April 1998 arXiv papers — page 4

J. B. Oke, Marc Postman, Lori Lubin

We present a description of the observations and data reduction procedures for an extensive spectroscopic and multi-band photometric study of nine high redshift, optically-selected cluster candidates. The primary goal of the survey is to establish new constraints on cluster and galaxy evolution, with specific emphasis on the evolution of galaxy morphology an

Piero Madau

The history of the transition from a neutral intergalactic medium to one that is almost fully ionized can reveal the character of cosmological ionizing sources. In this talk I will discuss the implications for rival reionization scenarios of the rapid decline observed in the space density of quasars and star-forming galaxies at redshifts z>3. The hydrogen co

Ren Xin Xu, Guo Jun Qiao

It is suggested in this paper that the `bare' strange star might be not bare, and there could be a magnetosphere around it. As a strange star might be an intensely magnetized rotator, the induced unipolar electric field would be large enough to construct a magnetosphere around the strange matter core. This kind of magnetosphere is very similar to that of

Roman Juszkiewicz, Karl B. Fisher, Istvan Szapudi

Using an Eulerian perturbative calculation, we show that the distribution of relative pairwise velocities which arises from gravitational instability of Gaussian density fluctuations has asymmetric (skewed) exponential tails. The negative skewness is induced by the negative mean streaming velocity of pairs (the infall prevails over expansion), while the expo

Alessandro B. Romeo

Modelling gravity is a fundamental problem that must be tackled in N-body simulations of stellar systems, and satisfactory solutions require a deep understanding of the dynamical effects of softening. In a previous paper (Romeo 1997), we have devised a method for exploring such effects, and we have focused on two applications that reveal the dynamical differ

H. Quaintrell, R. P. Fender

We present JHK photometry and spectroscopy of RX J0019.8+2156. The spectrum appears to be dominated by the accretion disc to at least 2.4 microns, over any other source of emission. We find Paschen, Brackett and HeII lines strongly in emission, but no HeI. There are satellite lines approximately 850km/s either side of the strongest, unblended hydrogen lines.

R. A. Burenin, A. A. Vikhlinin, O. V. Terekhov, S. Yu. Sazonov

We search for angular correlation of gamma-ray bursts with cataloged quasars, BL Lac objects, and AGN using a large sample of relatively well-localized bursts detected by WATCH on board GRANAT and EURECA, IPN, and BATSE (327 bursts total). A statistically significant (99.99% confidence) correlation between GRB and M_B<-21 AGN in the redshift range 0.1<z<0.32

V. Rezania, Y. Sobouti

The post-Newtonian approximation of general relativistic Liouville&#39;s equation is presented. Two integrals of it, generalizations of the classical energy and angular momentum, are obtained. Polytropic models are constructed as an application.

T. M. Aliev, M. Savci

The radiative B_c -> l nu gamma decay is investigated in the Standard Model in framework of the light cone QCD. The transition form factors and decay width are calculated. A comparison of light cone QCD and constituent quark model predictions on these quantities is presented.

R. De Pietri, L. Freidel

In this note we study the correspondence between the ``relativistic spin foam&#39;&#39; model introduced by Barrett, Crane and Baez and the so(4) Plebanski action. We argue that the $so(4)$ Plebanski model is the continuum analog of the relativistic spin foam model. We prove that the Plebanski action possess four phases, one of which is gravity and outline t

Bozhidar Z. Iliev

We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one but it is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it a pure state of some quantum system is described by a state section (a

M. Kleckner, A. Ron

It is demonstrated that an electromagnetic pulse, which is made to tunnel trough a barrier, would not be photo-detected before an identical pulse, which travels the same distance in vacuum.

Cristian D. Gonzalez-Avilés

Let $K/F$ be a finite Galois extension of number fields with Galois group $G$, let $A$ be an abelian variety defined over $F$, and let ${\cyr W}(A_{^{/ K}})$ and ${\cyr W}(A_{^{/ F}})$ denote, respectively, the Tate-Shafarevich groups of $A$ over $K$ and of $A$ over $F$. Assuming that these groups are finite, we derive, under certain restrictions on $A$ and

V. R. Zoller

The color dipole gBFKL phenomenology of a diffraction cone for photo- and electroproduction $γ^{*}N \to VN$ of heavy vector mesons (charmonium & bottonium) at HERA and in fixed target experiments is presented. A substantial shrinkage of the diffraction cone from the CERN/FNAL to the HERA range of c.m.s. energy $W$ is predicted. The $Q^{2}$-controlled selecti

V. R. Zoller

The running BFKL equation gives rise to a series of moving poles in the complex $j$-plane. The first nodes for all subleading solutions (color dipole cross sections) accumulate at $r_1\sim 0.1 fm$.Therefore the processes dominated by the dipole sizes $r\sim r_1 $ are free of subleading BFKL corrections. An example - the leptoproduction of charm. The calculat

E. Gotsman, E. Levin, U. Maor

The energy dependence for the survival probability of large rapidity gaps (LRG) $< \mid S \mid^2 >$, is calculated in an Eikonal model assuming a Gaussian opacity. The parameters determining $< \mid S \mid^2 >$ are evaluated directly from experimental data, without further recourse to models. We find that $< \mid S \mid^2 >$ decreases with increasing energy,

A. Sinkovics, R. Akhoury, V. I. Zakharov

We consider the infrared sensitivity of the inclusive heavy quark decay width in perturbation theory. It is shown by explicit calculations to the second loop order (when the non-abelian nature of the QCD interactions first become apparent) that all infrared sensitive terms to logarithmic and linear accuracy cancel when the decay width is expressed in terms o

Aleksandar Bogojevic, Dejan Stojkovic

We present a completely integrable deformation of the CGHS dilaton gravity model in two dimensions. The solution is a singularity free black hole that at large distances asymptoticaly joins to the CGHS solution.

Giorgio Fontana

Recent measurements on a class of high-Tc superconductors (HTSC) have shown that Cooper-pairs binding may be associated to a d-wave, while in another class, d and s waves may coexist. When d-wave Cooper-pairs are injected in a superconductor that can sustain s-wave binding, d-wave pairs decay to s-wave pairs and energy is irradiated by means of gravitons. We

Cheongho Han, Youngjin Jeong

Currently, 6 candidate binary lens events have been reported, while only a single candidate binary source event has been reported. To account for the rarity of binary source events, Dominik pointed out that for a typical binary source event the separation between the component source stars is very large, resulting in large difference in impact parameters bet

Cheongho Han, Youngjin Jeong

Recently Alard\markcite{alard1996} proposed to detect the shift of a star&#39;s image centroid, $δx$, as a method to identify the lensed source among blended stars. Goldberg & Woźniak\markcite{goldberg1997} actually applied this method to the OGLE-1 database and found that 7 out of 15 events showed significant centroid shifts of $δx \gtrsim 0.2$ arcsec. The

Osamu Yasuda

Superkamiokande atmospheric neutrino data for 535 days are analyzed in the framework of three flavor oscillations with mass hierarchy. It is shown that the best fit point is very close to the pure maximal $\nu_\mu\leftrightarrow\nu_\tau$ case and $\Delta m^2 \simeq 7\times10^{-3}$ eV$^2$. The allowed region at 90 %CL is given and the implications to the long

Arsen G. Khachatryan

The influence of motion of ions and electron temperature on nonlinear one-dimensional plasma waves with velocity close to the speed of light in vacuum is investigated. It is shown that although the wavebreaking field weakly depends on mass of ions, the nonlinear relativistic wavelength essentially changes. The nonlinearity leads to the increase of the strong

Koji Hashimoto, Hiroyuki Hata, Naoki Sasakura

Extending our previous work on SU(3), we construct spherically symmetric BPS saturated regular configurations of N=4 SU(N) supersymmetric Yang-Mills theory preserving 1/4 supersymmetry, and investigate their features. We also give exact solutions in the case some of the free parameters of the general solutions take certain values. These field theory BPS stat

Nobuyuki Ishibashi

We show that Dirichlet p-brane can be expressed as a configuration of infinitely many Dirichlet (p-2)-branes in the bosonic string theory. Using this fact, we interpret the massless fields on the p-brane worldvolume as deformations of the configuration of the (p-2)-branes. Especially we find that the worldvolume gauge field parametrizes part of the group of

Sunggoo Cho

We find the covariant deformed Heisenberg algebra and the Laplace-Beltrami operator on the extended $h$-deformed quantum plane and solve the Schrödinger equations explicitly for some physical systems on the quantum plane. In the commutative limit the behaviour of a quantum particle on the quantum plane becomes that of the quantum particle on the Poincaré hal

Bishwajyoti Dey, Avinash Khare

The stability of the recently discovered compacton solutions is studied by means of both linear stability analysis as well as Lyapunov stability criteria. From the results obtained it follows that, unlike solitons, all the allowed compacton solutions are stable, as the stability condition is satisfied for arbitrary values of the nonlinearity parameter. The r

D. Bazeia, E. P. Raposo

We investigate the presence of soliton solutions in some classes of nonlinear partial differential equations, namely generalized Korteweg-de Vries-Burgers, Korteveg-de Vries-Huxley, and Korteveg-de Vries-Burgers-Huxley equations, which combine effects of diffusion, dispersion, and nonlinearity. We emphasize the chiral behavior of the travelling solutions, wh

Tewodros Amdeberhan

Using WZ pairs we present an infinite family of accelerated series for computing $ζ(3)$.

Giovanni Porru, Tewodros Amdeberhan, S. Vernier-Piro

In this paper we investigate maximum principles for functionals defined on solutions to special partial differential equations of elliptic type, extending results by Payne and Philippin. We apply such maximum principles to investigate one overdetermined problem.

Tewodros Amdeberhan, Shalosh B. Ekhad

We give a generalization and a short mechanized proof of determinant conjectured by G. Kuperberg and J. Propp. Further generalizations and applications of the method to some q-analogues may be found in http://www.math.temple.edu/~tewodros

A. Corti, M. Hanamura

For a quasiprojective variety S, we define a category CHM(S) of pure Chow motives over S. Assuming conjectures of Grothendieck and Murre, we show that the decomposition theorem holds in CHM(S). As a consequence, the intersection complex of S makes sense as an object IS of CHM(S). In the forthcoming part II we will give an unconditional definition of intersec

George Jaroszkiewicz, Keith Norton

Principles of discrete time mechanics are applied to the quantisation of Maxwell&#39;s equations. Following an analysis of temporal node and link variables, we review the classical discrete time equations in the Coulomb and Lorentz gauges and conclude that electro-magneto duality does not occur in pure discrete time electromagnetism. We discuss the role of b

E. Sassaroli

A physical model which describes the CKM matrix is analyzed. The elements of such a matrix are field-strength renormalization factors. Each column gives the probability amplitude for the field operators of the coupled Lagrangian to create a one-particle eigenfunction of definite energy. The total conserved charge is the sum of the flavor charges which are no

Alexander V. Vereshagin, Vladimir V. Vereshagin

In this paper (second in the series) we study the properties of tree-level binary amplitudes of the infinite-component effective field theory of strong interaction obeying the requirements of quark-hadron duality and maximal analyticity. In contrast to the previous paper, here we derive the results following from less restrictive --- Regge-like --- boundedne

Tadashi Kadowaki, Hidetoshi Nishimori

We introduce quantum fluctuations into the simulated annealing process of optimization problems, aiming at faster convergence to the optimal state. Quantum fluctuations cause transitions between states and thus play the same role as thermal fluctuations in the conventional approach. The idea is tested by the transverse Ising model, in which the transverse fi

F. Frontera, J. Greiner, L. A. Antonelli, E. Costa

We report results of a ROSAT High-Resolution Imager (HRI) observation of the X-ray error box given by the BeppoSAX Wide Field Camera for the gamma-ray burst that occurred on 1997 February 28. The observation started 10 days after the burst and ended three days later, with a total exposure of 34.3 ks. An X-ray source was detected within the 3&#39; WFC error b

S. V. Bashinsky, R. L. Jaffe

We suggest a method of constructing gauge invariant quark and gluon distributions that describe an abstract QCD observable and apply this method to analyze angular momentum of a hadron. In addition to the known quark and gluon polarized structure functions, we obtain gauge invariant distributions for quark and gluon orbital angular momenta, and consider some

Xin-Nian Wang

Because of the rapidly falling particle spectrum at large $p_T$ from jet fragmentation at the CERN SPS energy, the high-$p_T$ hadron distribution should be highly sensitive to parton energy loss inside a dense medium as predicted by recent perturbative QCD (pQCD) studies. A careful analysis of recent data from CERN SPS experiments via pQCD calculation shows

H. J. Weber

The spin fractions and deep inelastic structure functions of the proton are analyzed using chiral field theory involving Goldstone bosons. A detailed comparison with recent chiral models sheds light on their successful description of the spin fractions of the proton as being due to neglecting helicity non-flip chiral transitions. This approximation is valid

R. Cabanac, E. F. Borra, M. Beauchemin

The NASA Orbital Debris Observatory (NODO) astronomical survey uses a transit 3-m liquid mirror telescope to observe a strip of sky in 20 narrow-band filters. In this article, we analyze a subset of data from the 1996 observing season. The catalog consists of 18,000 objects with 10<V<19 observed in 10 narrow-band filters ranging from 500 nm to 950 nm. We fir

Hitoshi Nishino

We show that parity is conserved in vector-like supersymmetric theories, such as supersymmetric QCD with massive quarks with no cubic couplings among chiral multiplets, based on fermionic path-integrals, originally developed by Vafa and Witten. We also look into the effect of supersymmetric breaking through gluino masses, and see that the parity-conservation

Eric G. Blackman

The $α$ turbulent viscosity formalism for accretion discs must be interpreted as a mean field theory. The extent to which the disc scale exceeds that of the turbulence determines the precision of the predicted luminosity $L_ν$. The assumption of turbulence and use of $\a$ implies: (1) Field line stretching generates a magnetic pressure $\gsim \a^2/6$ of the

M. Benayoun, H. B. O&#39;Connell

We study the various existing implementations of SU(3) breaking in the Hidden Local Symmetry model for the low energy hadronic sector following a mechanism originally proposed by Bando, Kugo and Yamawaki (BKY). We pay particular attention to hermiticity and current conservation. Following this, we present a new method for including symmetry breaking effects

R. S. Willey

We consider the subtleties involved in the application of the Equivalence Theorem to the decay of an unstable Higgs particle. This is formally justified from consideration of unitarity and resonant elastic scattering of the stable decay products. By explicit perturbative calculation we find that the imaginary parts of the one-loop amplitudes for that decay a

Valeria Ferrari, Sabino Matarrese, Raffaella Schneider

We analyse the stochastic background of gravitational radiation emitted by a cosmological population of core-collapse supernovae. The supernova rate as a function of redshift is deduced from an observation-based determination of the star formation rate density evolution. We then restrict our analysis to the range of progenitor masses leading to black hole co

Kenji Sakamoto, Kiyoshi Shiraishi

An exact solution for a nonrotating boson star in (2+1) dimensional gravity with a negative cosmological constant is found. The relations among mass, particle number, and radius of the (2+1) dimensional boson star are shown.

Q. H. Zhang

Any-order pion inclusive distribution for a chaotic source in high energy collisions are given which can be used in both theory and experiment to analyze any-order pion interferometry. Multi-pion correlations effects on two-pion and three-pion interferometry are discussed.

Thorsten Emig, Thomas Nattermann

The behavior of interfaces in the presence of both lattice pinning and random field (RF) or random bond (RB) disorder is studied using scaling arguments and functional renormalization techniques. For the first time we show that there is a continuous disorder driven roughening transition from a flat to a rough state for internal interface dimensions 2<D<4. Th

E. Brézin, C. De Dominicis

We reconsider Ising spins in a Gaussian random field within the replica formalism. The corresponding continuum model involves several coupling constants beyond the single one which was considered in the standard $ϕ^4$ theory approach. These terms involve more than one replica, and therefore in a mean field theory they do not contribute to the zero-replica li

Peter Huebner

This is the first of a series of papers describing a numerical implementation of the conformally rescaled Einstein equation, an implementation designed to calculate asymptotically flat spacetimes, especially spacetimes containing black holes. In the present paper we derive the new first order time evolution equations to be used in the scheme. These time evol

A. Pelissetto, P. Rossi, E. Vicari

We study the crossover between classical and nonclassical critical behaviors. The critical crossover limit is driven by the Ginzburg number G. The corresponding scaling functions are universal with respect to any possible microscopic mechanism which can vary G, such as changing the range or the strength of the interactions. The critical crossover describes t

M. Kiselev, F. Bouis, F. Onufrieva, P. Pfeuty

We study the ordered &#34;excitonic&#34; states which develop around the quantum critical point (QCP) associated with the electronic topological transition (ETT) in a 2D electron system on a square lattice. We consider the case of hopping beyond nearest neighbors when ETT has an unusual character. We show that the amplitude of the order parameter (OP) and of

Masahiro Kubo, Ziro Maki, Mikio Nakahara, Takesi Saito

The SU(5) grand unified theory (GUT) is derived from the geometrical point of view of gauge theory on three-sheeted space-time, i.e., $M_4 \times Z_3$ manifold without recourse to noncommutative geometry. A derivation of SO(10) GUT is also discussed in the same point of view.

Y. Ashkenazy, M. Lewkowicz, J. Levitan, H. Moelgaard

We demonstrate that it is possible to distinguish with a complete certainty between healthy subjects and patients with various dysfunctions of the cardiac nervous system by way of multiresolutional wavelet transform of RR intervals. We repeated the study of Thurner et al on different ensemble of subjects. We show that reconstructed series using a filter whic

Andreas W. Schreiber, Tom Sizer, Anthony G. Williams

We study the dimensionally regularized fermion propagator Dyson-Schwinger equation in quenched nonperturbative QED. We work in arbitrary covariant gauge and perform nonperturbative renormalization numerically. The nonperturbative fermion propagator is solved in D = 4 - 2 * epsilon dimensional Euclidean space for a large number of values of epsilon. Results f

C. M. Bhat, P. C. Bhat, M. Paterno, H. B. Prosper

We present a study of recent solar neutrino data using a Bayesian method. Assuming that only $ν_e$ are observed in the Super-Kamiokande experiment our results show a marked supression of the survival probability at about 1 MeV, in good agreement with $χ^2$-based analyses. When the detection of $ν_μ$ by Super-Kamiokande is taken into account, assuming $ν_e$ t

J. G. Naeini, X. K. Chen, J. C. Irwin, M. Okuya

We report the results of Raman scattering experiments on single crystals of La(2-x)Sr(x)CuO(4) that span the range from underdoped (x = 0.10) to overdoped (x =0.22). The spectra are consistent with the existence of a strong anisotropic quasiparticle interaction that results in a normal state depletion of spectral weight from regions of the Fermi surface loca

Leonard J. Schulman, Umesh Vazirani

Nuclear magnetic resonance offers an appealing prospect for implementation of quantum computers, because of the long coherence times associated with nuclear spins, and extensive laboratory experience in manipulating the spins with radio frequency pulses. Existing proposals, however, suffer from a signal-to-noise ratio that decays exponentially in the number

H. B. Nersisyan, C. Deutsch

The results of a theoretical investigation on the stopping power of ion pair in a magnetized electron plasma are presented, with particular emphasis on the two-ion correlation effects. The analysis is based on the assumptions that the magnetic field is classically strong ($λ_B\ll a_c\ll λ_D$, where $λ_B$, $a_c$ and $λ_D$ are respectively the electron de Brog

G. Parzen

Tracking studies have indicated that for a lattice whose elements all have a single field multipole present, all having the same order k, the dynamic aperture approaches a non zero limit when k becomes very large. The dynamic aperture and other properties of the lattice, as k becomes large, will be called the high multipole limit. It will be shown that the h

R. Rapp

Medium Effects in low-mass dilepton production in ultra-relativistic heavy-ion collisions are investigated using hadronic models. The rescattering of pions and rho mesons within a hot and dense hadron gas leads to substantial modifications in the $π^+π^- \to e^+ e^-$ annihilation process, which are shown to be important for understanding the recently observe

U. Eichmann, J. Reinhardt, W. Greiner, S. Schramm

We calculate the asymptotic high-energy amplitude for electrons scattering at one ion as well as at two colliding ions, respectively, by means of perturbation theory. We show that the interaction with one ion eikonalizes and that the interaction with two ions causally decouples. We are able to put previous results on perturbative grounds and propose further

Tewodros Amdeberhan, Doron Zeilberger

Using WZ forms, Apery-style proofs of the irrationality of the q-analogues of the Harmonic seires and Ln(2) are given. For the q-analogue of Ln(2), this method of proof produces an improved irrationality measure.

Tewodros Amdeberhan, Doron Zeilberger

Based on the WZ method, some series acceleration formulas are given. These formulas allow to write down an infinite family of parametrized identities from any given identity of WZ type. Further, this family, in the case of the Riemann Zeta function, gives rise to many accelerated expressions for $ζ(3)$. The present method produced a formula, given at the end

Sagun Chanillo, Michael Kiessling

For certain nonlinear elliptic PDE problems in two dimensions, the classical isoperimetric inequality produces a sharp inequality that violates a Pohozaev identity except for radial symmetric, decreasing solutions. A generalized version of this technique is used here to prove radial symmetry of curl-free Ginzburg-Landau vortices.

Ilka Agricola, Thomas Friedrich

We prove that the ring $\Aff{\R}{M}$ of all polynomials defined on a real algebraic variety $M\subset\R^n$ is dense in the Hilbert space $L^2(M,e^{-|x|^2}\deμ)$, where $\deμ$ denotes the volume form of $M$ and $\deν=e^{-|x|^2}\deμ$ the Gaussian measure on $M$.

I. Antoniadis, N. Arkani-Hamed, S. Dimopoulos, G. Dvali

Recently, a new framework for solving the hierarchy problem has been proposed which does not rely on low energy supersymmetry or technicolor. The gravitational and gauge interactions unite at the electroweak scale, and the observed weakness of gravity at long distances is due the existence of large new spatial dimensions. In this letter, we show that this fr

Gunn A. Quznetsov

The Clifford pentad of the 4X4 matrices defines the 5-dimensional space. Each weak isospin transformation divides an electron on two components, which scatter in the 2-dimensional subspace and which indiscernible in the orthogonal 3-dimensional subspace. PACS 12.15.-y

Paul H. Frampton

In this talk I begin with some general discussion of the history of CP violation, then move on to aspects of the aspon model including the production of new particles at LHC, implications for B decay, generalized Cabibbo mixing and a reevaluation of kaon CP violation. Finally there is a summary.

David Atwood, Amarjit Soni

A systematic experimental search for two-body hadronic decays of the b-quark of the type b to quark + meson is proposed. These reactions have a well defined experimental signature and they should be theoretically cleaner compared to exclusive decays. Many modes have appreciable branching ratios and partial rate asymmetries may also be quite large (about 8-50

J. Bernabeu, D. Gomez Dumm, J. Vidal

We show that the $ηγZ$ anomaly can be measured by analysing parity-violating effects in the $η-->γμ+μ-$ decay. In this sense, we find that the longitudinal polarization of the outgoing $μ^+$ is an appropriate observable to be considered in future high-statistics $η$ factories. The effect is expected to lie in the range $10^{-5}-10^{-6}$ in the Standard Model

A. A. Andrianov, P. Osland, A. A. Pankov, N. V. Romanenko

The phenomenology of an additional U(1) neutral gauge boson Z&#39; coupled to the third family of fermions is discussed. One might expect such a particle to contribute to processes where taus, b and t quarks are produced. Precision data from LEP1 put severe constraints on the mixing and heavy-boson mass. We find that the effects of such a particle could not

Andreas Hauck, Reinhard Alkofer, Lorenz von Smekal

A truncation scheme for the Dyson-Schwinger equations of QCD in Landau gauge is presented which implements the Slavnov-Taylor identities for the 3-point vertex functions. Neglecting contributions from 4-point correlations such as the 4-gluon vertex function and irreducible scattering kernels, a closed system of equations for the propagators is obtained. For

R. N. Lee, A. I. Milstein, V. M. Strakhovenko

Various differential cross sections of high-energy photon splitting in the electric fields of heavy atoms are calculated exactly in the parameter \al. The consideration is based on the quasiclassical approach applicable for small angles between all photon momenta. The expressions obtained are valid for arbitrary transverse momenta of final photons . The deta

Jose Socorro, Alfredo Macias, Friedrich W. Hehl

Computer algebra programs are presented for application in general relativity, in electrodynamics, and in gauge theories of gravity. The mathematical formalism used is the calculus of exterior differential forms, the computer algebra system applied Hearn&#39;s Reduce with Schruefer&#39;s exterior form package Excalc. As a non-trivial example we discuss a met

Luis C. B. Crispino, Atsushi Higuchi, George E. A. Matsas

We investigate whether the equality found for the response of static scalar sources interacting (i) with {\em Hawking radiation in Schwarzschild spacetime} and (ii) with the Fulling-Davies-Unruh thermal bath in the Rindler wedge is maintained in the case of electric charges. We find a finite result in the Schwarzschild case, which is computed exactly, in con

K. A. Bronnikov, G. Clement, C. P. Constantinidis, J. C. Fabris

We study the structure and stability of spherically symmetric Brans-Dicke black-hole type solutions with an infinite horizon area and zero Hawking temperature, existing for negative values of the coupling constant $ω$. These solutions split into two classes, depending on finite (B1) or infinite (B2) proper time needed for an infalling particle to reach the h

Giovanni Amelino-Camelia

I investigate the relation between an operative definition of the area of a surface specified by matter fields and the area operators recently introduced in the canonical/loop approach to Quantum Gravity and in Rovelli&#39;s variant of the Husain-Kuchar Quantum-Gravity toy model. The results suggest that the discreteness of the spectra of the area operators

R. Mikulla, J. Stadler, F. Krul, H. -R. Trebin

Crack propagation is studied in a two dimensional decagonal model quasicrystal. The simulations reveal the dominating role of highly coordinated atomic environments as structure intrinsic obstacles for both dislocation motion and crack propagation. For certain overloads, these obstacles and the quasiperiodic nature of the crystal result in a specific crack p

Lene Vestergaard Hau, B. D. Busch, Chien Liu, Zachary Dutton

We present quantitative measurements of the spatial density profile of Bose-Einstein condensates of sodium atoms confined in a new &#39;4D&#39; magnetic bottle. The condensates are imaged in transmission with near resonant laser light. We demonstrate that the Thomas-Fermi surface of a condensate can be determined to better than 1%. More generally, we obtain

Lene Vestergaard Hau, B. D. Busch, Chien Liu, Michael M. Burns

We have succeded in creating Bose-Einstein condensates with 2 million sodium atoms in a &#39;4D&#39; magnetic trap. We show the dynamic formation of a condensate as evaporative cooling proceeds. We also present a series of trap-release pictures clearly showing the distinctly different modes of expansion of condensate and thermal cloud. We further give two ex

A. T. Yinnon, D. A. Lidar, R. B. Gerber, P. Zeppenfeld

An approach based on He scattering is used to develop an atomic-level structural model for an epitaxially grown disordered sub-monolayer of Ag on Pt(111) at 38K. Quantum scattering calculations are used to fit structural models to the measured angular intensity distribution of He atoms scattered from this system. The structure obtained corresponds to narrowl

Rolf Nicodemus, Siegfried Grossmann, Martin Holthaus

We present numerical solutions to the extended Doering-Constantin variational principle for upper bounds on the energy dissipation rate in plane Couette flow, bridging the entire range from low to asymptotically high Reynolds numbers. Our variational bound exhibits structure, namely a pronounced minimum at intermediate Reynolds numbers, and recovers the Buss

Rolf Nicodemus, Siegfried Grossmann, Martin Holthaus

We present numerical solutions to the extended Doering-Constantin variational principle for upper bounds on the energy dissipation rate in turbulent plane Couette flow. Using the compound matrix technique in order to reformulate this principle&#39;s spectral constraint, we derive a system of equations that is amenable to numerical treatment in the entire ran

David J. Bergeron, Wilfried Clauss, Denis L. Pilloud, P. Leslie Dutton

We have used scanning probe microscopy to investigate self-assembled monolayers of chemically synthesized peptides. We find that the peptides form a dense uniform monolayer, above which is found a sparse additional layer. Using scanning tunneling microscopy, submolecular resolution can be obtained, revealing the alpha helices which constitute the peptide. Th

Rolf Nicodemus, Siegfried Grossmann, Martin Holthaus

We extend the Doering-Constantin approach to upper bounds on energy dissipation in turbulent flows by introducing a balance parameter into the variational principle. This parameter governs the relative weight of different contributions to the dissipation rate. Its optimization leads to improved bounds without entailing additional technical difficulties. For

G. Oshanin, J. De Coninck, A. M. Cazabat, M. Moreau

We study the behavior of a monolayer, which occupies initially a bounded region on an ideal crystalline surface and then evolves in time due to random hopping motion of the monolayer particles. In the case when the initially occupied region is the half-plane $X \leq 0$, we determine explicitly, in terms of an analytically solvable mean-field-type approximati

M. P. Valignat, G. Oshanin, S. Villette, A. M. Cazabat

We study experimentally the molecular weight $M$ dependence of spreading rates of molecularly thin precursor films, growing at the bottom of droplets of polymer liquids. In accord with previous observations, we find that the radial extension R(t) of the film grows with time as R(t) = (D_{exp} t)^{1/2}. Our data substantiate the M-dependence of D_{exp}; we sh

Bing-Hong Wang, Lei Wang, P. M. Hui, Bambi Hu

Exact mean field equations are derived analytically to give the fundamental diagrams, i.e., the average speed - car density relations, for the Fukui-Ishibashi one-dimensional traffic flow cellular automaton model of high speed vehicles $(v_{max}=M>1) $ with stochastic delay. Starting with the basic equation describing the time evolution of the number of empt

V. V. Moshchalkov, V. Bruyndoncx, E. Rosseel, L. Van Look

We have studied quantization and confinement effects in nanostructured superconductors. Three different types of nanostructured samples were investigated: individual structures (line, loop, dot), 1-dimensional (1D) clusters of loops and 2D clusters of antidots, and finally large lattices of antidots. Hereby, a crossover from individual elementary &#34;plaque

Hiroyuki Mori

The interplay between impurities and interactions is studied in the gapless phase of two-chain Hubbard model in order to see how the screening of impurity potentials due to repulsive interactions in single-chain model will be changed by increasing the number of channels. Renormalization group calculations show that charge stiffness, and hence persistent curr

J. Piekarewicz, J. R. Shepard

We compute bulk properties of Heisenberg spin-1/2 ladders using Rayleigh-Schrödinger perturbation theory in the rung and plaquette bases. We formulate a method to extract high-order perturbative coefficients in the bulk limit from solutions for relatively small finite clusters. For example, a perturbative calculation for an isotropic $2\times 12$ ladder yiel

J. G. S. Lok, A. K. Geim, B. Tieke, J. C. Maan

We report anomalous behavior in a double-layer two dimensional hole gas (2DHG) at even integer filling factors which includes hysteresis in the longitudinal and Hall resistances and a very weak temperature dependence of the resistance minima. All anomalies disappear and the conventional quantum Hall effect behavior recovers when a thin metal film is placed o

Franco Bagnoli, Michele Bezzi

In this paper we consider a microscopic model of a simple ecosystem. The basic ingredients of this model are individuals, and both the phenotypic and genotypic levels are taken in account. The model is based on a long range cellular automaton (CA); introducing simple interactions between the individuals, we get some of the complex collective behaviors observ

Itai Arad, Brindesh Dhruva, Susan Kurien, Victor S. L&#39;vov

We analyze turbulent velocity signals measured by two probes in the atmosphere, both at the height of 35 meters but displaced by 40 cm nominally orthogonal to the mean wind. Choosing a suitable coordinate system with respect to that of the mean wind, we derive theoretical forms for second order structure functions, and fit them to experimental data. We show

Baowen Li, Marko Robnik, Bambi Hu

In this paper we have tested several general numerical methods in solving the quantum billiards, such as the boundary integral method (BIM) and the plane wave decomposition method (PWDM). We performed extensive numerical investigations of these two methods in a variety of quantum billiards: integrable systens (circles, rectangles, and segments of circular an

V. Tatischeff, R. Ramaty, B. Kozlovsky

We have developed in detail the theory of X-ray line and continuum production due to atomic interactions of accelerated ions, incorporating in our calculations information from a broad range of laboratory measurements. We applied our calculations to the Orion region from which nuclear gamma-ray lines were observed with the COMPTEL instrument on CGRO. The acc

J. E. Grove, J. E. Grindlay, B. A. Harmon, X. -M. Hua

Observations of galactic BHCs made by the Compton GRO in the hard X-ray and gamma-ray bands have significantly enhanced our knowledge of the emission properties of these objects. Understanding these observations presents a formidable challenge to theoretical models of the accretion flow onto the compact object and of the physical mechanisms that generate hig

B. McKernan, T. Yaqoob

The colossal power output of active galactic nuclei (AGN) is believed to be fueled by the accretion of matter onto a supermassive black hole. This central accreting region of AGN has hitherto been spatially unresolved and its structure therefore unknown. Here we propose that a previously reported `deep minimum&#39; in the X-ray intensity of the AGN MCG-6-30-