July 2000 arXiv papers — page 16

Kristen Menou

The boundary layers of weakly-magnetized white dwarfs (WDs) accreting at rates <=10^16 g/s are radially extended, hot, optically-thin, and they advect some of their internally-dissipated energy (Narayan & Popham 1993). Motivated by this, I construct here idealized spectral models of an Advection-Dominated Accretion Flow (ADAF) around a WD, for application to

Remi A. Cabanac, Valerie de Lapparent, Paul Hickson

The UH8K wide field camera of the CFHT was used to image 0.68 deg^2 of sky. From these images, ~20,000 galaxies were detected to completeness magnitudes V<23.5 and I<22.5. The angular correlation function of these galaxies is well represented by the parameterization omega(theta) = A_W*theta^-delta. The slope delta=-0.8 shows no significant variation over the

W. Bednarek

We consider propagation of very high energy (VHE) gamma-rays in the radiation field of a massive star in the binary system Cen X-3, which has been reported as a source of gamma-ray photons in the GeV and TeV energies. VHE gamma-rays or electrons, injected by the compact object, should develop inverse Compton pair cascades. We predict the gamma-ray spectra an

J D Anand, V K Gupta, Ashok Goyal, S Singh

We study the effect of magnetic field on the bulk viscosity of nuclear matter in neutron stars. We employ the framework of relativistic mean field theory to observe the dense nuclear matter in neutron stars. The effects are first studied for the case when the magnetic field does not exceed the critical value to confine the electrons to the lowest Landau leve

G. Duchene, J. Bouvier, J. Eisloffel, T. Simon

In this review, we summarize the observed statistical properties of visual binaries in various young stellar clusters. The binary frequency, orbital period distribution and mass ratio distribution are considered for populations of both low-mass and high-mass stars. These properties are then compared to numerical models of the dynamical evolution of stellar c

Andrea Ferrara

In this summary paper I will focus on the four main topics discussed at this Conference: (i) First luminous sources in the universe, (ii) Reionization, (iii) Intergalactic medium and (iv) Galaxy formation. In addition to provide a necessarily sketchy summary of the various talks on these subjects, I will also outline some of potentially important issues that

Heinz Oberhummer, Attila Csoto, Helmut Schlattl

The bulk of the carbon in our universe is produced in the triple-alpha process in helium-burning red giant stars. We calculated the change of the triple-alpha reaction rate in a microscopic 12-nucleon model of the C-12 nucleus and looked for the effects of minimal variations of the strengths of the underlying interactions. Stellar model calculations were per

C. L. Fryer, S. E. Woosley, A. Heger

Growing theoretical evidence suggests that the first generation of stars may have been quite massive (~100-300 solar masses). If they retain their high mass until death, such stars will, after about 3Myr, make pair-instability supernovae. We consider the complete evolution of two zero-metallicity stars of 250 and 300 solar masses. Explosive oxygen and silico

Brian E. Wood, Margarita Karovska

We use radiative transfer calculations to reproduce the basic appearance of Mg II lines observed from Mira variables. These lines have centroids that are blueshifted by at least 30 km/s from the stellar rest frame. It is unlikely that flow velocities in the stellar atmospheres are this fast, so radiative transfer effects must be responsible for this behavior

T. J. Davidge

Near-infrared images obtained with the CFHT AOB are used to investigate the stellar content of the Local Group elliptical galaxy M32. Observations of a field 2.3 arcmin from the galaxy center reveal a large population of AGB stars, and comparisons with models indicate that these objects have an age log(t_Gyr) < 9.3. It is concluded that intermediate age star

Brian E. Wood, Carol W. Ambruster, Alexander Brown, Jeffrey L. Linsky

We analyze local ISM absorption observed in the Lyman-alpha and Mg II h & k lines of six nearby K dwarf stars, using UV spectra of these stars obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. For four of the six stars, we detect an absorption component with a velocity and column density consistent with the Local Interstel

Brian E. Wood, Hans-Reinhard Mueller, Gary P. Zank

We use self-consistent kinetic/hydrodynamic models of the heliosphere to predict H I Lyman-alpha absorption profiles for various lines of sight through the heliosphere. These results are compared with Lyman-alpha absorption lines of six nearby stars observed by the Hubble Space Telescope. The directions of these lines of sight range from nearly upwind (36 Op

Achim Tappe

There is strong evidence for a large fraction of dark matter in the Universe. Some of the evidence and candidates for dark matter are reviewed. Dark matter in spiral galaxies may be in the form of cold dense clouds of molecular hydrogen. This model is presented in more detail and perspectives for detecting the cold H_2 are discussed.

S. Mrenna

Neutralino and tau slepton pair production can naturally produce an excess of tau lepton pairs at the current LEP collider energies. We describe the constraints this has on the values of the mass parameters in the softly broken Supersymmetric Lagrangian, and consider the consequences for superpartner production at LEP and at the Fermilab Tevatron collider. T

A. B. Kuklov, J. L. Birman

We discuss mechanisms of decoherence of a confined Bose-Einstein condensate at finite temperatures under the explicit condition of conservation of the total number of bosons $N$ in the trap. A criterion for the irreversible decay of the condensate two-time correlator is formulated in terms of the {\it Orthogonality Catastrophe} (OC) for the exact N-body eige

J. Huefner, Yu. P. Ivanov, B. Z. Kopeliovich, A. V. Tarasov

Elastic virtual photoproduction cross sections gamma^*p -> J/psi(psi&#39;)p and total charmonium-nucleon cross sections for J/psi, psi&#39; and chi states are calculated in a parameter free way with the light-cone dipole formalism and the same input: factorization in impact parameters, light-cone wave functions for the gamma^* and the charmonia, and the univ

John Michael Williams

Numerous estimates of upper bounds on the (anti)neutrino rest mass have been published based on the SN1987A observations. Here, we use a nonkinematic (thermal) time extent to provide a rest mass estimate of a few eV (as mc^2 mass), if not zero. In the solution, we find that a typical upper bound formula for the mass implies that this thermal extent was attri

Ziwei Lin, C. M. Ko

The cross sections of $Υ$ absorption by $π$ and $ρ$ mesons are evaluated in a meson-exchange model. Including form factors with a cutoff parameter of 1 or 2 GeV, we find that due to the large threshold of these reactions the thermal average of their cross sections is only about 0.2 mb at a temperature of 150 MeV. Our results thus suggest that the absorption

M. B. Voloshin

It is pointed out that, contrary to some claims in the literature, the domain walls cannot be a source of a correlated at large scales primordial magnetic field, even if the fermionic modes bound on the wall had ferromagnetic properties. In a particular model with massive (2+1) dimensional fermions bound to a domain wall, previously claimed to exhibit a ferr

M. Bertolini, P. Di Vecchia, M. Frau, A. Lerda

We study the classical geometry produced by a stack of stable (i.e. tachyon free) non-BPS D-branes present in K3 compactifications of type II string theory. This classical representation is derived by solving the equations of motion describing the low-energy dynamics of the supergravity fields which couple to the non-BPS state. Differently from what expected

Tarun Kanti Ghosh

We derive the equation of motion for the velocity fluctuations of a 2D deformed trapped Bose gas above the critical temperature in the hydrodynamical regime. From this equation, we calculate the eigenfrequencies for a few low-lying excitation modes. Using the method of averages, we derive a dispersion relation in a deformed trap that interpolates between the

S. Collins, C. T. H. Davies, J. Hein, G. P. Lepage

We present results for the B_s meson decay constant f_{B_s} from simulations at three lattice spacings in the range a^{-1}=1.1 to 2.6 GeV using NRQCD heavy quarks and clover light quarks in the quenched approximation. We study scaling of this quantity and check the consistency between mesons decaying from rest and from a state with nonzero spatial momentum.

N. Sasaki, O. Miyamura, S. Muroya, C. Nonaka

We evaluate charge diffusion constant of dense and hot hadronic matter based on the molecular dynamical method by using a hadronic collision generator which describes nuclear collisions at energies 10 < E < 100 GeV/A and satisfies detailed balance at low temperatures (T < 200 MeV). For the hot and dense hadronic matter of the temperature range, 100 < T < 200

E. Elizalde

A simple model is introduced in which the cosmological constant is interpreted as a true Casimir effect on a scalar field filling the universe (e.g. $\mathbf{R} \times \mathbf{T}^p\times \mathbf{T}^q$, $\mathbf{R} \times \mathbf{T}^p\times \mathbf{S}^q, ...$). The effect is driven by compactifying boundary conditions imposed on some of the coordinates, assoc

K. Kajantie, M. Laine, K. Rummukainen, Y. Schroder

The strict coupling constant expansion for the free energy of hot QCD plasma shows bad convergence at all reasonable temperatures, and does not agree well with its 4d lattice determination. This has recently lead to various refined resummations, whereby the agreement with the lattice result should improve, at the cost of a loss of a formal agreement with the

John McDonald

Observation indicates that the expansion of the Universe is accelerating and favours a dynamical cosmological constant, Λ(t). We consider the possibility that this is due to a scalar field which has undergone a very recent phase transition. We study a simple class of model, corresponding to a ϕ^4 potential with a time-dependent mass squared term. For the mod

Eliana Biolatti, Rita C. Iotti, Paolo Zanardi, Fausto Rossi

An all optical implementation of quantum information processing with semiconductor macroatoms is proposed. Our quantum hardware consists of an array of semiconductor quantum dots and the computational degrees of freedom are energy-selected interband optical transitions. The proposed quantum-computing strategy exploits exciton-exciton interactions driven by u

C. Quesne

The $C_λ$-extended oscillator spectrum generating algebra is shown to be a $C_λ$-extended $(λ-1)$th-degree polynomial deformation of su(1,1). Its coherent states are constructed. Their statistical and squeezing properties are studied in detail. Such states include both some Barut-Girardello and the standard $λ$-photon coherent states as special cases.

M. V. Savina, S. V. Shmatov, N. V. Slavin, P. I. Zarubin

In the framework of the HIJING model global characteristics of nucleus- nucleus collisions are studied for a Large Hadron Collider energy scale. An interesting model prediction is the presence of a central bump over a pseudorapidity plateau of a total transverse energy distribution. The bump is induced by a jet quenching effect in a dense nuclear matter. It

K. Morawetz, M. Ploszajczak, V. D. Toneev

The expansion velocity profile in central heavy-ion reactions in the Fermi energy domain is examined. The radial expansion is non-hubblean and in the surface region it scales proportional to a higher exponent ($α> 1$) of the radius. The anomalous expansion velocity profile is accompanied by a power law nucleon density profile in the surface region. Both thes

D. C. Cabra, A. De Martino, M. D. Grynberg, S. Peysson

The magnetization behavior of q-periodic antiferromagnetic spin 1/2 Heisenberg chains under uniform magnetic fields is investigated in a background of disorder exchange distributions. By means of both real space decimation procedures and numerical diagonalizations in XX chains, it is found that for binary disorder the magnetization exhibits wide plateaux at

L. Rosa, P. Vitale, C. Wetterich

The phase transition of the Gross-Neveu model with N fermions is investigated by means of a non-perturbative evolution equation for the scale dependence of the effective average action. The critical exponents and scaling amplitudes are calculated for various values of N in d=3. It is also explicitely verified that the Neveu-Yukawa model belongs to the same u

G. J. Kramer, H. P. Blok, L. Lapikas

The apparent discrepancy between spectroscopic factors obtained in (e,e&#39;p) and (d,3He) experiments is investigated. This is performed first for 48Ca(e,e&#39;p) and 48Ca(d,3He) experiments and then for other nuclei. It is shown that the discrepancy disappears if the (d,3He) experiments are re-analyzed with a non-local finite range DWBA analysis with a bou

G. Colangelo, J. Gasser, H. Leutwyler

We match the known chiral perturbation theory representation of the pi pi scattering amplitude to two loops with a phenomenological description that relies on the Roy equations. On this basis, the corrections to Weinberg&#39;s low energy theorems for the S-wave scattering lengths are worked out to second order in the expansion in powers of the quark masses.

G. J. Gounaris, P. I. Porfyriadis

The helicity amplitudes for the process $γγ\to A^0 A^0$ are studied to 1-loop order in the minimal SUSY (MSSM) model, where $A^0$ is the CP-odd Higgs particle. Simple exact analytic formulae are obtained, in terms of the $C_0$ and $D_0$ Passarino-Veltman functions; in spite of the fact that the loop-diagrams often involve different particles running along th

Kanehisa Takasaki

We show several examples of integrable systems related to special K3 and rational surfaces (e.g., an elliptic K3 surface, a K3 surface given by a double covering of the projective plane, a rational elliptic surface, etc.). The construction, based on Beauvilles&#39;s general idea, is considerably simplified by the fact that all examples are described by hyper

Li Chiang, Shi-shyr Roan

We present our recent understanding on resolutions of Gorenstein orbifolds, which involves the finite group representation theory. We shall concern only the quotient singularity of hypersurface type. The abelian group $A_r(n)$ for $A$-type hypersurface quotient singularity of dimension $n$ is introduced. For $n=4$, the structure of Hilbert scheme of group or

Sergei Nayakshin, Roland Svensson

It is currently believed that the ``standard'' accretion disk theory under-predicts the observed X-ray luminosity from Soft X-ray Transients (SXT) in quiescence by as much as 4 to 6 orders of magnitude. This failure of the standard model is considered to be an important argument for the existence of the alternative mode of accretion -- Advection Dominated Ac

Hideo Hasegawa

An associative memory has been discussed of neural networks consisting of spiking N (=100) Hodgkin-Huxley (HH) neurons with time-delayed couplings, which memorize P patterns in their synaptic weights. In addition to excitatory synapses whose strengths are modified after the Willshaw-type learning rule with the 0/1 code for quiescent/active states, the networ

Satyan Bhongale, Murray Holland

Demonstrating that despite loss processes, Bose-Einstein condensates can be formed in steady state is a prerequisite for obtaining a coherent beam of atoms in a continuous-wave atom laser. In this paper we propose a method for loading atoms into the thermal component of a Bose condensed cloud confined in a magnetic trap. This method is aimed at allowing stea

Rosa Brouri, Alexios Beveratos, Jean-Philippe Poizat, Philippe Grangier

The fluorescence of a single dipole excited by an intense light pulse can lead to the generation of another light pulse containing a single photon. The influence of the duration and energy of the excitation pulse on the number of photons in the fluorescence pulse is studied. The case of a two-level dipole with strongly damped coherences is considered. The pr

Rocco A. Servedio, Steven J. Gortler

We consider quantum versions of two well-studied classical learning models: Angluin&#39;s model of exact learning from membership queries and Valiant&#39;s Probably Approximately Correct (PAC) model of learning from random examples. We give positive and negative results for quantum versus classical learnability. For each of the two learning models described

Piotr Kochanski, Zofia Bialynicka-Birula, Iwo Bialynicki-Birula

The notion of the Trojan state of a Rydberg electron, introduced by I.Bialynicki-Birula, M.Kaliński, and J.H.Eberly (Phys. Rev. Lett. 73, 1777 (1994)) is extended to the case of the electromagnetic field quantized in acavity. The shape of the electronic wave packet describing the Trojan state is practically the same as in the previously studied externally dr

Rosa Brouri, Alexios Beveratos, Jean-Philippe Poizat, Philippe Grangier

We have observed photon antibunching in the fluorescence light emitted from a single N-V center in diamond at room temperature. The possibility of generating triggerable single photons with such a solide state system is discussed

L. C. Kwek, Yong Liu, C. H. Oh, Xiang-Bin Wang

A general procedure based on shift operators is formulated to deal with anharmonic potentials. It is possible to extract the ground state energy analytically using our method provided certain consistency relations are satisfied. Analytic expressions for the exact ground state energy have also been derived specifically for a large class of the one-dimensional

E. L. Afraimovich, A. T. Altyntsev, E. A. Kosogorov, N. S. Larina

This paper presents data from first GPS measurements of global response of the ionosphere to solar flares of September 23, 1998 and July 29, 1999. The analysis used novel technology of a global detection of ionospheric effects from solar flares (GLOBDET) as developed by one of the authors (Afraimovich E. L.). The essence of the method is that use is made of

L. Frappat, A. Sciarrino, P. Sorba

Using the crystal basis model of the genetic code, a set of relations between the physical-chemical properties of the amino acids are derived and compared with the experimental data. A prevision for the not yet measured thermodynamical parameters of three amino acids is done.

T. Grava

We study the Cauchy problem for the Whitham modulation equations for monotone increasing smooth initial data. The Whitham equations are a collection of one-dimensional quasi-linear hyperbolic systems. This collection of systems is enumerated by the genus g=0,1,2,... of the corresponding hyperelliptic Riemann surface. Each of these systems can be integrated b

N. V. Antonov

A brief review is given of recent results devoted to the effects of large-scale anisotropy on the inertial-range statistics of the passive scalar quantity $θ(t,{\bf x})$, advected by the synthetic turbulent velocity field with the covariance $\proptoδ(t-t&#39;)|{\bf x}-{\bf x&#39;}|^{\eps}$. Inertial-range anomalous scaling behavior is established, and expli

M. Alber, S. Lueck, C. Renner, J. Peinke

The notion of self-similar energy cascades and multifractality has long since been connected with fully developed, homogeneous and isotropic turbulence. We introduce a number of amendments to the standard methods for analysing the multifractal properties of the energy dissipation field of a turbulent flow. We conjecture that the scaling assumption for the mo

William L. Paschke

We consider certain positive definite functions on a finitely generated free group G that are defined with respect to a given basis in terms of word length and the number of negative-to-positive generator exponent switches. Some of these functions are eigenfunctions for right convolution by the sum of the generators, and give rise to irreducible unitary repr

Joerg Winkelmann

We study Hilbert&#39;s fourteenth problem from a geometric point of view. Nagata&#39;s celebrated counterexample demonstrates that for an arbitrary group action on a variety the ring of invariant functions need not be isomorphic to the ring of functions of an affine variety. Nevertheless one can prove that such a ring of invariants is always isomorphic to th

Yaacov Tzeitlin

In the present article we describe a class of algebraic curves on which rational functions of two arguments may reach all their possible limiting values. We also solve a similar question for functions that can be represented as a uniform limit of a sequence of bounded rational functions.

Marie-Amélie Bertin

The Castelnuovo-Mumford regularity of varieties of degree r and dimension n in the r-dimensional projective space that have an extremal secant line, is at least d-r+n+1. We classify these varieties and show that their regularity is exactly d-r+n+1, as predicted by the regularity conjecture.

Sze Kui Ng

We propose a gauge model of quantum electrodynamics (QED) and its nonabelian generalization from which we derive knot invariants such as the Jones polynomial. Our approach is inspired by the work of Witten who derived knot invariants from quantum field theory based on the Chern-Simon Lagrangian. From our approach we can derive new knot and link invariants wh

Martin Pikaart

We determine the largest (i.e. smallest index) characteristic subgroup of surface groups not containing any simple loops.

Jifeng Yang

New equations governing the scale transformation behaviors of a QFT with underlying structures are derived. These equations, with their several equivalent versions, can yield some new and significant insights and results that are difficult to see in the conventional renormalization programs. Among the several equivalent versions, one is similar to the usual

J. Barcelos-Neto

We show that the spontaneous compactification of the Abelian and non-Abelian two-form gauge field theories from $D=4+1$ to $D=3+1$ leads to the same theories plus the Maxwell and Yang-Mills ones, respectively. The vector potential comes from the zero mode of the fifth component of the tensor gauge field in D=5. Concerning to the non-Abelian case, it is neces

Oskar Pelc

A D3 brane in the background of NS5 branes is studied semi-classically. The conditions for preserved supersymmetry are derived, leading to a differential equation for the shape of the D3 brane. The solutions of this equation are analyzed. For a D3 brane intersecting the NS5 branes, the angle of approach is known to be restricted to discrete values. Four diff

P. Claus, J. Rahmfeld, H. Robins, J. Tannenhauser

We derive explicit forms for the superisometries of a wide class of supercoset manifolds, including those with fermionic generators in the stability group. We apply the results to construct the action of SU(2,2|4) on three supercoset manifolds: (10|32)-dimensional AdS_5 x S^5 superspace, (4|16)-dimensional conformal superspace, and a novel (10|16)-dimensiona

Martin Fleck

The embedding procedure of Batalin, Fradkin, and Tyutin, which allows to convert a second-class system into a first-class one, is employed to convert second-class interacting models. Two cases are considered. One, is the Self-Dual model minimally coupled to a Dirac fermion field. The other, the Self-Dual model minimally coupled to a charged scalar field. In

Anton Alekseev, Volker Schomerus

We consider the contribution of the B-field into the RR charge of a spherical D2-brane. Extending a recent analysis of Taylor, we show that the boundary and bulk contributions do not cancel in general. Instead, they add up to an integer as observed by Stanciu. The general formula is applied to compute the RR charges of spherical D-branes of the SU(2) WZW mod

S. Lienart, P. Ruelle, O. Verhoeven

We classify the possible finite symmetries of conformal field theories with an affine Lie algebra su(2) and su(3), and discuss the results from the perspective of the graphs associated with the modular invariants. The highlights of the analysis are first, that the symmetries we found in either case are matched by the graph data in a perfect way in the case o

Rabin Banerjee, Bhabani Prasad Mandal

Using the technique of finite field dependent BRST transformations we show that the classical massive Yang-Mills theory and the pure Yang-Mills theory whose gauge symmetry is broken by a gauge fixing term are identical from the view point of quantum gauge symmetry. The explicit infinitesimal transformations which leave the massive Yang-Mills theory BRST inva

Johannes Blümlein, Bodo Geyer, Markus Lazar, Dieter Robaschik

A quantum field theoretic treatment of the leading light-cone part of the virtual Compton amplitude is presented. The twist-decomposition of the operators is performed by a group-theoretic procedure respecting the Lorentz group O(3,1). The twist-2 contributions to the Compton amplitude are calculated and it is shown that the electromagnetic current is conser

A. Arrizabalaga, B. J. Nauta, Ch. G. van Weert

We show that the logarithmic divergences that appear in the classical approximation of the finite temperature SU(N) self-energy are transverse. We use the Ward identities in linear gauges and the fact that the superficial degree of divergence d of a classical diagram only depends on the number of loops l via d=2-l. We comment on the relevance of this result

A. S. Galoyan, V. V. Uzhinskii

Elliptic flow of hard partons (P>5 GeV), squeeze-out of soft partons (P<=5 GeV) and produced particles are predicted in the framework of the HIJING model. They are caused due to jet quenching and heterogeneity of the interaction region.

A. Bacchetta, P. J. Mulders

In this paper we analyze deep inelastic one-particle inclusive processes for the case of spin-one targets or for the case of spin-one produced hadrons, such as rho mesons. This allows the measurement of new distribution and fragmentation functions not available in the spin-half case, and provides new ways to probe functions otherwise difficult to measure. We

V. Fadin, D. Ivanov, M. Kotsky

We present the results of the calculation of the one-loop correction to the effective vertex for the quark-antiquark pair production in collisions of the virtual photon with the Reggeized gluon. This vertex is supposed then to be used for the calculation of the virtual photon impact factor, which is extremely important, for instance, for the description of t

Alessandro Papa

The property of gluon Reggeization plays an essential role in the derivation of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation for the cross sections at high energy $\sqrt s$ in perturbative QCD. This property has been proved to all orders of perturbation theory in the leading logarithmic approximation and it is assumed to be valid also in the next-to-lea

I. D. Lawrie, D. B. McKernan

A partial resummation of perturbation theory is described for field theories containing spin-1/2 particles in states that may be far from thermal equilibrium. This allows the nonequilibrium state to be characterized in terms of quasiparticles that approximate its true elementary excitations. In particular, the quasiparticles have dispersion relations that di

John Ellis, A. Ferstl, K. A. Olive

We explore the possible cross sections for the elastic scattering of neutralinos chi on nucleons p,n in the minimal supersymmetric extension of the standard model (MSSM). Universality of the soft supersymmetry-breaking scalar masses for the Higgs multiplets is not assumed, but the MSSM parameters are nevertheless required to lead consistently to an electrowe

W. Bietenholz

Lattice fermions obeying the Ginsparg-Wilson relation do correctly represent the physical properties related to chirality. This can be achieved by local fermions, which involve an infinite number of couplings, however. For practical purposes, it is useful to first construct approximate Ginsparg-Wilson fermions within a short range. We report on a successful

P. Hernández, K. Jansen, M. Lüscher

Domain-wall fermions preserve chiral symmetry up to terms that decrease exponentially when the lattice size in the fifth dimension is taken to infinity. The associated rates of convergence are given by the low-lying eigenvalues of a simple local operator in four dimensions. These can be computed using the Ritz functional technique and it turns out that the c

PACS Collaboration, A. Ali Khan, S. Aoki, Y. Aoki

We investigate the chiral properties of quenched domain-wall QCD (DWQCD) at the lattice spacings $a^{-1} \simeq 1$ and 2 GeV for both plaquette and renormalization-group (RG) improved gauge actions. In the case of the plaquette action we find that the quark mass defined through the axial Ward-Takahashi identity remains non-vanishing in the DWQCD chiral limit

E787 Collaboration

We have performed a measurement of the K^+ -> pi^+ pi^0 gamma decay and have observed 2 X 10^4 events. The best fit to the decay spectrum gives a branching ratio for direct photon emission of (4.7\pm0.8\pm0.3) X 10^{-6} in the pi^+ kinetic energy region of 55 to 90 MeV and requires no component due to interference with inner bremsstrahlung.

Rainer E. Zimmermann

Referring to a conception put forward by Stuart Kauffman in his &#34;Investigations&#34;, it is shown how the onset of classicity can be visualized in terms of an emergent process originating in entangled ensemble states of knotted spin networks. The latter exhibit a suitable autocatalytic behaviour effectively producing knots by knots acting upon other knot

Arkadiusz Wojs, John J. Quinn

The photoluminescence (PL) spectrum of a two-dimensional electron gas (2DEG) in the fractional quantum Hall regime is studied as a function of the separation $d$ between the electron and valence hole layers. The abrupt change in the response of the 2DEG to the optically injected hole at $d$ of the order of the magnetic length $λ$ results in a complete recons

Nicola A. Hill, Umesh Waghmare

We present a first-principles study of the relationship between stress, temperature and electronic properties in piezoelectric ZnO. Our method is a plane wave pseudopotential implementation of density functional theory and density functional linear response within the local density approximation. We observe marked changes in the piezoelectric and dielectric

M. E. J. Newman

We investigate the structure of scientific collaboration networks. We consider two scientists to be connected if they have authored a paper together, and construct explicit networks of such connections using data drawn from a number of databases, including MEDLINE (biomedical research), the Los Alamos e-Print Archive (physics), and NCSTRL (computer science).

G. M. Schütz, I. Ispolatov, G. T. Barkema, B. Widom

We establish the equivalence of a recently introduced discrete model of the hydrophobic interaction, as well as its extension to continuous state variables, with the Ising model in a magnetic field with temperature-dependent strength. In order to capture the effect of symmetries of the solvent particles we introduce a generalized multi-state model. We solve

I. Ispolatov, K. Koga, B. Widom

Occupation probabilities for primary-secondary-primary cell strings and correlation functions for primary sites of a decorated lattice model are expressed through the well-studied partition function and correlation functions of the Ising model. The results are analogous to those found in related lattice models of hydrophobic interactions and are interpreted

Abhik Basu

We show that effective interactions mediated by disorder between two directed polymers can be modelled as the crosscorrelation of noises in the Kardar-Parisi-Zhang (KPZ) equations satisfied by the respective free energies of these polymers. When there are two polymers, disorder introduces attractive interactions between them. We analyze the phase diagram in

Francesco Sciortino, Piero Tartaglia

We present evidence in favor of the possibility of treating an out-of-equilibrium supercooled simple liquid as a system in quasi-equilibrium. Two different temperatures, one controlled by the external bath and one internally selected by the system characterize the quasi-equilibrium state. The value of the internal temperature is explicitly calculated within

Claudio Donati, Francesco Sciortino, Piero Tartaglia

The connectivity of the potential energy landscape in supercooled atomic liquids is investigated through the calculation of the instantaneous normal modes spectrum and a detailed analysis of the unstable directions in configuration space. We confirm the hypothesis that the mode-coupling critical temperature is the $T$ at which the dynamics crosses over from

Jörg Lehmann, Peter Reimann, Peter Hänggi

We consider the thermally activated escape of an overdamped Brownian particle over a potential barrier in the presence of periodic driving. A time-dependent path-integral formalism is developed which allows us to derive asymptotically exact weak-noise expressions for both the instantaneous and the time-averaged escape rate. Our results comprise a conceptiona

Asher Yahalom, Robert Englman

The geometric and open path phases of a four-state system subject to time varying cyclic potentials are computed from the Schrödinger equation. Fast oscillations are found in the non-adiabatic case. For parameter values such that the system possesses degenerate levels, the geometric phase becomes anomalous, undergoing a sign switch. A physical system to whic

O. Pilla, A. Cunsolo, A. Fontana, C. Masciovecchio

The dynamical structure factor (S(Q,E)) of vitreous silica has been measured by Inelastic X-ray Scattering varying the exchanged wavevector (Q) at fixed exchanged energy (E) - an experimental procedure that, contrary to the usual one at constant Q, provides spectra with much better identified inelastic features. This allows the first direct evidence of Brill

Pierre Villain, Patrik Ohberg, Maciej Lewenstein

We consider the evolution of a dilute Bose-Einstein condensate in an optical trap formed by a doughnut laser mode. By solving a one dimensional Gross-Pitaevskii equation and looking at the variance and the statistical entropy associated with the position of the system we can study the dynamical behavior of the system. It is shown that for small condensates n

E. Persson, I. Rotter, H. -J. Stoeckmann, M. Barth

The coupling of a quantum mechanical system to open decay channels has been theoretically studied in numerous works, mainly in the context of nuclear physics but also in atomic, molecular and mesoscopic physics. Theory predicts that with increasing coupling strength to the channels the resonance widths of all states should first increase but finally decrease

R. P. Venkataraman

For studying the thermodynamic properties of systems using statistical mechanics we propose an ensemble that lies in between the familiar canonical and microcanonical ensembles. From a comparative study of these ensembles we conclude that all these ensembles may not yield the same results even in the thermodynamic limit except at high temperatures. An invest

Toshimasa Fujisawa, Wilfred G. van der Wiel, Leo P. Kouwenhoven

Coupling a quantum system to a bosonic environment always give rise to inelastic processes, which reduce the coherency of the system. We measure energy dependent rates for inelastic tunneling processes in a fully controllable two-level system of a double quantum dot. The emission and absorption rates are well repro-duced by Einstein&#39;s coefficients, which

Irene Giardina, Jean-Philippe Bouchaud, Marc Mezard

We investigate the competition between barrier slowing down and proliferation induced superdiffusion in a model of population dynamics in a random force field. Numerical results in $d=1$ suggest that a new intermediate diffusion behaviour appears. We introduce the idea of proliferation assisted barrier crossing and give a Flory like argument to understand qu

A. J. Weinberger, R. M. Rich, E. E. Becklin, B. Zuckerman

We investigate the stellar environment of the Beta Pictoris-like star HD 141569 with optical spectroscopy and near infrared imaging. The B9.5Ve primary, and an M2 and an M4 type star both located in projection less than nine arseconds away have the same radial velocity and proper motion and therefore almost certainly form a triple star system. From their x-r

L. M. Young

The nearby dwarf elliptical galaxy NGC 205 offers a unique opportunity for high resolution studies of the interstellar medium in an elliptical galaxy. This paper investigates the distribution of molecular gas, molecular line ratios, and the relationships between atomic gas, molecular gas, and dust in NGC 205. The line ratios 12CO(2-1)/(1-0) and 12CO(1-0)/13C

Patrick B. Hall, H. K. C. Yee, Huan Lin, Simon L. Morris

We present a sample of 47 confirmed and 14 candidate Active Galactic Nuclei (AGN) discovered in the Canadian Network for Observational Cosmology field galaxy redshift survey (CNOC2). The sample consists of 38 objects identified from broad emission lines, 8 from narrow [NeV] emission, and 15 candidates from FeII or MgII absorption lines, one of which has been

Amina Helmi, P. Tim de Zeeuw

We run numerical simulations of the disruption of satellite galaxies in a Galactic potential to build up the entire stellar halo, in order to investigate what the next generation of astrometric satellites will reveal by observing the halo of the Milky Way. We generate artificial DIVA, FAME and GAIA halo catalogues, in which we look for the signatures left by

Joel R. Primack, Michael A. K. Gross

Cosmological dark matter in the form of neutrinos with masses of up to a few electron volts is known as hot dark matter. After an historical review of the subject, this article considers constraints on hot dark matter from current data on neutrino oscillations and on cosmology. The atmospheric neutrino oscillation data imply a lower limit on the HDM contribu

J. L. Hou, N. Prantzos, S. Boissier

Based on a simple, but fairly successful, model of the chemical evolution of the Milky Way disk, we study the evolution of the abundances of the elements He, C, N, O, Ne, Mg, Al, Si, S, Ar and Fe. We use metallicity dependent yields for massive stars with and without mass loss. We find that most observed abundance profiles are correctly reproduced by massive

C. Vignali, A. Comastri, M. Cappi, G. G. C. Palumbo

We briefly discuss the latest ASCA results on the X-ray spectral properties of high-redshift radio-quiet quasars.