May 1995 arXiv papers — page 10

Dean Rasheed

The most general electrically and magnetically charged rotating black hole solutions of 5 dimensional \KK\ theory are given in an explicit form. Various classical quantities associated with the black holes are derived. In particular, one finds the very surprising result that the gyromagnetic and gyroelectric ratios can become {\tenit arbitrarily large}. The

Masaru Kamata, Takao Koikawa

The Einstein-Maxwell equations with a negative cosmological constant in 2+1 spacetime dimensions discussed by Banados, Teitelboim and Zanelli are solved by assuming a self(anti-self)dual equation. The solution describes an electrically charged extreme black hole with an angular momentum.

H. Abramowicz, A. Caldwell, R. Sinkus

We present an electron identification algorithm based on a neural network approach applied to the ZEUS uranium calorimeter. The study is motivated by the need to select deep inelastic, neutral current, electron proton interactions characterized by the presence of a scattered electron in the final state. The performance of the algorithm is compared to an elec

Zoltan Neda

Finite 3D Ising ferromagnets are studied in periodic magnetic fields both by computer simulations and mean-field theoretical approaches. The phenomenon of stochastic resonance is revealed. The characteristic peak obtained for the correlation function between the external oscillating magnetic field and magnetization versus the temperature of the system, is st

Pascale Fung

We present a pattern matching method for compiling a bilingual lexicon of nouns and proper nouns from unaligned, noisy parallel texts of Asian/Indo-European language pairs. Tagging information of one language is used. Word frequency and position information for high and low frequency words are represented in two different vector forms for pattern matching. N

Avery Meiksin, Francois R. Bouchet

We present a novel technique for calculating the two-point autocorrelation function of the Lyman-alpha forest based on the relation between the two-point correlation function and the Neighbor Probability Distribution Functions. The technique appears to reduce the scatter in estimates of the correlation function by a factor of about two from the traditional p

Jonathan Bagger, Erich Poppitz, Lisa Randall

We examine the stability of the mass hierarchy in hidden-sector supergravity theories. We show that a quadratically divergent tadpole can appear at two loops, even in minimal supergravity theories, provided the theory has a gauge- and global-symmetry singlet with renormalizable couplings to the visible fields. This tadpole can destabilize the hierarchy. We a

J. A. Marck, A. Lioure, S. Bonazzola

We present a formalism well adapted to the numerical study of the encounter of an ordinary main sequence star with a massive black hole. Symmetry considerations, the use of a well adapted moving grid and a well adapted moving frame along with integration of the partial differential equations by means of pseudo-spectral methods result in a very powerful and a

A. Gorsky, I. Krichever, A. Marshakov, A. Mironov

The exact Seiberg-Witten (SW) description of the light sector in the $N=2$ SUSY $4d$ Yang-Mills theory is reformulated in terms of integrable systems and appears to be a Gurevich-Pitaevsky (GP) solution to the elliptic Whitham equations. We consider this as an implication that dynamical mechanism behind the SW solution is related to integrable systems on the

Dirk Kreimer

Work is reported on finite integral representations for 2-loop massive 2-, 3- and 4-point functions, using orthogonal and parallel space variables. It is shown that this can be utilized to cover particles with arbitrary spin (tensor integrals), and that UV divergences can be absorbed in an algebraic manner. This includes a classification of UV divergences by

Andreas Albrecht, David Coulson, Pedro Ferreira, Joao Magueijo

Fluctuations in the cosmic microwave background (CMB) temperature are being studied with ever increasing precision. Two competing types of theories might describe the origins of these fluctuations: ``inflation'' and ``defects''. Here we show how the differences between these two scenarios can give rise to striking signatures in the microwave

W. Younes, J. A. Cizewski, H. -Q. Jin, L. A. Bernstein

Prompt, in-beam $γ$ rays following the reaction $^{170}$Yb + 142 MeV $^{28}$Si were measured at the ATLAS facility using 10 Compton-suppressed Ge detectors and the Fragment Mass Analyzer. Transitions in $^{194}$Po were identified and placed using $γ$-ray singles and coincidence data gated on the mass of the evaporation residues. A level spectrum up to J$\app

P. S. Howe, J. M. Izquierdo, G. Papadopoulos, P. K. Townsend

We construct a new class of $(p,q)$-extended Poincaré supergravity theories in 2+1 dimensions as Chern-Simons theories of supersymmetry algebras with both central and automorphism charges. The new theories have the advantage that they are limits of corresponding $(p,q)$ adS supergravity theories and, for not too large a value of $N=p+q$, that they have a nat

I. Jack, D. R. T. Jones, K. L. Roberts

We calculate the particle spectrum of the SSM which follows from the assumption that the commonly assumed universal form of the soft supersymmetry --breaking terms is invariant under renormalisation. It is argued that this ``strong'' universality might be approached as an infra--red fixed point for the unified theory above the unification scale.

J. I. Collar

Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce in elastic scattering off nuclei in organic tissue create radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia and oncogenesis. Using a c

Denis V. Juriev

A convenient algebraic structure to describe some forms of dynamics of two hamiltonian systems with nonpotential (magnetic--type) interaction is considered. An algebraic mechanism of generation of such dynamics is explored on simple "toy" examples and models. Nonpotential chains and their continuum limits are also considered. Examples of hybrid coupl

Victor Vassiliev

Homology groups of spaces of nonsingular polynomial embeddings ${\bf R}^1 \to {\bf R}^n$ of degrees $\le 4$ are calculated. A general algebraic technique of such calculations for spaces of polynomial knots of arbitrary degrees is described.

S. Giller, C. Gonera, P. Kosiński, P. Maślanka

The quantum Galilei group $G_{\varkappa}$ is defined. The bicrossproduct structure of $G_{\varkappa}$ and the corresponding Lie algebra is revealed. The projective representations for the two-dimensional quantum Galilei group are constructed.

A. Filippetti, David Vanderbilt, W. Zhong, Yong Cai

We propose a systematic method of analyzing pseudopotential transferability based on linear-response properties of the free atom, including self-consistent chemical hardness and polarizability. Our calculation of hardness extends the approach of Teter\cite{teter} not only by including self-consistency, but also by generalizing to non-diagonal hardness matric

S. J. Gates, Oleg A. Soloviev

We Describe a one-parameter family of c=1 CFT's as a continuous conformal deformation of the SL(2)_4/U(1) coset.

M. Alimohammadi, F. Ardalan

The transformation of the $SL(2,R)/U(1)$ black hole under a boost of the subgroup U(1) is studied. It is found that the tachyon vertex operators of the black hole go into those of the $c=1$ conformal field theory coupled to gravity. The discrete states of the black hole also tend to the discrete states of the 2-d gravity theory. The fate of the extra discret

Cécile Martin

We apply the time-dependent variational principle of Balian and Vénéroni to the $ Φ^4$ theory. An appropriate parametrization for the variational objects allows us to write coupled dynamical equations from which we derive approximations for the two-time correlation functions involving two, three or four field operators.

E. Elizalde, P. Fosalba-Vela, S. Naftulin, S. D. Odintsov

Taking advantage of the representation of dilatonic gravity with the $R^2$-term under the form of low-derivative dilatonic gravity coupled to an additional scalar, we construct a general renormalizable model motivated by this theory. Exact black hole solutions are found for some special versions of the model, and their thermodynamical properties are describe

P. Teotonio-Sobrinho

String theory in 4 dimensions has the unique feature that a topological term, the oriented self-intersection number, can be added to the usual action. It has been suggested that the corresponding theory of random surfaces wold be free from the problem encountered in the scaling of the string tension. Unfortunately, in the usual dynamical triangulation it is

M. A. Walker

An analysis of a $SU(2)_L \times SU(2)_R$ invariant, supersymmetric effective theory is given. The resulting leading and next to leading independent invariants are stated in terms of the underlying Killing vectors and Kähler potential. The appendices are devoted to the relationship between this geometrical point of view and the standard unitary matrix formul

S. A. Abel, P. L. White

We consider the production of baryon number from collapsing domain walls, and in particular examine the magnitude of CP violation which is required in such schemes. Taking the conventional solution to the domain wall problem in the Next-to-Minimal Supersymmetric Standard Model as an example, we show that the observed baryon assymmetry of the universe may hav

Howard E. Haber

In models with a non-minimal Higgs sector, the lightest scalar state may be a neutral CP-even Higgs boson, whose properties are nearly identical to those of the minimal Higgs boson of the Standard Model. In such a scenario, the other Higgs scalars are significantly heavier than $m_Z$; their effects rapidly decouple from the low-energy theory. The decoupling

B. Ananthanarayan, Saurabh D. Rindani

Certain momentum correlations in the production and subsequent decay of heavy fermion pairs in $e^+e^-$ collisions have increased sensitivity to CP-violating electric and ``weak" dipole form factors of the fermion in the presence of longitudinal polarization of the $e^+e^-$ beams. However, unless the polarizations of $e^+$ and $e^-$ are equal and opposit

Matthias Neubert

I discuss the theoretical uncertainties in the extraction of $|\,V_{cb}|$ from semilep\-to\-nic decays of $B$ mesons, taking into account the most recent theoretical developments. The main sources of uncertainty are identified both for the exclusive decay mode $B\to D^*\ell\,\barν$ and for the inclusive channel $B\to X\,\ell\,\barν$. From an analysis of the

Bing An Li

The chiral theory of mesons of two flavors have been extended to mesons containing strange flavor. Two new mass relations between vector and axial-vector mesons have been obtained. In chiral limit, the physical processes of normal parity and abnormal parity have been studied. Due to the universality of the coupling of this theory many interesting results hav

Zheng Huang, Mahiko Suzuki

We examine the validity of the notion of the coherent state for pions and the quantum scattering effect in the final state of pion emission. When the number of particles is large, the effect caused by the small but finite mass difference between the neutral and charged pions can add up substantially in the quantum evolution of an initially coherent state. As

J. Creighton, R. B. Mann

We consider an Einstein-Hilbert-Dilaton action for gravity coupled to various types of Abelian and non-Abelian gauge fields in a spatially finite system. These include Yang-Mills fields and Abelian gauge fields with three and four-form field strengths. We obtain various quasilocal quantities associated with these fields, including their energy and angular mo

Uwe C. T"auber, David R. Nelson

We study the ground state and low energy excitations of vortices pinned to columnar defects in superconductors, taking into account the long--range interaction between the fluxons. We consider the ``underfilled'' situation in the Bose glass phase, where each flux line is attached to one of the defects, while some pins remain unoccupied. By exploiting

Fernando Moraes

This communication concerns the structure of the electromagnetic quantum vacuum in a disclinated insulator. It is shown that a nonzero vacuum energy density appears when the rotational symmetry of a continuous insulating elastic medium is broken by a disclination. An explicit expression is given for this Casimir energy density in terms of the parameter descr

A. Dotsenko

A bi-layer quantum frustrated antiferromagnet is studied using an effective action approach. The action derived from the microscopical Hamiltonian has the form of the O(3) non-linear sigma model. It is solved in the mean field approximation with the ultraviolet cut off chosen to fit numerical results. The obtained phase diagram displays a decrease in the cri

Victor Sofonea

A lattice Boltzmann model with interacting particles was developed in order to simulate the magneto-rheological characteristics of magnetic fluids. In the frame of this model, $6\, +\,1$ species of particles are allowed to move across a $2D$ triangular lattice. Among these species, $6$ of them carry an individual magnetic dipole moment and interact themselve

Robert P. Futrelle, Nikos Nikolakis

This paper describes substantial advances in the analysis (parsing) of diagrams using constraint grammars. The addition of set types to the grammar and spatial indexing of the data make it possible to efficiently parse real diagrams of substantial complexity. The system is probably the first to demonstrate efficient diagram parsing using grammars that easily

Pablo Gervas

Tableaux originate as a decision method for a logical language. They can also be extended to obtain a structure that spells out all the information in a set of sentences in terms of truth value assignments to atomic formulas that appear in them. This approach is pursued here. Over such a structure, compositional rules are provided for obtaining the presuppos

Norbert Reithinger, Elisabeth Maier

In this paper, we present a statistical approach for dialogue act processing in the dialogue component of the speech-to-speech translation system \vm. Statistics in dialogue processing is used to predict follow-up dialogue acts. As an application example we show how it supports repair when unexpected dialogue states occur.

D. L. Gonzalez, L. Morettini, F. Sportolari, O. Rosso

The ability of the auditory system to perceive the fundamental frequency of a sound even when this frequency is removed from the stimulus is an interesting phenomenon related to the pitch of complex sounds. This capability is known as ``residue'' or ``virtual pitch'' perception and was first reported last century in the pioneering work of See

Dany Page, Yu. A. Shibanov, V. E. Zavlin

We present a model to explain the decrease in the amplitude of the pulse profile with increasing energy observed in Geminga's soft X-ray surface thermal emission. We assume the presence of plates surrounded by a surface with very distinct physical properties: these two regions emit spectra of very distinct shapes which present a crossover, the warm plate

Anthony N. Aguirre, Robert H. Brandenberger

Cosmic strings with small-scale structure have a coarse-grained mass per unit length $μ$ which is larger than the string tension. This leads to an effective Newtonian gravitational line source and to a characteristic translational velocity which is smaller than for strings without small-scale structure. Here, the accretion of hot dark matter onto such string

Stephane Colombi, Scott Dodelson, Lawrence M. Widrow

Warm dark matter (WDM) is an intriguing model of structure formation from the point of view of both cosmology and particle physics. We consider a one-parameter family of WDM models. The linear power spectra for these models is calculated and compared with the corresponding spectra for cold dark matter (CDM), hot dark matter (HDM) and mixed dark matter (MDM)

P. Vauterin, H. Dejonghe

We explore a series expansion method to calculate the modes of oscillations for a variety of uniformly rotating finite disks, either with or without a dark halo. Since all models have the same potential, this survey focuses on the role of the distribution function in stability analyses. We show that the stability behaviour is greatly influenced by the struct

S. N. Nazin, K. A. Postnov

Calculation of gravitational radiation during binary inspiral leading to possible formation of a Thorne-Zytkow (TZ) object (a neutron star inside a supergiant core) is performed. The calculations were done for polytropic density distributions with different indeces $n$, as well as for realistic models of supergiants. A maximum frequency of the emitted gravit

F. Guillén, V. Navarro Aznar

Let $k$ be a field of characteristic zero. By using Hironaka's desingularisation theorem, we prove an extension criterion for a functor defined on nonsingular k-schemes and taking values on a category of complexes. Roughly speaking, the criterion shows that if such a functor satisfies the standard exact sequence of a blowing-up, then the functor can be e

Ichiro Shimada

A couple of complex projective plane curves are said to make a Zariski pair if they have the same degree and the same type of singularities, but their embeddings in the projective plane are topologically different. In this paper, we present a method to construct certain type of Zariski pairs, and make infinite series of examples.

Nicholas P. Buchdahl

The relationship between stable holomorphic vector bundles on a compact complex surface and the same such objects on a blowup of the surface is investigated, where "stability" is with respect to a Gauduchon metric on the surface and naturally derived such metrics on the blowup. The main results are: descriptions of holomorphic vector bundles on a blo

Nicholas P. Buchdahl

When identified with sequences of irreducible Hermitian-Einstein connections, sequences of stable holomorphic bundles of fixed topological type and bounded degree on a compact complex surface equipped with a Gauduchon metric are shown to have strongly convergent subsequences after blowing-up and pulling-back sufficiently many times.

Francisco Figueirido, Gabriela S. Del Buono, Ronald M. Levy

We discuss the origin and relevance for computer simulations of a strong finite-size effect that appears when using the Ewald summation formula. It can be understood as arising from a volume-dependent shift of the potential in a finite, periodic box relative to the infinite volume limit. This shift is due to the fact that the ``zero of energy'' for a

Aberto S. Cattaneo, Paolo Cotta-Ramusino, Juerg Froehlich, Maurizio Martellini

In this paper we discuss topological BF theories in 3 and 4 dimensions. Observables are associated to ordinary knots and links (in 3 dimensions) and to 2-knots (in 4 dimensions). The vacuum expectation values of such observables give a wide range of invariants. Here we consider mainly the 3-dimensional case, where these invariants include Alexander polynomia

M. A. Clayton

The arguments leading to the introduction of the massive Nonsymmetric Gravitational action are reviewed \cite{Moffat:1994,Moffat:1995b}, leading to an action that gives asymptotically well-behaved perturbations on GR backgrounds. Through the analysis of spherically symmetric perturbations about GR (Schwarzschild) and NGT (Wyman-type) static backgrounds, it i

Atsushi Moriwaki

Let K be a function field and C a non-isotrivial curve of genus g >= 2 over K. In this paper, we will show that if C has a global stable model with only geometrically irreducible fibers, then Bogomolov conjecture over function fields holds.

Paul S. Aspinwall, David R. Morrison

We analyze the U-duality group for the case of a type II superstring compactified to four dimensions on a K3 surface times a torus. The various limits of this theory are considered which have interpretations as type IIA and IIB superstrings, the heterotic string, and eleven-dimensional supergravity, allowing all these theories to be directly related to each

Zdenek Hradil

Canonical quantization of electromagnetic field inside the time--spatially dispersive inhomogeneous dielectrics is presented. Interacting electromagnetic and matter excitation fields create the closed system, Hamiltonian of which may be diagonalized by generalized polariton transformation. Resulting dispersion relations coincide with the classical ones obtai

V. D. Lyakhovsky

The branching rules between simple Lie algebras and its regular (maximal) simple subalgebras are studied. Two types of recursion relations for anomalous relative multiplicities are obtained. One of them is proved to be the factorized version of the other. The factorization property is based on the existence of the set of weights $Γ$ specific for each injecti

Attila Csoto, Rezso G. Lovas

In a recent publication Zheng, Vary, and Barrett reproduced the negative quadrupole moment of Li-6 and the low-lying positive-parity states of He-5 by using a no-core shell model. In this Comment we question the meaning of these results by pointing out that the model used is inadequate for the reproduction of these properties.

S. Gardner, C. J. Horowitz, J. Piekarewicz

We consider charge-symmetry violations in the nucleon-nucleon force which result from isospin-violating meson-baryon coupling constants. The vector mesons are assumed to couple to the nucleon's electromagnetic current, which we decompose into isoscalar and isovector quark components. We compute these currents in the context of a constituent quark model.

Emanuel Knill, S. Muthukrishnan

In group testing, the task is to determine the distinguished members of a set of objects L by asking subset queries of the form ``does the subset Q of L contain a distinguished object?'' The primary biological application of group testing is for screening libraries of clones with hybridization probes. This is a crucial step in constructing physical m

H. J. de Vega, I. L. Egusquiza

Multistring solutions of the string equations of motion are found for inflationary spacetimes with expansion factor $R(η)\propto η^k$ for any $k<0$ and $η$ conformal time. If $0>k>-1$ only two-string solutions can be found within our ansatz, whereas for $k=-1-1/n$, with $n=1,2,\ldots$, multistring solutions exist with an infinite number of strings [In the sp

G. Au, B. Spence

New formulations of the solutions of N=1 and N=2 super Toda field theory are introduced, using Hamiltonian Reduction of the N=1 and N=2 super WZNW Models to the super Toda Models. These parameterisations are then used to present the Hamiltonian formulations of the super Toda theories on the spaces of solutions.

I. T. Dyatlov

A multiflavor model for dynamical chiral breaking reveals a solution highly suitable for stimulation of flavor mass hierarchy and mixings. The mechanism triggering the both phenomena simultaneously suppresses flavor changings. Thus, the main features of the observed quark system may spontaneously appear as inherent properties of a specific ground state.

David Atwood, Amarjit Soni

CP violating asymmetries in both the production and the decays of $s$-channel neutral Higgs bosons at $μ^+μ^-$ colliders can be large. If the CP violation occurs in the muon-Higgs coupling, one observes a production asymmetry with transversely polarized $μ^+μ^-$ beams. Likewise if the CP violation occurs in the top-Higgs or $τ$-Higgs coupling, one observes a

Chi-Yee Cheung, Wei-Min Zhang, Guey-lin Lin

The heavy quark effective theory is developed on the light-front. Based on this effective theory, a light-front heavy meson bound state with definite spin and parity is constructed. Within the effective theory, the Isgur-Wise function is derived in terms of the asymptotic light-front bound state amplitudes in the limit $m_Q\rightarrow\infty$; the result is a

A. Pich

These lectures provide an overview of Quantum Chromodynamics (QCD), the $SU(3)_C$ gauge theory of the strong interactions. After briefly reviewing the empirical considerations which lead to the introduction of {\it colour}, the QCD Lagrangian is discussed. The running of the strong coupling and the associated property of {\it Asymptotic Freedom} are analyzed

E. Laenen, S. Riemersma

We discuss the calculation of $F_2^γ({\rm charm})$ to next-to-leading order (NLO) in QCD, including contributions from both hadronlike and pointlike photons. We show that the former dominates strongly below $x\simeq 0.01$, and the latter above this value. This fact makes $F_2^γ({\rm charm})$ for $x \geq 0.01$ calculable, whereas for $x \leq 0.01$ it serves t

A. A. Gvozdev, A. V. Kuznetsov, N. V. Mikheev, L. A. Vassilevskaya

I report the recent studies\cite{1,2} on the low--energy manifestations of a minimal extension of the Standard Model based on the quark-lepton symmetry $SU(4)_V \otimes SU(2)_L \otimes G_R$ of the Pati-Salam type. Given this symmetry the third type of mixing in the interactions ot the $SU(4)_V$ leptoquarks with quarks and leptons is shown to be required. An

J. L. Hewett

We examine the indirect effects of new physics on a variety of processes in the $B$ system, such as the $Z\to b\bar b$ vertex, the decays $B\to X_s γ$ and $B\to X_s\ell^+\ell^-$, and CP violation. {Presented at the 4th International Conference on Physics Beyond the Standard Model, Lake Tahoe, CA, December 13-18, 1994}

H1 Collaboration

Deep inelastic scattering (DIS) events, selected from 1993 data taken by the H1 experiment at HERA, are studied in the Breit frame of reference. The fragmentation function of the quark is compared with those of \ee data. It is shown that certain aspects of the quarks emerging from within the proton in \ep interactions are essentially the same as those of qua

Carlo Rovelli, Lee Smolin

We introduce a new basis on the state space of non-perturbative quantum gravity. The states of this basis are linearly independent, are well defined in both the loop representation and the connection representation, and are labeled by a generalization of Penrose&#39;s spin netoworks. The new basis fully reduces the spinor identities (SU(2) Mandelstam identit

M. C. Chang, Q. Niu

We develop a semiclassical theory for the dynamics of electrons in a magnetic Bloch band, where the Berry phase plays an important role. This theory, together with the Boltzmann equation, provides a framework for studying transport problems in high magnetic fields. We also derive an Onsager-like formula for the quantization of cyclotron orbits, and we find a

S. Kobe, T. Klotz

A misfit parameter is used to characterize the degree of frustration of ordered and disordered systems. It measures the increase of the ground-state energy due to frustration in comparison with that of a relevant reference state. The misfit parameter is calculated for various spin-glass models. It allows one to compare these models with each other. The exten

A. Yu. Tretyakov, N. Inui

We study mixed site-bond directed percolation on 2D and 3D lattices by using time-dependent simulations. Our results are compared with rigorous bounds recently obtained by Liggett and by Katori and Tsukahara. The critical fractions $p_{site}^c$ and $p_{bond}^c$ of sites and bonds are extremely well approximated by a relationship reported earlier for isotropi

A. B. Harris, C. Micheletti, J. M. Yeomans

We study the effect of quantum fluctuations on the multiphase point of the Heisenberg model with first- and second-neighbor competing interactions and strong uniaxial spin anisotropy $D$. By studying the structure of perturbation theory we show that the multiphase degeneracy which exists for $S=\infty$ (i.e., for the ANNNI model) is lifted and that the effec

M. E. Raikh, L. I. Glazman

We show that the tunnel coupling between semiclassical states localized in different minima of a smooth random potential increases when magnetic field is applied. This increase originates from the difference in gauge factors which electron wave functions belonging to different electron ``lakes&#39;&#39; acquire in the presence of the field. We illustrate the

Victor M. Yakovenko, Hsi-Sheng Goan

The influence of the motion of a magnetic-field-induced spin-density wave (FISDW) on the quantum Hall effect in a quasi-one-dimensional conductor is studied theoretically. In the ideal case of a free FISDW, it is found that the counterflow of the FISDW precisely cancels the quantum Hall current, so the resultant Hall conductivity is zero. In real systems, th

Christian Jacquemin

Terminological acquisition is an important issue in learning for NLP due to the constant terminological renewal through technological changes. Terms play a key role in several NLP-activities such as machine translation, automatic indexing or text understanding. In opposition to classical once-and-for-all approaches, we propose an incremental process for term

Rajeev Agarwal

Semantic clusters of a domain form an important feature that can be useful for performing syntactic and semantic disambiguation. Several attempts have been made to extract the semantic clusters of a domain by probabilistic or taxonomic techniques. However, not much progress has been made in evaluating the obtained semantic clusters. This paper focuses on an

Alex Kim, Ariel Goobar, Saul Perlmutter

Photometric measurements show that as a group nearby type Ia supernovae follow similar lightcurves and reach similar peak magnitudes Thus, these supernovae can serve as standard candles or calibrated candles at cosmological distances. Magnitudes of local and distant supernovae, both in the same filter band, are compared using a $K$ correction to account for

S. Perlmutter, C. R. Pennypacker, G. Goldhaber, A. Goobar

We have begun a program to discover high-redshift supernovae ($z \approx$ 0.25--0.5), and study them with follow-up photometry and spectroscopy. We report here our first discovery, a supernova at $z = 0.458$. The photometry for this supernova closely matches the lightcurve calculated for this redshift from the template of well-observed nearby Type Ia superno

Ariel Goobar, Saul Perlmutter

We explore the feasibility of resurrecting the apparent magnitude-redshift relation for a ``standard candle&#39;&#39; to measure the cosmological constant and mass density. We show that type Ia supernovae, if measured with 0.15 mag uncertainty out to a redshift of z=1, may provide a good standard candle or calibrated candle for this purpose. The recent disco

Dave Syer, Cathie Clarke

We demonstrate, using a simple analytic model, that the presence of a massive satellite can globally modify the structure and emission properties of an accretion disc to which it is tidally coupled. We show, using two levels of numerical approximation, that the analytic model gives reasonable results. The results are applicable to two astrophysical situation

Christina M. Bird, Richard F. Mushotzky, Christopher A. Metzler

Most studies of correlations between X-ray and optical properties of galaxy clusters have used the largest samples of data available, regardless of the morphological types of clusters included. Given the increasing evidence that morphology is related to a cluster&#39;s degree of dynamical evolution, we approach the study of X-ray and optical correlations dif

Robert J. Nemiroff, Andrew Gould

Two spacecraft separated by $\sim 1\,\au$ and equipped with gamma-ray burst (GRB) detectors could detect or rule out a cosmological density of Massive Compact Halo Objects (MACHOs) in the mass range $10^{-15} M_{\odot}\lsim M \lsim 10^{-7} M_{\odot}$ provided that GRBs prove to be cosmological. Previously devised methods for detecting MACHOs have spanned the

Ann I. Zabludoff, Dennis Zaritsky

We present direct evidence of a collision of subclusters in the galaxy cluster Abell 754. Our comparison of new optical data and archival ROSAT PSPC X-ray data reveal three collision signatures predicted by n-body/hydrodynamical simulations of hierarchical cluster evolution. First, there is strong evidence of a non-hydrostatic process; neither of the two maj

Zuhui Fan, J. M. Bardeen

We discuss the probability distributions of Fourier modes of cosmological density fields using the central limit theorem as it applies to weighted integrals of random fields. It is shown that if the cosmological principle holds in a certain sense, i.e., the universe approaches homogeneity and isotropy sufficiently rapidly on very large scales, the one-point

Bohdan Paczynski

If the dark halo of our galaxy is made of compact objects as massive as M = 10^6 solar masses, their detection by means of ordinary microlensing searches would take a very long time as the characteristic time scale of such a lensing event, t_0, is approximately 200 years. Fortunately, the very high magnification events of the numerous faint stars, which are

Douglas Scott, Joe Silk, Martin White

Fluctuations in the temperature of the cosmic microwave background have now been detected over a wide range of angular scales, and a consistent picture seems to be emerging. This article describes some of the implications for cosmology. Analysis of all the published detections suggests the existence of a peak on degree scales of height 2.4 to 10 (90%CL) rela

Ichiro Shimada

We formulate and prove a weighted version of Zariski&#39;s hyperplane section theorem on the topological fundamental groups of the complements of hypersurfaces in a projective space. As an application, we calculate fundamental groups of the complements of certain singular projective plane curves.

Theodore C. Belding

This paper extends previous work done by Tanese on the distributed genetic algorithm (DGA). Tanese found that the DGA outperformed the canonical serial genetic algorithm (CGA) on a class of difficult, randomly-generated Walsh polynomials. This left open the question of whether the DGA would have similar success on functions that were more amenable to optimiz

A. M. Smondyrev, G. B. Loriot, R. A. Pelcovits

We present molecular dynamics simulation measurements of the viscosities of the Gay-Berne phenomenological model of liquid crystals in the nematic and isotropic phases. The temperature dependence of the rotational and shear viscosities, including the nonmonotonic behavior of one shear viscosity are in good agreement with experimental data. The bulk viscositi

D. S. L. Soares

Binary galaxies are modeled as point-masses obeying the non-Newtonian MOND and Mannheim-Kazanas (MKG) theories of gravity. Random samples of such systems are generated by means of Monte Carlo simulations of binary orbits. Model pairs have total masses and mass ratios similar to pairs in the cataloged sample used in the analysis. General features of synthetic

Piljin Yi

We study quantum aspects of the accelerated black holes in some detail. Explicitly shown is the fact that a uniform acceleration stabilizes certain charged black holes against the well-known thermal evaporation. Furthermore, a close inspection of the geometry reveals that this is possible only for near-extremal black holes and that most nonextremal varieties

C. N. Lovett-Turner, C. J. Maxwell

Exact large-$N_{f}$ results for the QCD Adler $D$-function and Deep Inelastic Scattering sum rules are used to resum to all orders the portion of QCD perturbative coefficients containing the highest power of $b$=$\frac{1}{6}(11N$--$2N_{f})$, for SU($N$) QCD with $N_{f}$ quark flavours. These terms correspond to renormalon singularities in the Borel plane and

Nobuo Furukawa

The Kondo lattice model with Hund&#39;s ferromagnetic spin coupling is investigated as a microscopic model of the perovskite-type $3d$ manganese oxide (R,A)MnO$_3$ where $R$ and $A$ are rare earth element and alkaline earth element, respectively. We take the classical spin limit $S=\infty$ for the simplicity of the calculation, since the quantum exchange pro

Eyal Doron, Steffen D. Frischat

We study quantum-mechanical tunneling between symmetry-related pairs of regular phase space regions that are separated by a chaotic layer. We consider the annular billiard, and use scattering theory to relate the splitting of quasi-degenerate states quantized on the two regular regions to specific paths connecting them. The tunneling amplitudes involved are

Nobuo Furukawa

Using the Kondo lattice model with classical spins in infinite dimension, magnetic phase transition in the perovskite-type $3d$ transition-metal oxide (La,Sr)MnO$_3$ is theoretically studied. On the Bethe lattice, the self-consistency equations are solved exactly. Curie temperatures at the region of double-exchange ferromagnetism $0.1 < x < 0.25$ as well as

Keith R. Dienes, Alon E. Faraggi

A long-standing problem in string phenomenology has been the fact that the string unification scale disagrees with the GUT scale obtained by extrapolating low-energy data within the framework of the minimal supersymmetric standard model (MSSM). In this paper we examine several effects that may modify the minimal string predictions and thereby bring string-sc

V. I. Man&#39;ko, G. M. Tino

We discuss the implications of an experiment in which the frequencies of two laser beams are compared for different intensities in order to search for a dependence of the frequency of light on its intensity. Since no such dependence was found it is possible to place bounds on a description of the electromagnetic field in terms of q-oscillators. We conclude t

Alexander Verbovetsky

Quantum algebra of differential operators are studied