April 1998 arXiv papers — page 12

V. K. Petrov

Fermion determinant is computed analytically on extremely large lattices $% N_τ\to \infty $ in the toy model approximation in which action is truncated so that in the Hamiltonian limit of $a_τ\to 0$ all terms of order $a_τ/a_σ$ are discarded$.$ Chiral condensate is studied in the area of small ($m<<T$) quark masses.

Rosario N. Mantegna, H. Eugene Stanley

We compare our results on empirical analysis of financial data with simulations of two stochastic models of the dynamics of stock market prices. The two models are (i) the truncated Lévy flight recently introduced by us and (ii) the ARCH(1) and GARCH(1,1) processes. We find that the TLF well describes the scaling and its breakdown observed in empirical data,

Vipin Srivastava

text of abstract (Integer quantum Hall effect (IQHE) has been analysed considering the degeneracies of localized and extended states separately. Occupied localized and extended states are counted and their variation is studied as a function of magnetic field. The number of current carrying electrons is found to have a saw-tooth variation with magnetic field.

Akira Shimizu

The conductance of one-dimensional interacting electron systems is calculated in a manner similar to Landauer&#39;s argument for non-interacting systems. Unlike in previous studies in which the Kubo formula was used, the conductance is directly evaluated as the ratio of current $J$ to the chemical potential difference $Δμ$ between right-going and left-going

Akira Shimizu, Takayuki Miyadera

We derive an effective 1D theory from the Hamiltonian of the 3D system which consists of a mesoscopic conductor and reservoirs. We assume that the many-body interaction have the same magnitude in the conductor as that in the reservoirs, in contrast to the previous theories which made the ad hoc assumption that the many-body interaction were absent in the res

A. Y. Potekhin, A. V. Ivanchik, D. A. Varshalovich, K. M. Lanzetta

Multidimensional cosmologies allow for variations of fundamental physical constants over the course of cosmological evolution, and different versions of the theories predict different time dependences. In particular, such variations could manifest themselves as changes of the proton-to-electron mass ratio μ=m_p/m_e over the period of ~ 10^{10} years since th

Dimitrios Tsimpis

We derive certain boundary conditions in Nahm&#39;s equations by considering a system of N parallel D1-branes perpendicular to a D3-brane in type IIB string theory.

Z. Kollath, J. P. Beaulieu, J. R. Buchler, P. Yecko

The numerical hydrodynamic modelling of beat Cepheid behavior has been a longstanding quest in which purely radiative models have failed miserably. We find that beat pulsations occur naturally when turbulent convection is accounted for in our hydrodynamics codes. The development of a relaxation code and of a Floquet stability analysis greatly facilitates the

J. Diaz Alonso, L. Mornas

We investigate the modification induced on the nucleon-nucleon cross section by screening of the interaction inside nuclear matter. The interaction is described by the relativistic one boson exchange of $σ$, $ω$ and $π$ mesons. Medium effects enter as loop corrections to the meson propagators and are characterized not only by density, but also by temperature

M. S. Freedman, G. R. Ringo, T. W. Dombeck

The use of an ultracold neutron interferometer incorporating an electrostatic accelerator having a strong electric field gradient to accelerate neutrons by their possible electric moments is proposed as a method of measuring the neutron electric dipole moment. Such electrical acceleration, followed by an amplifier and a generator of phase difference, could d

B. Julia, S. Silva

E. Noether&#39;s general analysis of conservation laws has to be completed in a Lagrangian theory with local gauge invariance. Bulk charges are replaced by fluxes of superpotentials. Gauge invariant bulk charges may subsist when distinguished one-dimensional subgroups are present. As a first illustration we propose a new {\it Affine action} that reduces to G

A. Ramani, B. Grammaticos, S. Lafortune

We examine a family of 3-point mappings that include mappings solvable through linearization. The different origins of mappings of this type are examined: projective equations and Gambier systems. The integrable cases are obtained through the application of the singularity confinement criterion and are explicitly integrated.

B. Grammaticos, A. Ramani, S. Lafortune

We examine critically the Gambier equation and show that it is the generic linearisable equation containing, as reductions, all the second-order equations which are integrable through linearisation. We then introduce the general discrete form of this equation, the Gambier mapping, and present conditions for its integrability. Finally, we obtain the reduction

O. Tsuchiya

Using the Quantum Inverse Scattering Method for the XXZ model with open boundary conditions, we obtained the determinant formula for the six vertex model with reflecting end.

Yu. E. Lozovik, A. M. Popov

Theory of adsorption on a surface with nanolocal defects is proposed. Two efficacy parameters of surface modification for nanotechnological purposes are introduced, where the modification is a creation of nanolocal artificial defects. The first parameter corresponds to applications where it is necessary to increase the concentration of certain particles on t

P. M. Gensini, R. Hurtado, G. Violini

We present results from a dispersion--relation investigation on a coupled--channel analysis of $\bar{K}N$--initiated processes in the low-- and intermediate--energy region. The analysis demonstrates both the effectiveness of these relations to constrain the parameters of the unmeasurable $πY$ channels and the need for better data in the low--energy region, s

Davar Khoshnevisan

We show that the image of a 2-dimensional set under d-dimensional, 2-parameter Brownian sheet can have positive Lebesgue measure, if and only if the set in question has positive (d/2)-dimensional Bessel-Riesz capacity. Our methods solve a problem of J.-P. Kahane.

Atsushi Moriwaki

In this note, we would like to propose a suitable extension of the arithmetic Chow group of codimension one, in which the Hodge index theorem holds. We also prove an arithmetic analogue of Bogomolov&#39;s instability theorem for rank 2 vector bundles on arbitrary regular projective arithmetic varieties.

M. Borunda, M. Ruiz-Altaba

The beautiful scenario of pre-big-bang cosmology is appealling not only because it is more or less derived from string theory, but also because it separates clearly the problem of the initial conditions for the universe from that of high curvatures. Recently, the pre-big-bang program was subject to attack from on the grounds that pre-big-bang cosmology does

Hubert Saleur, Prospero Simonetti

We introduce a new family of integrable theories with $N$ bosons and $N$ freely adjustable mass parameters. These theories restrict in particular limits to the ``generalized supersymmetric&#39;&#39; sine-Gordon models, as well as to the flavor anisotropic chiral Gross Neveu models (studied recently by N. Andrei and collaborators). The scattering theory invol

J. -M. Chung, B. K. Chung

We point out that there is a missing portion in the two-loop effective potential of the massless O(N) phi^4 theory obtained by Jackiw in his classic paper, Phys. Rev. D 9, 1686 (1974).

D. V. Boulatov

We demonstrate how some problems arising in simplicial quantum gravity can be successfully addressed within the framework of combinatorial group theory. In particular, we argue that the number of simplicial 3-manifolds having a fixed homology type grows exponentially with the number of tetrahedra they are made of. We propose a model of 3D gravity interacting

M. Yu. Kuchiev

Conventional non-Abelian SO(4) gauge theory is able to describe gravity provided the gauge field possesses a specific polarized vacuum state. In this vacuum the instantons and anti-instantons have a preferred direction of orientation. Their orientation plays the role of the order parameter for the polarized phase of the gauge field. The interaction of a weak

D. Black, A. H. Fariborz, F. Sannino, J. Schechter

Motivated by the $1/N_c$ expansion, we study a simple model in which the pi-K scattering amplitude is the sum of a current-algebra contact term and resonance pole exchanges. This phenomenological model is crossing symmetric and, when a putative light strange scalar meson, kappa, is included, satisfies the unitarity bounds to well above 1 GeV. The model also

G. Lopez Castro, J. Pestieau

We propose the relations 1/e - e =3 and tan(2theta_W)=3/2, where e is the positron charge and theta_W is the weak angle. Present experimental data support these relations to a very high accuracy. We suggest that some duality relates the weak isospin and hypercharge gauge groups of the standard electroweak theory.

Bachir Moussallam

A sum rule due to Das et al. is reanalyzed using a euclidian space approach and a Padé resummation procedure. It is shown that the result is essentially determined by the matrix elements of dimension six and dimension eight operators which have recently been measured by the ALEPH collaboration. The result is further improved by using the vector spectral func

S. Filipponi, G. Pancheri, Y. Srivastava

Maximally complex Regge trajectories are introduced for which both Re $α(s)$ and Im $α(s)$ grow as $s^{1-ε}$ ($ε$ small and positive). Our expression reduces to the standard real linear form as the imaginary part (proportional to $ε$) goes to zero. A scaling formula for the total widths emerges: $Γ_{TOT}/M\to$ constant for large M, in very good agreement wit

G. A. Kozlov

The &#34;standard&#34; iso-singlet scalar particle $σ$ is reconsidered in the reduced normal-ordering (RNO) framework to the effective SU(2) theory. Recent reanalysis of the $ππ$-phase shift [1] is used.

S. Y. Choi, Jake Lee, J. Song

CP violation from physics beyond the Standard Model (SM) is investigated in the Cabbibo-suppressed decay $τ\to Kπν_τ$ with polarized $τ$ leptons, to which both the ${\rm J}^{P}=1^-$ resonance $K^*$ and the $ J^{P}=0^+$ resonance $K^*_0$ contribute. In addition to the CP-odd rate asymmetry, $τ$ polarization enables us to construct three additional CP-odd pola

A. Mondragon, E. Rodriguez-Jauregui

Recent interest in flavour or horizontal symmetry building (mass textures) has been spurred mainly by the large top mass and, hence, the strong hierarchy in quark masses. Recently, various symmetry breaking schemes have been proposed based on the discrete, non-Abelian group S3L x S3R, which is broken according to S3L x S3R > S3_diag > S2_diag. The group S3 t

W. Lee, D. Weingarten

We construct a systematic mean-field-improved coupling constant and quark loop expansion for corrections to the valence (quenched) approximation to vacuum expectation values in the lattice formulation of QCD. Terms in the expansion are evaluated by a combination of weak coupling perturbation theory and a Monte Carlo algorithm.

P. Breitenlohner, H. Hollmann, D. Maison

The Reissner--Nordström family of solutions can be understood to arise from the spherically symmetric sector of a nonlinear SO(2,1)/SO(1,1) sigma model coupled to three dimensional Euclidean gravity. In this context a group theoretical quantization is performed. We identify the observables of the theory and calculate their spectra.

S. I. Tertychniy

It is shown that, in the case of Kerr-Newman space-time, the complex electromagnetic strength E + i H and analogous complex intensity of the gravitational field share the common complexified spatial direction.

Carey Huscroft, Richard T. Scalettar

It has only recently been possible to study the superconducting state in the attractive Hubbard Hamiltonian via a direct observation of the formation of a gap in the density of states N(w). Here we determine the effect of random chemical potentials on N(w) and show that at weak coupling, disorder closes the gap concurrently with the destruction of supercondu

V. Metlushko, U. Welp, I. Aranson, S. Scheidl

The vortex response to various ac-drives has been studied in high quality $YBa_2Cu_4O_8$ single crystals. Well within the vortex solid phase a re-entrant resistive state has been observed that is characterized by long relaxation times. Pulse current response and IV characteristics reveal that in this state the driven vortex system relaxes in a way to increas

Paolo Politi

A high-symmetry crystal surface may undergo a kinetic instability during the growth, such that its late stage evolution resembles a phase separation process. This parallel is rigorous in one dimension, if the conserved surface current is derivable from a free energy. We study the problem in presence of a physically relevant term breaking the up-down symmetry

S. Subbiah, D. J. Driebe

The generalized spectral decomposition of the Frobenius-Perron operator of the tent map with varying height is determined at the band-splitting points. The decomposition includes both decay onto the attracting set and the approach to the asymptotically periodic state on the attractor. Explicit compact expressions for the polynomial eigenstates are obtained u

B. Gremaud, P. Gaspard

In this paper, we examine the properties of the 1Se and 1Po states of helium, combining perimetric coordinates and complex rotation methods. We compute Fourier transforms of quantities of physical interest, among them the average of the operator cos(theta_12), which measures the correlation between the two electrons. Graphs obtained for both 1Se and 1Po stat

Eric J. Lentz, David Branch, E. Baron

The observed map of 1.809 MeV gamma-rays from radioactive Al-26 (Oberlack et al, 1996) shows clear evidence of Galactic plane origin with an uneven distribution. We have simulated the map using a Monte Carlo technique together with simple assumptions about the spatial distributions and yields of Al-26 sources (clustered core-collapse supernovae and Wolf Raye

Ioannis Contopoulos, Glenn E. Ciolek, Arieh Konigl

We obtain self-similar solutions that describe the gravitational collapse of nonrotating, isothermal, magnetic molecular cloud cores. We use simplifying assumptions but explicitly include the induction equation, and the semianalytic solutions we derive are the first to account for the effects of ambipolar diffusion following the formation of a central point

Glenn E. Ciolek, Arieh Konigl

We present a numerical simulation of the dynamical collapse of a nonrotating magnetic molecular cloud core and follow the core&#39;s evolution through the formation of a central point mass and its subsequent growth to a 1 solar-mass protostar. The epoch of point-mass formation (PMF) is investigated by a self- consistent extension of previously presented mode

A. P. Lobanov

We discuss a technique for mapping the synchrotron turnover frequency distribution using nearly simultaneous, multi--frequency VLBI observations. The limitations of the technique arising from limited spatial sampling and frequency coverage are investigated. The errors caused by uneven spatial sampling of typical multi--frequency VLBA datasets are estimated t

Andrew A. Cole

We show that the luminosity dependence of the red clump stars on age and metallicity can cause a difference of up to < ~0.6 mag in the mean absolute I magnitude of the red clump between different stellar populations. We show that this effect may resolve the apparent ~0.4 mag discrepancy between red clump-derived distance moduli to the Magellanic Clouds and t

J. Lequeux, F. Combes, M. Dantel-Fort, J. -C. Cuillandre

We report on further observations of the luminous halo of NGC 5907. New V, I and B deep photometry confirms the existence of an extended stellar halo redder than the disk. Our data are consistent with a faint halo, or very thick disk, composed of a metal-rich old stellar population. We propose that it could be the remnant of a merged small elliptical, and we

B. W. Stappers, M. Bailes, R. N. Manchester, J. S. Sandhu

We have carried out high-precision timing observations of the eclipsing binary PSR J2051-0827 in the 3.3 years since its discovery. These data indicate that the orbital period is decreasing at a rate of dPb/dt = (-11+-1)X10^-12. If secular, this orbital period derivative implies a decay time for the orbit of only 25 Myr which is much shorter than the expecte

Fumihiko Usui, Shogo Nishida, Yoshiharu Eriguchi

We have computed line profiles from self-gravitating toroids around black holes. The specific angular momentum of the toroids is assumed to be constant in space. The images of the toroids show peculiar feature in the rear side of the black holes. Concerning the line profiles, the red wing extends to the very small frequency region because the location of the

Li-Zhi Fang, Y. P. Jing

We propose that the majority of quasars at redshift $z\sim 1 - 5$ formed in the environment of new born collapsed halos with 1-D velocity dispersion $σ_v^{1d} \sim 400 \kms$. The harboring coefficient $f$ of quasars per halo and the lifetime of quasars depend only on local process, not modulated by the density inhomogeneities on scales larger than the size o

J. Russo, A. A. Tseytlin

We derive the complete covariant action for the type IIA superstring in a simple D=10 background which represents a 7-brane with a magnetic Ramond-Ramond vector field (and is U-dual to the Kaluza-Klein Melvin solution). This curved background can be obtained by dimensional reduction from a flat (but topologically non-trivial) D=11 space-time. The action of a

F. Bonetto, N. I. Chernov, J. L. Lebowitz

We studied numerically the validity of the fluctuation theorem, introduced by Evans,Cohen and Morris and proved by Gallavotti and Cohen, for a 2-dimensional system of particles maintained in a steady shear flow by Maxwell daemon boundary conditions (see Chernov and Lebowitz). The theorem was found to hold if one considers the total phase space contraction $σ

J. Merino, J. B. Marston

The Kondo effect may be observable in some atom-surface scattering experiments, in particular, those involving alkaline-earth atoms. By combining Keldysh techniques with the NCA approximation to solve the time-dependent Newns-Anderson Hamiltonian in the infinite-U limit, Shao, Nordlander and Langreth found an anomalously strong surface-temperature dependence

C. Wexler, D. J. Thouless

Recent work gives a transverse force on an isolated moving vortex which is independent of the normal fluid velocity, but it is widely believed that the asymmetry of phonon scattering by a vortex leads to a transverse force dependent on the relative motion of the normal component and the vortex. We show that a widely accepted derivation of the transverse forc

M. J. Hardcastle, C. R. Lawrence, D. M. Worrall

We report on ROSAT HRI observations of the z=0.61 radio galaxy 3C220.1. The X-ray emission from this object consists of an extended component, which we attribute to luminous cluster emission, and a compact central source. The compact component is too bright to be modelled as a cooling flow under some plausible assumptions for the hot gas temperature and dist

D. Vollhardt, N. Blümer, K. Held, M. Kollar

Metallic ferromagnetism is in general an intermediate to strong coupling phenomenon. Since there do not exist systematic analytic methods to investigate such types of problems, the microscopic origin of metallic ferromagnetism is still not sufficiently understood. However, during the last two or three years remarkable progress was made in this field: It is n

M. Rooman, Ph. Spindel

We show that the non flat factor of the Godel metric belongs to a one parameter family of 2+1 dimensional geometries that also includes the anti-de Sitter metric. The elements of this family allow a generalization a la Kaluza-Klein of the usual 3+1 dimensional Godel metric. Their lightcones can be viewed as deformations of the anti-de Sitter ones, involving

Kenji Bekki, Yasuhiro Shioya

We investigate the nature of stellar populations of major galaxy mergers between late-type spirals considerably abundant in interstellar medium by performing numerical simulations designed to solve both the dynamical and chemical evolution in a self-consistent manner. We particularly consider that the star formation history of galaxy mergers is a crucial det

A. Damascelli, D. van der Marel, M. Grueninger, C. Presura

We investigated the temperature-dependent optical conductivity of NaV2O5 in the energy range 4 meV-4 eV. The intensities and the polarization dependence of the detected electronic excitations give a direct indication for a broken-parity electronic ground-state and for a non-centrosymmetric crystal structure of the system in the high-temperature phase. A dire

A. Bartl, H. Eberl, K. Hidaka, S. Kraml

We perform a detailed study of the decays of the heavier top and bottom squarks (stop_2 and sbottom_2) in the Minimal Supersymmetric Standard Model (MSSM). We show that the decays into Higgs or gauge bosons can be dominant in a wide range of the model parameters due to the large Yukawa couplings and mixings of stops and sbottoms. Compared to the conventional

S. R. Gevorkyan, E. A. Kuraev, A. Schiller, V. G. Serbo

We consider the production of ultrarelativistic positronium (Ps) in $γA \to Ps + A$ and $e A \to Ps + e A$ processes where $A$ is an atom or a nucleus with charge $Ze$. For the photoproduction of para- and ortho-Ps and the electroproduction of para-Ps we obtain the most complete description compared with previous works. It includes high order $Z α$ correctio

Andreas Karch, Dieter Lust, George Zoupanos

In this paper we discuss some aspects of the behavior of superconformal N=1 models under Seiberg&#39;s duality. Our claim is that if an electric gauge theory is superconformal on some marginal subspace of all coupling constants then its magnetic dual must be also superconformal on a corresponding moduli space of dual couplings. However this does not imply th

Masato Hisakado

We consider the (coupled) Davey-Stewartson (DS) system and its Bäcklund transformations (BT). Relations among the DS system, the double Kadomtsev-Petviashvili (KP) system and the Ablowitz-Ladik hierarchy (ALH) are established. The DS hierarchy and the double KP system are equivalent. The ALH is the BT of the DS system in a certain reduction. {From} the BT of

J. Harnad, J. McKay

Solutions to a class of differential systems that generalize the Halphen system are determined in terms of automorphic functions whose groups are commensurable with the modular group. These functions all uniformize Riemann surfaces of genus zero and have $q$--series with integral coefficients. Rational maps relating these functions are derived, implying subg

Richard Berkovits

Using exact diagonalization numerical methods, as well as analytical arguments, we show that for the typical electron densities in chaotic and disordered dots the peak spacing distribution is not bimodal, but rather Gaussian. This is in agreement with the experimental observations. We attribute this behavior to the tendency of an even number of electrons to

S. V. Mikhailov

Contributions to QCD non-singlet evolution kernels $P(z)$ for the DGLAP equation and $V(x,y)$ for the Brodsky-Lepage evolution equation are calculated for a certain class of diagrams which include renormalon chains. Closed expressions are presented for the sums of these contributions that dominate for a large number of flavors $N_f \gg 1$. Calculations are p

Gang Su, Masuo Suzuki

The quantum statistical mechanics of an ideal gas with a general free-particle energy obeying fractional exclusion statistics are systematically investigated in arbitrary dimensions. The pressure relations, the relation between pressure and internal energy, the equation of state, as well as the thermodynamic properties are thoroughly discussed. Some novel re

Karol Zyczkowski, Pawel Horodecki, Anna Sanpera, Maciej Lewenstein

A natural measure in the space of density matrices describing N-dimensional quantum systems is proposed. We study the probability P that a quantum state chosen randomly with respect to the natural measure is not entangled (is separable). We find analytical lower and upper bounds for this quantity. Numerical calculations give P = 0.632 for N=4 and P=0.384 for

David A. Meyer

A Dirac particle is represented by a unitarily evolving state vector in a Hilbert space which factors as $H_{spin} \otimes H_{position}$. Motivated by the similarity to simple models of decoherence consisting of a two state system coupled to an environment, we investigate the occurence of decoherence in the Dirac equation upon tracing over position. We concl

Carsten Henkel, Jean-Yves Courtois

We derive the quantum-mechanical master equation (generalized optical Bloch equation) for an atom in the vicinity of a flat dielectric surface. This equation gives access to the semiclassical radiation pressure force and the atomic momentum diffusion tensor, that are expressed in terms of the vacuum field correlation function (electromagnetic field susceptib

Ethan D. Gershon, Matthew C. Wiener, Peter E. Latham, Barry J. Richmond

We would like to know whether the statistics of neuronal responses vary across cortical areas. We examined stimulus-elicited spike count response distributions in V1 and IT cortices of awake monkeys. In both areas the distribution of spike counts for each stimulus was well-described by a Gaussian, with the log of the variance in the spike count linearly rela

M. Yu. Kuchiev, V. N. Ostrovsky

The processes with three or more charged particles in the final state exhibit particular threshold behavior, as inferred by the famous Wannier law for (2e + ion) system. We formulate a general solution which determines the threshold behavior of the cross section for multiple fragmentation. Applications to several systems of particular importance with three,

G. Q. Li, R. Machleidt

Based upon the Bonn meson-exchange model for the nucleon-nucleon ($NN$) interaction, we study systematically the charge-symmetry-breaking (CSB) of the $NN$ interaction due to nucleon mass splitting. Particular attention is payed to CSB generated by the $2π$-exchange contribution to the $NN$ interaction, $πρ$ diagrams, and other multi-meson-exchanges. We calc

D. E. Kahana, S. H. Kahana

A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy ion-ion collisions is applied to the production of strangeness at SPS energies $\sqrt{s}=17-20$. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons, including strange mesons,

M. Beyer, C. Kuhrts, H. J. Weber

Orthonormal spin-flavor wave functions of Lorentz covariant quark models of the Bakamjian-Thomas type are constructed for nucleon resonances. Three different bases are presented. The manifestly Lorentz covariant Dirac-Melosh basis is related to the Pauli-Melosh basis and the symmetrized Bargmann-Wigner basis that are manifestly orthogonal.

N. V. Shevchenko, S. A. Rakityansky, S. A. Sofianos, V. B. Belyaev

The nuclear reaction e + He3 + He4 ---> e + Be7 is considered at thermonuclear energies. The motion of the electron is treated within the adiabatic approximation and the He3-He4 scattering state is calculated using an effective He3-He4 potential constructed via the Marchenko inverse scattering method. The reaction rate thus obtained for solar interior condit

B. Loiseau, T. E. O. Ericson, J. Rahm, J. Blomgren

A novel extrapolation method has been used to deduce the charged Pion-Nucleon coupling constant from backward $np$ differential scattering cross sections. We applied it to new measurements performed at 162 MeV at the The Svedberg Laboratory in Uppsala. In the angular range $150^\circ-180^\circ$, the carefully normalized data are steeper than those of most pr

Italo Guarneri

Time averaging over the trajectory of a wavepacket up to time T defines a statistical operator (density matrix). The corresponding (Von Neumann) entropy is proven to asymptotically increase with time like D.log T, with D the Hausdorff dimension of the Local Density of States, at least if the latter measure has good scaling properties. In more general cases,

J. C. Hurtubise, E. Markman

A correspondence between 1) rank 2 completely integrable systems of Jacobians of algebraic curves and 2) (holomorphically) symplectic surfaces was established in a previous paper by the first author. A more general abelian variety that occurs as a Liouville torus of integrable systems is a prym variety associated to a triple (S,W,V) consisting of a curve S,

D. Abramovich, J. M. Rojas

We show that a projective triangulation of a subcomplex of a polyhedral complex can be extended to the whole complex. As a result, we show that the weak semistable reduction result of Abramovich - Karu alg-geom/9707012 can be refined, so that the resulting morphism is semistable in codimension 1.

Edward Odell, Nicole Tomczak-Jaegermann

Tsirelson&#39;s space $T$ is known to be distortable but it is open as to whether or not $T$ is arbitrarily distortable. For $n\in {\Bbb N}$ the norm $\|\cdot\|_n$ of the Tsirelson space $T(S_n,2^{-n})$ is equivalent to the standard norm on $T$. We prove there exists $K<\infty$ so that for all $n$, $\|\cdot\|_n$ does not $K$ distort any subspace $Y$ of $T$.

Dietmar Bisch, Sorin Popa

Let H and K be two finite groups with a properly outer action on the II_1 factor M. We prove that the group type inclusions $M^H \subset M \rtimes K$, studied earlier by Bisch and Haagerup, have property T in the sense of Popa if and only if the group generated by H and K in the outer automorphism group of M has Kazhdan&#39;s property T. This construction yi

Emil Kowalczyk

The Poisson structures on two-dimensional Galilei group, classified in the author previous paper are quantized. The dual quantum Galilei Lie algebras are found.

V. V. Ezhov, A. V. Isaev

We show that the maximal prolongation of a certain algebra associated with a non-degenerate Hermitian form on ${\Bbb C}^n\times{\Bbb C}^n$ with values in ${\Bbb R}^k$ is canonically isomorphic to the Lie algebra of infinitesimal holomorphic automorphisms of the corresponding quadric in ${\Bbb C}^{n+k}$. This fact creates a link between different approaches t

V. V. Ezhov, A. V. Isaev, G. Schmalz

We reduce CR-structures on smooth elliptic and hyperbolic manifolds of CR-codimension 2 to parallelisms thus solving the problem of global equivalence for such manifolds. The parallelism that we construct is defined on a sequence of two principal bundles over the manifold, takes values in the Lie algebra of infinitesimal automorphisms of the quadric correspo

A. Knutson, E. Sharpe

In this article we review some recent developments in heterotic compactifications. In particular we review an ``inherently toric&#39;&#39; description of certain sheaves, called equivariant sheaves, that has recently been discussed in the physics literature. We outline calculations that can be performed with these objects, and also outline more general pheno

Yoshinori Gotoh, Ikuo Okouchi

In D=10 N=1 super Yang-Mills theory we give the background breaking a half of supersymmetry. In the background there is a six-dimensional object so called D=10 5-brane.

Emilio Elizalde, Antonio Filippi, Luciano Vanzo, Sergio Zerbini

In a recent work, S. Dowker has shed doubt on a recipe used in computing the partition function for a matrix valued operator. This recipe, advocated by Benson, Bernstein and Dodelson, leads naturally to the so called multiplicative anomaly for the zeta-function regularized functional determinants. In this letter we present arguments in favour of the mentione

Emilio Elizalde, Antonio Filippi, Luciano Vanzo, Sergio Zerbini

In a recent work, T.S. Evans has claimed that the multiplicative anomaly associated with the zeta-function regularization of functional determinants is regularization dependent. We show that, if one makes use of consistent definitions, this is not the case and clarify some points in Evans&#39; argument.

Shinichi Deguchi, Tomoaki Mukai, Tadahito Nakajima

We derive a dual theory of the four-dimensional anomalous U(1) gauge theory with a Wess--Zumino (WZ) term and with a Stückelberg type mass term by means of a duality transformation at each of the classical and quantum levels. It is shown that in the dual anomalous U(1) gauge theory, the $BF$ term with a rank-two antisymmetric tensor field plays the roles of

Anton Kapustin

A number of N=2 gauge theories can be realized by brane configurations in Type IIA string theory. One way of solving them involves lifting the brane configuration to M-theory. In this paper we present an alternative way of analyzing a subclass of these theories (elliptic models). We observe that upon compactification on a circle one can use a version of mirr

D. V. Antonov

By making use of the duality transformation, gauge field correlators of the Abelian Higgs Model are studied in the London limit. The obtained results are in a good agreement with the dual Meissner scenario of confinement and with the Stochastic Model of QCD vacuum. The nontrivial contribution to the quartic correlator arising due to accounting for the finite

P. Pronin, K. Stepanyantz

We investigate nonperturbative effects in N=1 and N=2 supersymmetric theories using a relation between perturbative and exact anomalies as a starting point. For N=2 supersymmetric SU(n) Yang-Mills theory we derive the general structure of the Picard-Fuchs equations; for N=1 supersymmetric Yang-Mills theories we find holomorphic part of the superpotential (wi

Oleg Yakovlev, Alexander Yelkhovsky

We discuss the resummation of the potentially large O((β_0α_s)^n) QCD corrections to the total cross section of the process e^+e^- \to t \bar t near the threshold. In this approximation, the cross section factorization into the short- and long-distance parts is valid. The short-distance correction is reduced to the production vertex renormalization. It amoun

T. Fukuyama, K. Matsuda, H. Nishiura

From the analyses of the recent data of neutrino oscillation experiments (especially the CHOOZ and the Super KAMIOKANDE experiments), we discuss how these data affect the neutrinoless double beta decay ($(ββ)_{0ν}$) rate and vice versa assuming that neutrinos are Majorana particles. For the case that $m_1 \sim m_2 \ll m_3$ ($m_i$ are neutrino masses), we obt

F. Farchioni, C. B. Lang, M. Wohlgenannt

We study the spectrum properties for a recently constructed fixed point lattice Dirac operator. We also consider the problem of the extraction of the fermion condensate, both by direct computation, and through the Banks-Casher formula by analyzing the density of eigenvalues of a redefined antihermitean lattice Dirac operator.

Achille Giacometti, Albert Diaz-Guilera

Critical exponents of the infinitely slowly driven Zhang model of self-organized criticality are computed for $d=2,3$ with particular emphasis devoted to the various roughening exponents. Besides confirming recent estimates of some exponents, new quantities are monitored and their critical exponents computed. Among other results, it is shown that the three d

Ian Affleck, Masaki Oshikawa, Hubert Saleur

Boundary critical phenomena are studied in the 3- State Potts model in 2 dimensions using conformal field theory, duality and renormalization group methods. A presumably complete set of boundary conditions is obtained using both fusion and orbifold methods. Besides the previously known free, fixed and mixed boundary conditions a new one is obtained. This ill

Linda Fabbian, Rolf Schilling, Francesco Sciortino, Piero Tartaglia

We apply to a liquid of linear molecules the semischematic mode-coupling model, previously introduced to describe the center of mass (COM) slow dynamics of a network-forming molecular liquid. We compare the theoretical predictions and numerical results from a molecular dynamics simulation, both for the time and the wave-vector dependence of the COM density-d

J. van Mourik, K. Y. Michael Wong, D. Bolle&#39;

A model of noise reduction (NR) for signal processing is introduced. Each noise source puts a symmetric constraint on the space of the signal vector within a tolerable overlap. When the number of noise sources increases, sequences of transitions take place, causing the solution space to vanish. We found that the transition from an extended solution space to

F. Demichelis, G. Viliani, G. Ruocco

We use computer simulation to investigate the topology of the potential energy $V(\{{\bf R}\})$ and to search for doublewell potential&#39;s (DWP) in a model glass . By a sequence of Newtonian and dissipative dynamics we find different minima of $V(\{{\bf R}\})$ and the energy profile along the least action paths joining them. At variance with previous sugge

G. Daldoss, O. Pilla, G. Viliani, G. Ruocco

We develop an efficient numerical algorithm for the identification of a large number of saddle points of the potential energy function of Lennard- Jones clusters. Knowledge of the saddle points allows us to find many thousand adjacent minima of clusters containing up to 80 argon atoms and to locate many pairs of minima with the right characteristics to form

Laurent Laloux, Marc Potters, Rama Cont, Jean-Pierre Aguilar

We critically review recent claims that financial crashes can be predicted using the idea of log-periodic oscillations or by other methods inspired by the physics of critical phenomena. In particular, the October 1997 `correction&#39; does not appear to be the accumulation point of a geometric series of local minima.