December 1995 arXiv papers — page 7

R. Vogt, S. J. Brodsky

Fermilab experiment E791, measuring charmed hadron production in $π^- A$ interactions at 500 GeV with high statistics, has observed a strong asymmetry between the hadroproduction cross sections for leading $D$ mesons which contain projectile valence quarks and the nonleading charmed mesons without projectile valence quarks. Such correlations of the charge of

Yong-Bin He, Wei-Qin Chao, Chong-Shou Gao

While presently available p-A data observe that the nuclear dependence of $J/ψ$ and $ψ^{\prime}$ production is the same within errors, we show that different nuclear dependence of $J/ψ$ and $ψ^{\prime}$ production in the kinematic region uncovered by the present p-A data can be predicted based on two different nuclear absorption scenarios. It is found that t

Th. Lippert, G. Ritzenhöfer, U. Glässner, H. Hoeber

We investigate the performance gains from hyper-systolic implementations of n^2-loop problems on the massively parallel computer Quadrics, exploiting its 3-dimensional interprocessor connectivity. For illustration we study the communication aspects of an exact molecular dynamics simulation of n particles with Coulomb (or gravitational) interactions. We compa

Stefano Demichelis

In a previous preprint we defined an energy associated to every embedding of a surface into $R^n$ or $S^n$. This energy is invariant under Moebius tranformations and the "round" sphere is its only absolute minimum. Here we sketch a proof of the compactness property for a variant of it. The details will appear elsewhere.

Jeong-Man Park, T. C. Lubensky

In the preceding paper, we derived Coulomb-gas and sine-Gordon Hamiltonians to describe the Kosterlitz-Thouless transition on a fluctuating surface. These Hamiltonians contain couplings to Gaussian curvature not found in a rigid flat surface. In this paper, we derive renormalization-group recursion relations for the sine-Gordon model using field-theoretic te

Jeong-Man Park, T. C. Lubensky

We investigate the Kosterlitz-Thouless transition for hexatic order on a free fluctuating membrane and derive both a Coulomb gas and a sine-Gordon Hamiltonian to describe it. The Coulomb-gas Hamiltonian includes charge densities arising from disclinations and from Gaussian curvature. There is an interaction coupling the difference between these two densities

Jeong-Man Park, T. C. Lubensky

We investigate the Kosterlitz-Thouless transition for hexatic order on a free fluctuating membrane and derive both a Coulomb gas and a sine-Gordon Hamiltonian to describe it. In the former, both disclinations and Gaussian curvature contribute to the charge density. In the latter, there is a linear coupling between a scalar field and the Gaussian curvature. W

T. J. Newman, Harald Kallabis

We present an exact solution of the {\it deterministic} Kardar-Parisi-Zhang (KPZ) equation under the influence of a local driving force $f$. For substrate dimension $d \le 2$ we recover the well-known result that for arbitrarily small $f>0$, the interface develops a non-zero velocity $v(f)$. Novel behaviour is found in the strong-coupling regime for $d > 2$,

S. Krompiewski, F. Süss, U. Krey

First-principles calculations have been performed in order to determine effective exchange integrals between strongly and weakly exchange-biased Co monolayers in the modulated CoCu$_2$/CoCu$_n$ superlattices. For $3\le n\le 6$ it has been found that the respective exchange integrals have opposite signs and differ for $n\ne 4$ from each other by one order of

A. V. Onufriev, J. B. Marston

Charge transfer between hyperthermal alkali atoms and metallic scattering surfaces is an experimental and theoretical arena for many-body interactions. To model new facets, we use a generalized time-dependent Newns-Anderson Hamiltonian which includes electron spin, multiple atomic orbitals with image shifted levels, intra-atomic Coulomb repulsion, and resona

Tobias Brandes

We calculate the electronic transport properties of a system which is irradiated by a homogeneous microwave field. Within a Boltzmann equation approach, a general expression for the conductivity tensor is derived and evaluated for a quasi one-dimensional ballistic quantum wire and a two dimensional system with impurity scattering. For the latter, deviations

Milan Palus

A method for classification of complex time series using coarse-grained entropy rates (CER's) is presented. The CER's, which are computed from information-theoretic functionals -- redundancies, are relative measures of regularity and predictability, and for data generated by dynamical systems they are related to Kolmogorov-Sinai entropy. A determinis

Carl de Marcken

We present an unsupervised learning algorithm that acquires a natural-language lexicon from raw speech. The algorithm is based on the optimal encoding of symbol sequences in an MDL framework, and uses a hierarchical representation of language that overcomes many of the problems that have stymied previous grammar-induction procedures. The forward mapping from

Ole Martin Løvvik, Roar Aspesæter Olsen

We summarize and discuss some of the available experimental and theoretical data important for understanding the role played by subsurface sites in dissociative chemisorption calculations for the H$_2$/Pd(111) system. Then we use a semi-empirical potential energy surface (PES) to model the interaction of a H$_2$ molecule impinging on a Pd(111) surface. The L

Pawan Kumar, Eliot Quataert, John N. Bahcall

We argue that the solar g-modes are unlikely to have caused the discrete peaks in the power spectrum of the solar wind flux observed by Thomson et al. (1995). The lower limit to the energy of individual g-modes, using the amplitudes given by Thomson et al., is estimated to be at least 10$^{36}$ erg for low order g-modes; the resulting surface velocity amplit

Frederic A. Rasio

Equilibrium fluid configurations for close binary systems can become {\em globally unstable\/}. Instabilities arise from the strong tidal interaction between the two components, which tends to make the effective two-body potential governing the orbital motion steeper than $1/r$. As a result, a circular orbit can become unstable to small radial perturbations.

C. S. Frenk, C. M. Baugh, S. Cole

We give a brief review of current theoretical work in galaxy formation. Recent results from N-body and N-body/hydrodynamic simulations, and from semianalytic modelling are discussed. We present updated versions of some figures from Cole et al (1994). In particular, we show the effect of using the revised stellar population synthesis model of Bruzual and Char

S. Cristiani

The properties of the Lyman-$α$ absorptions observed in the spectra of QSOs are reviewed: the distribution of column densities and Doppler widths, the redshift evolution, the ``inverse effect'', the clustering. By interpreting the statistics of the line parameters insight is gained about the nature of the absorbers, their sizes, temperatures, confini

Robert Braun

High quality data are presented of neutral hydrogen emission and absorption in the fields of eleven of the nearest spiral galaxies. Multi-configuration VLA observations have provided angular resolution of 6~arcsec (corresponding to about 100~pc at the average galaxy distance of 3.5~Mpc) and velocity resolution of 6~km~s$^{-1}$, while accurately recovering th

E. J. Wampler, G. M. Williger, J. A. Baldwin, R. F. Carswell

We present results from 12 km/s resolution echelle spectroscopy of the bright $z=4.694$ QSO BR1202-0725. A preliminary analysis shows that high metallicity narrow line absorption clouds are present up to the redshift of the quasar. A damped Ly$α$ system with an HI column density of $3.1 \times 10^{20}$ cm$^{-2}$ at $z=4.383$ has an [O/H] ratio that is about

Simone Bianchi, Andrea Ferrara, Carlo Giovanardi

We present Monte Carlo simulations of dusty spiral galaxies, modelled as bulge + disk systems, aimed to study their extinction and polarization properties. The extinction parameters (absorption and scattering) of dust grains are calculated from Mie's theory for a full distribution of sizes and materials; the radiation transfer is carried on for the four

P. T. de Zeeuw, N. W. Evans, M. Schwarzschild

A general solution of the Jeans equations for oblate scale-free logarithmic potentials is given. This provides all possible second velocity moments that can hold up a stellar population of flattened scale-free density against the gravity field. A two-parameter subset of second moments for the self-consistent density of Binney's model is examined in detai

Tomasz Bulik, George Pavlov

We investigate the properties of the normal modes in a strongly magnetized hydrogen gas for conditions expected in atmospheres of isolated neutron stars. We derive and compute the polarizations and absorption coefficients of the normal modes from the polarizabily tensor using both analytical approximations and numerical calculations. We find that the spectra

Robert Botet, Marek Ploszajczak

We investigate a new model of binary fragmentation with inhibition, driven by the white noise. In a broad range of fragmentation probabilities, the power-law spatiotemporal correlations are found to arise due to self-organized criticality (SOC). We find in the SOC phase a non-trivial power spectrum of the temporal sequence of the fragmentation events. The $1

S. Baskal, Y. S. Kim

Four $SL(2,C)$ spinors are considered within the framework of Wigner's little groups which dictate internal space-time symmetries of relativistic particles. It is indicated that the little group for a massive particle at rest is $O(3)$, while it is $O(3)$-like for a moving massive particle. The little group becomes like $E(2)$ in the infinite-momentum/ze

Vladimir Dotsenko, Marco Picco, Pierre Pujol

Using 1-loop renormalisation group equations, we analyze the effect of randomness on multi-critical unitary minimal conformal models. We study the case of two randomly coupled $M_p$ models and found that they flow in two decoupled $M_{p-1}$ models, in the infra-red limit. This result is then extend to the case with $M$ randomly coupled $M_p$ models, which wi

J. Michael Owen, Jens V. Villumsen, Paul R. Shapiro, Hugo Martel

This paper presents an alternative formulation of the ASPH algorithm for evolving anisotropic smoothing kernels, in which the geometric approach of Shapiro et al. (1996; Paper I) is replaced by an approach involving a local transformation of coordinates to those in which the underlying anisotropic volume changes appear to be isotropic. The ASPH method is pre

M. Daumer, D. Duerr, S. Goldstein, N. Zanghi

We remark that the often ignored quantum probability current is fundamental for a genuine understanding of scattering phenomena and, in particular, for the statistics of the time and position of the first exit of a quantum particle from a given region, which may be simply expressed in terms of the current. This simple formula for these statistics does not ap

Kenneth Dalton

The classical concept of "mass density" is not fundamental to the quantum theory of matter. Therefore, mass density cannot be the source of gravitation. Here, we treat electromagnetic energy, momentum, and stress as its source. The resulting theory predicts that the gravitational potential near any charged elementary particle is many orders of magnit

A. E. Koshelev

We propose a simple model which explains experimental behavior of $c$-axis resistivity in layered High-T$_c$ superconductors at high fields in a limited temperature range. It is generally accepted that the in-plane dissipation at low temperatures is caused by small concentration of mobile pancake vortices whose diffusive motion is thermally activated. We dem

S. A. Apikyan, C. J. Efthimiou

In this letter, we continue the work we started at a previous paper and we propose new series of integrable models in quantum field theory. These models are obtained as perturbed models of the minimal conformal field theories on the hyper-elliptic surfaces by particular relevant operators of the untwisted sector. The quantum group symmetry of the models is a

Hagai El-Ad, Tsvi Piran, Luiz Nicolaci da Costa

We present a new void search algorithm for automated detection of voids in three-dimensional redshift surveys. Based on a model in which the main features of the LSS of the Universe are voids and walls, we classify the galaxies into wall galaxies and field galaxies and we define voids as continuous volumes that are devoid of any wall galaxies. Field galaxies

Jordi Comellas, Yuri Kubyshin, Enrique Moreno

The exact renormalization group approach (ERG) is developed for the case of pure fermionic theories by deriving a Grassmann version of the ERG equation and applying it to the study of fixed point solutions and critical exponents of the two-dimensional chiral Gross-Neveu model. An approximation based on the derivative expansion and a further truncation in the

Takeo Inami, Hitoshi Konno, Yao-Zhong Zhang

Construction of integrable field theories in space with a boundary is extended to fermionic models. We obtain general forms of boundary interactions consistent with integrability of the massive Thirring model and study the duality equivalence of the MT model and the sine-Gordon model with boundary terms. We find a variety of integrable boundary interactions

D. C. Dunbar, P. S. Norridge

We present unitarity as a method for determining the infinities present in graviton scattering amplitudes. The infinities are a combination of IR and UV. By understanding the soft singularities we may extract the UV infinities and relate these to counter-terms in the effective action. As an demonstration of this method we rederive the UV infinities present a

I. Bartos, B. Rosenstein

Energies and wave functions of edge states in twodimensional electron gas are evaluated for a finite step potential barrier model. The spectrum, instead of smooth bending of Landau branches in the vicinity of the barrier acquires a steplike form; unexpected edge plateaus and significant energy gap reduction take place between the neighbouring Landau branches

Kazuhiko Kuroki, Hideo Aoki

A possibility of the electronic origin of the high-temperature superconductivity in cuprates is probed with the quantum Monte Carlo method by revisiting the three-band Hubbard model comprising Cu$3d_{x^2-y^2}$ and O$2p_σ$ orbitals. The $d_{x^2-y^2}$ pairing correlation is found to turn into an increasing function of the repulsion $U_d$ within the $d$ orbital

Tetsuro Saso, Masatoshi Itoh

Magnetization curve and changes of the single-particle excitation spectra by magnetic field are calculated for the periodic Anderson model at half-filling in infinite spatial dimension by using the exact diagonalization method. It is found that the field-induced insulator-to-metal transition occurs at a critical field $H_c$, which is of the order of the sing

Michael R. Douglas

We discuss a set of universal couplings between superstring Ramond-Ramond gauge fields and the gauge fields internal to D-branes, with emphasis on their topological consequences, and argue that instanton solutions in these internal theories are equivalent to D-branes. A particular example is the Dirichlet 5-brane in type I theory, which Witten recently showe

F. I. Cooperstock, V. Faraoni, G. P. Perry

The Brill-Hartle gravitational geon construct as a spherical shell of small amplitude, high frequency gravitational waves is reviewed and critically analyzed. The Regge-Wheeler formalism is used to represent gravitational wave perturbations of the spherical background as a superposition of tensor spherical harmonics and an attempt is made to build a non-sing

F. J. Weiper, J. Ankerhold, H. Grabert

Employing the path integral approach, we calculate the semiclassical equilibrium density matrix of a particle moving in a nonlinear potential field for coordinates near the top of a potential barrier. As the temperature is decreased, near a critical temperature $T_c$ the harmonic approximation for the fluctuation path integral fails. This is due to a caustic

A. Bohm, P. Kielanowski

The time reversal and irreversibility in conventional quantum mechanics are compared with those of the rigged Hilbert space quantum mechanics. We discuss the time evolution of Gamow and Gamow-Jordan vectors and show that the rigged Hilbert space case admits a new kind of irreversibility which does not appear in the conventional case. The origin of this irrev

Michael Penkava

An associative algebra is nothing but an odd quadratic codifferential on the tensor coalgebra of a vector space, and an A-infinity algebra is simply an arbitrary odd codifferential. Hochschild cohomology classifies the deformations of an associative algebra into an A-infinity algebra, and cyclic cohomology in the presence of an invariant inner product classi

P. Stovicek

The coadjoint orbits for the series $B_l,\ C_l$ and $D_l$ are considered in the case when the base point is a multiple of a fundamental weight. A quantization of the big cell is suggested by means of introducing a $\ast$-algebra generated by holomorphic coordinate functions. Starting from this algebraic structure the irreducible representations of the deform

D. E. Post, B. Braams, J. Mandrekas, W. Stacey

It is planned to use atomic processes to spread out most of the heating power over the first wall and side walls to reduce the heat loads on the plasma facing components in ITER to ~ 50 MW. Calculations indicate that there will be 100 MW in bremstrahlung radiation from the plasma center, 50 MW of radiation from the plasma edge inside the separatrix and 100 M

M. Ploszajczak, A. A. Shanenko, V. D. Toneev

We reconsider the Hung and Shuryak arguments in favour of searching for the deconfinement phase transition in heavy ion collisions {\em downward} from the nominal SPS energy, at $E_{lab} \approx 30 \ GeV/A$ where the fireball lifetime is the longest one. Using the recent lattice QCD data and the mixed phase model, we show that the deconfinement transition mi

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

Quantum algebras are a mathematical tool which provides us with a class of symmetries wider than that of Lie algebras, which are contained in the former as a special case. After a self-contained introduction to the necessary mathematical tools ($q$-numbers, $q$-analysis, $q$-oscillators, $q$-algebras), the su$_q$(2) rotator model and its extensions, the cons

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

Various applications of quantum algebraic techniques in nuclear structure physics and molecular physics are briefly reviewed. Contains 81 references.

Alessio Filippetti, Vincenzo Fiorentini, Kurt Stokbro, Riccardo Valente

Ab initio local-density-functional-theory calculations of formation energies, surface stress, and multilayer relaxations are reported for the (111), (100), and (110) surfaces of Rh. The study is performed using ultrasoft pseudopotentials and plane waves in a parallel implementation. Calculated values are in good agreement with previous studies where they exi

Michael Christ, Georgi Karadzhov, Detlef Müller

Local solvability is analyzed for natural families of partial differential operators having double characteristics. In some families the set of all operators that are not locally solvable is shown to have both infinite dimension and infinite codimension.

Beata Randrianantoanina

Suppose that a real nonatomic function space on $[0,1]$ is equipped with two re\-arran\-ge\-ment-invariant norms $\|\cdot\|$ and $|||\cdot|||$. We study the question whether or not the fact that $(X,\|\cdot\|)$ is isometric to $(X,|||\cdot|||)$ implies that $\|f\|= |||f|||$ for all $f$ in $X$. We show that in strictly monotone Orlicz and Lorentz spaces this

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis

The generalized deformed oscillator schemes introduced as unified frameworks of various deformed oscillators are proved to be equivalent, their unified representation leading to a correspondence between the deformed oscillator and the N=2 supersymmetric quantum mechanics (SUSY-QM) scheme. In addition, several physical systems (two identical particles in two

E. Sezgin

We discuss an extension of the super-Poincaré algebra in $D=11$ which includes an extra fermionic charge and super two-form charges. We give a geometrical reformulation of the $D=11$ supermembrane action which is manifestly invariant under the extended super-Poincaré transformations. Using the same set of transformations, we also reformulate a superstring ac

Antonio Ferrera, Alejandra Melfo

Within the context of a first-order phase transition in the early Universe, we study the collision process for vacuum bubbles expanding in a plasma. The effects of the plasma are simulated by introducing a damping term in the equations of motion for a $U(1)$ global field. We find that Lorentz-contracted spherically symmetric domain walls adequately describe

J. Ellis, J. Lopez, D. Nanopoulos

We re-examine the possible magnitude of the supersymmetric contribution to $R_b\equivΓ(Z^0\to\bar b b)/Γ(Z^0\to{\rm all})$ in the light of the constraints imposed by the absence of light charginos at LEP~1.5, implementing also other available phenomenological constraints. We find the supersymmetric contribution to be $R^{\rm susy}_b < 0.0017$, and discuss th

John F. Donoghue

I briefly summarized some recent work which uses the techniques of effective field theory to make quantum predictions in general relativity. In contrast to conventional expectations, these are in fact well behaved. The leading quantum correction to the interaction of two heavy masses is used as a specific example.

R. S. Willey

We comment on different results from three recent effective potential calculations of the Higgs mass lower bound.

John N. Bahcall

This talk answers a series of questions. Why study solar neutrinos? What does the combined standard model (solar plus electroweak) predict for solar neutrinos? Why are the calculations of neutrino fluxes robust? What are the three solar neutrino problems? What have we learned in the first thirty years of solar neutrino research? For the next decade, what are

T. Gehrmann

The production of $J/ψ$-pairs as a possible measure of the polarized gluon distribution $ΔG(x)$ is studied for proton--nucleon collisions at $\sqrt{s} =40\;\mbox{GeV}^2$ (HERA-$\vec{\rm N}$). Possibilities of reconstructing the helicity state of at least one of the $J/ψ$&#39;s are critically reviewed. The observation of production asymmetries in the single p

Chengxing Zhai

The gauge-fixing parameter $ξ$ dependence of two-point gauge variant correlation functions is studied for QED and QCD. We show that, in three Euclidean dimensions, or for four-dimensional thermal gauge theories, the usual procedure of getting a general covariant gauge-fixing term by averaging over a class of covariant gauge-fixing conditions leads to a nontr

Keyan Yang

The presence of a heavy fermion doublet of fourth generation in the standard model would lead to a anomalous decay with fermion number non-conservation. The anomalous decay path in the background of the electroweak instanton is demonstrated by numerical calculation. If the mass of fermion exceeds the critical value $m_f^{\rm cr}$=9.2 TeV (for $M_H=M_W$), it

Karl Jansen, Beat Jegerlehner, Chuan Liu

We present a performance comparison of the Kramers equation and the boson algorithms for simulations of QCD with two flavors of dynamical Wilson fermions and gauge group $SU(2)$. Results are obtained on $6^312$, $8^312$ and $16^4$ lattices. In both algorithms a number of optimizations are installed.

Petr Hajicek

The discussion is limited to first-class parametrized systems, where the definition of time evolution and observables is not trivial, and to finite dimensional systems in order that technicalities do not obscure the conceptual framework. The existence of reasonable true, or physical, degrees of freedom is rigorously defined and called {\em local reducibility

Ian Affleck

Recently, a new approach, based on boundary conformal field theory, has been applied to a variety of quantum impurity problems in condensed matter and particle physics. A particularly enlightening example is the multi-channel Kondo problem. In this review some earlier approaches to the Kondo problem are discussed, the needed material on boundary conformal fi

D. N. Sheng, Z. Y. Weng, Q. Gao

A breakdown of integer quantum Hall effect (IQHE) at strong disorder is studied numerically in a lattice model. We find a generic sequence by which the integer quantum Hall plateaus disappear: higher IQHE plateaus always vanish earlier than lower ones. We show that extended levels between these plateaus do not float up in energy but keep merging together aft

Thomas Pruschke, Qi Qin, Thomas Obermeier, Joachim Keller

We present a theory for the spin correlation function of the t-J model in the framework of the dynamical mean-field theory. Using this mapping between the lattice and a local model we are able to obtain an intuitive expression for the non-local spin susceptibility, with the corresponding local correlation function as input. The latter is calculated by means

Alexander D. Mirlin

The spatial structure of wave functions of anomalously localized states (ALS) in disordered conductors is studied in the framework of the $σ$--model approach. These states are responsible for slowly decaying tails of various distribution functions. In the quasi-one-dimensional case, properties of ALS governing the asymptotic form of the distribution of eigen

A. P. Jauho, K. Johnsen

We introduce and analyze the properties of dynamical Franz-Keldysh effect, i.e. the change of density-of-states, or absorption spectra, of semiconductors under the influence of {\it time-dependent} electric fields. In the case of a harmonic time-dependence, we predict the occurence of significant fine structure, both below and above the zero-field band-gap,

Junwu Gan, Dung-Hai Lee, Per Hedegard

We investigate the effect of hole doping on the strong-coupling Hubbard model at half-filling in spatial dimensions $D\ge 1$. We start with an antiferromagnetic mean-field description of the insulating state, and show that doping creates solitons in the antiferromagnetic background. In one dimension, the soliton is topological, spinless, and decoupled from t

O. Heinonen, Sebastian Eggert

We consider the effect of electron-phonon interactions on edge states in quantum Hall systems with a single edge branch. The presence of electron-phonon interactions modifies the single-particle propagator for general quantum Hall edges, and, in particular, destroys the Fermi liquid even at integer filling. The effect of the electron-phonon interactions may

F. Lesage, H. Saleur, S. Skorik

We develop in this letter an analytical approach using form- factors to compute time dependent correlations in integrable quantum impurity problems. As an example, we obtain for the first time the frequency dependent conductivity $G(ω)$ for the tunneling between the edges in the $ν=1/3$ fractional quantum Hall effect, and the spectrum $S(w)$ of the spin-spin

Kristian Jauregui, Wolfgang Häusler, Dietmar Weinmann, Bernhard Kramer

The transition matrix elements between the correlated $N$ and $N\!+\!1$ electron states of a quantum dot are calculated by numerical diagonalization. They are the central ingredient for the linear and non--linear transport properties which we compute using a rate equation. The experimentally observed variations in the heights of the linear conductance peaks

Jean Pierre Boon, David Dab, Raymond Kapral, Anna Lawniczak

Reactive lattice gas automata provide a microscopic approachto the dynamics of spatially-distributed reacting systems. After introducing the subject within the wider framework of lattice gas automata (LGA) as a microscopic approach to the phenomenology of macroscopic systems, we describe the reactive LGA in terms of a simple physical picture to show how an a

V. Loreto, G. Paladin, M. Pasquini, A. Vulpiani

We discuss the characterization of chaotic behaviours in random maps both in terms of the Lyapunov exponent and of the spectral properties of the Perron-Frobenius operator. In particular, we study a logistic map where the control parameter is extracted at random at each time step by considering finite dimensional approximation of the Perron-Frobenius operato

F. Halzen, J. E. Jacobsen, E. Zas

We have simulated the response of a high energy neutrino telescope in deep Antarctic ice to the stream of low energy neutrinos produced by a supernova. The passage of a large flux of MeV-energy neutrinos during a period of seconds will be detected as an excess of single counting rates in all individual optical modules. We update here a previous estimate of t

S. Barwick, F. Halzen, P. B. Price

The hope is that in the near future neutrino astronomy, born with the identification of thermonuclear fusion in the sun and the particle processes controlling the fate of a nearby supernova, will reach throughout and beyond our Galaxy and make measurements relevant to cosmology, astrophysics, cosmic-ray and particle physics. The construction of a high-energy

Arjun Dey, Hyron Spinrad

We report the discovery of broad MgII emission from the high redshift radio galaxy 3C265 (z=0.81). We detect the broad line in the nuclear spectrum and in the spatially extended galaxian component, both near the nucleus and in the spectrum of an off-nuclear knot located 31 kpc south east of the nucleus of the galaxy. These data provide strong support for the

Thomas S. Statler, Tammy Smecker-Hane, Gerald N. Cecil

We have measured the stellar motions in the elliptical galaxy NGC 1700 along four position angles, to very large radii, using absorption features in spectra obtained with the Multiple Mirror Telescope. Our data extend the coverage of the stellar velocity field by a factor of 5 (2.5 times further in radius and twice as many PAs) beyond previous work. We have

Frederic A. Rasio

The hydrodynamics of collisions and mergers of main-sequence stars is discussed in the light of recent 3-D calculations using the smoothed particle hydrodynamics (SPH) method. Theoretical models for the formation of blue stragglers are reviewed in the context of recent comparisons between the observed properties of blue stragglers in dense globular clusters

J. I. Katz, L. M. Canel

Data from the 3B Catalogue suggest that short and long GRB are the results of different classes of events, rather than different parameter values within a single class: Short bursts have harder spectra in the BATSE bands, but chiefly long bursts are detected at photon energies over 1 MeV, implying that their hard photons are radiated by a process not found i

Marek Gierlinski, Andrzej A. Zdziarski, W. Neil Johnson, Bernard F. Phlips

We present the results of 4 simultaneous observations of Cygnus X-1 by Ginga and OSSE. The X-ray/gamma-ray spectra can be described by an intrinsic continuum and a component due to Compton reflection including an iron K-alpha line. The intrinsic spectrum at X-ray energies is a power-law with a photon spectral index of Gamma=1.6. The intrinsic gamma-ray spect

Dan Maoz

I review the UV properties of LINERs (low-ionization nuclear emission-line regions), based mostly on the recent {\it HST} UV imaging survey of nearby galaxies by Maoz et al. (1995). 25 of the galaxies in the northern subsample host a LINER nucleus. Six of these display a prominent compact ($<$ few pc) nuclear UV ($\sim 2300$Å) source in the {\it HST} images.

H. Russ, M. Morita, M. Kasai, G. Boerner

The gravitational instability of inhomogeneities in the expanding universe is studied by the relativistic second-order approximation. Using the tetrad formalism we consider irrotational dust universes and get equations very similar to those given in the Lagrangian perturbation theory in Newtonian cosmology. Neglecting the cosmological constant and assuming a

Jayaram N. Chengalur, A. G. de Bruyn, R. Braun, C. L. Carilli

Ground based optical observations have yielded considerable information on the statistics of damped-lyman alpha systems. In particular these systems are known to be the dominant repository of the observed neutral gas at high redshift. However, particularly at high redshift, there is the possibility that optical observations could be biased due to the exclusi

Robert Braun

We briefly review the beginnings of HI astronomy, proceed to an assessment of our current capabilities in this area, and continue by considering what will be necessary to push back the frontier to cosmological distances. We then consider how such a leap in performance might be realized.

S. T. Tanaka, A. C. Clapp, M. J. Devlin, N. Figueiredo

We present measurements of cosmic microwave background (CMB) anisotropy near the stars HR5127 and Phi Herculis from the fifth flight of the Millimeter-wave Anisotropy eXperiment (MAX). We scanned 8\arcdeg\ strips of the sky with an approximately Gaussian 0\fdg5 FWHM beam and a 1\fdg4 peak to peak sinusoidal chop. The instrument has four frequency bands cente

Eric D&#39;Hoker, Darius G. Gagne

We derive a worldline path integral representation for the effective action of a multiplet of Dirac fermions coupled to the most general set of matrix-valued scalar, pseudoscalar, vector, axial vector and antisymmetric tensor background fields. By representing internal degrees of freedom in terms of worldline fermions as well, we obtain a formulation which m

A M Semikhatov, I Yu Tipunin

A general construction is found for `topological&#39; singular vectors of the twisted N=2 superconformal algebra. It demonstrates many parallels with the known construction for sl(2) singular vectors due to Malikov--Feigin--Fuchs, but is formulated independently of the latter. The two constructions taken together provide an isomorphism between topological an

K. Langanke, T. D. Shoppa, C. A. Barnes, C. Rolfs

We reanalyze the low-energy 3He(d,p)4He cross section measurements of Engstler et al. using recently measured energy loss data for proton and deuteron beams in a helium gas. Although the new 3He(d,p)4He S-factors are significantly lower than those reported by Engstler et al. they clearly show the presence of electron screening effects. From the new S-factors

Todd A. Brun, Nicolas Gisin

In computing the spectra of quantum mechanical systems one encounters the Fourier transforms of time correlation functions, as given by the quantum regression theorem for systems described by master equations. Quantum state diffusion (QSD) gives a useful method of solving these problems by unraveling the master equation into stochastic trajectories; but ther

D. V. Anchishkin, W. A. Zajc, G. M. Zinovjev

The corrections for two pion correlations due to electromagnetic final state interactions at high secondary multiplicities are investigated. It is shown that these result in a noticeable deviation from the standard Gamov factor. This conclusion changes drastically in a model of the pion system with expansion. The critical parameter which determines the size

Adrian Kent

We consider Gell-Mann and Hartle&#39;s consistent histories formulation of quantum cosmology in the interpretation in which one history, chosen randomly according to the decoherence functional probabilities, is realised from each consistent set. We show that in this interpretation, if one assumes that an observed quasiclassical structure will continue to be

I. T. Ivanov, M. Rocek

The Legendre transform and its generalizations, originally found in supersymmetric sigma-models, are techniques that can be used to give constructions of hyperkahler metrics. We give a twistor space interpretation to the generalizations of the Legendre transform construction. The Atiyah-Hitchin metric on the moduli space of two monopoles is used as a detaile

S. Deser

The usual equivalence between the Palatini and metric (or affinity and vielbein) formulations of Einstein theory fails in two spacetime dimensions for its "Kaluza--Klein" reduced (as well as for its standard) version. Among the differences is the necessary vanishing of the cosmological constant in the first order forms. The purely affine Eddington formulatio

G. D&#39;Agostini

Bayesian statistics is based on the subjective definition of probability as {\it ``degree of belief&#39;&#39;} and on Bayes&#39; theorem, the basic tool for assigning probabilities to hypotheses combining {\it a priori} judgements and experimental information. This was the original point of view of Bayes, Bernoulli, Gauss, Laplace, etc. and contrasts with la

Thomas D. Cohen

Two ideas have greatly contributed to our understanding of baryon structure in the framework of Quantum Chromodynamics (QCD). The first, chiral symmetry, received its fundamental justification from QCD and has been developed into the powerful technique of chiral perturbation theory. The other notion is the large-$N_c$ limit, namely the behavior of QCD in the

Jacek Dziarmaga

We analyze statistical interactions of skyrmions in the quantum Hall system near a critical filling fraction in the framework of the Ginzburg-Landau model. The phase picked up by the wave-function during an exchange of two skyrmions close to $ν=1/(2n+1)$ is $π[S+1/2(2n+1)]$, where $S$ is the skyrmion&#39;s spin. In the same setting an exchange of two fully p

Anders Irbäck, Carsten Peterson, Frank Potthast

The question of whether proteins originate from random sequences of amino acids is addressed. A statistical analysis is performed in terms of blocked and random walk values formed by binary hydrophobic assignments of the amino acids along the protein chains. Theoretical expectations of these variables from random distributions of hydrophobicities are compare

Piotr Zenczykowski

Weak radiative hyperon decays present us with a long-standing puzzle, namely the question of validity of a hadron-level theorem proved by Hara. We briefly discuss the conflict between expectations based on Hara&#39;s theorem and experiment as well as the way in which the quark model evades the theorem. Violation of Hara&#39;s theorem in the quark model is tr

P. Exner, P. Šeba, M. Tater, D. Vaněk

We consider a pair of parallel straight quantum waveguides coupled laterally through a window of a width $ \ell $ in the common boundary. We show that such a system has at least one bound state for any $ \ell>0 $. We find the corresponding eigenvalues and eigenfunctions numerically using the mode--matching method, and discuss their behavior in several situat