July 1999 arXiv papers — page 6

E. Oset, A. Ramos, E. Marco, J. C. Nacher

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a stand

Swapan K. Saha, W. W. Daehnick, R. W. Flammang, J. T. Balewski

The spin correlation coefficient combinations Axx + Ayy, Axx - Ayy and the analyzing powers Ay(theta) were measured for pp-->pnpi+ at beam energies of 325, 350, 375 and 400 MeV. A polarized internal atomic hydrogen target and a stored, polarized proton beam were used. These polarization observables are sensitive to contributions of higher partial waves. A co

Francisco J. Herranz, Mariano Santander

The families of quasi-simple or Cayley--Klein algebras associated to antihermitian matrices over R, C and H are described in a unified framework. These three families include simple and non-simple real Lie algebras which can be obtained by contracting the pseudo-orthogonal algebras so(p,q) of the Cartan series $B_l$ and $D_l$, the special pseudo-unitary alge

Se-Goo Kim

Virtual knots, defined by Kauffman, provide a natural generalization of classical knots. Most invariants of knots extend in a natural way to give invariants of virtual knots. In this paper we study the fundamental groups of virtual knots and observe several new and unexpected phenomena. In the classical setting, if the longitude of a knot is trivial in the k

Nicolai Reshetikhin, Leon Takhtajan

We present an explicit formula for the deformation quantization on Kähler manifolds.

Preeti Parashar, Angel Ballesteros, Francisco J. Herranz

In order to obtain a classification of all possible quantum deformations of the two-photon algebra $h_6$, we introduce its corresponding general Lie bialgebra, which is a coboundary one. Two non-standard quantum deformations of $h_6$, together with their associated quantum universal R-matrix, are presented; each of them contains either a quantum harmonic osc

Angel Ballesteros, Francisco J. Herranz

The complete integrability of the hyperbolic Gaudin Hamiltonian and other related integrable systems is shown to be easily derived by taking into account their sl(2,R) coalgebra symmetry. By using the properties induced by such a coalgebra structure, it can be proven that the introduction of any quantum deformation of the sl(2,R) algebra will provide an inte

Nicole Lemire, Martin Lorenz

Let S_n denote the symmetric group on n letters. We consider the S_n-root lattice A_{n-1} = {(z1,...,zn) in Z^n | z1+...+zn = 0}, where S_n acts on Z^n by permuting the coordinates, and its tensor, symmetric, and exterior squares. For odd values of n, we show that the tensor square is equivalent, in the sense of Colliot-Thelene and Sansuc, to the exterior sq

Pawel Hanus, Mariusz Urbanski

Recently O. Sarig has introduced and explored the concept of positively recurrent functions. In this paper we construct a natural wide class of such functions and we showthat they have stronger ergodic properties than the general functions considered in Sarig's paper.

R. Fioresi, M. A. Lledo

In this paper we consider the problem of deformation quantization of the algebra of polynomial functions on coadjoint orbits of semisimple lie groups. The deformation of an orbit is realized by taking the quotient of the universal enveloping algebra of the Lie algebra of the given Lie group, by a suitable ideal. A comparison with geometric quantization in th

Gerald V. Dunne, Christian Schubert

We study the divergence of large-order perturbation theory in the worldline expression for the two-loop Euler-Heisenberg QED effective Lagrangian in a constant magnetic field. The leading rate of divergence is identical, up to an overall factor, to that of the one-loop case. From this we deduce, using Borel summation techniques, that the leading behaviour of

José P. S. Lemos, Richard Kerner

We investigate the properties of non-linear electromagnetism based on the Born-Infeld Lagrangian in multi-dimensional theories of Kaluza-Klein type. We consider flat space-time solutions only, which means that the space-time metric is constant, and the only supplementary variable is the dilaton field, a scalar. We show that in the case of Kaluza-Klein theory

Chris Beasley, Brian R. Greene, C. I. Lazaroiu, M. R. Plesser

We investigate field theories on the worldvolume of a D3-brane transverse to partial resolutions of a $\Z_3\times\Z_3$ Calabi-Yau threefold quotient singularity. We deduce the field content and lagrangian of such theories and present a systematic method for mapping the moment map levels characterizing the partial resolutions of the singularity to the Fayet-I

Kurt Haller, Lusheng Chen

We construct a set of states that implement the non-Abelian Gauss's law for QCD. We also construct a set of gauge-invariant operator-valued quark and gluon fields by establishing an explicit unitary equivalence between the Gauss's law operator and the `pure glue' part of the Gauss's law operator. This unitary equivalence enables us to use the

Kurt Haller

We discuss the transformation of the QCD temporal-gauge Hamiltonian to a representation in which it can be expressed as a functional of gauge-invariant quark and gluon fields. We show how this objective can be realized by implementing the non-Abelian Gauss's law, and by using the mathematical apparatus developed for that purpose to also construct gauge-i

Daniel Boer, R. Jakob, P. J. Mulders

We present the leading order unpolarized and polarized cross sections in electroweak semi-inclusive deep inelastic leptoproduction. The azimuthal dependences in the cross section differential in the transverse momentum of the vector boson arise due to intrinsic transverse momenta of the quarks. However, the presented asymmetries are not suppressed by inverse

Ernest Ma

Assuming equal tree-level Majorana masses for the standard-model neutrinos, either from the canonical seesaw mechanism or from a heavy scalar triplet, I discuss how their radiative splitting may be relevant to neutrinoless double beta decay and neutrino oscillations.

R. Rapp, J. Wambach

Using a rather complete description of the in-medium $ρ$ spectral function - being constrained by various independent experimental information - we calculate pertinent dilepton production rates from hot and dense hadronic matter. The strong broadening of the $ρ$ resonance entails a reminiscence to perturbative $q\bar q$ annihilation rates in the vicinity of

J. C. Collins, M. Diehl

We show that in hard exclusive electroproduction, ep-->eVp, the leading-twist hard-scattering coefficient for the production of a transversely polarized vector meson V vanishes to all orders of perturbation theory. This implies that this process cannot be used to measure the skewed transversity distribution of quarks in a hadron. In contrast, a recent calcul

C. Anastasiou, E. W. N. Glover, C. Oleari

We study massive one-loop integrals by analytically continuing the Feynman integral to negative dimensions as advocated by Halliday and Ricotta and developed by Suzuki and Schmidt. We consider n-point one-loop integrals with arbitrary powers of propagators in general dimension D. For integrals with m mass scales and q external momentum scales, we construct a

A. V. Kuznetsov, N. V. Mikheev

An influence of the magnetized electron - positron plasma on the absorption and loss of the energy and momentum in a process of neutrino propagation is investigated. A total contribution of all crossed processes, $\nu \to \nu e^- e^+$, $\nu e^- \to \nu e^-$, $\nu e^+ \to \nu e^+$, $\nu e^- e^+ \to \nu$, is found for the first time, which appears not to depen

H. Walliser, G. Holzwarth

One-loop quantum corrections to the classical vortices in 2+1 dimensional O(3)-models are evaluated. Skyrme and Zeeman potential terms are used to stabilize the size of topological solitons. Contributions from zero modes, bound-states and scattering phase-shifts are calculated for vortices with winding index n=1 and n=2. For both cases the S-matrix shows a p

C. S. Lam

Relations between integrals of time-ordered product of operators, and their representation in terms of energy-ordered products are studied. Both can be decomposed into irreducible factors and these relations are discussed as well. The energy-ordered representation was invented to separate various infrared contributions in gauge theories. It is shown that the

A. Bianconi, S. Boffi, R. Jakob, M. Radici

We present a model calculation of leading order interference fragmentation functions arising from the distribution of two hadrons produced in the same jet of a fragmenting quark in a hard process. Using a simple spectator model for the mechanism of the hadronization process, for the first time we give a complete calculation and numerical estimates for the ex

I. M. Dremin, C. S. Lam, V. A. Nechitailo

The second and third factorial moments of the multiplicity distributions of gluon and quark jets are calculated up to the next-to-next-to-next-to leading order in perturbative QCD, using the equations for generating functions. The results are confronted with experimental data. A general discussion on high order corrections revealed by such an approach is giv

L. D. Soloviev

The relativistic quantum string quark model, proposed earlier, is applied to all mesons, from pion to $Υ$, lying on the leading Regge trajectories (i.e., to the lowest radial excitations in terms of the potential quark models). The model describes the meson mass spectrum, and comparison with measured meson masses allows one to determine the parameters of the

C. Giunti

It is shown that only two four-neutrino schemes are compatible with the results of all neutrino oscillation experiments. These two schemes have a mass spectrum composed of two pairs of neutrinos with close masses separated by the "LSND gap" of the order of 1 eV.

Wang Qin, Li Zhiming, Liu Lianshou

The Non-thermal phase transition in high energy collisions is studied in some detail in the framework of random cascade model. The relation between the characteristic parameter $λ_q$ of phase transition and the rank $q$ of moment is obtained using Monte Carlo simulation, and the existence of two phases in self-similarly cascading multiparticle systems is sho

Jeffrey E. Mandula

We discuss the current state of what is known non-perturbatively about the gluon propagator in QCD, with emphasis on the information coming from lattice simulations. We review the specification of the lattice Landau gauge and the procedure for calculating the gluon propagator on the lattice. We also discuss some of the difficulties in non-perturbative calcul

C. B. Lang

With the Schwinger model as example I discuss properties of lattice Dirac operators, with some emphasis on Monte Carlo results for topological charge, chiral fermions and eigenvalue spectra.

Marta Felcini

The results of the experimental searches for Higgs particles at LEP, using the data collected at centre-of-mass energies up to 189 GeV, are reviewed and the prospects for the near future outlined.

Beverly K. Berger

The method of consistent potentials is used to explain how a minimally coupled (classical) scalar field can suppress Mixmaster oscillations in the approach to the singularity of generic cosmological spacetimes.

Sawa Manoff, Rumyan Lazov

The invariant projections of the energy-momentum tensors of Lagrangian densities for tensor fields over differentiable manifolds with contravariant and covariant affine connections and metrics [$(\bar{L}_n,g)$-spaces] are found by the use of an non-null (non-isotropic) contravariant vector field and its corresponding projective metrics. The notions of rest m

Bernd Borchert, Lane A. Hemaspaandra, Joerg Rothe

One way of suggesting that an NP problem may not be NP-complete is to show that it is in the class UP. We suggest an analogous new approach---weaker in strength of evidence but more broadly applicable---to suggesting that concrete~NP problems are not NP-complete. In particular we introduce the class EP, the subclass of NP consisting of those languages accept

Joerg Rothe, Lane A. Hemaspaandra

In this note, we study the easy certificate classes introduced by Hemaspaandra, Rothe, and Wechsung, with regard to the question of whether or not surjective one-way functions exist. This is an important open question in cryptology. We show that the existence of partial one-way permutations can be characterized by separating P from the class of UP sets that,

Lane A. Hemaspaandra, Joerg Rothe

It is known that for any class C closed under union and intersection, the Boolean closure of C, the Boolean hierarchy over C, and the symmetric difference hierarchy over C all are equal. We prove that these equalities hold for any complexity class closed under intersection; in particular, they thus hold for unambiguous polynomial time (UP). In contrast to th

Robert Shrock, Shan-Ho Tsai

We present exact calculations of the zero-temperature partition function of the $q$-state Potts antiferromagnet on arbitrarily long strips of the square, triangular, and kagomé lattices with width $L_y=2$ or 3 vertices and with periodic longitudinal boundary conditions. From these, in the limit of infinite length, we obtain the exact ground-state entropy $S_

Fabian Braun, Jan von Delft

We use two truly canonical approaches to describe superconductivity in ultrasmall metallic grains: (a) a variational fixed-N projected BCS-like theory and (b) an exact solution of the model Hamiltonian developed by Richardson in context with Nuclear Physics. Thereby we obtain a description of the entire crossover from the bulk BCS regime (mean level spacing

V. M. Pudalov, G. Brunthaler, A. Prinz, G. Bauer

We have found that the conduction in Si-MOS structures has a substantial imaginary component in the metallic phase for the density range 6 \times n_c > n > n_c, where n_c is the critical density of the metal-insulator transition. For high mobility samples, the corresponding delay (or advance) time equals approximately to 0.1 - 10ms and increases exponentiall

O. P. Sushkov

To investigate spin dimerization in the t-J model we consider the extended t-J-δmodel with explicit spin dimerization introduced via parameter δ. At zero doping the dimerized spin liquid is unstable at δ< δ_c = 0.3. We demonstrate that the doping stabilizes the dimerized stripe phase: the δ_c(x) decreases when doping x increases. At doping larger than critic

Alexander I. Olemskoi

The statistical ensemble of avalanche intensities is considered to investigate diffusion in ultrametric space of hierarchically subordinated avalanches. The stationary intensity distribution and the steady-state current are obtained. The critical avalanche intensity needed to initiate the global avalanche formation is calculated depending on noise intensity.

Alexander I. Olemskoi, Valerii A. Brazhnyi

The effective motion equation that describes the different monomer alternation along the heteropolymer chain is proposed. On its basis the supersymmetry field scheme that allows to obtain the equations for the structure factor and Green function is built up. The memory and ergodicity breaking effects are investigated depending on the temperature and quenched

S. Zelakiewicz, H. Noh, T. J. Gramila, L. N. Pfeiffer

The response of composite Fermions to large wavevector scattering has been studied through phonon drag measurements. While the response retains qualitative features of the electron system at zero magnetic field, notable discrepancies develop as the system is varied from a half-filled Landau level by changing density or field. These deviations, which appear t

M. Dube, M. Rost, K. Elder, M. Alava

The propagation and roughening of a liquid-gas interface moving through a disordered medium under the influence of capillary forces is considered. The system is described by a phase-field model with conserved dynamics and spatial disorder is introduced through a quenched random field. Liquid conservation leads to slowing down of the average interface positio

A. C. M. Green, D. M. Edwards

Previously a many-body coherent potential approximation (CPA) was used to study the double exchange (DE) model with quantum local spins S, both for S=1/2 and for general S in the paramagnetic state. This approximation, exact in the atomic limit, was considered to be a many-body extension of Kubo&#39;s one-electron dynamical CPA for the DE model. We now exten

D. Bolle, T. Verbeiren

The optimal capacity of graded-response perceptrons storing biased and spatially correlated patterns with non-monotonic input-output relations is studied. It is shown that only the structure of the output patterns is important for the overall performance of the perceptrons.

N. A. Pertsev, V. G. Koukhar

A thermodynamic theory is developed for dense laminar domain structures in epitaxial ferrolectric films. It is found that, at some critical misfit strain between the film and substrate, the 90 degrees c/a/c/a domain structure becomes unstable with respect to the appearance of the polarization component parallel to domain walls, which results in the formation

D. Bolle, G. Jongen, G. M. Shim

This contribution reviews the parallel dynamics of Q-Ising neural networks for various architectures: extremely diluted asymmetric, layered feedforward, extremely diluted symmetric, and fully connected. Using a probabilistic signal-to-noise ratio analysis, taking into account all feedback correlations, which are strongly dependent upon these architectures th

R. Shankar, D. Shubashree

In this paper, we study the phases of the Heisenberg model on the \kagome lattice with antiferromagnetic nearest neighbour coupling $J_1$ and ferromagnetic next neighbour coupling $J_2$. Analysing the long wavelength, low energy effective action that describes this model, we arrive at the phase diagram as a function of $χ= \frac{J_2}{J_1} $. The interesting

Masaki Oshikawa

Based on a Renormalization-Group picture of $Z_n$ symmetric models in three dimensions, we derive a scaling law for the $Z_n$ order parameter in the ordered phase. An existing Monte Carlo calculation on the three-state antiferromagnetic Potts model, which has the effective $Z_6$ symmetry, is shown to be consistent with the proposed scaling law. It strongly s

J. S. Urbach, J. S. Olafsen

A large number (~10,000) of uniform stainless steel balls comprising less than one layer coverage on a vertically shaken plate provides a rich system for the study of excited granular media. Viewed from above, the horizontal motion in the layer shows interesting collective behavior as a result of inelastic particle-particle collisions. Clusters appear as loc

V. V. Sokolov, O. V. Zhirov, D. Alonso, G. Casati

The quantum kicked rotor (QKR) map is embedded into a continuous unitary transformation generated by a time-independent quasi-Hamiltonian. In some vicinity of a quantum resonance of order $q$, we relate the problem to the {\it regular} motion along a circle in a $(q^2-1)$-component inhomogeneous &#34;magnetic&#34; field of a quantum particle with $q$ intrins

MACHO, GMAN collaborations, :, C. Alcock et al

We present the lightcurves of 21 gravitational microlensing events from the first six years of the MACHO Project gravitational microlensing survey which are likely examples of lensing by binary systems. These events were manually selected from a total sample of ~350 candidate microlensing events which were either detected by the MACHO Alert System or discove

Carlos Allende Prieto, Ramon J. Garcia Lopez, David L. Lambert, Basilio Ruiz Cobo

An inversion technique to recover LTE one-dimensional model photospheres for late-type stars, which was previously applied to the Sun (Allende Prieto et al. 1998), is now employed to reconstruct, semi-empirically, the photospheres of cooler dwarfs: the metal-poor Gmb1830 and the active star of solar-metallicity Eps Eri. The model atmospheres we find reproduc

Arlin P. S. Crotts, Stephen R. Heathcote

We present several different measurements of the velocities of structures within the circumstellar envelope of SN 1987A, including the inner, equatorial ring (ER), outer rings (ORs), and the diffuse nebulosity at radii < 5 pc, based on CTIO 4m and HST data. A comparison of STIS and WFPC2 [N II]6583 loci for the rings show that the ER is expanding in radius a

C. Adami, B. Holden, A. Mazure, F. Castander

We present the first results of the COP survey about the reality of the PDCS clusters, about their velocity dispersions and dynamic and about the periodicity of the structures along the line of sight.

William G. Mathews, Fabrizio Brighenti

X-ray emission from hot (T = 10^7 K) interstellar gas in massive elliptical galaxies indicates that 10^{10} M_sun has cooled over a Hubble time, but optical and radio evidence for this cold gas is lacking. We provide detailed theoretical support for the hypothesis that this gas has formed into low luminosity stars. Within several kpc of the galactic center,

Vladimir Osherovich, Lev Titarchuk

The recent model of quasi-periodic oscillations in neutron star binaries (Osherovich and Titarchuk 1999, Titarchuk and Osherovich 1999) has suggested the existence of two branches of QPOs due to the influence of Coriolis force on the linear Keplerian oscillator: one branch with frequencies from 400 to 1200 Hz and another branch with frequencies an order of m

Kerstin Weis, Wolfgang J. Duschl, You-Hua Chu

Eta Carinae is one of the most extreme cases of a Luminous Blue Variable star. A bipolar nebula of 17&#34; size surrounds the central object. Even further out, a large amount of filamentary material extends to a distance of 30&#34; or about 0.3 pc. In this paper we present a detailed kinematic and morphological analysis of some outer filaments in this nebula

Vladimir Osherovich, Lev Titarchuk

Since the discovery of kHz quasi-periodic oscillations (QPO) in neutron star binaries, the difference between peak frequencies of two modes in the upper part of the spectrum, i.e. Delta (omega)=omega_h-omega_K has been studied extensively. The idea that the difference Delta(omega) is constant and (as a beat frequency) is related to the rotational frequency o

L. R. Yungelson, M. Livio

We discuss the cosmic history of supernovae on the basis of various assumptions and recent data on the star formation history. We show that supernova rates as a function of redshift can be used to place significant constraints on progenitor models, on the star formation history, and on the importance of dust obscuration. We demonstrate that it is unlikely th

Zhi-Yun Li

In the standard picture of isolated star formation, dense ``starless&#39;&#39; cores are formed out of magnetic molecular clouds due to ambipolar diffusion. Under the simplest spherical geometry, I demonstrate that ``starless&#39;&#39; cores formed this way naturally exhibit a large scale inward motion, whose size and speed are comparable to those detected r

J. Rossa, C. Tappert, Th. Augusteijn, J. Maza

We present the discovery of two new quasars, that initially appeared as candidate cataclysmic variables (CVs) in a list of the Calan-Tololo objective prism survey. However, additional spectroscopic and photometric observations revealed their true nature. Furthermore we present data for a third quasar, CTCV J0322-4653, which has also been found in our study,

T. Morel, L. N. Georgiev, Y. Grosdidier, N. St-Louis

In recent years, much studies have focused on determining the origin of the large-scale line-profile and/or photometric patterns of variability displayed by some apparently single Wolf-Rayet stars, with the existence of an unseen (collapsed?) companion or of spatially extended wind structures as potential candidates. We present observations of WR 1 which hig

C. Afonso

We present a catalog containing 290 LMC and 590 SMC Cepheids which have been obtained using the two 4k $\times$ 8k CCD cameras of the EROS~2 microlensing survey. The Cepheids were selected from 1,134,000 and 504,000 stars in the central regions of the LMC and SMC respectively, that were monitored over 150 nights between October 1996 and February 1997, at a r

R. P. Olling, M. R. Merrifield

In order to test the reliability of determinations of the shapes of galaxies&#39; dark matter halos, we have made such measurements for the Milky Way by two independent methods, which make use of the stellar kinematics in the solar neighbourhood and the observed flaring of the Galactic HI layer to estimate the flattening of the Galactic dark halo. These tech

J. C. Lee, A. C. Fabian, W. N. Brandt, C. S. Reynolds

We report on a joint ASCA and RXTE observation spanning an $\sim$ 400~ks time interval of the bright Seyfert~1 galaxy MCG--6-30-15. The data clearly confirm the presence of a broad skewed iron line ($W_{Kα} \sim$ 266 eV) and Compton reflection continuum at higher energies reported in our previous paper. We also investigate whether the gravitational and Doppl

B. Vollmer, V. Cayatte, A. Boselli, C. Balkowski

We present new HI (20&#34; resolution) and CO observations of NGC 4548, an anemic galaxy in the Virgo cluster. The atomic gas distribution shows a ring structure which is distorted at the northern edge. The overall rotation curve is derived with a tilted ring model. We compare our rotation curve with previous ones and discuss the differences. The velocity fi

Jesper Sommer-Larsen

The hypothesis that the Damped Ly-alpha systems (DLAs) are large, galactic disks (Milky Way sized) is tested by confronting predictions of models of the formation and evolution of (large) disk galaxies with observations, in particular the Zinc abundance distribution with neutral hydrogen column density found for DLAs. A pronounced mismatch is found strongly

Aurelien Barrau

The origin of observed extremely high energy cosmic rays remains an astrophysical enigma. We show that a single evaporating primordial black hole should produce 8.5*10^14 particles over a 10^20 eV threshold. This emission results from direct production of fundamental constituants and from hadronization of quarks and gluons. The induced flux on the Earth is s

Luigi Stella, Mario Vietri, Sharon Morsink

A remarkable correlation between the centroid frequencies of quasi periodic oscillations, QPOs, (or peaked noise components) from low mass X-ray binaries, has been recently discovered by Psaltis, Belloni and van der Klis (1999). This correlation extends over nearly 3 decades in frequency and encompasses both neutron star and black hole candidate systems. We

W. K. Huchtmeier, I. D. Karachentsev, V. E. Karachentseva

We report detection of HI-emission from three &#39;new&#39; dwarf galaxies Perseus A, Perseus B, and Camelopardalis D in the IC342/Maffei group of galaxies and of Draco A. The actual number of (probable) members of this group increases to 19 galaxies. Its velocity dispersion is 87 km/s. With a distance of 2.2+-0.5 Mpc this group is the nearest to the Local G

D. Belitz, T. R. Kirkpatrick

The concept of a disordered Fermi-liquid fixed point is introduced and used to understand various properties of disordered metals within a unifying framework. Corrections to scaling near this fixed point give what are commonly called weak-localization effects. Various instabilities of the disordered Fermi-liquid phase are discussed. These include two distinc

Stanislaw Mrowczynski

The event-by-event azimuthal fluctuations in high-energy heavy-ion collisions are analyzed by means of the so-called Phi-measure. The fluctuations due to the collective transverse flow and those caused by the quantum statistics and resonance decays in the hadron gas are discussed in detail.

A. Majumder, S. Das Gupta

We compute the populations of isotopes of Boron, Carbon and Nitrogen measured experimentally in intermediate energy heavy ion collisions. A two component soluble statistical model is used to find the initial populations of different nuclei at a finite temperature. These initial populations are both in particle stable and particle unstable states. The particl

P. Danielewicz

The status of flow in heavy-ion collisions and of inference of hadronic-matter properties is reviewed.

Alexei Borodin, Andrei Okounkov

We prove a formula expressing a general n by n Toeplitz determinant as a Fredholm determinant of an operator 1-K acting on l_2({n,n+1,...}), where the kernel K admits an integral representation in terms of the symbol of the original Toeplitz matrix. The proof is based on the results of one of the authors, see math.RT/9907127, and a formula due to Gessel whic

M. P. Infante, N. Sanchez

We find the spectrum P(w)dw of the gravitational wave background produced in the early universe in string theory. We work in the framework of String Driven Cosmology, whose scale factors are computed with the low-energy effective string equations as well as selfconsistent solutions of General Relativity with a gas of strings as source. The scale factor evolu

I. Antoniadis, G. D&#39;Appollonio, E. Dudas, A. Sagnotti

We discuss Z_2 \times Z_2 orientifolds where the orbifold twists are accompanied by shifts on momentum or winding lattice states. The models contain variable numbers of D5 branes, whose massless (and, at times, even massive) modes have variable numbers of supersymmetries. We display new type-I models with partial supersymmetry breaking N=2 \to N=1, N=4 \to N

L. Freidel, K. Krasnov, R. Puzio

It is well known that, in the first-order formalism, pure three-dimensional gravity is just the BF theory. Similarly, four-dimensional general relativity can be formulated as BF theory with an additional constraint term added to the Lagrangian. In this paper we show that the same is true also for higher-dimensional Einstein gravity: in any dimension gravity

G. Moortgat-Pick, H. Fraas, A. Bartl, W. Majerotto

We study the production of neutralinos e^+ e^- ->chi^0_i χ^0_j with polarized beams and the subsequent decays chi^0_i -> chi^0_k l^+ l^- and chi^0_j -> chi^0_l l^+ l^-, including the complete spin correlations between production and decay. We present analytical formulae for the differential cross section of the combined process of production and decay of neu

D. Neyret, T. Pussieux

The performances of the calorimeter of the Jlab Hall A Compton Polarimeter have been measured using the Mainz tagged photon beam.

Moshe Carmeli

We review cosmological relativity, a new special theory of relativity that was recently developed for cosmology, and discuss in detail some of its aspects.

M. P. Infante, N. Sanchez

We study several approaches for constructing a minimal model of Universe evolution by matching different stages of scale factor laws. We discuss the continuity in the transitions among the stages and the time variables involved. We develop a way to modelize these transitions without loss of observational predictability. The key is the scale factor and its co

Moshe Carmeli, Shimon Malin

A new approach to quantize the gravitational field is presented. It is based on the observation that the quantum character of matter becomes more significant as one gets closer to the big bang. As the metric loses its meaning, it makes sense to consider Schrodinger&#39;s three generic types of manifolds - unconnected differentiable, affinely connected, and m

J. Madore

A short historical review is made of some recent literature in the field of noncommutative geometry, especially the efforts to add a gravitational field to noncommutative models of space-time and to use it as an ultraviolet regulator. An extensive bibliography has been added containing reference to recent review articles as well as to part of the original li

Edith Hemaspaandra, Lane A. Hemaspaandra, Joerg Rothe

A decade ago, a beautiful paper by Wagner developed a ``toolkit&#39;&#39; that in certain cases allows one to prove problems hard for parallel access to NP. However, the problems his toolkit applies to most directly are not overly natural. During the past year, problems that previously were known only to be NP-hard or coNP-hard have been shown to be hard eve

Lane A. Hemaspaandra, Joerg Rothe

Rice&#39;s Theorem states that every nontrivial language property of the recursively enumerable sets is undecidable. Borchert and Stephan initiated the search for complexity-theoretic analogs of Rice&#39;s Theorem. In particular, they proved that every nontrivial counting property of circuits is UP-hard, and that a number of closely related problems are SPP-

Lane A. Hemaspaandra, Zhigen Jiang, Joerg Rothe, Osamu Watanabe

We prove that the join of two sets may actually fall into a lower level of the extended low hierarchy than either of the sets. In particular, there exist sets that are not in the second level of the extended low hierarchy, EL_2, yet their join is in EL_2. That is, in terms of extended lowness, the join operator can lower complexity. Since in a strong intuiti

Edith Hemaspaandra, Lane A. Hemaspaandra, Joerg Rothe

In 1876, Lewis Carroll proposed a voting system in which the winner is the candidate who with the fewest changes in voters&#39; preferences becomes a Condorcet winner---a candidate who beats all other candidates in pairwise majority-rule elections. Bartholdi, Tovey, and Trick provided a lower bound---NP-hardness---on the computational complexity of determini

Lane A. Hemaspaandra, Joerg Rothe, Gerd Wechsung

Can easy sets only have easy certificate schemes? In this paper, we study the class of sets that, for all NP certificate schemes (i.e., NP machines), always have easy acceptance certificates (i.e., accepting paths) that can be computed in polynomial time. We also study the class of sets that, for all NP certificate schemes, infinitely often have easy accepta

Lane A. Hemaspaandra, Zhigen Jiang, Joerg Rothe, Osamu Watanabe

We introduce a generalization of Selman&#39;s P-selectivity that yields a more flexible notion of selectivity, called (polynomial-time) multi-selectivity, in which the selector is allowed to operate on multiple input strings. Since our introduction of this class, it has been used to prove the first known (and optimal) lower bounds for generalized selectivity

A. Sudbø, A. K. Nguyen, J. Hove

The existence of a {\it stable critical point}, separate from the Gaussian and XY critical points, of the Ginzburg-Landau theory for superconductors, is demonstrated by direct extraction via Monte-Carlo simulations, of a negative anomalous dimension $η_ϕ$ of a complex scalar field $ϕ$ forming a dual description of a neutral superfluid. The dual of the neutra

A. K. Nguyen, A. Sudbø

We study the effect of critical fluctuations on the $(B,T)$ phase diagram in extreme type-II superconductors in zero and finite magnetic field using large-scale Monte Carlo simulations on the Ginzburg-Landau model in a frozen gauge approximation. We show that a vortex-loop unbinding gives a correct picture of the zero field superconducting-normal transition

Renato A. Dupke, Raymond E. White

We present constraints on theoretical models of Type Ia supernovae using spatially resolved ASCA X-ray spectroscopy of three galaxy clusters: Abell 496, Abell 2199 and Abell 3571. All three clusters have central iron abundance enhancements; an ensemble of abundance ratios are used to show that most of the iron in the central regions of the clusters comes fro

Adolf N. Witt, Karl D. Gordon

We present and discuss the results of new multiple-scattering radiative transfer calculations for three representative types of galactic environments, filled with either homogeneous or two-phase clumpy dust distributions. Extinction and scattering properties for two types of interstellar dust, similar to those found in the average diffuse medium of the Milky

Hugo Garcia-Compean, Jerzy F. Plebanski

Recently M. Kontsevich found a combinatorial formula defining a star-product of deformation quantization for any Poisson manifold. Kontsevich&#39;s formula has been reinterpreted physically as quantum correlation functions of a topological sigma model for open strings as well as in the context of D-branes in flat backgrounds with a Neveu-Schwarz B-field. Her

Christopher J. Miller, Adrian Melott, Patrick Gorman

Galaxy clusters approximate a planar (FP) distribution in a three-dimensional parameter space which can be characterized by optical luminosity, half-light radius, and X-ray luminosity. Using a high-quality catalog of cluster redshifts, we find the nearest neighbor cluster for those common to an FP study and the cluster catalog. Examining scatter about the FP

W. Chen

This note presents a new definition of nonlinear statistics mean and variance to simplify the nonlinear statistics computations. These concepts aim to provide a theoretical explanation of a novel nonlinear weighted residual methodology presented recently by the present author.

Steven R. White, D. J. Scalapino

We make a critical analysis of numerical results for and against phase separation and stripe formation in the t-J model. We argue that the frustrated phase separation mechanism for stripe formation requires phase separation at too high a doping for it to be consistent with existing numerical studies of the t-J model. We compare variational energies for vario