March 2000 arXiv papers — page 19

E. V. Tsiper

It is shown that the lowest excitation energies of a quantum many-fermion system in the random phase approximation (RPA) can be obtained by minimizing an effective classical energy functional. The minimum can be found very efficiently using generalized Lanczos technique. Application of the new technique to molecular spectra allows to compute excited states a

Michael Catanese, Rita M. Sambruna

We present X-ray observations of the BL Lacertae (BL Lac) object Markarian 501 (Mrk 501), taken with the Rossi X-ray Timing Explorer in 1998 May as part of a multi-wavelength campaign. The X-ray light curve shows a very rapid flare in which the 2-10 keV flux increased by ~60% in <200 seconds. This rapid rise is followed by a drop-off in the 2-10 keV flux of

M. Cocchi, A. Bazzano, L. Natalucci, P. Ubertini

During more than 3 years (August 1996-October 1999) monitoring of a 40x40 degree sky region around the Galactic Centre by the Wide Field Cameras on board BeppoSAX, a total of 8 type-I bursts have been detected from a sky position consistent with that of 4U 1812-12, a likely neutron-star low-mass X-ray binary. We present the results of a detailed study of the

Rosemary F. G. Wyse

I review the understanding of bulges that emerged from the lively discussions and presentations during the meeting, and emphasize areas for future work. The evidence is for a diversity of `bulges&#39;, and of formation mechanisms.

G. Ostlin

I will discuss the presence of massive star clusters in starburst galaxies with an emphasis on low mass galaxies outside the local group. I will show that such galaxies, with respect to their mass and luminosity, may be very rich in young luminous clusters.

C. Soubiran, M. Odenkirchen, J. -F. Le Campion

NGC 2355 is an old open cluster in the outer part of the galactic disk (l=203 deg, b=+11 deg) which has been little studied until now. This paper presents the first astrometric and spectroscopic investigation of this cluster. We have measured precise absolute proper motions from old Carte du Ciel plates, POSS-I plates and recent CCD observations obtained wit

P. G. Tuthill, J. D. Monnier, W. C. Danchi, E. H. Wishnow

We report the first use of Michelson interferometry on the Keck I telescope for diffraction-limited imaging in the near infrared JHK and L bands. By using an aperture mask located close to the f/25 secondary, the 10 m Keck primary mirror was transformed into a separate-element, multiple aperture interferometer. This has allowed diffraction-limited imaging of

P. G. Tuthill, W. C. Danchi, D. S. Hale, J. D. Monnier

The results of a high-resolution interferometric campaign targeting the symbiotic long-period variable (LPV) R~Aqr are reported. With both near-infrared measurements on baselines out to 10m and mid-infrared data extending to 32m, we have been able to measure the characteristic sizes of regions from the photosphere of the LPV and its extended molecular atmosp

D. M. Alexander, A. Efstathiou, J. H. Hough, D. Aitken

We present ISOPHOT_S, ISOSWS and 8 to 13 micron ground based observations of Centaurus A that show prominent PAH and silicate features. These and other data are used to construct a model for the infrared continuum. We find that in a nuclear sized aperture (~4 arcsec, ~60 pc) the SED is characteristic of emission from a starburst and AGN torus; in larger aper

Kyoko Matsushita, Takaya Ohashi, Kazuo Makishima

We have analyzed ASCA data of 27 early-type galaxies, and studied the properties of their X-ray emitting ISM (Inter Stellar Medium) in detail. We found that overlapping lines and free-bound continuum cause strong coupling in the derived abundances of various elements. The abundance determination is also difficult due to the uncertainties in the Fe-L atomic p

M. Boettcher, E. P. Liang

We present a theoretical model for the alternating phase lags associated with QPO fundamental and harmonic frequencies observed in some Galactic black-hole candidates. We assume that the accretion flow exhibits a transition from an outer cool, optically thick accretion disk to a hot, inner advection-dominated accretion flow (ADAF), and that the QPOs are rela

Markus Kissler-Patig

We present an overview of observational progress in the study of extragalactic globular cluster systems. Globular clusters turn out to be excellent tracers not only for the star-formation histories in galaxies, but also for kinematics at large galactocentric radii. Their properties can be used to efficiently constrain galaxy formation and evolution. After a

Csaba Csaki, Joshua Erlich, Timothy J. Hollowood, John Terning

We study the long distance behaviour of brane theories with quasi-localized gravity. The 5D effective theory at large scales follows from a holographic renormalization group flow. As intuitively expected, the graviton is effectively four dimensional at intermediate scales and becomes five dimensional at large scales. However in the holographic effective theo

John McGreevy, Leonard Susskind, Nicolaos Toumbas

It has been known for some time that the AdS/CFT correspondence predicts a limit on the number of single particle states propagating on the compact spherical component of the AdS-times-sphere geometry. The limit is called the stringy exclusion principle. The physical origin of this effect has been obscure but it is usually thought of as a feature of very sma

J. J. van der Bij, Eugen Radu

Regular and black-hole solutions of the spontaneously broken Einstein-Yang-Mills-Higgs theory with nonminimal coupling to gravity are shown to exist. The main characteristics of the solutions are presented and differences with respect to the minimally coupled case are studied. Since negative energy densities are found to be possible, traversable wormhole sol

R. N. Mohapatra, A. Pérez-Lorenzana, C. A. de S. Pires

We discuss inflation in models with large extra dimensions, driven by a bulk scalar field. The brane inflaton is then a single effective field, obtained from the bulk scalar field by scaling. The self interaction terms of the effective brane inflaton are then naturally suppressed. The picture is consistent with a fundamental string scale in the TeV range wit

Martin B. Einhorn, Leopoldo A. Pando Zayas

It is shown that magnetic seven-branes previously considered as different objects are members of a one-parametric family of supersymmetric seven branes. We enlarge the class of seven-branes by constructing new magnetically and also electrically charged seven branes. The solutions display a kink-like behavior. We also construct a solution that naturally gener

Paolo Diodati, Stefano Piazza

Several pieces of different musical kinds were studied measuring $N(A)$, the output amplitude of a peak detector driven by the electric signal arriving to the loudspeaker. Fixed a suitable threshold $\bar{A}$, we considered $N(A)$, the number of times that $A(t)>\bar{A}$, each of them we named event and $N(t)$, the distribution of times $t$ between two conse

Mei-Rong Li, P. J. Hirschfeld, P. Woelfle

A systematic perturbation theory is developed to describe the magnetic field-induced subdominant $s$- and $d_{xy}$-wave order parameters in the mixed state of a $d_{x^2-y^2}$-wave superconductor, enabling us to obtain, within weak-coupling BCS theory, analytic results for the free energy of a d-wave superconductor in an applied magnetic field $H_{c1}\ltsim H

H. R. Christiansen, J. Magnin

In this paper we study the gluon distribution functions in nucleons and pions at a low resolution $Q^2$ scale. This is an important issue since parton densities at low $Q^2$ have always been taken as an external input which is adjusted through DGLAP evolution to fit the experimental data at higher scales. Here, in the framework of a model recently developed,

Shaaban Khalil, Tatsuo Kobayashi, Oscar Vives

Non-universality in the soft breaking terms is a common feature in most superstring inspired SUSY models. This property is required to obtain sizeable CP violation effects from SUSY and, on the other hand, can be used to avoid the Electric Dipole Moment constraints. We take advantage of these qualities and explore a class of SUSY models based on type I strin

C. D. Batista, G. Ortiz

We present the quantum phase diagram of the one-dimensional $t$-$J_z$ model for arbitrary spin (integer or half-integer) and sign of the spin-spin interaction $J_z$, using an {\it exact} mapping to a spinless fermion model that can be solved {\it exactly} using the Bethe ansatz. We discuss its superconducting phase as a function of hole doping $ν$. Motivated

Lin Tian, Seth Lloyd

Off-resonant effects are a significant source of error in quantum computation. This paper presents a group theoretic proof that off-resonant transitions to the higher levels of a multilevel qubit can be completely prevented in principle. This result can be generalized to prevent unwanted transitions due to qubit-qubit interactions. A simple scheme exploiting

Zurab Berezhiani, Anna Rossi

We propose new textures for the fermion Yukawa matrices which are generalizations of the so-called Stech ansatz. We discuss how these textures can be realized in supersymmetric grand unified models with horizontal symmetry SU(3)_H among the fermion generations. In this framework the mass and mixing hierarchy of fermions (including neutrinos) can emerge in a

N. Alonso-Alberca, P. Meessen, T. Ortin

We extend the topological Kerr-Newman-aDS solutions by including NUT charge and find generalizations of the Robinson-Bertotti solution to the negative cosmological constant case with different topologies. We show how all these solutions can be obtained as limits of the general Plebanski-Demianski solution. We study the supersymmetry properties of all these s

S. R. M. Masalskiene, M. E. X. Guimaraes

The formation and evolution of cosmic string wakes in the framework of a scalar-tensor gravity are investigated in this work. We consider a simple model in which cold dark matter flows past an ordinary string and we treat this motion in the Zel&#39;dovich approximation. We make a comaprison between our results and previous results obtained in the context of

A. V. Kisselev, V. A. Petrov

The multiplicity of charged hadrons in the current fragmentation region of both the c.m.s. and the Breit frame of deep inelastic scattering is calculated and compared with the HERA data. The results are in agreeement with Yang&#39;s hypothesis that the efficiency of high energy processes increases at larger momentum transfer.

I. Jack, D. R. T. Jones

We show that in a minimal extension of the MSSM by means of an extra U(1) gauge group, the negative mass-squared problem characteristic of the Anomaly Mediated Supersymmetry Breaking scenario is naturally solved by means of Fayet-Iliopoulos D-terms. We derive a set of sum rules for the sparticle masses which are consequences of the resulting framework.

S. Bouarroudj

Let M be a manifold endowed with a symmetric affine connection $Γ.$ The aim of this paper is to describe a quantization map between the space of second-order polynomials on the cotangent bundle T^{*} M and the space of second-order linear differential operators, both viewed as modules over the group of diffeomorphisms and the Lie algebra of vector fields on

Ivan S. Booth, Jolien D. E. Creighton

We present a method for computing the flux of energy through a closed surface containing a gravitating system. This method, which is based on the quasilocal formalism of Brown and York, is illustrated by two applications: a calculation of (i) the energy flux, via gravitational waves, through a surface near infinity and (ii) the tidal heating in the local asy

Gad Eilam, Frank Krauss

We discuss the decays X^* -> Xe^+e^- (``Dalitz decays&#39;&#39;) of excited heavy mesons into their ground states and an electron-positron pair. We argue that the measurement of the invariant mass spectrum of the lepton pair gives clear indication on the quantum numbers of the excited meson and thus provides an experimental test of the quark model prediction

X. Y. Pham

In the minimal extension of the standard electroweak theory with ultra massive Majorana neutrinos, the process e- + e- -> mu- + mu- could be observable, in sharp contrast with the reaction e- + e- -> W- + W- which is entirely controlled by neutrinoless double beta decay $ββ_{0 ν}$ data. Our result provides the process background that must be confronted &#34;

Hyun-Chul Kim, Michal Praszalowicz, Klaus Goeke

Using the known experimental data for the hyperon semileptonic decay constants, we calculate integrated quark densities $Δq_Λ$ and $% ΔΣ_Λ$ for the hyperon $Λ$ with flavor SU(3) symmetry breaking taken into account. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by

R. S. Bhalerao

We show that the model which naturally explains the $\bar u \ne \bar d$ asymmetry in the nucleon and is in quantitative agreement with the Gottfried sum rule data, also predicts that in the proton $\Delta \bar u > 0 > \Delta \bar s > \Delta \bar d$ and $\Delta \bar u - \Delta \bar d > \bar d - \bar u > 0$. At the input scale, these results can be derived eve

Takayuki Tatekawa, Kei-ichi Maeda

Two-point correlation function of galaxy distribution shows that the structure in the present Universe is scale-free up to a certain scale (at least several tens Mpc), which suggests that a fractal structure may exist. If small primordial density fluctuations have a fractal structure, the present fractal-like nonlinear structure below the horizon scale could

Peter L. Christiansen, Yuri B. Gaididei, Serge F. Mingaleev

We consider a curved chain of nonlinear oscillators and show that the interplay of curvature and nonlinearity leads to a number of qualitative effects. In particular, the energy of nonlinear localized excitations centered on the bending decreases when curvature increases, i.e. bending manifests itself as a trap for excitations. Moreover, the potential of thi

Enrique Gaztanaga, Alberto Lobo

We reconsider the problem of gravitational structure formation inside and outside General Relativity (GR), both in the weakly and strongly non-linear regime. We show how these regimes can be explored observationally through clustering of high order cumulants and through the epoch of formation, abundance and clustering of collapse structures, using Press-Sche

Zhenjun Xiao, Chong Sheng Li, Kuang-Ta Chao

In the framework of general two-Higgs-doublet models, we calculate the branching ratios of various inclusive charmless b decays by using the low energy effective Hamiltonian including next-to-leading order QCD corrections, and examine the current status and the new physics effects on the determination of the charm multiplicity $n_c$ and semileptonic branchin

C. De Conti, A. P. Galeao, F. Krmpotic

The Gamow-Teller resonances are discussed in the context of a self-consistent RPA, based on the relativistic mean field theory. We inquire on the possibility of substituting the phenomenological Landau-Migdal force by a microscopic nucleon-nucleon interaction generated from the rho-nucleon tensor coupling. The effect of this coupling turns out to be very sma

Simon C. Benjamin, Patrick M. Hayden

In a recent paper, Eisert et al. presented a quantum mechanical generalization of Prisoner&#39;s Dilemma. They asserted that the maximally entangled game exhibits a unique Nash equilibrium which yields a pay-off equivalent to cooperative behaviour. In this comment we show that their observation is incorrect: there is no Nash equilibrium in the space of deter

Lance Fortnow

The complexity of quantum computation remains poorly understood. While physicists attempt to find ways to create quantum computers, we still do not have much evidence one way or the other as to how useful these machines will be. The tools of computational complexity theory should come to bear on these important questions. Quantum computing often scares away

Masanao Ozawa

Every measurement on a quantum system causes a state change from the system state just before the measurement to the system state just after the measurement conditional upon the outcome of measurement. This paper determines all the possible conditional state changes caused by measurements of nondegenerate discrete observables. For this purpose, the following

Robert Olkiewicz

A subclass of dynamical semigroups induced by the interaction of a quantum system with an environment is introduced. Such semigroups lead to the selection of a stable subalgebra of effective observables. The structure of this subalgebra is completely determined.

Ding-Yu Chung

All leptons, quarks, and gauge bosons can be placed in the periodic table of elementary particles. The periodic table is derived from dualities of string theory and a Kaluza-Klein substructure for the six extra spatial dimensions. As a molecule is the composite of atoms with chemical bonds, a hadron is the composite of elementary particles with hadronic bond

B. G. Sidharth

In this brief paper we justify observations made in El Naschie&#39;s paper &#34;On the Unification of the Fundamental Forces...&#34;, on the Planck scale, fractal space time and the unification of interactions, from different standpoints.

A. Bonasera

We describe the properties of quark matter at zero temperature and finite baryon densities within microscopic Vlasov/molecular dynamics approaches. We use an inter-quark Richardson&#39;s potential consistent with the indications of Lattice QCD calculations. The color degrees of freedom are explicitly taken into account. We explicitly demonstrate that the Vla

J. Dobaczewski, P. Magierski, W. Nazarewicz, W. Satula

Odd-even staggering of binding energies is studied in finite fermion systems with pairing correlations. We discuss contributions of the pairing and mean-field to the staggering, and we construct the binding-energy filters which measure the magnitude of pairing correlations and the effective single-particle spacings in a given system The analysis is based on

Hiranmaya Mishra

We discuss here a model of QCD vacuum in terms of quark antiquark and gluon condensates alongwith their fluctuations. The correlation functions of hadronic currents in such a vacuum are evaluated to extract hadron properties. The presence of fluctuations of the condensates are emphasized. The structure of vacuum is then generalised to finite temperatures to

Boris A. Malomed, Horacio G. Rotstein

We propose an indirect approach to the generation of a two-dimensional quasiperiodic (QP) pattern in convection and similar nonlinear dissipative systems where a direct generation of stable uniform QP planforms is not possible. An {\it eightfold} QP pattern can be created as a broad transient layer between two domains filled by square cells (SC) oriented und

Gregorio Falqui, Franco Magri, Marco Pedroni, Jorge P. Zubelli

We present a fairly new and comprehensive approach to the study of stationary flows of the Korteweg-de Vries hierarchy. They are obtained by means of a double restriction process from a dynamical system in an infinite number of variables. This process naturally provides us with a Lax representation of the flows, which is used to find their bi-Hamiltonian for

Sandro Graffi, Kenji Yajima

We prove that the Floquet spectrum of a class of time-periodic Schroedinger equations under a a mildly nonlinear resonant forcing is purely absolutely continuous.

Alexei Borodin

We use discrete analogs of Riemann-Hilbert problem&#39;s methods to derive the discrete Bessel kernel which describes the poissonized Plancherel measures for symmetric groups. To do this we define discrete analogs of a Riemann-Hilbert problem and of an integrable integral operator and show that computing the resolvent of a discrete integrable operator can be

Andreas Cap, Michael Eastwood

We generalise the notion of contact manifold by allowing the contact distribution to have codimension two. There are special features in dimension six. In particular, we show that the complex structure on a three-dimensional complex contact manifold is determined solely by the underlying contact distribution.

Nguyen Viet Hai

Using $\star$-product on Co-adjoint orbits (K-orbits) of the $\MD_4$- groups we obtain quantum half-planes, quantum hyperbolic cylinders, quantum hyperbolic paraboloids...via Fedosov deformation quantization. From this we have corresponding unitary representations of the $\MD_4$- groups. Particularly, for groups $\G_{4,2,3(ϕ)}; \G_{4,2,4}; \G_{4,3,4(ϕ)}$ and

Vadim E. Levit, Eugen Mandrescu

The stability number of a graph G, denoted by alpha(G), is the cardinality of a stable set of maximum size in G. A graph is well-covered if every maximal stable set has the same size. G is a Koenig-Egervary graph if its order equals alpha(G) + mu(G), where mu(G) is the cardinality of a maximum matching in G. In this paper we characterize $α^{++}$-stable grap

Krzysztof Burdzy, Jean-Francois Le Gall

We consider super-Brownian motion whose historical paths reflect from each other, unlike those of the usual historical super-Brownian motion. We prove tightness for the family of distributions corresponding to a sequence of discrete approximations but we leave the problem of uniqueness of the limit open. We prove a few results about path behavior for process

Michael Schröder

This paper derives integral representations for the Black-Scholes price of arithmetic-average Asian options. Their proof is by Laplace inverting the 1992 Laplace transform of Geman-Yor using complex analytic methods. The analysis ultimately rests on the gamma function which in this sense is at the base of Asian options. The results of Geman-Yor are corrected

U. Bunke, M. Olbrich

We derive a formula for the regularized trace of operators with compact spectrum which act on the space of square integrable functions on the quotient of a semisimple Liegroup of real rank one by a convex-cocompact subgroup. The sum of normalized orbital integrals associated to the hyperbolic conjugacy classes of this subgroup is an invariant distribution on

Vladimir Hinich

In 1998 D. Tamarkin announced a proof of Kontsevich formality theorem based on the existence of structure of homotopy Gerstenhaber algebra in the Hochschild cochains of an associative algebra. In this note we give a detailed explanation of Tamarkin&#39;s result.

C. Faber, R. Pandharipande

We describe a new perspective on the intersection theory of the moduli space of curves involving both Virasoro constraints and Gorenstein conditions. The main result of the paper is the computation of a basic 1-point Hodge integral series occurring in the tautological ring of the moduli space of nonsingular curves. In the appendix by D. Zagier, &#34;Polynomi

Ian I. Kogan, Graham G. Ross

We consider a modification of gravity at large distances in a Brane Universe which was discussed recently. In these models the modification of gravity at large distances is ultimately connected to existence of negative tension brane(s) and exponentially small tunneling factor. We discuss a general model which interpolates between Bi-gravity model and GRS mod

Haru-Tada Sato, Michael G. Schmidt, Claus Zahlten

Within the framework of the world-line formalism we write down in detail a two-loop Euler-Heisenberg type action for gluon loops in Yang-Mills theory and discuss its divergence structure. We exactly perform all the world-line moduli integrals at two loops by inserting a mass parameter, and then extract divergent coefficients to be renormalized.

Y. Arakane, H. Itoyama

We consider the five dimensional $USp(2k)$ gauge theory which consists of one antisymmetric and $n_{f}$ fundamental hypermultiplets. This gauge theory is a many-probe generalization of the SU(2) gauge theory in five dimensions considered by Seiberg in the context of probing type I superstring by a D4-brane. This gauge theory can also be obtained from the USp

Stefan Forste, Debashis Ghoshal, Stefan Theisen

The Wilson loop in N=4 supersymmetric Yang-Mills theory admits a dual description as a macroscopic string configuration in the adS/CFT correspondence. We discuss the correction to the quark anti-quark potential arising from the fluctuations of the superstring.

M. R. Ahmady, E. Kou

We estimate the quantity |f_eta&#39;^(c)| which is associated with the charm content of eta&#39; meson from the experimentally known ratio R=B(psi ->eta&#39; gamma )/B(psi ->eta_c gamma). It is shown that due to the off-shellness of the c\bar c component of eta&#39;, which has been overlooked so far, f_eta&#39;^(c) is further suppressed. Assuming that psi ->

I. Hinchliffe, N. Kersting

Possible CP violation in supersymmetric (SUSY) extensions of the Standard Model (SM) is discussed. The consequences of CP violating phases in the gaugino masses, trilinear soft supersymmetry-breaking terms and the `mu&#39; parameter are explored. Utilizing the constraints on these parameters from electron and neutron electric dipole moments, possible CP viol

A. Le Yaouanc, D. Melikhov, V. Morénas, L. Oliver

We explicitly check quark-hadron duality to order $(m_b-m_c)Λ/m_b^2$ for $b \to c lν$ decays in the limit $m_b-m_c \ll m_b$ including ground state and orbitally excited hadrons. Duality occurs thanks to a new sum rule which expresses the subleading HQET form factor $ξ_3$ or, in other notations, $a_+^{(1)}$ in terms of the infinite mass limit form factors and

J. C. Montero, V. Pleitez, M. C. Rodriguez

By considering left-right (L-R) asymmetries we study the capabilities of lepton colliders in searching for new exotic vector bosons. Specifically we study the effect of a doubly charged bilepton boson and an extra neutral vector boson appearing in a 3-3-1 model on the L-R asymmetries for the processes $e^-e^-\to e^-e^-$, $μ^-μ^-\toμ^-μ^-$ and $e^-μ^-\to e^-μ

A. Gehrmann-De Ridder, G. Kramer, H. Spiesberger

The production of a hard and isolated photon accompanied by one or two jets in large-Q2 deep inelastic ep scattering is calculated at next-to-leading order. We include consistently contributions from quark-to-photon fragmentation and study various differential cross sections and their dependence on isolation cut parameters. Numerical results relevant for HER

K. Redlich, H. Satz, G. M. Zinovjev

Using J/psi and open charm photoproduction data, we apply the vector meson dominance model to obtain constraints on the energy dependence of the inelastic J/psi-nucleon cross section. Predictions of short distance QCD are in accord with these constraints, while recently proposed hadronic models for J/psi dissociation strongly violate them.

J. Manjavidze, A. Sissakian, H. Torosian

The very high multiplicity (VHM) processes are considered to investigate consequences of the dual resonance models reach (exponential) mass spectrum. The virial decomposition is developed for description of the produced particles short-rang (resonance) correlations. It is shown that the reach mass spectrum is able to do more flat the VHM distribution: $\s_n=

Nicole F. Bell

We investigate the mixing of heavy gauge singlet neutrinos in a mirror matter model employing the seesaw mechanism. The parameter constraints that must be satisfied to prevent the overproduction of mirror matter in the early universe are deduced. We find that no fine tuning in the heavy neutral fermion sector is required for this mirror matter model to satis

Fritz W. Bopp

Two distinct interactions of Pomerons should occur in dense multi-string events. Besides the usual triple Pomeron processes transitions to membraned cylinders can be expected to contribute in a significant way. They offer an efficient mechanism for central baryon production and for the long range transport of initial baryons. The slope of such an exchange sh

A. Misra

This is a progress report on the extension of the analysis of hep-ph/9909498 to constructing a complete list of O(q^4) terms in the presence of external fields, directly within Heavy Baryon Chiral Perturbation Theory (HBChPT) {\it without having to first construct the relativistic BChPT Lagrangian and then carry out the ${1\over\rm m}$-reduction}. In additio

CERES collaboration

The CERES/Na45 experiment at CERN SPS measured transverse momentum spectra of charged-pions in the range 1<pt<4GeV/c near mid-rapidity in 158 AGeV/c Pb-Au collisions. The invariant transverse momentum spectra are exponential over the entire observed range. The average inverse slope is 245+/- 5MeV/c, it shows a 2.4% increase with centrality of the collision o

H1 Collaboration, C. Adloff

The production of hard di-jet events in photoproduction at HERA is dominated by resolved photon processes in which a parton in the photon with momentum fraction x_gamma is scattered from a parton in the proton. These processes are sensitive to the quark and gluon content of the photon. The differential di-jet cross-section dsigma/dlog(x_gamma) is presented h

Domenico Giulini

We review the framework of Refined Algebraic Quantization and the method of Group Averaging for quantizing systems with first-class constraints. Aspects and results concerning the generality, limitations, and uniqueness of these methods are discussed.

I. Brevik, S. V. Pettersen

A Bianchi type -I metric of Kasner form is considered, when the space is filled with a viscous fluid. Whereas an ideal (nonviscous) fluid permits the Kasner metric to be anisotropic provided that the fluid satisfies the Zel&#39;dovich equation of state, the viscous fluid does not permit the Kasner metric to be anisotropic at all. In the latter case, we calcu

László Á. Gergely

The radiative evolution of the relative orientations of the spin and orbital angular momentum vectors ${\bf S}_{\bf 1}, {\bf S}_{\bf 2}$ and ${\bf L}$, characterizing a binary system on eccentric orbit is studied up to the second post-Newtonian order. As an intermediate result, all Burke-Thorne type instantaneous radiative changes in the spins are shown to a

Tomohiro Harada, Hideo Iguchi, Ken-ichi Nakao

It is known that the gravitational collapse of a dust ball results in naked singularity formation from an initial density profile which is physically reasonable. In this paper, we show that explosive radiation is emitted during the formation process of the naked singularity.

Antonis Kakas, Rob Miller, Francesca Toni

Planning is a natural domain of application for frameworks of reasoning about actions and change. In this paper we study how one such framework, the Language E, can form the basis for planning under (possibly) incomplete information. We define two types of plans: weak and safe plans, and propose a planner, called the E-Planner, which is often able to extend

Pedro Cabalar, Manuel Cabarcos, Ramon P. Otero

The current document contains a brief description of a system for Reasoning about Actions and Change called PAL (Pertinence Action Language) which makes use of several reasoning properties extracted from a Temporal Expert Systems tool called Medtool.

Steffen Hoelldobler, Hans-Peter Stoerr

The paper reports on first preliminary results and insights gained in a project aiming at implementing the fluent calculus using methods and techniques based on binary decision diagrams. After reporting on an initial experiment showing promising results we discuss our findings concerning various techniques and heuristics used to speed up the reasoning proces

Yi-Dong Shen, Li-Yan Yuan, Jia-Huai You, Neng-Fa Zhou

Infinite loops and redundant computations are long recognized open problems in Prolog. Two ways have been explored to resolve these problems: loop checking and tabling. Loop checking can cut infinite loops, but it cannot be both sound and complete even for function-free logic programs. Tabling seems to be an effective way to resolve infinite loops and redund

Sofie Verbaeten, Danny De Schreye, Konstantinos Sagonas

Tabled logic programming is receiving increasing attention in the Logic Programming community. It avoids many of the shortcomings of SLD execution and provides a more flexible and often extremely efficient execution mechanism for logic programs. In particular, tabled execution of logic programs terminates more often than execution based on SLD-resolution. In

Adnan Darwiche

We introduced decomposable negation normal form (DNNF) recently as a tractable form of propositional theories, and provided a number of powerful logical operations that can be performed on it in polynomial time. We also presented an algorithm for compiling any conjunctive normal form (CNF) into DNNF and provided a structure-based guarantee on its space and t

Panagiotis Ipeirotis, Luis Gravano, Mehran Sahami

Many text databases on the web are &#34;hidden&#34; behind search interfaces, and their documents are only accessible through querying. Search engines typically ignore the contents of such search-only databases. Recently, Yahoo-like directories have started to manually organize these databases into categories that users can browse to find these valuable reso

Yuliya Babovich, Esra Erdem, Vladimir Lifschitz

We generalize a theorem by Francois Fages that describes the relationship between the completion semantics and the answer set semantics for logic programs with negation as failure. The study of this relationship is important in connection with the emergence of answer set programming. Whenever the two semantics are equivalent, answer sets can be computed by a

Antonis Kakas, Rob Miller, Francesca Toni

E-RES is a system that implements the Language E, a logic for reasoning about narratives of action occurrences and observations. E&#39;s semantics is model-theoretic, but this implementation is based on a sound and complete reformulation of E in terms of argumentation, and uses general computational techniques of argumentation frameworks. The system derives

Bae-Yeun Ha, Andrea J. Liu

When multivalent salts are added to dilute DNA solution, the DNA chains condense into bundles of a well-defined size. We explore two physical problems motivated by this phenomenon: the origin of the attractive interactions between the highly-negatively charged DNA chains that cause them to concentrate into bundles, and the mechanism that provents the bundles

L. Schuelke, B. Zheng

A short-time dynamic approach to weak first order phase transitions is proposed. Taking the 2-dimensional Potts models as examples, from short-time behaviour of non-equilibrium relaxational processes starting from high temperature and zero temperature states,x pseudo critical points K^{*} and K^{**} are determined. A clear difference of the values for K^{*}

J. Roth, A. R. Denton

In recent computer simulations of a simple monatomic system interacting via the Dzugutov pair potential, freezing of the fluid into an equilibrium dodecagonal quasicrystal has been reported [M. Dzugutov, Phys. Rev. Lett. 70, 2924 (1993)]. Here, using a combination of molecular dynamics simulation and thermodynamic perturbation theory, we conduct a detailed a

D. van der Marel, A. Tsvetkov, M. Grueninger, D. Dulic

A review is given of the experimental status of the interlayer coupling energy in the cuprates. A second c-axis plasmon is identified in the double layer compound Y123 for various dopings. The anomalous transport properties along the c-direction and in the planar directions are compared to model calculations based on strongly anisotropic scattering. An excel

Anupam Garg

The perfect quenching of spin tunneling first predicted for a model with biaxial symmetry, and recently observed in the magnetic molecule Fe_8, is further studied using the discrete phase integral (or Wentzel-Kramers-Brillouin) method. The analysis of the previous paper is extended to the case where the magnetic field has both hard and easy components, so th

Fernando Ojeda, Rodolfo Cuerno, Roberto Salvarezza, Luis Vazquez

We study the surface dynamics of silica films grown by low pressure chemical vapor deposition. Atomic force microscopy measurements show that the surface reaches a scale invariant stationary state compatible with the Kardar-Parisi-Zhang (KPZ) equation in three dimensions. At intermediate times the surface undergoes an unstable transient due to shadowing effe

Pierre Sens, Matthew S. Turner

Motivated by numerous X-ray scattering studies of lamellar phases with membrane proteins, amphiphilic peptides, polymers, or other inclusions, we have determined the modifications of the classical Caille law for a smectic phase as a function of the nature and concentration of inclusions added to it. Besides a fundamental interest on the behavior of fluctuati

A. M. Mariz, F. van Wijland, H. J. Hilhorst, S. R. Gomes Junior

The Riemann walk is the lattice version of the Levy flight. For the one-dimensional Riemann walk of Levy exponent 0<α<2 we study the statistics of the support, i.e. the set of visited sites, after t steps. We consider a wide class of support related observables M(t), including the number S(t) of visited sites and the number I(t) of sequences of visited sites

F. Mazzanti, A. Polls

A detailed discussion of the coherent and incoherent dynamic structure function of the free Fermi gas at finite temperature is presented. Their behavior and evolution with the momentum transfer and the temperature is analyzed, while particular attention is paid to the way in which their relative contribution changes with respect to the $\tilde{T}=0$ case. Th

F. Mazzanti, A. Polls, J. Boronat

A detailed calculation of the coherent and incoherent dynamic structure functions of the free Fermi gas, starting from their expressions in terms of the one- and semi-diagonal two-body density matrices, is derived and discussed. Their behavior and evolution with the momentum transfer is analyzed, and particular attention is devoted to the contributions that

D. Thopart, A. Wahl, A. Maignan, Ch. Simon

Both the in-plane and out-of-plane magnetoresistivities have been measured in the normal state of an optimally doped Bi2Sr2Ca0.8Y0.2Cu2O8+d single crystal with a magnetic field applied parallel and perpendicular to the CuO2 planes. Whatever the magnetic field and the current directions are, a negative magnetoresistivity is obtained over a wide range of tempe