August 1999 arXiv papers — page 17

Chinlin Guo, Herbert Levine, David Kessler

Understanding the mechanism of protein secondary structure formation is an essential part of protein-folding puzzle. Here we describe a simple model for the formation of the $β$-hairpin, motivated by the fact that folding of a $β$-hairpin captures much of the basic physics of protein folding. We argue that the coupling of ``primary'' backbone stiffne

A. Pukhov, E. Boos, M. Dubinin, V. Edneral

CompHEP is a package for automatic calculations of elementary particle decay and collision properties in the lowest order of perturbation theory (the tree approximation). The main idea prescribed into the CompHEP is to make available passing on from the Lagrangian to the final distributions effectively with a high level of automation.

Enrique Vázquez-Semadeni

I review recent results derived from numerical simulations of the turbulent interstellar medium (ISM), in particular concerning the nature and formation of turbulent clouds, methods for comparing the structure in simulations and observations, and the effects of projection of three-dimensional structures onto two dimensions. Clouds formed as turbulent density

B. Semelin, N. Sanchez, H. J. de Vega

This work studies the hydrodynamics of self-gravitating compressible isothermal fluids. We show that the hydrodynamic evolution equations in absence of viscosity are scale covariant. We study the evolution of the time dependent fluctuations around singular and regular isothermal spheres. We linearize the fluid equations around such stationary solutions and a

ZEUS Collaboration

Exclusive electroproduction of rho^0 mesons has been measured using the ZEUS detector at HERA in two Q^2 ranges, 0.25<Q^2<0.85 GeV^2 and 3<Q^2<30 GeV^2. The low-Q^2 data span the range 20<W<90 GeV; the high-Q^2 data cover the 40<W<120 GeV interval. Both samples extend up to four-momentum transfers of |t|=0.6 GeV^2. The distribution in the azimuthal angle bet

A. P. Bakulev, S. V. Mikhailov

We re-estimate the tensor susceptibility of QCD vacuum, $χ$, and to this end, we re-estimate the leptonic decay constants for transversely polarized $ρ$- ,~$ρ&#39;$- and b_1-mesons. The origin of the susceptibility is analyzed using duality between $ρ$- and b_1- channels in a 2-point correlator of tensor currents. We confirm the results in Nucl.Phys. B283(19

Marco A. Diaz, Diego A. Restrepo, Jose W. F. Valle

We study the decays of the lightest top squark in supergravity models with and without R-parity. Using the simplest model with an effective explicit bilinear breaking of R-parity and radiative electroweak symmetry breaking we show that, below the threshold for decays into charginos $\tilde t_1\to cχ^+_1$, the lightest stop decays mainly into third generation

Haye Hinrichsen, Andrea Jimenez-Dalmaroni, Yadin Rozov, Eytan Domany

We introduce and investigate a simple model to describe recent experiments by Douady and Daerr on flowing sand. The model reproduces experimentally observed compact avalanches, whose opening angle decreases linearly as a threshold is approached. On large scales the model exhibits a crossover from compact directed percolation to directed percolation; we predi

A. J. Banday, S. Zaroubi, K. M. Gorski

In this paper we pursue the origin of the non-Gaussianity determined by a bispectrum analysis of the COBE-DMR 4-year sky maps. The robustness of the statistic is demonstrated by the rebinning of the data into 12 coordinate systems. By computing the bispectrum statistic as a function of various data partitions - by channel, frequency, and time interval, we sh

Michael Gershenson

What is the lowest temperature to which one can trace the growth of the dephasing time in low-dimensional conductors? I consider the fundamental limitation, the crossover from weak to strong localization, as well as several experimental reasons for frequently observed saturation of the dephasing time (hot-electron effects, dephasing by external noise). Recen

A. Belavin, Yu. Stroganov

We consider the integrable XXZ model with the special open boundary conditions. We perform Quantum Group reduction of this model in roots of unity and use it for the definition Minimal Models of Interable lattice theory. It is shown that after this Quantum Group reduction Sklyanin&#39;s transfer-matrices satisfy the closed system of the truncated functional

S. Melinte, N. Freytag, M. Horvatic, C. Berthier

Using a `standard&#39; NMR spin-echo technique we determined the spin polarization of two-dimensional electrons, confined to GaAs quantum wells, from the hyperfine shift of Ga nuclei in the wells. Concentrating on the temperature and magnetic field dependencies of spin polarization at Landau level filling factor $ν=1/2$, we find that the results are describe

F. R. Pearce, P. A. Thomas, H. M. P. Couchman, A. C. Edge

In this paper, we investigate the effect of cooling on the X-ray properties of galaxy clusters. We have performed N-body, hydrodynamical simulations both with and without the effects of radiative cooling, but neglecting the effects of star formation and feedback. We show that radiative cooling produces an inflow of high-entropy gas from the outer parts of th

R. Coquereaux, A. O. Garcia, R. Trinchero

We define a quantum generalization of the algebra of functions over an associated vector bundle of a principal bundle. Here the role of a quantum principal bundle is played by a Hopf-Galois extension. Smash products of an algebra times a Hopf algebra H are particular instances of these extensions, and in these cases we are able to define a differential calcu

G. D&#39;Agostini

Subjective probability is based on the intuitive idea that probability quantifies the degree of belief that an event will occur. A probability theory based on this idea represents the most general framework for handling uncertainty. A brief introduction to subjective probability and Bayesian inference is given, with comments on typical misconceptions which t

Alex Lewin, Andreas Albrecht

We consider the consequences of an observed Cosmic Microwave Background (CMB) temperature anisotropy spectrum containing no secondary oscillations. While such a spectrum is generally considered to be a robust signature of active structure formation, we show that such a spectrum {\em can} be produced by (very unusual) inflationary models or other passive evol

Bodo Huckestein, Roland Ketzmerick, Caio H. Lewenkopf

We study transport through a two-dimensional billiard attached to two infinite leads by numerically calculating the Landauer conductance and the Wigner time delay. In the generic case of a mixed phase space we find a power law distribution of resonance widths and a power law dependence of conductance increments apparently reflecting the classical dwell time

Chin-Kun Hu, E. V. Ivashkevich, Chai-Yu Lin, V. B. Priezzhev

Statistics of waves of topplings in the Sandpile model is analysed both analytically and numerically. It is shown that the probability distribution of dissipating waves of topplings that touch the boundary of the system obeys power-law with critical exponent 5/8. This exponent is not indeendent and is related to the well-known exponent of the probability dis

Takahiko Matsubara

A general formula for the correlation function in redshift space is derived in linear theory. The formula simultaneously includes wide-angle effects and cosmological distortions. The formula is applicable to any pair with arbitrary angle $θ$ between lines of sight, and arbitrary redshifts, $z_1$, $z_2$, which are not necessarily small. The effects of the spa

I. N. McArthur

The nature of $κ$-symmmetry transformations is examined for p-branes embedded in a class of coset superspaces G/H, where G is an appropriate supergroup and H is the Lorentz subgroup. It is shown that one of the conditions $δZ^M E_M{}^a = 0$ which characterizes $κ$-symmetry transformations arises very naturally if they are implemented in terms of a right acti

Johann Rafelski, Jean Letessier

In a dynamical model of QGP at RHIC we obtain the temporal evolution of strange phase space occupancy at conditions expected to occur in 100+100A GeV nuclear collisions. We show that the sudden QGP break up model developed to describe the SPS experimental results implies dominance of both baryon and antibaryon abundances by the strange baryon and antibaryon

A. V. Mikhailov, V. V. Sokolov

In this paper we give definitions of basic concepts such as symmetries, first integrals, Hamiltonian and recursion operators suitable for ordinary differential equations on associative algebras, and in particular for matrix differential equations. We choose existence of hierarchies of first integrals and/or symmetries as a criterion for integrability and jus

C. R. Hagen

The scattering cross section associated with a two dimensional delta function has recently been the object of considerable study. It is shown here that this problem can be put into a field theoretical framework by the construction of an appropriate Galilean covariant theory. The Lee model with a standard Yukawa interaction is shown to provide such a realizat

E. Paspalakis, N. J. Kylstra, P. L. Knight

We study the absorption and dispersion properties of a ${\bf Λ}$-type atom which decays spontaneously near the edge of a photonic band gap (PBG). Using an isotropic PBG model, we show that the atom can become transparent to a probe laser field, even when other dissipative channels are present. This transparency originates from the square root singularity of

Emmanuel Paspalakis

We revisit the problem of laser-induced suppression of quantum dynamical tunneling in a model system studied by Kilin et al. [Phys. Rev. Lett. 76 (1996) 3297]. This quantum system consists of a ground state symmetric double-well potential which is coupled by a strong laser field to an excited state asymmetric double-well potential. By analyzing the assumptio

T. Garavaglia

Both the classical and quantum approximate invariants are found for the nonlinar r time-dependent oscillator of sextupole transverse betatron dynamics. They are represented in terms of the elements of a Lie algebra associated with powers of phase space coordinates. The first order quantum correction to the classical quasi-invariant is found.

Stephan I. Tzenov

A kinetic equation for the joint probability distribution for fixed values of the classical action, momentum and density has been derived. Further, the hydrodynamic equations of continuity and balance of momentum density have been transformed into a Schroedinger-like equation, describing particle motion in an effective electro-magnetic field and an expressio

Juan P. Torres, Jack Boyce, Raymond Y. Chiao

We show the existence of a region in the parameter space that defines the field dynamics in a Fabry-Perot cylindrical cavity, where three output stable stationary states of the light are possible for a given localized incident field. Two of these states do not preserve the bilateral (i.e. left-right) symmetry of the entire system. These broken-symmetry state

G. V. Danilov, E. V. Shuryak

Multiplicity fluctuations in heavy ion collisions obtain comparable contributions both from initial stage of the collisions, and from final stage interaction. We calculate the former component, using the ``wounded nucleon&#39;&#39; model and standard assumptions about nuclei and NN cross section. Combining it with the second one, calculated previously by Ste

P. Braun-Munzinger, K. Redlich

We consider the production of charmonium by $D\bar D$ annihilation during the mixed and hadronic phase of Pb-Pb collision at LHC energy. The calculations for secondary $J/ψ$ and $ψ^,$ production are performed within a kinetic model taking into account the space-time evolution of a longitudinally and transversely expanding medium. It is shown that the yield o

Gerald A. Miller

High energy scattering experiments involving nuclei are typically analyzed in terms of light front variables. The desire to provide realistic, relativistic wave functions expressed in terms of these variables led me to try to use light front dynamics to compute nuclear wave functions. The progress is summarized here.

K. A. Bugaev, M. I. Gorenstein

The particle emission in relativistic hydrodynamic model is formulated assuming a sharp 3-dimensional space-time freeze-out hypersurface. The boundary conditions correspond to the energy-momentum and charge conservation between fluid and the gas of free particles. The emission and possible feedback of particles are included into the self-consistent hydrodyna

Cesar Castilho

In this paper we study the motion of a charged particle on a Riemannian surface under the influence of a positive magnetic field B. Using Moser&#39;s Twist Theorem and ideas from classical pertubation theory we find sufficient conditions to perpetually trap the motion of a particle with a sufficiently large charge in a neighborhood of a level set of the magn

G. F. Dell&#39;Antonio, R. Figari, A. Teta

We consider the motion of a non relativistic quantum particle in R^3 subject to n point interactions which are moving on given smooth trajectories. Due to the singular character of the time-dependent interaction, the corresponding Schrodinger equation does not have solutions in a strong sense and, moreover, standard perturbation techniques cannot be used. He

G. Panati, A. Teta

The flux-across-surfaces theorem establishes a fundamental relation in quantum scattering theory between the asymptotic outgoing state and a quantity which is directly measured in experiments. We prove it for a hamiltonian with a point interaction, using the explicit expression for the propagator. The proof requires only assuptions on the initial state and i

Palle E. T. Jorgensen, Gestur Ólafsson

The notions of reflection, symmetry, and positivity from quantum field theory are shown to induce a duality operation for a general class of unitary representations of Lie groups. The semisimple Lie groups which have this $c$-duality are identified and they are placed in the context of Harish-Chandra&#39;s legacy for the unitary representations program. Our

Dorothea M. Eberz-Wagner

Part I of the thesis gives a complete analysis of gaps in a one-dimensional creation-annihilation model. Part II contains a proof of the existence of infinitely many holes in the two-dimensional DLA cluster.

Jim Pitman, Richard Stanley

We define an n-dimensional polytope Pi_n(x), depending on parameters x_i>0, whose combinatorial properties are closely connected with empirical distributions, plane trees, plane partitions, parking functions, and the associahedron. In particular, we give explicit formulas for the volume of Pi_n(x) and, when the x_i&#39;s are integers, the number of integer p

Richard Rochberg, Nik Weaver

We state several equivalent noncommutative versions of the Cauchy-Riemann equations and characterize the unbounded operators on L^2(R) which satisfy them. These operators arise from the creation operator via a functional calculus involving a class of entire functions, identified by Newman and Shapiro [D. J. Newman and H. S. Shapiro, Fischer spaces of entire

S. A. Pol&#39;shin, A. A. Zheltukhin

We construct a tensionless string model in a four-dimensional space-time ${\bf R}^{2,2}$ with the (2,2) signature and solve the string equations. We find that the signature change radically changes the structure of the holonomy group of the null worldsheet. As a result the introduction of the worldsheet Dirac operator invariant under the holonomy group becom

Richard J. Szabo

Canonical quantization of abelian BF-type topological field theory coupled to extended sources on generic d-dimensional manifolds and with curved line bundles is studied. Sheaf cohomology is used to construct the appropriate topological extension of the action and the topological flux quantization conditions, in terms of the Cech cohomology of the underlying

Morten Krogh

In this thesis we will discuss various aspects of noncommutative geometry and compactified Little-String theories. First we will give an introduction to the use of noncommutative geometry in string theory. Thereafter we will present a proof of the connection between D-brane dynamics and noncommutative geometry. Then we will explain the concept of instantons

Kasper Olsen, Richard J. Szabo

A detailed review of recent developments in the topological classification of D-branes in superstring theory is presented. Beginning with a thorough, self-contained introduction to the techniques and applications of topological K-theory, the relationships between the classic constructions of K-theory and the recent realizations of D-branes as tachyonic solit

Christos Epameinonda Kokorelis

We construct new F-theory vacua in 8-dimensions. They are coming by projective realizations of F-theory on $K_3$ surfaces admitting double covers onto $¶^2$, branched along a plane sextic curve, the so called double sextics. The new vacua are associated with singular $K_3$ surfaces. In this way the stable picture of the heterotic string is mapped at the trip

Oliver DeWolfe, Tamas Hauer, Amer Iqbal, Barton Zwiebach

In a previous paper we explored how conjugacy classes of the modular group classify the symmetry algebras that arise on type IIB [p,q] 7-branes. The Kodaira list of finite Lie algebras completely fills the elliptic classes as well as some parabolic classes. Loop algebras of E_N fill additional parabolic classes, and exotic finite algebras, hyperbolic extensi

Oliver DeWolfe, Tamas Hauer, Amer Iqbal, Barton Zwiebach

We begin a classification of the symmetry algebras arising on configurations of type IIB [p,q] 7-branes. These include not just the Kodaira symmetries that occur when branes coalesce into a singularity, but also algebras associated to other physically interesting brane configurations that cannot be collapsed. We demonstrate how the monodromy around the 7-bra

E. V. Shuryak

Brief review of current status of the field.

P. Christova, M. Jack, S. Riemann, T. Riemann

ZFITTER is a Fortran package for the description of fermion-pair production in e+e- annihilation. We report on results of a rederivation of the complete set of analytical O(alpha) formulae for the treatment of photonic corrections to the total cross-section and the integrated forward-backward asymmetry with combined cuts on acollinearity angle, acceptance an

V. John, G. S. Krishnaswami, S. G. Rajeev

We derive the Deep Inelastic anti-quark distribution in a baryon at a low value of Q^2 using the variational principle of Quantum HadronDynamics, an alternative formulation of Quantum ChromoDynamics. It is determined by a variational approach generalizing the ``valence&#39;&#39; quark approximation of earlier papers. We find that the ``primordial&#39;&#39; a

M. Knecht, S. Peris, M. Perrottet, E. de Rafael

The counterterm combination that describes the decay of pseudoscalar mesons into charged lepton pairs at lowest order in chiral perturbation theory is considered within the framework of QCD in the limit of a large number of colours Nc. When further restricted to the lowest meson dominance approximation to large-Nc QCD, our results agree well with the availab

Marcus J. Thatcher, Michael J. Morgan

The behaviour of electromagnetic waves propagating through an electroweak homilia string network is examined. This string network is topologically stable as a cosmic texture, and is characterized by the spatial variation of the isospin rotation of the Higgs field. As a consequence the photon field couples to the intermediate vector bosons, producing a finite

V. Barone

I present a brief update on the transverse polarization distributions, focusing on model calculations and phenomenological perspectives.

C. Boros, F. M. Steffens, J. T. Londergan, A. W. Thomas

To date, the strongest indication of charge symmetry violation in parton distributions has been obtained by comparing the $F_2$ structure functions from CCFR neutrino data and NMC muon data. We show that in order to make precise tests of charge symmetry with the neutrino data, two conditions must be satisfied. First, the nuclear shadowing calculations must b

G. S. Krishnaswami, S. G. Rajeev

We use the variational principle of Quantum HadronDynamics, an alternative formulation of Quantum ChromoDynamics, to determine the wavefunction of valence quarks in a baryon at a low value of Q^2. This can be used to predict the structure function xF_3(x,Q^2) at higher values of Q^2 using the evolution equations of perturbative QCD. This prediction is compar

S. G. Rajeev

We show that two dimensional QCD can, to a good approximation, describe the hadronic structure functions measured in Deep Inelastic Scattering. We transform this theory into a new form, Quantum HadronDynamics (QHD), whose semi-classical approximation is closer to nature. The Baryon is then a topological soliton, and its structure function can be predicted by

S. Collins, C. T. H. Davies, J. Hein, J. Shigemitsu

We present preliminary results for the decay constant of the Bs meson, fBs, at three values of beta=5.7, 6.0 and 6.2 using NRQCD and clover fermions for the heavy and light quarks respectively. As a consistency check the decay constant has also been extracted from the axial-vector current at finite momentum. In addition, we discuss the cancellation of O(alph

The SLD Collaboration

We present a preliminary study of correlations in rapidity between pairs of identified charged pions, kaons and protons using the entire SLD data sample of 550,000 hadronic Z^0 decays. Short range charge correlations are observed between all combinations of these hadron species, indicating local conservation of quantum numbers and charge ordering in the jet

L. G. Landsberg

In this talk the Coulomb production reactions at high energy are discussed as well as the study of electromagnetic properties of hadrons (mesons and hyperons) in these processes. The results of previous investigations are summed together with some recent data of SELEX(Fermilab) and SPHINX(IHEP) experiments.

The SLD Collaboration

We have updated our results on identified charged hadron production using the full SLD data sample of 550,000 hadronic Z^0 decays taken between 1993 and 1998. The SLD Cherenkov Ring Imaging Detector allows the identification of clean samples of charged pions, kaons and protons over a wide momentum range, providing precise tests of perturbative QCD calculatio

SLD Collaboration

We present preliminary results of a new measurement of the inclusive b quark fragmentation function in Z0 decays using a novel kinematic B hadron energy reconstruction technique. The measurement is performed using 150,000 hadronic Z0 events recorded in the SLD experiment at SLAC between 1996 and 1997. The small and stable SLC beam spot and the CCD-based vert

SLD Collaboration, K. Abe

Angular asymmetries have been measured in polarized Z0 decays to bbg collected by the SLD experiment at the SLC. A high purity bbg event sample is selected by utilizing B lifetime information given by the SLD CCD pixel vertex detector and the stable micron-size SLC beams, and the b- and bbar-jets are identified using lifetime information and momentum-weighte

T. E. Browder, CLEO Collaboration

Using the CLEO II detector operating at the CESR e+e- collider, we have measured the structure functions in the decay tau+/- --> pi+/- pi0 pi0 nu, based on a sample corresponding to 4*10E6 produced tau-pair events. We determine the integrated structure functions, which depend only on the three pion invariant mass, as well as the structure functions different

T. E. Coan, CLEO Collaboration

We search for CP violating asymmetries in five charmless hadronic B meson decays using the full CLEO II and CLEO II.V data samples totalling 9.7 million BBbar events. The resulting Acp measurements have a precision that varies from +-0.12 to +-0.25 (absolute) depending on mode. No significant nonzero asymmetry is observed in any mode but 90% CL limits are st

Kenji Abe et al

We present a preliminary measurement of the rate of gluon splitting into bottom quarks, g -> b bbar, in hadronic Z0 decays collected by SLD between 1996 and 1998. The analysis was performed by looking for secondary bottom production in 4-jet events of any primary flavour. 4-jet events were identified, and a topological vertex-mass technique was applied to ea

Kenji Abe et al

The structure of e+e- -> bbg events was studied using Z0 decays recorded in the SLD experiment at SLAC. Three-jet final states were selected and the CCD-based vertex detector was used to identify two of the jets as b or bbar. Distributions of the gluon energy and polar angle were measured over the full kinematic range, and compared with perturbative QCD pred

A. Anastassov, CLEO Collaboration

We present an update of the search for the lepton family number violating decay $τ\to μγ$ using a complete CLEO II data sample of 12.6 million $τ^+τ^-$ pairs. No evidence of a signal has been found and the corresponding upper limit is $ \BR(τ\to μγ) < 1.0 \times 10^{-6} $ at 90% CL, significantly smaller than previous limits. All quoted results are prelimina

K. W. Edwards, CLEO Collaboration

The resonant structure of the four pion final state in the decay $τ\to 3ππ^0ν_τ$ is analyzed using 4.27 million $τ^+τ^-$ pairs collected by the CLEO II experiment. We search for second class currents in the decay $τ\to ωπν_τ$ using spin-parity analysis and establish an upper limit on the non-vector current contribution. The mass and width of the $ρ&#39;$ res

Harry N. Nelson

We present a compilation of predictions for the amplitudes of D0-D0bar mixing.

S. J. Richichi, CLEO Collaboration

In a sample of 19 million produced B mesons we have observed decays B -> eta K*, and improved our previous measurements of B -> eta&#39; K. The branching fractions we measure for these decay modes are B(B+ -> eta K*+) = (27.3 +9.6 -8.2 (stat) +- 5.0 (sys)) * 10^(-6), B(B0 -> eta K*0) = (13.8 +5.5 -4.4 +- 1.7) * 10^(-6), B(B+ -> eta&#39; K+) = (80 +10 -9 +- 8

M. Bishai, CLEO Collaboration

We present results of searches for B-meson decays to charmless final states that include a K*, rho, omega, or phi meson accompanied by a second meson. Using the entire data sample of 9.7 million BBbar pairs collected with the CLEO II and CLEO II.V detectors, we observe a signal for the decay B+ -> omega pi+, and measure a branching fraction of B(B+ -> omega

Matt Visser, Bruce Bassett, Stefano Liberati

We argue that ``effective&#39;&#39; superluminal travel, potentially caused by the tipping over of light cones in Einstein gravity, is always associated with violations of the null energy condition (NEC). This is most easily seen by working perturbatively around Minkowski spacetime, where we use linearized Einstein gravity to show that the NEC forces the lig

Aristophanes Dimakis, Folkert Muller-Hoissen

Several examples and models based on noncommutative differential calculi on commutative algebras indicate that a metric should be regarded as an element of the left-linear tensor product of the space of 1-forms with itself. We show how the metric compatibility condition with a linear connection generalizes to this framework.

Yasunori Fujii

We revisit a model of the two-scalar system proposed previously for understanding a small but nonzero cosmological constant. The model provides solutions of the scalar-fields energy $ρ_s$ which behaves truly constant for a limited time interval rather than in the way of tracker- or scaling-type variations. This causes a mini-inflation, as indicated by recent

Liao Liu, Yongge Ma

We show from one-loop quantum gravity and statistical thermodynamics that the thermodynamics of quantum foam in flat space-time and Schwarzschild space-time is exactly the same as that of Hawking-Unruh radiation in thermal equilibrium. This means we show unambiguously that Hawking-Unruh thermal radiation should contain thermal gravitons or the contribution o

Roberto A. Sussman

A physicaly reasonable interpretation is provided for the perfect fluid, sphericaly symmetric, conformally flat ``Stephani Universes&#39;&#39;. The free parameters of this class of exact solutions are determined so that the ideal gas relation $p=n k T$ is identicaly fulfiled, while the full equation of state of a classical monatomic ideal gas and a matter-ra

Arlen Anderson, Yvonne Choquet-Bruhat, James W. York

We discuss several explicitly causal hyperbolic formulations of Einstein&#39;s dynamical 3+1 equations in a coherent way, emphasizing throughout the fundamental role of the ``slicing function,&#39;&#39; $α$---the quantity that relates the lapse $N$ to the determinant of the spatial metric $\bar{g}$ through $N = \bar{g}^{1/2} α$. The slicing function allows u

Patrik Simons

The rules associated with propositional logic programs and the stable model semantics are not expressive enough to let one write concise programs. This problem is alleviated by introducing some new types of propositional rules. Together with a decision procedure that has been used as a base for an efficient implementation, the new rules supplant the standard

V. A. Ivanshin, J. Deisenhofer, H. -A. Krug von Nidda, A. Loidl

This is the first systematic ESR investigation of La_(1-x)Sr_(x)MnO_(3) single crystals for Sr concentrations x < 0.2. The rich phase diagram of this compound, which is dominated by the Jahn-Teller effect of Mn^(3+), is a matter of actual interest in connection with giant magnetoresistance phenomena. The ESR signal, which is due to both Mn^(3+) and Mn^(4+),

R. D. Antonov, A. T. Johnson

We observe current rectification in a molecular diode consisting of a semiconducting single-wall carbon nanotube and an impurity. One half of the nanotube has no impurity, and it has a current-voltage (I-V) charcteristic of a typical semiconducting nanotube. The other half of the nanotube has the impurity on it, and its I-V characteristic is that of a diode.

Ingve Simonsen, Alexei A. Maradudin, Tamara A. Leskova

We calculate the short-range contributions $C^{(1)}$ and $C^{(10)}$ to the angular intensity correlation function for the scattering of s-polarized light from a one-dimensional random interface between two dielectric media. The calculations are carried out on the basis of a new approach that separates out explicitly the contributions $C^{(1)}$ a nd $C^{(10)}

Chinlin Guo, Herbert Levine

Intracellular signaling often arises from ligand-induced oligomerization of cell surface receptors. This oligomerization or clustering process is fundamentally a cooperative behavior between near-neighbor receptor molecules; the properties of this cooperative process clearly affects the signal transduction. Recent investigations have revealed the molecular b

Yoshiyuki Kabashima, Tatsuto Murayama, David Saad

The performance of Gallager&#39;s error-correcting code is investigated via methods of statistical physics. In this approach, the transmitted codeword comprises products of the original message bits selected by two randomly-constructed sparse matrices; the number of non-zero row/column elements in these matrices constitutes a family of codes. We show that Sh

G. Modugno, C. Benko, P. Hannaford, G. Roati

We report laser cooling of fermionic K-40 atoms, with temperatures down to (15 +/- 5) microK, for an enriched sample trapped in a MOT and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of two of the lowest realizable rms velocity (~3.5v rec) in 3D o

Angsula Ghosh, Sadhan K. Adhikari

We study numerically the temperature dependencies of specific heat, susceptibility, penetration depth, and thermal conductivity of a coupled $(d_{x^2-y^2}+is)$-wave Bardeen-Cooper-Schreiffer superconductor in the presence of a weak s-wave component (1) on square lattice and (2) on a lattice with orthorhombic distorsion. As the temperature is lowered past the

Angsula Ghosh, Sadhan K. Adhikari

We study the phase transition from a $d_{x^2-y^2}$ to $d_{x^2-y^2}+d_{xy}$ superconductor using the tight-binding model of two-dimensional cuprates. As the temperature is lowered past the critical temperature $T_c$, first a $ d_{x^2-y^2}$ superconducting phase is created. With further reduction of temperature, the $ d_{x^2-y^2}+d_{xy}$ phase is created at te

M. E. Gershenson, Yu. B. Khavin, D. Reuter, P. Schafmeister

We have studied the non-ohmic effects in the conductivity of a two-dimensional system which undergoes the crossover from weak to strong localization with decreasing electron concentration. When the electrons are removed from equilibrium with phonons, the hopping conductivity depends only on the electron temperature. This indicates that the hopping transport

J. Ruostekoski, B. Kneer, W. P. Schleich

We theoretically study the coherent expansion of a Bose-Einstein condensate in the presence of a confining impenetrable hard-wall potential. The nonlinear dynamics of the macroscopically coherent matter field results in rich and complex spatio-temporal interference patterns demonstrating the formation of vorticity and solitonlike structures, and the fragment

P. Farkasovsky

The extrapolation of small-cluster exact-diagonalization calculations is used to examine the influence of correlated hopping on valence and metal-insulator transitions in the one-dimensional Falicov-Kimball model. It is shown that the ground-state phase diagram as well as the picture of valence and metal-insulator transitions found for the conventional Falic

Alexander I. Olemskoi, Dmitrii O. Kharchenko

The governed equations for the order parameter, one-time and two-time correlators are obtained on the basis of the Langevin equation with the white multiplicative noise which amplitude $x^{a}$ is determined by an exponent $0<a<1$ ($x$ being a stochastic variable). It turns out that equation for autocorrelator includes an anomalous average of the power-law fu

Z. Radovic, L. Dobrosavljevic--Grujic, B. Vujicic

The unconventional Josephson coupling in a ferromagnetic weak link between d-wave superconductors is studied theoretically. For strong ferromagnetic barrier influence, the unconventional coupling, with ground state phase difference across the link $0<ϕ_{\rm gs}\leq π$, is obtained at small crystal misorientation of the superconducting electrodes, in contrast

Przemyslaw Repetowicz, Uwe Grimm, Michael Schreiber

We investigate zero-field Ising models on periodic approximants of planar quasiperiodic tilings by means of partition function zeros and high-temperature expansions. These are obtained by employing a determinant expression for the partition function. The partition function zeros in the complex temperature plane yield precise estimates of the critical tempera

Fabio Bernardini, Vincenzo Fiorentini

Macroscopic polarization plays a major role in determining the optical and electrical properties of nitride nanostructures via polarization-induced built-in electrostatic fields. While currently fashionable, this field of endeavour is still by far in its early infancy. Here we contribute some clarifications on the conceptual issues involved in determining bu

Sang-Hoon Kim, Chul Koo Kim, Kyun Nahm

Physical properties of ideal Bose gas with the fractal dimensionality between D=2 and D=3 are theoretically investigated. Calculation shows that the characteristic features of the specific heat and the superfluid density of ideal Bose gas in fractal dimensions are strikingly similar to those of superfluid Helium-4 in porous media. This result indicates that

V. V. Makhro

The mechanism of the parametrical stimulated tunneling in the spectrum of the moving domain wall considered. It is shown that such a mechanism can to cause the initial phase of the parametrical evolution of domain wall&#39;s surface waves. In turn, this evolution leads to an appearance of essential features in domain walls dynamics.

F. Schaefer, C. Timm, D. Manske, K. H. Bennemann

In underdoped cuprates, T_c is thought to be determined by Cooper pair phase fluctuations because of the small superfluid density n_s. Experimentally, T_c is found to scale with n_s. The fluctuation-exchange approximation (FLEX) in its standard form fails to predict this behavior of T_c since it does not include phase fluctuations. We therefore extend the FL

K. Rateitschak, R. Klages, G. Nicolis

We present a novel mechanism for thermalizing a system of particles in equilibrium and nonequilibrium situations, based on specifically modeling energy transfer at the boundaries via a microscopic collision process. We apply our method to the periodic Lorentz gas, where a point particle moves diffusively through an ensemble of hard disks arranged on a triang

Rafael M. Gutierrez

In this work we address the feasibility of estimating and isolating the stationary and deterministic content of observational time series, {\bf Ots}, which in general have very limited characteristics. In particular, we study the valuable earth&#39;s surface mean temperature time series, {\bf Tts}, by applying several treatments intended to isolate the stati

Qingjuan Yu, Youjun Lu

Previous calculations of Fe K-alpha line profiles are based on axisymmetric emissivity laws. In this paper, we show line profiles driven by non-axial symmetric illumination which results from an off-axis X-ray point source. We find that source location and motion have significant effects on the red wing and blue horn of the line profiles. The disk region und

F. A. Harrison, P. S. Ray, D. A. Leahy, E. B. Waltman

The binary system, LSI+61 303, is unusual both because of the dramatic, periodic, radio outbursts, and because of its possible association with the 100 MeV gamma-ray source, 2CG135+01. We have performed simultaneous radio and Rossi X-ray Timing Explorer X-ray observations at eleven intervals over the 26.5 day orbit, and in addition searched for variability o

Anthony H. Gonzalez, Kurtis A. Williams, James S. Bullock, Tsafrir S. Kolatt

We present a galaxy circular velocity function, Psi(log v), derived from existing luminosity functions and luminosity-velocity relations. Such a velocity function is desirable for several reasons. First, it enables an objective comparison of luminosity functions obtained in different bands and for different galaxy morphologies, with a statistical correction