May 1999 arXiv papers — page 17

W. Mueck, K. S. Viswanathan

We illustrate the Dirichlet prescription of the AdS/CFT correspondence using the example of a massive scalar field and argue that it is the only entirely consistent regularization procedure known so far. Using the Dirichlet prescription, we then calculate the divergent terms for gravity in the cases $d=2,4,6$, which give rise to the Weyl anomaly in the bound

A. Donini, S. Rigolin

We review briefly the main features of the Large Extra Dimensions scenario in the framework of weakly coupled Type I string theory. Kaluza-Klein (KK) excitations of the graviton are expected, whereas no KK modes for the gauge bosons arise if the gauge group is tied to a D3-brane. In this scenario, typical signatures such as direct production of KK modes of t

Jonathan Bagger, Jonathan L. Feng, Nir Polonsky

The supersymmetric flavor, CP and Polonyi problems are hints that the fundamental scale of the soft supersymmetry breaking parameters may be above a TeV, in apparent conflict with naturalness. We consider the possibility that multi-TeV scalar masses are generated by Planck- or unification-scale physics, and find the conditions under which the masses of scala

M. F. McDermott

Cross sections for the diffractive photoproduction of the Upsilon-family at HERA energies, within the framework of the analysis by Frankfurt, Koepf and Strikman, are presented. They compare well with the recent preliminary data from ZEUS and H1. Two novel effects lead to a significant enhancement of the original calculation: the non-diagonal (or skewed) kine

L. Mankiewicz, G. Piller

We discuss the electroproduction of light vector mesons from transversely polarized photons. Here QCD factorization cannot be applied as shown explicitly in a leading order calculation of corresponding Feynman diagrams. It is emphasized that present infrared singular contributions cannot be regularized through phenomenological meson distribution amplitudes w

H. Abe, J. Hashida, T. Muta, A. Purwanto

The Casimir effect is an interesting phenomenon in the sense that it provides us with one of the primitive means of extracting the energy out of the vacuum. Since the original work of Casimir a number of works have appeared in extending the result to the case of more general topological and dynamical configurations of the boundary condition and to the circum

Vladimir Gribov

This is the third lecture on quark confinement given by V.N.Gribov in 1992 in Orsay. An extensive discussion of the consequences of all this for the structure of the Green function can be found in [5,6] - in the two last papers concluding his 20 years long study of the problem of quark confinement in QCD. The text was prepared for publication by Yu. Dokshitz

T. M. Aliev, M. Savci

The "g_{Delta N gamma}" coupling for the "Delta -> N gamma" decay is calculated in framework of the light cone QCD sum rules and is found to be g_{Delta N gamma} = (1.6 pm 0.2) GeV^(-1). Using this value of g_{Delta N gamma} we estimate the branching ratio of the Delta^+ -> N gamma decay, which is in a very good agreement with the experimenta

D. de Florian, Z. Kunszt

The production of the Standard Model Higgs boson of mass ~ 100-140 GeV at the LHC likely gives clear signals in the $γγ$ (1) and in the $γγjet$ (2) channels. The quantitative evaluation of the background to channel (1) is very hard since the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) QCD corrections are large. In particular, the con

J. Blümlein, B. Gezer, D. Robaschik

The Compton amplitude is calculated in terms of expectation values of light-ray quark operators. As a technical tool we apply the nonlocal light-cone expansion. Thereby we express the expectation value of the vector light-ray operator with the help of the expectation value of the corresponding scalar operator of twist 2. This allows important simplifications

K. Urbanowski

Using a more accurate effective Hamiltonian governing the time evolution in the particle-antiparticle subspace of states than the one obtained within the Lee-Oehme--Yang approach we show that in the case of particles created at the initial instant t = 0 only the masses of a stable particle and its antiparticle are the same at all t > 0 in a CPT invariant sys

Zoltan Ligeti, Mark B. Wise

The B -> K^* gamma branching fraction is predicted using heavy quark spin symmetry at large recoil to relate the tensor and (axial-)vector form factors, using heavy quark flavor symmetry to relate the B decay form factors to the measured D -> K^* l nu form form factors, and extrapolating the semileptonic B decay form factors to large recoil assuming nearest

M. Woods

We present an overview of the electroweak physics program of the SLD experiment at the Stanford Linear Accelerator Center (SLAC). A data sample of 550K Z0 decays has been collected. This experiment utilizes a highly polarized electron beam, a small interaction volume, and a very precise pixel vertex detector. We present a preliminary result for the weak mixi

S. Holst, H. -J. Matschull

Recently it has been shown that a 2+1 dimensional black hole can be created by a collapse of two colliding massless particles in otherwise empty anti-de Sitter space. Here we generalize this construction to the case of a non-zero impact parameter. The resulting spacetime, which may be regarded as a Gott universe in anti-de Sitter background, contains closed

E. I. Guendelman, A. B. Kaganovich

Summary of abstract Field theory models including gauge theories with SSB are presented where the energy density of the true vacuum state (TVS) is zero without fine tuning. The above models are constructed in the gravitational theory where a measure of integration Φin the action is not necessarily \sqrt{-g} but it is determined dynamically through additional

David H. Wolpert, Kevin R. Wheeler, Kagan Tumer

We consider the problem of how to design large decentralized multi-agent systems (MAS's) in an automated fashion, with little or no hand-tuning. Our approach has each agent run a reinforcement learning algorithm. This converts the problem into one of how to automatically set/update the reward functions for each of the agents so that the global goal is ac

David H. Wolpert, Kagan Tumer, Jeremy Frank

A COllective INtelligence (COIN) is a set of interacting reinforcement learning (RL) algorithms designed in an automated fashion so that their collective behavior optimizes a global utility function. We summarize the theory of COINs, then present experiments using that theory to design COINs to control internet traffic routing. These experiments indicate tha

Walter Eaves

This paper presents some fundamental collective choice theory for information system designers, particularly those working in the field of computer-supported cooperative work. This paper is focused on a presentation of Arrow's Possibility and Impossibility theorems which form the fundamental boundary on the efficacy of collective choice: voting and selec

I. Alexandrou, H. -J. Scheibe, C. J. Kiely, A. J. Papworth

Laser-Arc evaporation of a graphite target has been used to deposit carbon films that exhibit high hardness (45 GPa) and elastic recovery (85%). High Resolution Electron Microscopy (HREM) and Electron Energy Loss Spectroscopy (EELS) were subsequently used to study the microstructure and bonding of the resultant layers. The structure of the films from HREM is

A. Marco Saitta, Paul D. Soper, E. Wasserman, Michael L. Klein

Many experiments have been done to determine the relative strength of different knots, and these show that the break in a knotted rope almost invariably occurs at a point just outside the `entrance' to the knot. The influence of knots on the properties of polymers has become of great interest, in part because of their effect on mechanical properties. Kno

Alexander K. Hartmann

A ``ballistic-search'' algorithm is presented which allows the identification of clusters (or funnels) of ground states in Ising spin glasses even for moderate system sizes. The clusters are defined to be sets of states, which are connected in state-space by chains of zero-energy flips of spins. The technique can also be used to estimate the sizes of

Rose Du, Alexander Yu. Grosberg, Toyoichi Tanaka

In order to understand the nuclei which develop during the course of protein folding and unfolding, we examine phase segregation of a single heteropolymer chain which occurs in equilibrium. These segregated conformations are characterized by a nucleus of monomers which are superimposable upon the native conformation. We computationally generate the phase seg

Attila Szolnoki

A two-dimensional half-filled lattice gas model with nearest-neighbor attractive interaction is studied where particles are coupled to two thermal baths at different temperatures $T_1$ and $T_2$. The hopping of particles is governed by the heat bath at temperature $T_1$ with probability $p$ and the other heat bath $(T_2)$ with probability $1-p$ independently

G. Mohler, D. Stroud

We have carried out a model calculation of the flux noise produced by vortex avalanches in a Type-II superconductor, using a simple kinetic model proposed by Bassler and Paczuski. Over a broad range of frequencies, we find that the flux noise $S_Φ(ω)$ has a power-law dependence on frequency, $S_Φ(ω) \sim ω^{-s}$, with $s \sim 1.4$ in reasonable agreement wit

D. B. Saakian

The complete phase diagram of Random Energy Model (REM) is obtained for complex temperatures using the method proposed by Derrida. We find the density of zeroes for statistical sum. Then the method is applied to Generalized Random Energy Model (GREM). This allows us to propose new analytical method for investigating zeroes of statistical sum for finite-dimen

Sangsoo Yoon, Byeong-ho Eom, Jysoo Lee, Insuk Yu

We find that circular kinks form on the surface of granular material when the axis of rotation is tilted more than the angle of internal friction of the material. Radius of the kinks is measured as a function of the spinning speed and the tilting angle. Stability consideration of the surface results in an explanation that the kink is a boundary between the i

Sudhakar Yarlagadda, Gabriele F. Giuliani

The screened electron-electron interaction $W_{σ, σ'}$ and the electron self-energy in an infinitesimally polarized electron gas are derived by extending the approach of Kukkonen and Overhauser. Various quantities in the expression for $W_{σ, σ'}$ are identified in terms of the relevant response functions of the electron gas. The self-energy is obtai

P. Kratzer, C. G. Morgan, M. Scheffler

The initial steps of MBE growth of GaAs on beta 2-reconstructed GaAs(001) are investigated by performing total energy and electronic structure calculations using density functional theory and a repeated slab model of the surface. We study the interaction and clustering of adsorbed Ga atoms and the adsorption of As_2 molecules onto Ga atom clusters adsorbed o

Sudhakar Yarlagadda

In this paper, using different approaches we demonstrate the equality of the two mixed charge-spin response functions of a spin-polarized electron gas when orbital effects are negligible. Within a generalized STLS approximation we show that the two mixed responses are equal. We also present arguments for the equality of the two dynamic responses by consideri

Tai-Kai Ng

In this paper we discuss the construction and the dynamics of vortex-like topological spin excitations in the Schwinger-boson description of Heisenberg antiferromagnets in two dimensions. The topological spin excitations are Dirac fermions (with gap) when spin value $S$ is a half-integer. Experimental and theoretical implications of these excitations are bei

D. Ihle, C. Schindelin, A. Weisse, H. Fehske

The ground-state properties of the spin-1/2 antiferromagnetic Heisenberg model with spatially anisotropic couplings on a square lattice are investigated by a spin-rotation-invariant Green's-function approach and by Lanczos diagonalizations on lattices up to 36 sites supplemented by finite-size scaling. We focus on the anisotropy-driven transition from th

Patricia M. Knezek

We have completed a 21-cm survey of a 600 square degree region of the Centaurus A group of galaxies at a redshift of ~500 km/s as part of a larger survey of the entire southern sky. This group of galaxies was recently the subject of a separate and thorough optical survey (Cote et al. 1997), and thus presented an ideal comparison for us to test the survey per

R. Baptista, C. Silveira, J. E. Steiner, K. Horne

Time-resolved spectroscopy of the novalike variable UU Aquarii is analyzed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from disc centre in the range 3600-7000 Å. The spectrum of inner disc shows a blue continuum filled with deep, narrow absorption lines which transition

M. Hilker, L. Infante, T. Richtler

In this paper we briefly review the properties of the dwarf galaxy population at the core of the Fornax cluster, as well as the properties of the extraordinary rich globular cluster system and the cD halo around the central galaxy NGC 1399. In turn, the question whether a scenario in which dwarf galaxies have been accreted and dissolved in the cluster center

Eric Agol, Julian Krolik

We show how analysis of a quasar high-magnification microlensing event may be used to construct a map of the frequency-dependent surface brightness of the quasar accretion disk. The same procedure also allows determination of the disk inclination angle, the black hole mass (modulo the caustic velocity), and possibly the black hole spin. This method depends o

Ignasi Ribas, Carme Jordi, Jordi Torra

We present a detailed analysis of the detached eclipsing binary CD Tau. A large variety of observational data, in form of IR photometry, CORAVEL radial velocity observations and high-resolution spectra, are combined with the published light curves to derive accurate absolute dimensions and effective temperature of the components, as well as the metal abundan

Vinay Kashyap, Jeremy Drake

We compare the count-rates of active binaries observed by Einstein and ROSAT. We find significant evidence for short-term variability (approx 0.32) and marginal evidence for a larger variability at longer timescales (approx 0.38). Modeling this excess as cyclic variability, we place an upper limit on the relative amplitude of the cyclic component (I_cyc/I_mi

P. C. Frisch, J. M. Dorschner, J. Geiss, J. M. Greenberg

The gas-to-dust mass ratios found for interstellar dust within the Solar System, versus values determined astronomically for the cloud around the Solar System, suggest that large and small interstellar grains have separate histories, and that large interstellar grains preferentially detected by spacecraft are not formed exclusively by mass exchange with near

M. C. Rabello-Soares, Sarbani Basu, J. Christensen-Dalsgaard

The observed solar p-mode frequencies provide a powerful diagnostic of the internal structure of the Sun and permit us to test in considerable detail the physics used in the theory of stellar structure. Amongst the most commonly used techniques for inverting such helioseismic data are two implementations of the optimally localized averages (OLA) method, name

Xiang-Ping Wu, Yan-Jie Xue, Li-Zhi Fang

The relationships between the X-ray determined bolometric luminosity Lx, the temperature T of the intracluster gas, and the optical measured velocity dispersion sigma of the cluster galaxies are updated for galaxy clusters using the largest sample of 256 clusters drawn from literature. The newly established relationships, based on the doubly weighted orthogo

L. Valenziano, G. Dall'Oglio

Preliminary site testing at Dome C (Antarctica) is presented, using both Automatic Weather Station (AWS) meteorological data (1986-1993) and Precipitable Water Vapor (PWV) measurements made by the authors. A comparison with South Pole and other sites is made. The South Pole is a well established astrophysical observing site, where extremely good conditions a

P. Uttley, I. M. McHardy, I. E. Papadakis, M. Guainazzi

On 9-11 May 1998, the highly-variable, low luminosity Seyfert 1 galaxy NGC4051 was observed in an unusual low flux state by BeppoSAX (Guainazzi et al. 1998) RXTE and EUVE. We present fits of the 4-15 keV RXTE spectrum and BeppoSAX MECS spectrum obtained during this observation, which are consistent with the interpretation that the source had switched off, le

H. B. Ann, M. G. Lee, M. Y. Chun, S. -L. Kim

Open clusters are useful tools to investigate the structure and evolution of the Galactic disk. We have started a long-term project to obtain UBVI CCD Photometry of open clusters which were little studied before, using the Doyak 1.8 m telescope of Bohyunsan Optical Astronomy Observatory in Korea. The primary goals of this project are (1) to make a catalog of

D. Edidin, B. Hassett, A. Kresch, A. Vistoli

A natural question is to determine which algebraic stacks are qoutient stacks. In this paper we give some partial answers and relate it to the old question of whether, for a scheme X, the natural map from the Brauer goup (equivalence classes of Azumaya algebras) to the cohomological Brauer group (the torsion subgroup of $H^2(X,{\mathbb G}_m)$ is surjective.

M. I. Katsnelson, A. V. Trefilov

General expressions for the contributions of the Van Hove singularity (VHS)in the electron density of states to the thermodynamic potential $Ωare obtained in the framework of microscopic Fermi liquid theory. The renormalization of the singularities in $Ωconnected with the Lifshitz electronic topological transition (ETT) is found. Screening anomalies due to v

Ramchander R. Sastry

The infinite dimensional generalization of the quantum mechanics of extended objects, namely, the quantum field theory of extended objects is employed to address the hitherto nonrenormalizable gravitational interaction following which the cosmological constant problem is addressed. The response of an electron to a weak gravitational field (linear approximati

David H. Bailey, David J. Broadhurst

Let $\{x_1, x_2, ..., x_n\}$ be a vector of real numbers. An integer relation algorithm is a computational scheme to find the $n$ integers $a_k$, if they exist, such that $a_1 x_1 + a_2 x_2 + ... + a_n x_n= 0$. In the past few years, integer relation algorithms have been utilized to discover new results in mathematics and physics. Existing programs for this

Yosuke Imamura

By means of the heterotic/type IIB duality, we study properties of junctions on backgrounds with a positively charged orientifold seven-plane and D-branes, which are expected to give seven dimensional Sp(r) gauge theories. We give a modified BPS condition for the junctions and show that it reproduces the adjoint representation of the Sp(r) group.

Sheng Li

The topological structure of the Nieh-Yan form in 4-dimensional manifold is given by making use of the decomposition of spin connection. The case of the generalized Nieh-Yan form on $2^d$-dimensional manifold is discussed with an example of 8-dimensional case studied in detail. The chiral anomaly with nonvanishing torsion is studied also. The further contrib

B. G. Sidharth

Recent observations of distant supernovae show that the universe, contrary to popular belief, is expanding for ever. Similarly, recent experiments at the Superkamiokande facility demonstrate that the Neutrino has a non vanishing mass. Both these discoveries necessitate, at the very least, a re-examination of conventional theories-the Big Bang Theory and the

Alexander Turbiner

Harmonic oscillator in Fock space is defined. Isospectral as well as polynomiality-of-eigenfunctions preserving, translation-invariant discretization of the harmonic oscillator is presented. Dilatation-invariant and polynomiality-of-eigenfunctions preserving discretization is also given.

Masayuki Tanimoto

We study the averaging problem from a point of view of variation of spatial volume $V$. We show that in the space of spherically symmetric dust solutions which are regular on the spatial manifold $S^3$ the variation $δV$ vanishes at the Friedmann-Lemaitre-Robertson-Walker (FLRW) solution in an appropriate sense, which supports the validity of the FLRW soluti

S. F. Edwards, D. V. Grinev

We investigate universal features of the jamming transition in granular materials, colloids and glasses. We show that the jamming transition in these systems has common features: slowing of response to external perturbation, and the onset of structural heterogeneities.

Regina E. Schulte-Ladbeck, Ulrich Hopp, Mary M. Crone, Laura Greggio

We present evidence for the existence of an old stellar halo in the Blue Compact Dwarf galaxy VII Zw 403. VII Zw 403 is the first Blue Compact Dwarf galaxy for which a clear spatial segregation of the resolved stellar content into a "core-halo" structure is detected. Multicolor HST/WFPC2 observations indicate that active star formation occurs in the

E. Torbet, M. J. Devlin, W. B. Dorwart, T. Herbig

We report on a measurement of the angular spectrum of the anisotropy of the microwave sky at 30 and 40 GHz between l=50 and l=200 over approximately 600 sq. deg. The data support a rise in the angular spectrum to a maximum with $δT_l \approx 85 μ$K at l=200. We also give a 2-sigma upper limit of $δT_l < 122 μ$K at l=432 at 144 GHz. These results come from th

D. V. Gioutsos

In the context of MSSM, a novel improving procedure based on the renormalization group equation is applied to the effective potential in the Higgs sector. We focus on the one-loop radiative corrections computed in Landau gauge by using the mass independent renormalization scheme $\bar{DR}$. Thanks to the decoupling theorem, the well-known multimass scale pro

Masahiro Anazawa

It is known that if we compactify D0-branes on a torus with constant B-field, the resulting theory becomes SYM theory on a noncommutative dual torus. We discuss the extension to the case of a H-field background. In the case of constant H-field on a three-torus, we derive the constraints to realize this compactification by considering the correspondence to st

J. X. Lu, Shibaji Roy

Recently the space-time configurations of a set of non-threshold bound states, called the (F, Dp) bound states, have been constructed explicitly for every $p$ with $2 \le p \le 7$ in both type IIA (for $p$ even) and type IIB (for $p$ odd) string theories by the present authors. By making use of the SL(2, Z) symmetry of type IIB theory we construct a more gen

Xiao-Guang Wang

We show that the three quantum states (P$\acute{o}$lya states, the generalized non-classical states related to Hahn polynomials and negative hypergeometric states) introduced recently as intermediates states which interpolate between the binomial states and negative binomial states are essentially identical. By using the Hermitial-phase-operator formalism, t

Yaoyun Shi

We prove that, to compute a Boolean function $f$ on $N$ variables with error probability $ε$, any quantum black-box algorithm has to query at least $\frac{1 - 2\sqrtε}{2} ρ_f N = \frac{1 - 2\sqrtε}{2} \bar{S}_f$ times, where $ρ_f$ is the average influence of variables in $f$, and $\bar{S}_f$ is the average sensitivity. It&#39;s interesting to contrast this r

Rosanna Pearlstein

We study compact stable embedded minimal surfaces whose boundary is given by two collections of closed smooth Jordan curves in close planes of Euclidean 3-space. Our main result is a classification of these minimal surfaces, under certain natural geometric asymptotic constraints, in terms of certain associated varifolds which can be enumerated explicitely. O

Michel Lassalle

We prove an identity about partitions with a very elementary formulation. We had previously conjectured this identity, encountered in the study of shifted Jack polynomials (math.CO/9901040). The proof given is using a trivariate generating function. It would be interesting to obtain a bijective proof. We present a conjecture generalizing this identity.

J. M. F. Labastida

A brief review on the progress made in the study of Chern-Simons gauge theory since its relation to knot theory was discovered ten years ago is presented. Emphasis is made on the analysis of the perturbative study of the theory and its connection to the theory of Vassiliev invariants. It is described how the study of the quantum field theory for three differ

L. Rezzolla, M. Shibata, H. Asada, T. W. Baumgarte

We present a new set of 3.5 Post-Newtonian equations in which Newtonian hydrodynamics is coupled to the nonconservative effects of gravitational radiation emission. Our formalism differs in two significant ways from a similar 3.5 Post-Newtonian approach proposed by Blanchet (1993, 1997). Firstly we concentrate only on the radiation-reaction effects produced

Barry C. Barish

Gravitational wave emission is expected to arise from a variety of astrophysical phenomena. A new generation of detectors with sensitivity consistent with expectation from such sources is being developed. The Laser Interferometer Gravitational-Wave Observatory (LIGO), one of these ambitious undertakings, is being developed by a Caltech-MIT collaboration. It

Alberto Saa

Gauss-Bonnet formula is used to derive a new and simple theorem of nonexistence of vacuum static nonsingular lorentzian wormholes. We also derive simple proofs for the nonexistence of lorentzian wormhole solutions for some classes of static matter such as, for instance, real scalar fields with a generic potential obeying $ϕV&#39;(ϕ) \ge 0$ and massless fermi

Jun-ichi Inoue, Akira Shimizu

We propose a new method of calculating nonlinear optical responses of interacting electronic systems. In this method, the total Hamiltonian (system + system-pump interaction) is transformed into a different form that (apparently) does not have a system-pump interaction. The transformed Hamiltonian, which we call the pump built-in Hamiltonian, has parameters

P. Raychaudhuri, S. Mukherjee, A. K. Nigam, J. John

La0.7Ce0.3MnO3 is a relatively new addition in the family of colossal magnetoresistive manganites where the cerium ion is believed to be in the Ce4+ state. In this paper we report an extensive study the magnetotransport properties of laser ablated La0.7Ce0.3MnO3 films on LaAlO3 with variation in ambient oxygen pressure during growth and film thickness. We ob

Sa-Lin Cheng, H. A. Fertig

We investigate the effect of a ferromagnetic dot on a thin-film superconductor. We use a real-space method to solve the linearized Ginzburg-Landau equation in order to find the upper critical field, H_c_3. We show that H_c_3 is crucially dependent on dot composition and geometry, and may be significantly greater than H_c_2. H_c_3 is maximally enhanced when (

Raul O. Vallejos, Marcos Saraceno

We present a method for constructing a quantum Markov partition. Its elements are obtained by quantizing the characteristic function of the classical rectangles. The result is a set of quantum operators which behave asymptotically as projectors over the classical rectangles except from edge and corner effects. We investigate their spectral properties and dif

Raul O. Vallejos, Alfredo M. Ozorio de Almeida

Scattering on the energy shell is viewed here as the relation between the bound states of the Hamiltonian, restricted to sections on leads that are asymptotically independent, far away from the interaction region. The decomposition is achieved by sectioning this region and adding new leads, thus generating two new scatterers. So a resonant scatterer, whose $

Alfredo M. Ozorio de Almeida, Raul O. Vallejos

A scattering process can be described by suitably closing the system and considering the first return map from the entrance onto itself. This scattering map may be singular and discontinuous, but it will be measure preserving as a consequence of the recurrence theorem applied to any region of a simpler map. In the case of a billiard this is the Birkhoff map.

R. Benzi, M. Marrocu, A. Mazzino, E. Trovatore

Methods to quantify predictability properties of atmospheric flows are proposed. The ``Extended Self Similarity&#39;&#39; (ESS) technique, recently employed in turbulence data analysis, is used to characterize predictability properties at short and long times. We apply our methods to the low-order atmospheric model of Lorenz (1980). We also investigate how i

Ju-Fu Lu, Wei-Min Gu, Feng Yuan

We numerically solve the set of dynamical equations describing advection-dominated accretion flows (ADAF) around black holes, using a method similar to that of Chakrabarti (1996a). We choose the sonic radius of the flow $R_s$ and the integration constant in angular momentum equation $j$ as free parameters, and integrate the equations from the sonic point inw

James Robinson, Jonathan E. Baker

We carry out N-body simulations of several non-Gaussian structure formation models, including Peebles&#39; isocurvature cold dark matter model, cosmic string models, and a model with primordial voids. We compare the evolution of the cluster mass function in these simulations with that predicted by a modified version of the Press-Schechter formalism. We find

Thomas S. Statler

The nuclear rotation curve of M31, as observed by the Hubble Space Telescope Faint Object Camera Spectrograph, shows a significant disturbance coinciding with the off-center brightness peak, P1. This +/- 60 km/s feature is distinguished by a local velocity maximum centered on P1 and a local minimum approxmately 0.08&#34; closer to P2. If the M31 double nucle

Xin-he Meng

The early Universe inflation is well known as a promising theory to explain the origin of large scale structure of the Universe, a causal theory for the origin of primordial density fluctuations which may explain the observed density inhomogeneities and cosmic microwave fluctuations in the very early Universe, and to solve the early universe pressing problem

M. Joyce, M. Montuori, F. Sylos Labini, L. Pietronero

In a recent analysis of number counts in the ESP survey Scaramella et al. (1998) claim to find evidence for a cross-over to homogeneity at large scales, and against a fractal behaviour with dimension $D \approx 2$. In this comment we note firstly that, if such a cross-over exists as described by the authors, the scale characterizing it is ~ 100 - 300 Mpc/h.

Asantha R. Cooray

It is now well known that a combined analysis of the Sunyaev-Zel&#39;dovich (SZ) effect and the X-ray emission observations can be used to determine the angular diameter distance to galaxy clusters, from which the Hubble constant is derived. Given that the SZ/X-ray Hubble constant is determined through a geometrical description of clusters, the accuracy to w

I. Reinhard, C. Callegari, A. Conjusteau, K. K. Lehmann

Purely rotational transitions of a molecule, such as HCCCN, embedded in large $^4$He clusters have been detected for the first time. The saturation behavior shows that, in contrast to previous expectations, the microwave line profiles are dominated by inhomogeneous broadening mechanisms. Spectral holes and peaks produced by microwave-microwave double resonan

Jason Rhodes, Alexandre Refregier, Ed Groth

The weak distortions produced by gravitational lensing in the images of background galaxies provide a method to measure directly the distribution of mass in the universe. However this technique requires high precision measurements of the lensing shear and cautious corrections for systematic effects. Kaiser, Squires, & Broadhurst (1995) proposed a method to c

Eric Dennis

It has been known that quantum error correction via concatenated codes can be done with exponentially small failure rate if the error rate for physical qubits is below a certain accuracy threshold. Other, unconcatenated codes with their own attractive features-improved accuracy threshold, local operations-have also been studied. By iteratively distilling a c

K. Farakos, G. Koutsoumbas, N. E. Mavromatos, Arshad Momen

In this paper, we discuss the role of an external magnetic field on the dynamically generated fermion mass in even-flavor QED in three space-time dimensions. Based on some reasonable approximations, we present analytic arguments on the fact that, for weak fields, the magnetically-induced mass increases quadratically with increasing field, while at strong fie

A. I. Solomon, Y. Feng, V. Penna

We construct a macroscopic wave function that describes the Bose-Einstein condensate and weakly excited states, using the su(1,1) structure of the mean-field hamiltonian, and compare this state with the experimental values of second and third order correlation functions.

B. Nadgorny, R. J. Soulen,, M. S. Osofsky, I. I. Mazin

We present measurements of the transport spin polarization of Ni_xFe_{1-x} (0<x<1) using the recently-developed Point Contact Andreev Reflection technique, and compare them with our first principles calculations of the spin polarization for this system. Surpisingly, the measured spin polarization is almost composition-independent. The results clearly demonst

T. Gaitanos, H. H. Wolter, C. Fuchs

We analyze the thermodynamical state of nuclear matter in transport calculations of heavy--ion reactions. In particular we determine temperatures and radial flow parameters from an analysis of fragment energy spectra and compare to local microscopic temperatures obtained from an analysis of local momentum space distributions. The analysis shows that the spec

Mladen Prester

We report on our experimental evidence of a substantial geometrical ingredient characterizing the problem of incipient dissipation in high-T_c superconductors(HTS): high-resolution studies of differential resistance-current characteristics in absence of magnetic field enabled us to identify and quantify the fractal dissipative regime inside which the actual

W. Chen

Based on the matrix expression of general nonlinear numerical analogues presented by the present author, this paper proposes a novel philosophy of nonlinear computation and analysis. The nonlinear problems are considered an ill-posed linear system. In this way, all nonlinear algebraic terms are instead expressed as Linearly independent variables. Therefore,

Z. Farkas, P. Tegzes, A. Vukics, T. Vicsek

Motivated by recent advances in the investigation of fluctuation-driven ratchets and flows in excited granular media, we have carried out experimental and simulational studies to explore the horizontal transport of granular particles in a vertically vibrated system whose base has a sawtooth-shaped profile. The resulting material flow exhibits novel collectiv

G. Baur, C. A. Bertulani, D. Dolci

We study the effect of the spreading widths on the excitation probabilities of the double giant dipole resonance. We solve the coupled-channels equations for the excitation of the giant dipole resonance and the double giant dipole resonance. Taking Pb+Pb collisions as example, we study the resulting effect on the excitation amplitudes, and cross sections as

Boris Konopelchenko, Luis Martinez Alonso

A systematic reformulation of the KP hierarchy by using continuous Miwa variables is presented. Basic quantities and relations are defined and determinantal expressions for Fay&#39;s identities are obtained. It is shown that in terms of these variables the KP hierarchy gives rise to a Darboux system describing an infinite-dimensional conjugate net.

P. Petreczky, Zs. Szep, A. Patkos

The complete set of static screening masses is determined for the SU(2) Higgs model from one-loop coupled gap equations. Results from the version, containing scalar fields both in the fundamental and adjoint representations are compared with the model arising when the integration over the adjoint scalar field is performed. A non-perturbative and non-linear m

Tom Richtler, Georg Drenkhahn, Matias Gomez, Wilhelm Seggewiss

Type Ia supernovae are the best cosmological standard candles available. The intrinsic scatter of their decline-rate- and colour-corrected peak brightnesses in the Hubble diagram is within observational error limits, corresponding to an uncertainty of only 3km/s/Mpc of the Hubble constant. Any additional uncertainty, resulting from peak-brightness calibratio

F. Green, M. P. Das

We argue, physically and formally, that existing diffusive models of noise yield inaccurate microscopic descriptions of nonequilibrium current fluctuations. The theoretical shortfall becomes pronounced in quantum-confined metallic systems, such as the two-dimensional electron gas. In such systems we propose a simple experimental test of mesoscopic validity f

Youngman Kim, Hyun Kyu Lee

We calculate the density dependence of the $ρ$-meson mass and coupling constant($g_{ρNN}$) for $ρ$-nucleon-nucleon vertex at one loop using the lagrangian where the $ρ$-meson is included as a dynamical gauge boson of a hidden local symmetry. From the condition that thermodynamic potential should not depend on the arbitrary energy scale, renormalization scale

Warren G. Anderson, R. Balasubramanian

We present a time-frequency method to detect gravitational wave signals in interferometric data. This robust method can detect signals from poorly modeled and unmodeled sources. We evaluate the method on simulated data containing noise and signal components. The noise component approximates initial LIGO interferometer noise. The signal components have the ti

Richard J. Nelson, David G. Cory, Seth Lloyd

The Greenberger-Horne-Zeilinger (GHZ) effect provides an example of quantum correlations that cannot be explained by classical local hidden variables. This paper reports on the experimental realization of GHZ correlations using nuclear magnetic resonance (NMR). The NMR experiment differs from the originally proposed GHZ experiment in several ways: it is perf

Andris Ambainis, Richard Bonner, Rusins Freivalds, Marats Golovkins

Quantum finite automata were introduced by C.Moore, J.P. Crutchfield, and by A.Kondacs and J.Watrous. This notion is not a generalization of the deterministic finite automata. Moreover, it was proved that not all regular languages can be recognized by quantum finite automata. A.Ambainis and R.Freivalds proved that for some languages quantum finite automata m

M. D. Lukin, P. R. Hemmer

Two-photon optical transitions combined with long-range dipole-dipole interactions can be used for the coherent manipulation of collective metastable states composed of different atoms. We show that it is possible to induce optical resonances accompanied by the generation of entangled superpositions of the atomic states. Resonances of this kind can be used t

Lucien Hardy, David D. Song

We show that the condition of no faster-than-light signalling restricts the number of quantum states that can be cloned in a given Hilbert space. This condition leads to the constraints on a probabilistic quantum cloning machine (PQCM) recently found by Duan and Guo.