as a moderate cooling flow cluster. The Chandra image reveals two striking features -- a 100kpc long and 21kpc wide filament, extending from the center to the south-west and a nearly circular, 50kpc diameter depression 90 kpc

Sarah A. Yost, Re&#39;em Sari, Fiona A. Harrison, Edo Berger

We develop a model to fit the broadband afterglows of GRBs from the intrinsic parameters of the fireball&#39;s synchrotron emission, and apply it to a few well-studied events, with the goal of constraining the intrinsic variability of GRB parameters. We give an example here of fitting to the recent bright event GRB000926.

H. Garcia-Compean, O. Obregon, C. Ramirez

We propose a model for noncommutative quantum cosmology by means of a deformation of minisuperspace. For the Kantowski-Sachs metric we are able to find the exact wave function. We construct wave packets and show that new quantum states that ``compete&#39;&#39; to be the most probable state appear, in clear contrast with the commutative case. A tunneling proc

M. Danilov, L. Laptin, I. Tichomirov, M. Titov

The Muon Detector of the HERA-B experiment at DESY is a gaseous detector that provides muon identification in a high-rate hadronic environment. We present our studies on the properties of several fast gases, Ar/CF4/CH4 (74:20:6), Ar/CF4/CH4 (67:30:3) and Ar/CF4/CO2 (65:30:5), which have been found to fulfill muon detection requirements. The severe radiation

H. C. de Godoy Caldas, M. C. Nemes

Feynman&#39;s functional formulation of statistical mechanics is used to study the renormalizability of the well known Linear Chiral Sigma Model in the presence of fermionic fields at finite temperature in an alternative way. It is shown that the renormalization conditions coincide with those of the zero temperature model.

Felix Finster, Niky Kamran, Joel Smoller, Shing-Tung Yau

The Cauchy problem is considered for the massive Dirac equation in the non-extreme Kerr-Newman geometry, for smooth initial data with compact support outside the event horizon and bounded angular momentum. We prove that the Dirac wave function decays in L^\infty_loc at least at the rate t^{-5/6}. For generic initial data, this rate of decay is sharp. We deri

Benni Reznik, Yakir Aharonov, Berry Groisman

We present a systematic simple method for constructing deterministic remote operations on single and multiple systems of arbitrary discrete dimensionality. These operations include remote rotations, remote interactions and measurements. The resources needed for an operation on a two-level system are one ebit and a bidirectional communication of two cbits, an

J. Acosta, H. Blas

We consider a real Lagrangian off-critical submodel describing the soliton sector of the so-called conformal affine $sl(3)^{(1)}$ Toda model coupled to matter fields (CATM). The theory is treated as a constrained system in the context of Faddeev-Jackiw and the symplectic schemes. We exhibit the parent Lagrangian nature of the model from which generalizations

Ivan K. Kostov

We derive a constraint (string equation) which together with the Toda Lattice hierarchy determines completely the integrable structure of the compactified 2D string theory. The form of the constraint depends on a continuous parameter, the compactification radius R. We show how to use the string equation to calculate the free energy and the correlation functi

Daniel E. Reichart, Paul A. Price

It appears that the majority of rapidly-, well-localized gamma-ray bursts with undetected, or dark, optical afterglows, or `dark bursts&#39; for short, occur in clouds of size R > 10L_{49}^{1/2} pc and mass M > 3x10^5L_{49} M_{sun}, where L is the isotropic-equivalent peak luminosity of the optical flash. We show that clouds of this size and mass cannot be m

Asantha Cooray, Xuelei Chen

We discuss the kinetic Sunyaev-Zel&#39;dovich (SZ) contribution to cosmic microwave background (CMB) temperature fluctuations due to coherent rotational velocity component of electrons within halos. This effect produces a distinct dipole-like temperature distribution across the the cluster, and provides a promising way to measure the angular momentum distrib

J. Ringot, P. Szriftgiser, J. C. Garreau

We describe and characterize a setup for subrecoil stimulated Raman spectroscopy of cold cesium atoms. We study in particular the performances of a method designed to active control and stabilization of the magnetic fields across a cold-atom cloud inside a small vacuum cell. The performance of the setup is monitored by {\em copropagative-beam} stimulated Ram

S. W. Hwang, D. Y. Jeong, M. S. Jun, M. H. Son

Quantum computing (or generally, quantum information processing) is of prime interest for it potentially has a significant impact on present electronics and computations1-5. Essence of quantum computing is a direct usage of the superposition and entanglement of quantum mechanical states that are pronounced in nanoscopic particles such as atoms and molecules6

A. Loinger

The observational &#34;black holes&#34; are quite different objects from the theoretical black holes.

V. A. Plujko, O. M. Gorbachenko, M. O. Kavatsyuk

The retardation and temperature effects in two-body collisions are studied. The collision integral with retardation effects is obtained on the base of the Kadanoff- Baym equations for Green functions in a form with allowance for reaching the local equilibrium system. The collisional relaxation times of collective vibrations are calculated using both the tran

Yuri Latushkin, Roman Shvidkoy

We present a characterization of hyperbolicity for strongly continuous semigroups on Banach spaces in terms of Fourier multiplier properties of the resolvent of the generator. Hyperbolicity with respect to classical solutions is also considered. Our approach unifies and simplifies the M. Kaashoek-- S. Verduyn Lunel theory and multiplier-type results previous

Alex Eskin, Howard Masur, Martin Schmoll

We use Ratner&#39;s theorem to compute the asymptotics of the number of (cylinders of) periodic trajectories in a rectangle with a barrier, assuming that the location p/q of the barrier is rational. We also show that as q tends to infinity, the constant in the asymptotic formula tends to the constant for the generic genus 2 flat surface.

Zhou Hong, Ma Wen-Gan, Jiang Yi, Zhang Ren-You

We present the analytical and numerical investigations of top-charm associated production at the LHC in the framework of the R-parity violating MSSM. The numerical analysis of their production rates is carried out in the mSUGRA scenario with some typical parameter sets. The results show that the cross sections of associated $t\bar{c}(\bar{t}c)$ production vi

Tomohiro Matsuda

We consider the scenario of electroweak baryogenesis mediated by cosmological defects in a model of extra dimension. We consider the domain wall on the brane in higher-dimensional theories.The electroweak breaking scale is suppressed and the sphaleron interaction is activated in the false vacuum.

D. H. Rischke, D. T. Son, M. A. Stephanov

We discuss QCD with two light flavors at large baryon chemical potential mu. Color superconductivity leads to partial breaking of the color SU(3) group. We show that the infrared physics is governed by the gluodynamics of the remaining SU(2) group with an exponentially soft confinement scale Lambda_QCD&#39; Delta*exp[-a*mu/(g*Delta)], where Delta<<mu is the

Ding-Yu Chung

The masses of elementary particles and hadrons can be calculated from the periodic table of elementary particles. The periodic table is derived from dimensional hierarchy for the seven extra spatial dimensions. As a molecule is the composite of atoms with chemical bonds, a hadron is the composite of elementary particles with hadronic bonds. The masses of ele

Elena V. Palesheva

In this article a new stationary cylindrically symmetric solution of the Einstein&#39;s field equations with cosmological constant and Time machine is given. The garavitational field is created by ideal liquid with three massless scalar fields or by ideal liquid with electric-magnetic field and massless scalar field.

Hongya Liu, Paul S. Wesson

We present a rich class of exact solutions which contains radiation-dominated and matter-dominated models for the early and late universe. They include a variable cosmological ``constant&#39;&#39; which is derived from a higher dimension and manifests itself in spacetime as an energy density for the vacuum. This is in agreement with observational data and is

Alexander K. Hartmann

The four-dimensional +-J random-bond Ising model is studied using ground-state calculations. System sizes up to N=6^4 spins are considered. Here it is found that the ferromagnetic-spin glass transition occurs at a critical concentration p_c=0.28(1) of the antiferromagnetic bonds, which is comparable to values found previously by high-temperature series expan

Olexei Motrunich, Kedar Damle, David A. Huse

We revisit two-dimensional particle-hole symmetric sublattice localization problem, focusing on the origin of the observed singularities in the density of states $ρ(E)$ at the band center E=0. The most general such system [R. Gade, Nucl. Phys. B {\bf 398}, 499 (1993)] exhibits critical behavior and has $ρ(E)$ that diverges stronger than any integrable power-

Noam Soker

We present the many evolutionary routes that progenitors of bipolar planetary nebulae (BPNe) can take. Overall, there are about a hundred qualitatively different evolutionary routes, hence about a hundred qualitatively different types of BPNe. Within each type there are quantitative differences as well. Adding the dependence of the appearance on inclination,

Peter J. Boyce, Steven Phillipps, J. Bryn Jones, Simon P. Driver

We present the results of a study of the morphology of the dwarf galaxy population in Abell 868, a rich, intermediate redshift (z=0.154) cluster which has a galaxy luminosity function with a steep faint-end slope (alpha=-1.26 +/- 0.05). A statistical background subtraction method is employed to study the B-R colour distribution of the cluster galaxies. This

Donald Q. Lamb

We show that the clumpy structure of star-forming regions can naturally explain the fact that 50-70% of GRB afterglows are optical``dark.&#39;&#39; We also show that dust echos from the GRB and its afterglow, produced by the clumpy structure of the star-forming region in which the GRB occurs, can lead to temporal variability and peaks in the NIR, optical, an

Nevin Weinberg, Carlo Graziani, Donald Q. Lamb, Daniel E. Reichart

We exploit the 14 gamma-ray bursts (GRBs) with known redshifts z and the 7 GRBs for which there are constraints on z to determine the GRB rate R_{GRB}(z), using a method based on Bayesian inference. We find that, despite the qualitative differences between the observed GRB rate and estimates of the SFR in the universe, current data are consistent with R_{GRB

K. T. Reilly, E. D. Bloom, W. Focke, B. Giebels

We report on timing and spectral observations of the 2000 outburst of XTE J1550-564 made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS). We observe a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fracti

Daniel E. Reichart

The distances to which the optical flash destroys dust via sublimation, and the burst and afterglow change the size distribution of the dust via fragmentation, are functions of grain size. Furthermore, the sublimation distance is a decreasing function of grain size, while the fragmentation distance is a decreasing function of grain size for large grains and

Daniel E. Reichart, Sarah A. Yost

We present evidence that the majority of rapidly-, well-localized gamma-ray bursts with undetected, or dark, optical afterglows, or `dark bursts&#39; for short, are most likely the result of extinction by dust in the circumburst medium. First, we show that the dark bursts cannot be explained by a failure to image deeply enough quickly enough: We fit a variet

Cheongho Han

If gravitational microlensing occurs in a binary-source system, both source components are magnified, and the resulting light curve deviates from the standard one of a single source event. However, in most cases only one source component is highly magnified and the other component (the companion) can be treated as a simple blending source: blending approxima

G. E. Allen, R. Petre, E. V. Gotthelf

We present the results of a joint spectral analysis of RXTE PCA, ASCA SIS, and ROSAT PSPC data of the supernova remnant SN 1006. This work represents the first attempt to model both the thermal and nonthermal X-ray emission over the entire X-ray energy band from 0.12 to 17 keV. The thermal flux is described by a nonequilibrium ionization model with an electr

S. J. Brodsky, J. R. Hiller, G. McCartor

We present a new class of quantum field theories which are exactly solvable. The theories are generated by introducing Pauli-Villars fermionic and bosonic fields with masses degenerate with the physical positive metric fields. An algorithm is given to compute the spectrum and corresponding eigensolutions. We also give the operator solution for a particular c

Lawrence J. Hall, Hitoshi Murayama, Yasunori Nomura

Gauge symmetry breaking by boundary conditions on a manifold is known to be equivalent to Wilson-line breaking through a background gauge field, and is therefore spontaneous. These equivalent pictures are related by a non-periodic gauge transformation. However, we find that boundary condition gauge symmetry breaking on orbifolds is explicit; there is no gaug

Carl E. Carlson, Christopher D. Carone, Richard F. Lebed

Jurco, Moller, Schraml, Schupp, and Wess have shown how to construct noncommutative SU(N) gauge theories from a consistency relation. Within this framework, we present the Feynman rules for noncommutative QCD and compute explicitly the most dangerous Lorentz-violating operator generated through radiative corrections. We find that interesting effects appear a

Louis K. Scheffer

Anderson, et al. find the measured trajectories of Pioneer 10 and 11 spacecraft deviate from the trajectories computed from known forces acting on them. This unmodelled acceleration (and the less well known, but similar, unmodelled torque) can be accounted for by non-isotropic radiation of spacecraft heat. Various forms of non-isotropic radiation were propos

Stefano Liberati, Sebastiano Sonego, Matt Visser

Motivated by the recent attention on superluminal phenomena, we investigate the compatibility between faster-than-c propagation and the fundamental principles of relativity and causality. We first argue that special relativity can easily accommodate -- indeed, does not exclude -- faster-than-c signalling at the kinematical level. As far as causality is conce

R. Brent Tully, Rachel S. Somerville, Neil Trentham, Marc A. W. Verheijen

There is accumulating evidence that the faint end of the galaxy luminosity function might be very different in different locations. The luminosity function might be rising in rich clusters and flat or declining in regions of low density. If galaxies form according to the model of hierarchical clustering then there should be many small halos compared to the n

Vittorio Giovannetti, Seth Lloyd, Lorenzo Maccone

A method is proposed to employ entangled and squeezed light for determining the position of a party and for synchronizing distant clocks. An accuracy gain over analogous protocols that employ classical resources is demonstrated and a quantum-cryptographic positioning application is given, which allows only trusted parties to learn the position of whatever mu

Jonathan Mackey

It has recently been argued that the observed ellipticities of galaxies may be determined at least in part by the primordial tidal gravitational field in which the galaxy formed. Long-range correlations in the tidal field could thus lead to an ellipticity-ellipticity correlation for widely separated galaxies. I present results of a calculation of the angular

A. O. Barvinsky

We construct braneworld effective action in two brane Randall-Sundrum model and show that the radion mode plays the role of a scalar field localizing essentially nonlocal part of this action. Non-minimal curvature coupling of this field reflects the violation of AdS/CFT-correspondence for finite values of brane separation. Under small detuning of the brane t

W. Zheng, G. A. Kriss, J. X. Wang, M. Brotherton

We present a moderate-resolution (~20 km/s) spectrum of the mini broad-absorption-line QSO PG1351+64 between 915-1180 A, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). Additional spectra at longer wavelengths were also obtained with the HST and ground-based telescopes. Broad absorption is present on the blue wings of CIII 977, Ly-beta, OVI

V. Di Clemente, S. F. King, D. A. J. Rayner

We consider the problem of supersymmetry and electroweak breaking in a 5d theory compactified on an $S^{1}/Z_{2}$ orbifold, where the extra dimension may be large or small. We consider the case of a supersymmetry breaking 4d brane located at one of the orbifold fixed points with the Standard Model gauge sector, third family and Higgs fields in the 5d bulk, a

Spiros Cotsakis

We present an elementary account of mathematical cosmology through a series of important unsolved problems. We introduce the fundamental notion of `a cosmology&#39; and focus on the issue of singularities as a theme unifying many current, seemingly unrelated trends of this subject. We discuss problems associated with the definition and asymptotic structure o

M. Braden, O. Friedt, Y. Sidis, P. Bourges

In $\rm Sr_2RuO_4$ the spin excitation spectrum is dominated by incommensurate fluctuations at q=(0.3 0.3 q$_z$), which arise from Fermi-surface nesting. We show that upon Ti substitution, known to suppress superconductivity, a short range magnetic order develops with a propagation vector (0.307 0.307 1). This finding confirms that superconducting $\rm Sr_2R

Michael Flohr

In logarithmic conformal field theory, primary fields come together with logarithmic partner fields on which the stress-energy tensor acts non-diagonally. Exploiting this fact and global conformal invariance of two- and three-point functions, operator product expansions of logarithmic operators in arbitrary rank logarithmic conformal field theory are investi

Luis Anchordoqui, Haim Goldberg, Stephen Reucroft, John Swain

In this article we examine the hypothesis that the highest energy cosmic rays are complex nuclei from extragalactic sources. Under reasonable physical assumptions, we show that the nearby metally rich starburst galaxies (M82 and NGC 253) can produce all the events observed above the ankle. This requires diffusion of particles below $10^{20}$ eV in extragalac