August 1997 arXiv papers — page 4

R. Arnowitt, Pran Nath

Much curent theoretical analysis is based on the hypothesis that the physics beyond the Standard Model is a consequence of new principles that occur at the Planck scale. The question arises whether such principles can ever be directly tested. We show here that for a significant class of models, hypotheses made at the string or Planck scale can indeed be dire

D. N. Matsukevich, O. N. Metelitsa

The order - αradiative corrections to the differential decay rate of polarized orthopositronium are obtained. Their influences on the three photons coincidence rate as a function of positronium polarization is considered.

Finn Ravndal

Effective Lagrangians were originally used only at the tree level as so-called phenomenological Lagrangians since they were in general non-renormalizable. Today they are treated as effective field theories valid below a characteristic energy scale. Quantum corrections can then be calculated in a consistent way as for any renormalizable theory. A few applicat

Michael Creutz

This is a set of notes on phase transitions and critical phenomena prepared to accompany my lectures for the RHIC '97 summer school, held at Brookhaven from July 6 to 16, 1997.

Michael Creutz

Reassigning degrees of freedom in the standard model allows an interpretation where the SU(2) gauge group is vector-like and parity violation moves to the strong and electromagnetic interactions. In this picture, the electron is paired with an anti-quark. Requiring exact gauge invariance for the electromagnetic interaction clarifies the mechanism behind a re

Wolfgang Bock, Maarten Golterman, Yigal Shamir

As a first step towards a nonperturbative investigation of the gauge-fixing (Rome) approach to lattice chiral gauge theories we study a U(1) model with an action that includes a local gauge-fixing term and a mass counterterm for the gauge fields. The model is studied on the trivial orbit so that only the dynamics of the longitudinal gauge degrees of freedom

Ulli Wolff

We discuss the choice of parameters and report some results for unquenched simulations of the Schroedinger functional with a non-hermitean variant of Luescher's multi-boson algorithm.

Chuan Liu, Andreas Jaster, Karl Jansen

We study the phenomenon of lack of reversibility in molecular dynamics algorithms for the case of Wilson's lattice QCD. We demonstrate that the classical equations of motion that are employed in these algorithms are chaotic in nature. The leading Liapunov exponent is determined in a range of coupling parameters. We give a quantitative estimate of the con

CLEO Collaboration, B. Nemati et al

Using 3.1 fb$^{-1}$ of data accumulated at the $Υ$(4S) by the CLEO-II detector, corresponding to 3.3 million $B\bar{B}$ pairs, we have searched for the color-suppressed $B$ hadronic decay processes: $\bar{B}^0 \to D^0 (D^{*0}) X^0$, where $X^0$ is a light neutral meson $π^0$, $ρ^0$, $η$, $η'$ or $ω$. No obvious signal is observed. We set 90 % C.L. upper

A. Edery M. B. Paranjape

The cosmological sector to the full non-linear topologically massive gravity (TMG) is obtained for localized sources of mass $m$ and spin $σ$ besides the asymptotically spinning conical flat sector previously obtained. In a small region near but outside the sources, the metric resembles the spinning conical flat metric, but we find that the mass $m$ creates

V. A. Berezin, A. M. Boyarsky, A. Yu. Neronov

The geometrodynamics of the spherical gravity with a selfgravitating thin dust shell as a source is constructed. The shell Hamiltonian constraint is derived and the corresponding Schroedinger equation is obtained. This equation appeared to be a finite differences equation. Its solutions are required to be analytic functions on the relevant Riemannian surface

Boris S. Kruglikov

In this paper we define Kobayashi-Royden pseudonorm for almost complex manifolds. Its basic properties known from the complex analysis are preserved in the nonintegrable case as well. We prove that the pseudodistance induced by this pseudonorm coincides with the Kobayashi pseudodistance defined for the almost complex case earlier. We also consider a geometri

L. G. Caron, S. Moukouri

We study the application of the density matrix renormalization group (DMRG) to systems with one-dimensional acoustic phonons. We show how the use of a local oscillator basis circumvents the difficulties with the long-range interactions generated in real space using the normal phonon basis. When applied to a harmonic atomic chain, we find excellent agreement

S. R. Renn

Non-Ohmic tunnel junctions are believed to occur in systems where the exciton and orthogonality catastrophe effects significantly modify tunneling rates. Here we present a simple non-perturbative treatment of the thermodynamic and transport properties of subOhmic and superOhmic tunnel junctions. The large-N approximation demonstrates the existence of a quant

Frank Epperlein, Michael Schreiber, Thomas Vojta

We investigate the behavior of disordered interacting electrons in the insulating regime. Our study is based on the quantum Coulomb glass model which is obtained from the classical Coulomb glass by adding hopping matrix elements between neighboring sites. We use two different numerical methods, viz. a Hartree-Fock approximation and an exact diagonalization a

Thomas Vojta, Frank Epperlein, Michael Schreiber

The quantum Coulomb glass model describes disordered interacting electrons on the insulating side of a metal-insulator transition. By taking quantum fluctuations into account it can describe not only the localized limit but also the weakly localized regime. We discuss several possibilities to generalize the concept of Anderson localization to interacting ele

M. Dube, P. C. E. Stamp

We consider the quantum dynamics of a magnetic domain wall at low temperatures, where dissipative couplings to magnons and electrons are very small. The wall motion is then determined by its coupling to phonons and nuclear spins, and any pinning potentials. In the absence of nuclear spins there is a dominant superOhmic 1-phonon coupling to the wall velocity,

A. V. Zaitsev, D. V. Averin

We have developed a microscopic theory of ac Josephson effect in short ballistic superconducting constrictions with arbitrary electron transparency and in constrictions with diffusive electron transport. The theory is valid for arbitrary miscroscopic structure of the superconducting electrodes of the constriction. As applications of the theory we study smear

Eric L. Bolda, Dan F. Walls

We propose a method for taking a Bose-Einstein condensate in the ground trap state simultaneously to a different atomic hyperfine state and to a vortex trap state. This can be accomplished through a Raman scheme in which one of the two copropagating laser beams has a higher-order Laguerre-Gaussian mode profile. Coefficients relating the beam waist, pulse are

Ken Umeno

In molecular simulations, one of the most difficult points is to track the real dynamics of many-body systems from the first principle. The present study shows that step-size dependences have an unexpected effect on simulation results, even when we use the standard high-precision numerical integrators to apply to a simple system with a two-body interaction.

Stephen Holland, Gregory G. Fahlman, Harvey B. Richer

We present deep (V ~= 27) V- and I-band stellar photometry of G302 and G312, two globular star clusters in the halo of M31. These data were obtained using the Hubble Space Telescope's Wide Field/Planetary Camera 2. We find iron abundances of [Fe/H] = -1.85 +/- 0.12 for G302 and [Fe/H] = -0.56 +/- 0.03 for G312, consistent with spectroscopic measurements.

T. J. Turner, I. M. George, K. Nandra, R. F. Mushotzky

We discuss the spectral properties of a sample of type-2 Seyfert galaxies based upon the analysis of \asca data. In this paper we consider the sources for which the X-ray spectra appear to be dominated by the nuclear continuum, transmitted through a large column of absorbing material. We find that both Seyfert-2 galaxies and NELGs show iron K$α$ line profile

H. M. P. Couchman, P. J. E. Peebles

We present results of a numerical renormalization approximation to the self- similar growth of clustering of pressureless dust out of a power-law spectrum of primeval Gaussian mass density fluctuations (index n) in an Einstein-de Sitter cosmological model. The self-similar two-point correlation function, xi, seems to be well established. The renormalization

M. Geffert, M. Auriere, L. Koch-Miramond

Positions of stars of 47 Tuc have been derived by the use of photographic plates and CCD frames (ESO La Silla) and data from the Hubble Space Telescope (HST). The positions have been determined with respect to the PPM, which is based on the FK5 system. We have compared the positions of variable and blue stars in the core of 47 Tuc with those of the X-ray sou

Axel D. Schwope, K. Beuermann, D. A. H. Buckley, D. Ciardi

We review the main observational characteristics of AM Herculis stars (polars) at X-ray, EUV, UV, IR and optical wavelengths. Particular emphasis is given to multi-epoch, multi-wavelength observations of the eclipsing polar HU Aqr (RX J2107.9-0518). In AM Herculis stars the broad-band spectral energy distribution from X-rays to the IR is governed by only ver

A. M. Newsam, I. M. McHardy, L. R. Jones, K. O. Mason

We present deep K-band imaging at the positions of four very faint X-ray sources found in the UK ROSAT Deep Survey to have no optical counterpart brighter than R~23. Likely identifications are found within the ROSAT error circle in all four fields with R-K colours of between 3.2 +/- 0.4 and 6.4 +/- 0.6. From a consideration of the R-K colours and X-ray to op

Bahram Mobasher, Neil Trentham

We present K-band observations of the low-luminosity galaxies in the Coma cluster, which are responsible for the steep upturn in the optical luminosity function at M_R ~ -16, discovered recently. The main results of this study are (i) The optical$-$near-infrared colours of these galaxies imply that they are dwarf spheroidals. The median M-K colour for galaxi

P. Ivanov

We consider the simple inflationary model with peculiarity in the form of "plateau" in the inflaton potential. We use the formalism of coarse-grained field to describe the production of metric perturbations $h$ of an arbitrary amplitude and obtain non-Gaussian probability function for such metric perturbations. We associate the spatial regions having

Vassiliki Kalogera, Ronald F. Webbink

We study the formation of low-mass X-ray binaries (LMXBs) through helium star supernovae in binary systems that have each emerged from a common-envelope phase. LMXB progenitors must satisfy a large number of evolutionary and structural constraints, which imposed under the assumption of a symmetric supernova explosion, prohibit the formation of short-period L

Giovanni Fasano, Stefano Cristiani, Stephane Arnouts

We present the results of the detailed surface photometry of a sample of elliptical galaxies in the Hubble Deep Field. In the (surface_brightness-effective_radius) plane, the elliptical galaxies of the HDF turn out to follow a `rest frame' Kormendy relation, once the appropriate K+E corrections are applied. This evidence, linked to the dynamical informat

Piero Madau, Lucia Pozzetti, Mark Dickinson

We develop a method for interpreting faint galaxy data which focuses on the integrated light radiated from the galaxy population as a whole. The emission history of the universe at ultraviolet, optical, and near-infrared wavelengths is modeled from the present epoch to z~4 by tracing the evolution with cosmic time of the galaxy luminosity density, as determi

Marcia E. Knutt-Wehlau, R. B. Mann

We describe in superspace a theory of a massive superparticle coupled to a version of two dimensional N=1 dilaton supergravity. The (1+1) dimensional supergravity is generated by the stress-energy of the superparticle, and the evolution of the superparticle is reciprocally influenced by the supergravity. We obtain exact superspace solutions for both the supe

J. Bertrand, P. Bertrand

The study concerns a special symbolic calculus of interest for signal analysis. This calculus associates functions on the time-frequency half-plane f>0 with linear operators defined on the positive-frequency signals. Full attention is given to its construction which is entirely based on the study of the affine group in a simple and direct way. The correspond

De-Hone Lin

The path integral for the relativistic spinless Aharonov-Bohm-Coulomb system is solved, and the energy spectra are extracted from the resulting amplitude.

Y. N. Srivastava, A. Widom

A physical difference between Majorana neutrinos and Dirac neutrinos (which persists in the zero mass limit) is proved in two sentences.

Anindya Datta, Amitava Raychaudhuri

The Standard Model of electroweak interactions has one scalar doublet. The minimal extension of this sector is effected by adding a neutral, singlet scalar field. Depending on whether the singlet field has a non-zero vacuum expectation value, x, or not, the scenario has quite distinctive predictions. In particular, x unequal to 0 produces a mixing between th

M. Rainer, H. Salehi

We consider a net of *-algebras, locally around any point of observation, equipped with a natural partial order related to the isotony property. Assuming the underlying manifold of the net to be a differentiable, this net shall be kinematically covariant under general diffeomorphisms. However, the dynamical relations, induced by the physical state defining t

K. A. Bronnikov, U. Kasper, M. Rainer

We consider a D-dimensional self-gravitating spherically symmetric configuration of a generalized electro-magnetic n-form F and a dilatonic scalar field, admitting an interpretation in terms of intersecting p-branes. For theories with multiple times, selection rules are obtained, which obstruct the existence of p-branes in certain subspaces. General static s

Mirco Calura, Pierluigi Fortini, Enrico Montanari

We present a method to study the time variation of the orbital parameters of a Post-Keplerian binary system undergoing a generic external perturbation. The method is the relativistic extension of the planetary Lagrangian equations. The theory only assumes the smallness of the external perturbation while relativistic effects are already included in the unpert

F. De Paolis, Ph. Jetzer, G. Ingrosso, M. Roncadelli

Reasons supporting the idea that most of the dark matter in galaxies and clusters of galaxies is baryonic are discussed. Moreover, it is argued that most of the dark matter in galactic halos should be in the form of MACHOs and cold molecular clouds.

Myung Gyoon Lee, Eunhyeuk Kim, Doug Geisler

We present integrated Washington CT1 photometry of 18 bright blue objects discovered in the dwarf galaxy UGC 7636 which is located 5'.5 southeast of the giant elliptical galaxy NGC 4472, the brightest galaxy in the Virgo cluster. Several lines of evidence indicate that UGC 7636 is interacting violently with NGC 4472. These objects are very blue with colo

S. G. Djorgovski, R. R. de Carvalho, S. C. Odewahn, R. R. Gal

The analysis and an efficient scientific exploration of the Digital Palomar Observatory Sky Survey (DPOSS) represents a major technical challenge. The input data set consists of 3 Terabytes of pixel information, and contains a few billion sources. We describe some of the specific scientific problems posed by the data, including searches for distant quasars a

Stefan Bornholdt, Kim Sneppen

Boolean networks may be viewed as idealizations of biological genetic networks, where each node is represented by an on-off switch which is a function of the binary output from some other nodes. We evolve connectivity in a single Boolean network, and demonstrate how the sole requirement of sequential matching of attractors may open for an evolution that exhi

H. Itoyama, A. Tokura

We present a zero dimensional matrix model based on $USp(2k)$ with supermultiplets in symmetric, antisymmetric and fundamental representations. The four dimensional compactification of this model naturally captures the exact results of Sen \cite{Sen} in $F$ theory. Eight dynamical and eight kinematical supercharges are found, which is required for critical s

H. Bechmann-Pasquinucci, B. Huttner, N. Gisin

A non-linear quantum state transformation is presented. The transformation, which operates on pairs of spin-1/2, can be used to distinguish optimally between two non-orthogonal states. Similar transformations applied locally on each component of an entangled pair of spin-1/2 can be used to transform a mixed nonlocal state into a quasi-pure maximally entangle

M. Dakna, T. Opatrny, D. G. Welsch

It is shown that the exponential moments of the canonical phase can be directly sampled from the data recorded in balanced homodyne detection. Analytical expressions for the sampling functions are derived, which are valid for arbitrary states and bridge the gap between quantum and classical phase. The reconstruction of the canonical phase distribution from t

R. Simon, Mary Selvadoray, Arvind, N. Mukunda

We exploit results from the classical Stieltjes moment problem to bring out the totality of all the information regarding phase insensitive nonclassicality of a state as captured by the photon number distribution p_n. Central to our approach is the realization that n !p_n constitutes the sequence of moments of a (quasi) probability distribution, notwithstand

Denis V. Juriev

This third part of the series is a brief comment to certain aspects of the theory of classical $r$-matrix and bihamiltonian formalism, which motivations lie in constructions of the previous two parts.

Kenneth Halpern

In an effort to understand the physical implications of the newly discovered non-trivial directions in scalar field theory, we compute lowest order scattering amplitudes, cross sections, and the 1-loop effective potential. To lowest order, the primary effect of the nonpolynomial nature of the theories is a renormalization of the field. The high energy scalin

J. Frauendiener

We derive a general integral formula on an embedded hypersurface for general relativistic space-times. Suppose the hypersurface is foliated by two-dimensional compact ``sections'' $S_s$. Then the formula relates the rate of change of the divergence of outgoing light rays integrated over $S_s$ under change of section to geometric (convexity and curvat

G. Györgyi, P. Reimann

Pattern storage by a single neuron is revisited. Generalizing Parisi's framework for spin glasses we obtain a variational free energy functional for the neuron. The solution is demonstrated at high temperature and large relative number of examples, where several phases are identified by thermodynamical stability analysis, two of them exhibiting spontaneo

A. M. Thompson, M. A. Moore

The flux line lattice of superconductors has been investigated when there exists a periodicity in the underlying system, such as can occur in artificially layered structures. For small fields parallel to the layers the flux lines enter the sample in sequential rows, with the possibility of jumps in the magnetization as new rows are created. As the field is i

V. Berezinsky, M. Kachelriess, A. Vilenkin

We study the decays of ultraheavy (m_X \geq 10^{13}GeV) and quasistable (lifetime τ_X much larger than the age of the Universe t_0) particles as the source of Ultra High Energy Cosmic Rays (UHE CR). These particles are assumed to constitute a tiny fraction ξ_X of CDM in the Universe, with ξ_X being the same in the halo of our Galaxy and in the intergalactic

K. Subramanian

Turbulence with a large magnetic Reyonolds number, generically leads to rapidly growing magnetic noise over and above any mean field. We revisit the dynamics of this fluctuating field, in homogeneous, isotropic, helical turbulence. Assuming the turbulence to be Markovian, we first rederive, in a fairly transparent manner, the equation for the mean field, and

U. F. Wichoski, J. A. S. Lima

The temperature evolution law is determined for an expanding FRW type Universe with a mixture of matter and radiation where "adiabatic" creation of photons has taken place. Taking into account this photon creation we discuss the physical conditions for having a hot big bang Universe. We also compare our results to the ones obtained from the standard

Pierre Gosselin, Janos Polonyi

A non-Grassmanian path integral representation is given for the solution of the Klein-Gordon and the Dirac equations. The trajectories of the path integral are rendered differentiable by the relativistic corrections. The nonrelativistic limit is briefly discussed from the point of view of the renormalization group.

Nick Evans, Myck Schwetz

We identify the 4D field theories living on the world volume of D4 branes in non-supersymmetric type IIA string theory constructions. They are softly broken N=2 SQCD with the breakings introduced through vevs of the auxilliary fields in the spurion coupling field. Exact solutions of these theories for perturbing soft breakings exist in the literature. We cal

David H. Weinberg, Neal Katz, Lars Hernquist

We describe cosmological simulation techniques and their application to studies of cosmic structure formation, with particular attention to recent hydrodynamic simulations of structure in the high redshift universe. Collisionless N-body simulations with Gaussian initial conditions produce a pattern of sheets, filaments, tunnels, and voids that resembles the

Hitoshi Kitada, Lancelot R. Fletcher

The problem of time, considered as a problem in the usual physical context, is reflected in relation with the paper by Kauffman and Smolin (gr-qc/9703026). It is shown that the problem is a misposed problem in the sense that it was raised with a lack of the recognition of mathematically known facts.

Hans-Juergen Matschull, Max Welling

We study the phase space structure and the quantization of a pointlike particle in 2+1 dimensional gravity. By adding boundary terms to the first order Einstein Hilbert action, and removing all redundant gauge degrees of freedom, we arrive at a reduced action for a gravitating particle in 2+1 dimensions, which is invariant under Lorentz transformations and a

Takako T. Ishii, Hiroki Kurokawa, Tsutomu T. Takeuchi

Sunspot proper motions and flares of a super active region NOAA 5395, which was the biggest and the most flare-active region in the 22nd sunspot cycle, were analyzed in details. We measured sunspot proper motions by using the H-alpha - 5.0 A images obtained with the 60-cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University and found some pec

J. J. van der Bij, Boris Kastening

We study quadratically divergent radiative corrections to the oblique parameters at LEP1 induced by non-standard vector boson self-couplings. We work in the Stueckelberg formalism and regulate the divergences through a gauge-invariant higher derivative scheme. Using consistency arguments together with the data we find a limit on the anomalous magnetic moment

Ines Safi

We study a homogeneous Tomonaga-Luttinger liquid with backscattering potential. A perturbative computation of the conductance at and near resonance is given. We find that the backscattering of one electron dominates that of two electrons for an interaction parameter $K\geq 1/3$ and that the resonance point depends on temperature. Our results may be relevant

M. Porrati, A. Rozenberg

We propose a general method that allows to detect the existence of normalizable ground states in supersymmetric quantum mechanical systems with non-Fredholm spectrum. We apply our method to show the existence of bound states at threshold in two important cases: 1) the quantum mechanical system describing H-monopoles; 2) the quantum mechanics of D0 branes.

S. Kleiman, A. Thorup

Let A be a Noetherian local domain, N be a finitely generated torsion- free module, and M a proper submodule that is generically equal to N. Let A[N] be an arbitrary graded overdomain of A generated as an A-algebra by N placed in degree 1. Let A[M] be the subalgebra generated by M. Set C:=Proj(A[M]) and r:=dim C. Form the (closed) subset W of Spec(A) of prim

J. R. Bond, A. H. Jaffe, L. Knox

We develop two methods for estimating the power spectrum, C_l, of the cosmic microwave background (CMB) from data and apply them to the COBE/DMR and Saskatoon datasets. One method involves a direct evaluation of the likelihood function, and the other is an estimator that is a minimum-variance weighted quadratic function of the data. Applied iteratively, the

Tsutomu Sakai, Hideo Suganuma

We study the properties of H-dibaryon matter through the SO(3) Skyrmion solution on a three-dimensional hypersphere $S^3$. As the density increases, the swelling of H-dibaryon is found. Above a critical density, the system becomes uniform in terms of the baryon density. In this uniform phase, the critical order parameter is largely reduced, which can be inte

Saumen Datta, Rajiv V. Gavai

The phase diagram of SO(3) lattice gauge theory at finite temperature is investigated by Monte Carlo techniques with a view i) to understand the relationship between the deconfinement phase transitions in the SU(2) and SO(3) lattice gauge theories and ii) to resolve the current ambiguity of the nature of the high temperature phases of the latter. Phases with

Chi-Keung Chow, Soo-Jong Rey

Quenched and partially quenched chiral perturbation theory for vector mesons is developed and is used to extract chiral loop correction to the $ρ$ meson mass. Connections to fully quenched and totally unquenched chiral perturbation theory results are discussed. It is also shown that (partially) quenched perturbation theory for tensor mesons can be formulated

F. Gieres, S. Gourmelen

We construct and classify superconformally covariant differential operators defined on N=2 super Riemann surfaces. By contrast to the N=1 theory, these operators give rise to partial rather than ordinary differential equations which leads to novel features for their matrix representation. The latter is applied to the derivation of N=2 super W-algebras in ter

R. Simon, N. Mukunda

The nonnegativity of the density operator of a state is faithfully coded in its Wigner distribution, and this places constraints on the moments of the Wigner distribution. These constraints are presented in a canonically invariant form which is both concise and explicit. Since the conventional uncertainty principle is such a constraint on the first and secon

Luca Salasnich, Fabio Sattin

In this paper we prove a recent conjecture [Robnik M and Salasnich L 1997 J. Phys. A: Math. Gen. 30 1719] about the convergence of the WKB series for the angular momentum operator. We demonstrate that the WKB algorithm for the angular momentum gives the exact quantization formula if all orders are summed.

Luca Salasnich, Fabio Sattin

In this paper we solve the eigenvalue problem of the angular momentum operator by using the supersymmetric semiclassical quantum mechanics (SWKB), and show that it gives the correct quantization already at the leading order.

Leonid I. Korogodsky

A version of quantum orbit method is presented for real forms of equal rank of quantum complex simple groups. A quantum moment map is constructed, based on the canonical isomorphism between a quantum Heisenberg algebra and an algebra of functions on a family of quantum G-spaces. For the series $A$, we construct some irreducible $*$-representations of $U_q{\f

S. Zakrzewski

Quantum Lorentz groups H admitting quantum Minkowski space V are selected. Natural structure of a quantum space G = V x H is introduced, defining a quantum group structure on G only for triangular H (q=1). We show that it defines a braided quantum group structure on G for |q|=1.

P. P. Kulish, A. A. Stolin

Twisted Hopf algebra $sl_ξ(2)$ gives rise to a deformation of the Yangian ${\cal Y}(sl(2))$. The corresponding deformations of the integrable XXX-spin chain and the Gaudin model are discussed.

Frank Hausser, Florian Nill

Drinfeld showed that any finite dimensional Hopf algebra \G extends to a quasitriangular Hopf algebra \D(\G), the quantum double of \G. Based on the construction of a so--called diagonal crossed product developed by the authors, we generalize this result to the case of quasi--Hopf algebras \G. As for ordinary Hopf algebras, as a vector space the ``quasi--qua

D. J. Miller, A. Papanestis

An extension of the traditional modulation transfer function (MTF), the detective MTF, is proposed for the evaluation of the resolution of X-ray imaging detectors with non-uniform efficiency on the scale of individual detector elements. The dMTF is shown to give a better representation than does the MTF of the improved resolution reported when the readout of

T. Inoue, M. Oka, T. Motoba, K. Itonaga

Contributions of the direct quark mechanism are studied in the nonmesonic weak decays of light hypernuclei. The $ΛN \to NN$ transition is described by the one pion exchange mechanism and the direct quark mechanism, induced by the four-quark vertices in the effective weak Hamiltonian. By employing a realistic wave function of the $Λ$ inside the hypernuclei, n

Antonia W. Bluher

This paper gives additional background in algebraic geometry as an accompaniment to the article, ``Formal Groups, Elliptic Curves, and some Theorems of Couveignes'' [arXiv:math.NT/9708215]. Section 1 discusses the addition law on elliptic curves, and Sections 2 and 3 explain about function fields, uniformizers, and power series expansions with respec

Antonia W. Bluher

The formal group law of an elliptic curve has seen recent applications to computational algebraic geometry in the work of Couveignes to compute the order of an elliptic curve over finite fields of small characteristic. The purpose of this paper is to explain in an elementary way how to associate a formal group law to an elliptic curve and to expand on some t

Victor Goryunov

We classify simple singularities of functions on space curves. We show that their bifurcation sets have properties very similar to those of functions on smooth manifolds and complete intersections [1,2]: the k(pi, 1)-theorem for the bifurcations diagram of functions is true, and both this diagram and the discriminant are Saito's free divisors.

Robert Ghrist, Todd Young

We analyse the topological (knot-theoretic) features of a certain codimension-one bifurcation of a partially hyperbolic fixed point in a flow on $\real^3$ originally described by Shil'nikov. By modifying how the invariant manifolds wrap around themselves, or ``pleat,'' we may apply the theory of templates, or branched two-manifolds, to capture th

Peter Bantay

Explicit formulae describing the genus one characters and modular transformation properties of permutation orbifolds of arbitrary Rational Conformal Field Theories are presented, and their relation to the theory of covering surfaces is investigated.

Karl Landsteiner, Esperanza Lopez

We consider configurations of Neveu-Schwarz fivebranes, Dirichlet fourbranes and an orientifold sixplane in type IIA string theory. Upon lifting the configuration to M-theory and proposing a description of how to include the effects of the orientifold sixplane we derive the curves describing the Coulomb branch of N=2 gauge theories with orthogonal and symple

S. M. Lietti, S. F. Novaes

The effect of new operators that only modify the bosonic couplings of the Higgs boson, without altering the WWγor WWZ three-point functions, are examined in the e+e- -> ZZγand Zγγprocesses. We analyse the constraints on these interactions that can be imposed by the LEP II collider at CERN and at the Next Linear Collider.

V. Barger

The prospects for Higgs boson discovery and study at present and future colliders are reviewed, with emphasis on the Minimal Supersymmetric Standard Model (MSSM) states. The expected experimental coverages with different production and decay modes are outlined. Particular attention is given to the Higgs couplings predicted when the top quark Yukawa coupling

A. Pérez-Lorenzana, William A. Ponce, Arnulfo Zepeda

We show that it is possible to achieve one step gauge coupling unification in a general class of non supersymmetric models which at low energies have only the standard particle content and extra Higgs fields doublets. The constraints are the experimental values of $α_{em}$, $α_s$ and $\sin^2θ_W$ at $10^2 GeVs$, and the lower bounds for FCNC and proton decay

A. Pérez-Lorenzana, D. E. Jaramillo, William A. Ponce, Arnulfo Zepeda

We analize the different ways for the spontaneous breaking of the gauge symmetry, for the $[SU(6)]^3\otimes Z_3$ family unification model. In particular we study the consequences of a previous selection for the vacuum expectation values of the Higgs fields, showing that such set predicts unwanted flavor changing neutral currents at the $m_Z=91 GeVs$ mass sca

Nikolaos Kidonakis

We discuss the resummation of next-to-leading logarithms (NLL) in heavy quark production near threshold. Results are presented for top quark production at the Fermilab Tevatron.

G. Altarelli

I present a concise review of the possible evidence for new physics at HERA and of the recent work towards a theoretical interpretation of the signal. It is not clear yet if the excess observed at large Q^2 is a resonance or a continuum (this tells much about the quality of the signal). I discuss both possibilities. For the continuum case one considers eithe

Arnd Leike

Z' exclusion limits and errors of Z' model measurements are compared for different reactions at future linear colliders. The influence of the c.m. energy, integrated luminosity, beam polarization and systematic errors is discussed. The sensitivity to a Z' depends only on the product Ls and not on the integrated luminosity and the c.m. energy sepa

Keith G. Richardson, Michael C. Birse, Judith A. McGovern

The renormalisation of NN scattering in theories with zero-range interactions is examined using a cut-off regularisation and taking the cut-off to infinity. Inclusion of contact interactions that depend on energy as well as momentum allows the effective range to be fitted to experiment with any desired sign or magnitude. However, power counting breaks down:

A. Peshier, K. Schertler, M. H. Thoma

The complete one-loop self energies (real and imaginary parts) for photons, gluons, electrons and quarks at finite temperature are calculated numerically and compared to the results of the hard thermal loop (HTL) approximation used for the resummation technique of Braaten and Pisarski. In this way some light is shed on the validity of the weak coupling limit

Tomislav Prokopec

I review my recent work with Brian Greene and Thomas Roos. First I discuss the effect of a negative cross-coupling on the inflaton decay in two scalar field theories. Our main finding is a new effect, the negative coupling instability, which leads to explosive particle production and very fast inflaton decay. Then I discuss the consequences of this instabili

J. Madore, L. A. Saeger

A basic arbitrariness in the determination of the topology of a manifold at the Planck length is discussed. An explicit example is given of a `smooth' change in topology from the 2-sphere to the 2-torus through a sequence of noncommuting geometries. Applications are considered to the theory of D-branes within the context of the proposed $M$(atrix) theory

J. Etnyre, R. Ghrist

We draw connections between the field of contact topology and the study of Beltrami fields in hydrodynamics on Riemannian manifolds in dimension three. We demonstrate an equivalence between Reeb fields (vector fields which preserve a transverse nowhere-integrable plane field) up to scaling and rotational Beltrami fields on three-manifolds. Thus, we character

David P. Feldman, James P. Crutchfield

We review several statistical complexity measures proposed over the last decade and a half as general indicators of structure or correlation. Recently, Lopez-Ruiz, Mancini, and Calbet [Phys. Lett. A 209 (1995) 321] introduced another measure of statistical complexity C_{LMC} that, like others, satisfies the ``boundary conditions'' of vanishing in the

Jose Riera, Elbio Dagotto

The problem of two holes in the presence of strong antiferromagnetic fluctuations is revisited using computational techniques. Two-dimensional clusters and 2-leg ladders with up to 32 sites are studied with the Lanczos and Truncated Lanczos algorithms. The main motivation is the recently discussed spatial distribution of holes in ladders where the maximum pr

S. N. Evangelou, Shi-Jie Xiong, Ding-Yu Xing, E. N. Economou

A random lattice model with dilute interlayer bonds of density $p$ is proposed to describe the underdoped high--$T_c$ cuprates. We show analytically via an appropriate perturbation expansion and verify independently by numerical scaling of the conductance that for any finite $p$ the states remain extended in all directions, despite the presence of interlayer