January 1998 arXiv papers — page 6

Volker Serfling, ALADIN collaboration

Breakup temperatures in central collisions of 197Au + 197Au at bombarding energies E/A = 50 to 200 MeV were determined with two methods. Isotope temperatures, deduced from double ratios of hydrogen, helium, and lithium isotopic yields, increase monotonically with bombarding energy from 5 MeV to 12 MeV, in qualitative agreement with a scenario of chemical fre

Victor V. Batyrev

In this paper we explain the complete biregular classification of all 4-dimensional smooth toric Fano varieties. The main result states that there exist exactly 123 different types of toric Fano 4-folds up to isomorphism.

Arnaldo Garcia, Fernando Torres

We study geometrical properties of maximal curves having classical Weierstrass gaps.

J. Avan, L. Frappat, M. Rossi, P. Sorba

We extend to the sl(N) case the results that we previously obtained on the construction of W_{q,p} algebras from the elliptic algebra A_{q,p}(\hat{sl}(2)_c). The elliptic algebra A_{q,p}(\hat{sl}(N)_c) at the critical level c=-N has an extended center containing trace-like operators t(z). Families of Poisson structures indexed by N(N-1)/2 integers, defining

B. L. Cerchiai, J. Wess

The Hilbert space representations of a non-commutative q-deformed Minkowski space, its momenta and its Lorentz boosts are constructed. The spectrum of the diagonalizable space elements shows a lattice-like structure with accumulation points on the light-cone.

Mark Hovey, John Palmieri

Using Ohkawa's theorem that the collection of Bousfield classes is a set, we perform a number of constructions with Bousfield classes. In particular, we describe a greatest lower bound operator; we also note that a certain subset DL of the Bousfield lattice is a frame, and we examine some consequences of this observation. We make several conjectures abou

D. G. Barci, V. E. R. Lemes, C. Linhares de Jesus, M. B. D. Silva Maia Porto

The three dimensional abelian fermionic determinant of a two component massive spinor in flat euclidean space-time is resetted to a pure Chern-Simons action through a nonlinear redefinition of the gauge field.

Thordur Jonsson

We discuss the average length l of the shortest non-contractible loop on surfaces in the two-dimensional pure quantum gravity ensemble. The value of $γ_{str}$ and the explicit form of the loop functions indicate that l diverges at the critical point. Scaling arguments suggest that the critical exponent of l is 1/2. We show that this value of the critical exp

A. Mironov

This note gives a brief review of the integrable structures presented in the Seiberg-Witten approach to the N=2 SUSY gauge theories with emphasize on the case of the gauge theories with matter hypermultiplets included (described by spin chains). The web of different N=2 SUSY theories is discussed.

I. V. Gorbunov, S. L. Lyakhovich

A classical model of N=2, D=3 fractional spin superparticle (superanyon) is presented, whose first-quantization procedure combines the Berezin quantization for the superspin degrees of freedom and the canonical quantization for the space-time ones. To provide the supersymmetry for the quantised theory, certain quantum corrections are required to the N=2 supe

Frank E. Paige

Signatures for sleptons, which have been extensively studied for the Next Linear Collider, are reexamined taking into account some of the different features of a First Muon Collider.

Frank E. Paige

After a brief review of the Minimal Supersymmetric Standard Model (MSSM) and specifically the Minimal Supergravity Model (SUGRA), the prospects for discovering and studying SUSY at the CERN Large Hadron Collider are reviewed. The possible role for a future Lepton Collider --- whether $μ^+μ^-$ or $e^+e^-$ --- is also discussed.

Andrzej Czarnecki, William J. Marciano

Parity violating left-right scattering asymmetries at future high energy e+e- and e-e- colliders are examined. The utility of two polarized beams for precision measurements is pointed out. Sensitivity to ``new'' short-distance physics is briefly discussed. Electroweak radiative corrections due to the running of sin^2(theta_W)(q^2) are exhibited.

E. V. Shuryak

Radial flow observed at AGS/SPS energies is very strong, with collective velocities of matter reaching about 0.5c for central collisions of the heaviest ions. The lattice-based Equation of State (EOS) is however rather soft, due to the QCD phase transition. We show that both statements are consistent only if proper kinetic-based treatment of the freeze-out i

Marco A. Diaz, J. Ferrandis, Jorge C. Romao, Jose W. F. Valle

We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymmetric Standard Model (MSSM) which incorporates R-Parity violation through a bilinear superpotential term. Contrary to what happens in the MSSM, we show that bottom-tau unification at the scale M_GUT where the gauge couplings unify can be achieved for any value of

Sergio Caracciolo, Fabrizio Palumbo

In the framework of an approach to bosonization based on the use of fermionic composites as fundamental variables, a quadratic action in even Grassmann variables with the quantum numbers of the pions has been constructed. It includes the sigma-field in order to be invariant under SU(2)_L times SU(2)]_R transformations over the quarks. This action exhibits th

Ephraim Fischbach, Brian Woodahl

We examine several recent calculations of the self-energy of a neutron star arising from neutrino-exchange. It is shown that the results of Abada, et al. in 1+1 dimensions have no bearing on a 3-dimensional neutron star, since the criticality parameter (Gf N)/R^2 is always much smaller than unity in 1+1 dimensions. The calculation of Kiers and Tytgat in 3-di

S. Giani

From a mathematical point of view velocities can be larger than c. It has been shown that Lorentz transformations are easily extended in Minkowski space to address velocities beyond the speed of light. Energy and momentum conservation fixes the relation between masses and velocities larger than c, leading to the possible observation of negative mass squared

H. Neuberger

In a previous publication [hep-lat/9707022] I showed that the fermion determinant for strictly massless quarks can be written on the lattice as $\det D$, where $D$ is a certain finite square matrix explicitly constructed from the lattice gauge fields. Here I show that $D$ obeys the Ginsparg-Wilson relation $Dγ_5 D = Dγ_5 +γ_5 D$.

M. Engelhardt, K. Langfeld, H. Reinhardt, O. Tennert

Center projection of SU(2) lattice gauge theory allows to isolate magnetic vortices as confining configurations. The vortex density scales according to the renormalization group, implying that the vortices are physical objects rather than lattice artifacts. Here, the binary correlations between points at which vortices pierce a given plane are investigated.

Mary E Convery

MiniMax (Fermilab T-864) was a small test/experiment at the Tevatron designed to search for disoriented chiral condensates (DCC) in the forward direction. The MiniMax detector at the C0 collision region of the Tevatron was a telescope of 24 multi-wire proportional chambers (MWPC's) with a lead converter behind the eighth MWPC, allowing the detection of c

Beverly K. Berger, Vincent Moncrief

Numerical evidence supports the conjecture that polarized U(1) symmetric cosmologies have asymptotically velocity term dominated singularities.

Alfio Bonanno

A class of exact solutions of the field equations with higher derivative terms is presented when the matter field is a pressureless null fluid plus a Maxwellian static electric component. It is found that the stable solutions are black holes in anti de Sitter background. The issue of the stability of the Cauchy horizon is discussed.

Naresh Dadhich, L. K. Patel, Ramesh Tikekar

We consider the electromagnetic resolution of gravitational field. We show that under the duality transformation, in which active and passive electric parts of the Riemann curvature are interchanged, a fluid spacetime in comoving coordinates remains invariant in its character with density and pressure transforming, while energy flux and anisotropic pressure

Bin Wang, Ru-Keng Su, P. K. N. Yu

Geometrical properties of the extreme Kerr black holes in the topological sectors of nonextreme and extreme configurations are studied. We find that the Euler characteristic plays an essential role to distinguish these two kinds of extreme black holes. The relationship between the geometrical properties and the intrinsic thermodynamics are investigated.

Michael Pascaud, Gilles Montambaux

We describe the effects of phase coherence on transport and thermodynamic properties of a disordered conducting network. In analogy with weak-localization correction, we calculate the phase coherence contribution to the magnetic response of mesoscopic metallic isolated networks. It is related to the return probability for a diffusive particle on the correspo

L. O. Manuel, M. I. Micheletti, A. E. Trumper, H. A. Ceccatto

We investigate the ground state structure of the Heisenberg model on the 1/5-depleted square lattice for arbitrary values of the first- and second-neighbor exchange couplings. By using a mean-field Schwinger-boson approach we present a unified description of the rich ground-state diagram, which include the plaquette and dimer resonant-valence-bond phases, an

E. Cappelluti, C. Grimaldi, L. Pietronero

The nonadiabatic effects due to the breakdown of Migdal's theorem in high-$T_c$ superconductors are strongly affected by the opening of the superconducting gap. Here we report how the momentum-frequency dependence of vertex corrections is modified by the gap. A general effect is that the positive region of the vertex corrections is increased leading to a

Thomas A. Vilgis, Michael Stapper

The behavior of microgels near surfaces and their adsorption is studied by simple scaling theory. Two different types of microgels can be studied, i.e., fractal type microgels and randomly crosslinked polymer chains. In the first case the gel can be described mainly by introducing a spectral dimension. The second type requires more attention and uses the num

M. Buzzacchi, E. Del Giudice, G. Preparata, S. S. Xue

The many experimental puzzles of solid hydrogen, that seem to defy the generally accepted view of condensed matter, are shown to be a rather straightforward consequence of a new approach to condensed matter physics, that takes into account the coherent electrodynamic processes, predicted by Quantum ElectroDynamics (QED) that have been so far overlooked. As a

Robert A. Smith, Igor V. Lerner, Boris L. Altshuler

We show that the perturbative expansion of the two-level correlation function, $R(ω)$, in disordered conductors can be understood semiclassically in terms of self-intersecting particle trajectories. This requires the extension of the standard diagonal approximation to include pairs of paths which are non-identical but have almost identical action. The number

W. Fettes, I. Morgenstern

We perform numerical simulations of the Hubbard model using the projector Quantum Monte Carlo method. A novel approach for finite size scaling is discussed. We obtain evidence in favor of d-wave superconductivity in the repulsive Hubbard model. For U=4, $T_c$ is roughly estimated as $T_c\approx 30K$.

F. M. Izrailev, S. Ruffo, L. Tessieri

A new approach is applied to the 1D Anderson model by making use of a two-dimensional Hamiltonian map. For a weak disorder this approach allows for a simple derivation of correct expressions for the localization length both at the center and at the edge of the energy band, where standard perturbation theory fails. Approximate analytical expressions for stron

Craig Pryor

The electronic structure of an infinite 1D array of vertically coupled InAs/GaAs strained quantum dots is calculated using an eight-band strain-dependent k-dot-p Hamiltonian. The coupled dots form a unique quantum wire structure in which the miniband widths and effective masses are controlled by the distance between the islands, d. The miniband structure is

G. Boffetta, P. Giuliani, G. Paladin, A. Vulpiani

The predictability problem for systems with different characteristic time scales is investigated. It is shown that even in simple chaotic dynamical systems, the leading Lyapunov exponent is not sufficient to estimate the predictability time. This fact is due the saturation of the error on the fast components of the system which therefore do not contribute to

A. C. Quillen

NGC 2915 is a remarkable blue compact dwarf galaxy which contains an inner HI bar and strong spiral structure in its HI disk extending well beyond its optical disk. We propose here that NGC 2915 has a dark or faint (not yet observed) massive disk component. By massive we mean of the same order as the HI gas mass which ranges from 0.5 -- 10 Msol/pc^2. We pres

J. Patience, A. M. Ghez, I. N. Reid, A. J. Weinberger

A 2.2 micron speckle imaging survey of 167 bright (K $< 8.5$ mag) Hyades members reveals a total of 33 binaries with separations spanning 0.&#34;044 to 1.&#34;34 and magnitude differences as large as 5.5 mag. Of these binaries, 13 are new detections. Combining the results of this survey with previous radial velocity, optical speckle, and direct imaging Hyade

Jean-Marc Bonnet-Bidaud, Martine Mouchet

We present long slit spectral (375-725 nm) observations of the proposed identification of the transient 66s X-ray pulsar Cep X-4=GS2138+56. Spectra show features typical of Be/X-ray binaries. Superimposed on a weak emission from the IC 1396 nebula, strong H$α$ (4.5 nm EW) and H$β$ (0.3 nm EW) lines are seen in emission with the other Balmer lines in absorpti

W. E. Harris, G. L. H. Harris, D. E. McLaughlin

New VRI photometry is presented for the globular clusters in the innermost 140&#39;&#39; of the M87 halo. The results are used to discuss several issues concerning the formation and evolution of globular cluster systems in supergiant ellipticals like M87. (1) we find no significant change in the globular cluster luminosity function (GCLF) with galactocentric

I. M. Hook, P. A. Shaver, R. G. McMahon

We present results from two surveys for radio-loud quasars. These are (1) a northern survey reaching S(5GHz)=0.2Jy and (2) the Parkes QSO survey reaching S(2.7GHz)=0.25Jy, which together cover most of the sky. Both surveys use digitised plate material to identify the majority of the radio sources and CCD images to identify the optically fainter sources. The

Neil Cornish, David Spergel, Glenn Starkman

If the universe is finite and smaller than the distance to the surface of last scatter, then the signature of the topology of the universe is writ large on the microwave background sky. We show that the microwave background will be identified at the intersections of the surface of last scattering as seen by different ``copies&#39;&#39; of the observer. Since

P. A. Shaver, I. M. Hook, C. A. Jackson, J. V. Wall

We have obtained complete redshift information for a sample of 442 radio-loud quasars with flux densities S(11cm) >= 0.25Jy. These come from a completely-identified sample of 878 flat-spectrum radio sources, so there is no optical magnitude limit. With these quasars, therefore, we can map out the entire quasar epoch, unhindered by optical selection effects a

W. Pietsch, Th. Boller, S. Doebereiner, H. -U. Zimmermann

We present the first results of a program to identify so far unknown active nuclei (AGN) in galaxies. Candidate galactic nuclei have been selected for optical spectroscopy from a cross-correlation of the ROSAT All Sky Survey (RASS) bright source catalog with optical galaxy catalogs. A high X-ray flux has been used as pointer to galaxies with a high probabili

Alvio Renzini

Clusters of galaxies allow a direct estimate of the metallicity and metal production yield on the largest scale so far. It is argued that cluster metallicity (about 1/3 solar) should be taken as representative of the low-z universe as a whole. There is now compelling evidence that the bulk of stars not only in cluster ellipticals but also in field elliptical

Michael I. Eides, Howard Grotch, Valery A. Shelyuto

Radiative-recoil corrections to hyperfine splitting in muonium of orders $α(Zα)(m/M)^2E_F$ and $(Z^2α)(Zα)(m/M)^2E_F$ are calculated. These corrections are of the second order in the small electron-muon mass ratio. An analytic expression $[(-6 \ln2- \frac{3}{4})α(Zα) - \frac{17}{12} (Z^2 α) (Zα)](\frac{m}{M})^2 E_F$ is obtained. Numerically the correction is

Danny Birmingham

It is shown that the five-dimensional anti-de Sitter black hole is a supersymmetric solution of the low-energy field equations of type IIB string theory compactified on an Einstein space. A statistical interpretation of the mass dependence of the entropy can be obtained from considerations of the three-dimensional BTZ black hole.

L. Gamberg, H. Reinhardt, H. Weigel

We calculate the chiral odd quark distributions and the corresponding structure functions $h_T(x,Q^2)$ and $h_L(x,Q^2)$ within the Nambu-Jona-Lasinio chiral soliton model for the nucleon. The $Q^2$ evolution of the twist-2 contributions is performed according to the standard GLAP formalism while the twist-three piece, $\bar{h}_L(x)$, is evolved according to

S. Mignemi

We perform the Dirac hamiltonian analysis of a four-dimensional gauge theory of gravity with an action of topological type, which generalizes some well-known two-dimensional models. We show that, in contrast with the two-dimensional case, the theory has a non-vanishing number of dynamical degrees of freedom and that its structure is very similar to higher-di

S. Lubeck, L. Roters, K. D. Usadel

The Nagel-Schreckenberg traffic flow model shows a transition from a free flow regime to a jammed regime for increasing car density. The measurement of the dynamical structure factor offers the chance to observe the evolution of jams without the necessity to define a car to be jammed or not. Above the jamming transition the dynamical structure factor $S(k,ω)

Sandip Bhattacharyya, Alok Kumar, Subir Mukhopadhyay

We discuss the generalization of recently discovered BPS configurations, corresponding to the planar string networks, to non-planar ones by considering the U-duality symmetry of type II string theory in various dimensions. As an explicit example, we analyze the string solutions in 8-dimensional space-time, carrying SL(3) charges, and show that by aligning th

H. Neuberger

A recently claimed resolution to the lattice Gribov problem in the context of chiral lattice gauge theories is examined. Unfortunately, I find that the old problem remains.

V. Gimenez, L. Giusti, F. Rapuano, M. Talevi

We discuss the renormalization of different definitions of quark masses in the Wilson and the tree-level improved SW-Clover fermionic action. For the improved case we give the correct relationship between the quark mass and the hopping parameter. Using perturbative and non-perturbative renormalization constants, we extract quark masses in the $\MSbar$ scheme

R. Bonciani, S. Catani, M. L. Mangano, P. Nason

We compute the effect of soft-gluon resummation, at the next-to-leading-logarithmic level, in the hadroproduction cross-section for heavy flavours. Applications to top, bottom and charm total cross-sections are discussed. We find in general that the corrections to the fixed next-to-leading-order results are larger for larger renormalization scales, and small

K. Jacobs, P. L. Knight

We present a method for obtaining evolution operators for linear quantum trajectories. We apply this to a number of physical examples of varying mathematical complexity, in which the quantum trajectories describe the continuous projection measurement of physical observables. Using this method we calculate the average conditional uncertainty for the measured

G. Parisi, J. J. Ruiz-Lorenzo, D. Stariolo

By means of extensive computer simulations we analyze in detail the two dimensional $\pm J$ Ising spin glass with ferromagnetic next-nearest-neighbor interactions. We found a crossover from ferromagnetic to ``spin glass&#39;&#39; like order both from numerical simulations and analytical arguments. We also present evidences of a second crossover from the ``sp

Muktish Acharyya, Dietrich Stauffer

We have studied the nucleation in the nearest neighbour ferromagnetic Ising model, in different (d) dimensions, by extensive Monte Carlo simulation using the heat-bath dynamics. The nucleation time (tau) has been studied as a function of the magnetic field (h) for various system sizes in different dimensions (d=2,3,4). The logarithm of the nucleation time is

V. G. Baryshevsky, K. G. Batrakov, S. Cherkas

For the omega-hyperon passing through matter the phenomena of spin rotation and oscillation has investigated quantitatively. Connection of these phenomena with constituent quark rescattering has been determined. It allows one to investigate quark rescattering directly without background of a single scattering.

P. Teerikorpi, M. Hanski, G. Theureau, Yu. Baryshev

We have studied using the KLUN sample of 5171 spiral galaxies having Tully-Fisher distance moduli, the average radial space distribution of galaxies out to a distance of about 200 Mpc (for H_0=50 km/s/Mpc). One motivation came from the current debate on the fractal dimension D and maximum scale of fractality. To study this question, we used a new method base

J. G. Muga, R. Sala, J. P. Palao

The concept and the formalization of the arrival time in quantum mechanics are discussed. Different approaches based on trajectories, quantization rules, time operators, phase space techniques, renewal equations or operational procedures are reviewed or proposed. Open questions and loose ends are pointed out.

Daniel S. Abrams, Seth Lloyd

If quantum states exhibit small nonlinearities during time evolution, then quantum computers can be used to solve NP-complete problems in polynomial time. We provide algorithms that solve NP-complete and #P oracle problems by exploiting nonlinear quantum logic gates. It is argued that virtually any deterministic nonlinear quantum theory will include such gat

N. Brenner, O. Agam, W. Bialek, R. de Ruyter van Steveninck

We construct a model that predicts the statistical properties of spike trains generated by a sensory neuron. The model describes the combined effects of the neuron&#39;s intrinsic properties, the noise in the surrounding, and the external driving stimulus. We show that the spike trains exhibit universal statistical behavior over short times, modulated by a s

J. Rayford Nix, Daniel Strottman, Hubert W. van Hecke, Bernd R. Schlei

We use a nine-parameter expanding source model that includes special relativity, quantum statistics, resonance decays, and freeze-out on a realistic hypersurface in spacetime to analyze invariant pi+, K+, and K- one-particle multiplicity distributions and pi+ and pi- two-particle correlations in nearly central collisions of Pb + Pb at a laboratory bombarding

Thomas Papenbrock, George F. Bertsch

We present the first fully quantum mechanical calculation of photon radiation accompanying charged particle decay from a barrier resonance. The soft-photon limit agrees with the classical results, but differences appear at next-to-leading-order. Under the conditions of alpha-decay of heavy nuclei, the main contribution to the photon emission stems from Coulo

P. K. Sahu, A. Hombach, W. Cassing, U. Mosel

We calculate the baryon flow $< P_x/A(y) >$ in the energy range from .25 to $\le 2.5 AGeV$ in a relativistic transport model for $Ni+Ni$ and $Au+Au$ collisions employing various models for the baryon self energies. We find that to describe the flow data of the FOPI Collaboration the strength of the vector potential has to be reduced at high relative momentum

H. Nakada, Y. Alhassid

Total and parity-projected level densities of iron-region nuclei are calculated microscopically by using Monte Carlo methods for the nuclear shell model in the complete $(pf+0g_{9/2})$-shell. The calculated total level density is found to be in good agreement with the experimental level density. The Monte Carlo calculations offer a significant improvement ov

L. Frankfurt, G. Piller, M. Sargsian, M. Strikman

In this paper we discuss coherent photo- and leptoproduction of vector mesons from deuterons at intermediate (virtual) photon energies, 3 < nu < 30 GeV. We consider the scattering from unpolarized and polarized targets as well as processes where the polarization of the recoil deuteron is measured. Our main motivation results from the need for a quantitative

J. Hellmig, H. V. Klapdor-Kleingrothaus

The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated the large potential of double beta decay to search for new physics beyond the Standard Model. To increase by a major step the present sensitivity for double beta decay and dark matter search much bigger source strengths and much lower backgrounds are needed than used in experiments un

Steven N. Evans, Ruth J. Williams

If $u(t,x)$ is a solution of a one--dimensional, parabolic, second--order, linear partial differential equation (PDE), then it is known that, under suitable conditions, the number of zero--crossings of the function $u(t,\cdot)$ decreases (that is, does not increase) as time $t$ increases. Such theorems have applications to the study of blow--up of solutions

Adam Parusinski, Piotr Pragacz

We give a new formula for the Chern-Schwartz-MacPherson class of a hypersurface in a nonsigular compact complex analytic variety. In particular this formula generalizes our previous result on the Euler characteristic of such a hypersurface. Two different approaches are presented. The first is based on the theory of characteristic cycle and the works of Sabba

Richard E. Borcherds

In this paper we complete the proof of Ryba&#39;s modular moonshine conjectures. We do this by applying Hodge theory to the cohomology of the monster Lie algebra over the ring of p-adic integers in order to calculate the Tate cohomology groups of elements of the monster acting on the monster vertex algebra.

Kevin P. Knudson

We compute the completion of the groups SL_n(Z[t]) and SL_n(Z[t,t^{-1}]) relative to the obvious homomorphisms to SL_n(Q); this is a generalization of the classical Malcev completion. We also make partial computations of the rational second cohomology of these groups.

Kevin P. Knudson

Let F be a field of characteristic zero and let V be an irreducible representation of SL_n(F). In this paper, we compute the first cohomology of SL_n(F[t]) with coefficients in V. It agrees with H^1(SL_n(F),V) if V is not the adjoint representation, while if V = Ad, the two groups differ by an F-vector space X. We show that if n=2, X is infinite dimensional,

Kevin P. Knudson

We prove that if R is a Hensel local ring with infinite residue field k, the natural map H_i(GL(n,R),Z/p) ---> H_i(GL(n,k),Z/p) is an isomorphism for i <=3, p distinct from char(k). This implies rigidity for H_i(GL_n), i <=3, which in turn implies the Friedlander-Milnor conjecture in positive characteristic in degrees <=3.

Kevin P. Knudson

Let E be an elliptic curve defined via a Weierstrass equation F(x,y)=0 over an infinite field k. Denote by A the coordinate ring of E. In this note we compute the integral homology of PGL_2(A). We obtain a rigidity result as a corollary.

Kimmo Eriksson, Johan Karlander

In the theory of two-sided matching markets there are two well-known models: the marriage model (where no money is involved) and the assignment model (where payments are involved). Roth and Sotomayor (1990) asked for an explanation for the similarities in behavior between those two models. We address this question by introducing a common generalization that

Martin Markl

We will consider P-graph complexes, where P is a cyclic operad. P-graph complexes are natural generalizations of Kontsevich&#39;s graph complexes -- for P = the operad for associative algebras it is the complex of ribbon graphs, for P = the operad for commutative associative algebras, the complex of all graphs. We construct a `universal class&#39; in the coh

Peter E. John, Horst Sachs

This is a contribution to the number theory of the dimer problem. The number of dimer coverings (i.e., perfect matchings) of a square lattice graph is discussed modulo powers of 2.

S. M. Gusein-Zade, I. Luengo, A. Melle-Hernandez

We use the notion of Milnor fibres of the germ of a meromorphic function and the method of partial resolutions for a study of topology of a polynomial map at infinity (mainly for calculation of the zeta-function of a monodromy). It gives effective methods of computation of the zeta-function for a number of cases and a criterium for a value to be atypical at

M. Trigiante

The purpose of the present thesis is to give a self-contained review of the solvable Lie algebra approach to supergravity problems related with S, T and U dualities. After recalling the general features of dualities in both Superstring theory and Supergravity, we introduce the solvable Lie algebra formalism as an alternative description of the scalar manifol

Serge Lazzarini, Thomas Schucker

The unimodularity condition in Connes&#39; formulation of the standard model is rewritten in terms of group representations.

A. V. Smilga, A. I. Veselov

We study the spectrum of the domain walls interpolating between different chirally asymmetric vacua in supersymmetric QCD with the SU(3) gauge group and including 2 pairs of chiral matter multiplets in fundamental and anti-fundamental representations. For small enough masses m < m* = .286... (in the units of Λ), there are two different domain wall solutions

Alfred S. Goldhaber

Jackiw and Rebbi found two types of intrinsically stable or `fundamental&#39; soliton (kinks in 1+1 D and magnetic monopoles in 3+1 D) which can carry pieces of elementary-particle charges. After two decades there are no more, and it is argued here why that is inevitable.

Lincoln Wolfenstein

Contributions to B - \bar B mixing from physics beyond the standard model may be detected from CP-violating asymmetries in B decays. There exists the possibility of large new contributions that cannot be detected by first generation experiments because of a discrete ambiguity. Some possible strategies for resolving this are discussed.

Kenneth Lane

The motivations for studying dynamical scenarios of electroweak and flavor symmetry breaking are reviewed and the latest ideas, especially topcolor-assisted technicolor, are summarized. Technicolor's observable low-energy signatures are discussed. The superb energy resolution of the First Muon Collider may make it possible to resolve the extraordinarily narr

R. Mertig, R. Scharf

TARCER is an implementation of the recurrence algorithm of O.V. Tarasov for the reduction of two-loop propagator integrals with arbitrary masses to a small set of basis integrals. The tensor integral reduction scheme is adapted to moment integrals emerging in operator matrix element calculations.

N. G. Marchuk

A model in which quarks and leptons consist of three &#34;more elementary&#34; particles of spin 1/2 is proposed. A gauge field theory with SU(4) symmetry that corresponds to this model predicts the existence of two new bosons.

Edmond L. Berger

I discuss the motivation for resummation of the effects of initial-state soft gluon radiation, to all orders in the strong coupling strength, for processes in which the near-threshold region in the partonic subenergy is important. I summarize the method of &#34;perturbative resummation&#34; and its application to the calculation of the total cross section fo

A. I. Davydychev, P. Osland, O. V. Tarasov

The two-loop three-gluon vertex is calculated in an arbitrary covariant gauge, in the limit when one of the external momenta vanishes. The differential Ward-Slavnov-Taylor (WST) identity related to this limit is discussed, and the relevant results for the ghost-gluon vertex and two-point functions are obtained. Together with the differential WST identity, th

A. De Roeck

We give a brief account of some physics topics which could be addressed at a collider consisting of the HERA proton ring and the future e+e- Linear Collider. A few experimental aspects are also discussed.

G. P. Korchemsky

We study the spectrum of the reggeized gluon compound states in high-energy QCD. The energy of the states depends on the total set of quantum numbers whose values are constrained by the quantization conditions. To establish their explicit form we apply the methods of nonlinear WKB analysis to the Schrödinger equation for the $N$ reggeon state in the separate

C. E. M. Wagner

Gauge mediation of supersymmetry breaking in the observable sector is an attractive idea, which naturally alleviates the flavour changing neutral current problem of supersymmetric theories. Quite generally, however, the number and quantum number of the messengers are not known; nor is their characteristic mass scale determined by the theory. Using the recent

R. A. Alanakyan

In the framework of the supersymmetric theories with R-parity violation we consider the process $γγ\to ν_i \bar{ν_j}$ and its contribution into energy loss from the stars.Under some conditions the studied contribution exceeds the standard model contribution to the same process.

Marco A. Diaz, Steve F. King, Douglas A. Ross

One-loop radiative corrections to the production cross section of a pair of light charginos in e+e- colliders are calculated within the MSSM. Top and bottom quarks and squarks are considered in the loops, and they are renormalized using the MS-bar scheme. If the center of mass energy is equal to 192 GeV, positive corrections typically of 10% to 15% are found

Yu. L. Dokshitzer

Today&#39;s QCD problems, prospects and achievements are reviewed.

Michihiro Hori, Yuichiro Kiyo, Jiro Kodaira, Takashi Nasuno

We analyze spin correlations between top quark and anti-top quark produced at polarized e^+ e^- and gamma gamma colliders. We consider a generic spin basis to find a strong spin correlation. Optimal spin decompositions for top quark pair are presented for e^+ e^- and gamma gamma colliders. We show the cross-section in these bases and discuss the characterist

D. Pocanic

General interest in a precise determination of the threshold pi-pi amplitudes has recently increased markedly due to a controversy regarding the size of <0|qbar q|0>, the scalar quark condensate. This paper examines the current experimental information on the pi-pi scattering lengths, in particular the recent low energy pi N -> pi pi N data from several labo

X. Song

An unified scheme for describing both spin and orbital motion in symmetry-breaking chiral quark model is suggested. The analytic results of the spin and orbital angular momenta carried by different quark flavors in the nucleon are given. The quark spin reduction due to spin-flip in the chiral splitting processes is compensated by the increase of the orbital

L. Del Debbio, M. Faber, J. Giedt, J. Greensite

We discuss the implementation of the ``direct&#39;&#39; maximal center gauge (a gauge which maximizes the lattice average of the squared-modulus of the trace of link variables), and its use in identifying Z(2) center vortices in Yang-Mills vacuum configurations generated by lattice Monte Carlo. We find that center vortices identified in the vacuum state acco

D. A. Johnston

We investigate the Yang-Lee edge singularity on non-planar random graphs, which we consider as the Feynman Diagrams of various d=0 field theories, in order to determine the value of the edge exponent. We consider the hard dimer model on phi3 and phi4 random graphs to test the universality of the exponent with respect to coordination number, and the Ising mod

Piotr T. Chrusciel, Jacek Jezierski, Malcolm A. H. MacCallum

The usual approaches to the definition of energy give an ambiguous result for the energy of fields in the radiating regime. We show that for a massless scalar field in Minkowski space-time the definition may be rendered unambiguous by adding the requirement that the energy cannot increase in retarded time. We present a similar theorem for the gravitational f