June 1996 arXiv papers — page 11

Erik Koch

It has recently been suggested that an exactly solvable problem characterized by a new quantum number may underlie the electronic shell structure observed in the mass spectra of medium-sized sodium clusters. We investigate whether the conjectured quantum number 3n+l bears a similarity to the quantum numbers n+l and 2n+l, which characterize the hydrogen probl

J. Kierfeld, T. Hwa

The phase diagram of two interacting planar arrays of directed lines in random media is obtained by a renormalization group analysis. The results are discussed in the contexts of the roughening of reconstructed crystal surfaces, and the pinning of flux line arrays in layered superconductors. Among the findings are a glassy flat phase with disordered domain s

John Griffith

This paper describes a method for compiling a constraint-based grammar into a potentially more efficient form for processing. This method takes dependent disjunctions within a constraint formula and factors them into non-interacting groups whenever possible by determining their independence. When a group of dependent disjunctions is split into smaller groups

Augusta Mela, Christophe Fouquere

We propose a treatment of coordination based on the concepts of functor, argument and subcategorization. Its formalization comprises two parts which are conceptually independent. On one hand, we have extended the feature structure unification to disjunctive and set values in order to check the compatibility and the satisfiability of subcategorization require

M. H. van Kerkwijk

I review what properties of the white-dwarf companions of recycled pulsars can be inferred from optical observations, and discuss how these can help us understand the characteristics and evolution of these binaries. I focus on spectroscopic observations, describing results obtained recently, and looking forward to what may come.

F. Bresolin, R. Kennicutt, P. Stetson

The massive stellar content, the OB associations and the star clusters in an HST field in M101 = NGC 5457 are investigated. A clustering algorithm yields 79 putative associations. Their size distribution is similar to that found in the Magellanic Clouds, M31 and M33, with an average size around 90 pc. The V luminosity function for the stars contained within

Andrew Strominger, Shing-Tung Yau, Eric Zaslow

It is argued that every Calabi-Yau manifold $X$ with a mirror $Y$ admits a family of supersymmetric toroidal 3-cycles. Moreover the moduli space of such cycles together with their flat connections is precisely the space $Y$. The mirror transformation is equivalent to T-duality on the 3-cycles. The geometry of moduli space is addressed in a general framework.

Abdellatif Abada

As a first step toward circumventing the difficulty to obtain an attractive isospin-independent NN spin-orbit force from Skyrme-type models involving only pions, we investigate an improved Skyrme Lagrangian that incorporates the scalar-isoscalar meson εwhich can be viewed as the cause behind the enhancement of the $ππS$-wave. We find that at large distances,

Roumen Borissov

The evolution of spin network states in loop quantum gravity can be described by introducing a time variable, defined by the surfaces of constant value of an auxiliary scalar field. We regulate the Hamiltonian, generating such an evolution, and evaluate its action both on edges and on vertices of the spin network states. The analytical computations are carri

M. Casu, L. M. Sehgal

We analyse the baryon magnetic moments in a model that relates them to the parton spins $Δu$, $Δd$, $Δs$, and includes a contribution from orbital angular momentum. The specific assumption is the existence of a 3-quark correlation (such as a flux string) that rotates with angular momentum $\langle L_z \rangle$ around the proton spin axis. A fit to the baryon

Carl Carlson, Greg Dorata, Marc Sher

The decay $K_L\rightarrow π^oν\overlineν$ is an excellent probe of the nature of CP violation. It is almost entirely CP-violating, and hadronic uncertainties are negligible. Experiments which hope to detect the decay are currently being planned. We calculate the decay rate in several extensions of the standard model Higgs sector, including the Liu-Wolfenstei

J. -P. Blaizot, A. Krzywicki

The theoretical ideas relevant for the physics of the disoriented chiral condensate (DCC) are reviewed.

Dmitri Orlov

We consider derived categories of coherent sheaves on smooth projective varieties. We prove that any equivalence between them can be represented by an object on the product. Using this, we give a necessary and sufficient condition for equivalence of derived categories of two K3 surfaces.

Frédéric Mangolte, Joost van Hamel

For a real Enriques surface Y we prove that every homology class in H_1(Y(R), Z/2) can be represented by a real algebraic curve if and only if all connected components of Y(R) are orientable. Furthermore, we give a characterization of real Enriques surfaces which are Galois-Maximal and/or Z-Galois-Maximal and we determine the Brauer group of any real Enrique

V. B. Belyaev, A. K. Motovilov

The case of quantum-mechanical system (including electronic molecules) is considered where Hamiltonian allows a separation, in particular by the Faddeev method, of a weakly coupled channel. Width (i.e. the imaginary part) of the resonance generated by a discrete spectrum eigenvalue of the separated channel is studied in the case where main part of the Hamilt

D. V. Gal'tsov

Kinnersley--type representation is constructed for the four--dimensional Einstein--Maxwell--dilaton--axion system restricted to space--times possessing two non--null commuting Killing symmetries. New representation essentially uses the matrix--valued $SL(2,R)$ formulation and effectively reduces the construction of the Geroch group to the corresponding probl

Edward W. Kolb, Andrei Linde, Antonio Riotto

At the end of inflation the universe is frozen in a near zero-entropy state with energy density in a coherent scalar field and must be ``defrosted'' to produce the observed entropy and baryon number. We propose that the baryon asymmetry is generated by the decay of supermassive Grand Unified Theory (GUT) bosons produced non-thermally in a preheating

Willem M. de Muynck

A theory of joint nonideal measurement of incompatible observables is used in order to assess the relative merits of quantum tomography and certain measurements of generalized observables, with respect to completeness of the obtained information. A method is studied for calculating a Wigner distribution from the joint probability distribution obtained in a j

Alexander Molev

A factorial analogue of the supersymmetric Schur functions is introduced. It is shown that factorial versions of the Jacobi--Trudi and Sergeev--Pragacz formulae hold. The results are applied to construct a linear basis in the center of the universal enveloping algebra for the Lie superalgebra gl(m|n) and to obtain super-analogues of the higher Capelli identi

Y. Sugiyama, H. Yamada

We present an exactly solvable model for queue dynamics. Our model is very simple but provides the essential property for such dynamics. As an example, the model has the traveling cluster solution as well as the homogeneous flow solution. The model is the limiting case of Optimal Velocity (OV) model, which is proposed for the car following model to induce tr

M. Malheiro, A. Delfino, C. T. Coelho

An analysis is performed of the liquid-gas phase transition of nuclear matter obtained from different versions of scalar derivate coupling suggested by Zimanyi and Moszkowski (ZM) and the results are compared with those obtained from the Walecka model. We present the phase diagram for the models and one of them, the ZM3 model, has the lowest critical tempera

J. Zipprich, C. Fuchs, E. Lehmann, L. Sehn

We investigate the influence of the real part of the in-medium pion optical potential on the pion dynamics in intermediate energy heavy ion reactions at 1 GeV/A. For different models, i.e. a phenomenological model and the $Δ$--hole model, a pionic potential is extracted from the dispersion relation and used in Quantum Molecular Dynamics calculations. In addi

Donald E. Knuth

This expository note presents simplifications of a theorem due to Győri and an algorithm due to Franzblau and Kleitman: Given a family $F$ of $m$ intervals on a linearly ordered set of $n$ elements, we can construct in $O(m+n)^2$ steps an irredundant subfamily having maximum cardinality, as well as a generating family having minimum cardinality. The algorith

Zinaida A. Lykova

We prove that, for every extension of Banach algebras $ 0 \rightarrow B \rightarrow A \rightarrow D \rightarrow 0 $ such that $B$ has a left or right bounded approximate identity, the existence of an associated long exact sequence of Banach simplicial or cyclic cohomology groups is equivalent to the existence of one for homology groups. It follows from the c

D. V. Gal'tsov

The four-dimensional bosonic effective action of the toroidally compactified heterotic string incorporating a dilaton, an axion and one $U(1)$ vector field is studied on curved space-time manifolds with one and two commuting Killing vectors. In the first case the theory is reduced to a three-dimensional sigma model possessing a symmetric pseudoriemannian tar

Oren Bergman

We argue that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. We review the string-bit models, and suggest generalizations to incorporate p-bran

M. P. Fry

A lower bound is placed on the fermionic determinant of Euclidean quantum electrodynamics in three dimensions in the presence of a smooth, finite--flux, static, unidirectional magnetic field $\mathbf{B}(\mathbf{r})=(0,0,B(\mathbf{r}))$, where $B(\mathbf{r})\geq 0$ or $B(\mathbf{r})\leq 0$ and $\mathbf r$ is a point in the $xy\mbox{-plane}$. Bounds are also o

Elena Caceres, Vadim S. Kaplunovsky, I. Michael Mandelberg

We reconsider the issue of large-volume compactifications of the heterotic string in light of the recent discoveries about strongly-coupled string theories. Our conclusion remains firmly negative with respect to classical compactifications of the ten-dimensional field theory, albeit for a new reason: When the internal sixfold becomes large in heterotic units

Ichiro Oda

In this article we derive the Bekenstein-Hawking formula of black hole entropy from a single string. We consider a open string in the Rindler metric which can be obtained in the large mass limit from the Schwarzschild black hole metric. By solving the field equations we find a nontrivial solution with the exact value of the Hawking temperature. We see that t

M. Awada, F. Mansouri

We construct new superstring actions which are distinguished from standard superstrings by being space-time scale invariant. Like standard superstrings, they are also reparametrization invariant, space-time supersymmetric, and invariant under local scale transformations of the world sheet. We discuss scenarios in which these actions could play a significant

N. Kidonakis, J. Smith

The cross section for bottom quark production is calculated for the HERA-B experiment. We consider both the order $α_s^3$ cross section and the resummation of soft gluon corrections in all orders of QCD perturbation theory.

M. Passera, K. Sasaki

The $S$-matrix pinch technique is used to derive an effective gluon self-energy to one-loop order, when the theory is quantized in the Coulomb gauge (CG) and in the temporal axial gauge (TAG). When the pinch contributions are added, the gluon self-energies calculated in CG and TAG turn out to be identical and coincide with the result previously obtained with

V. Ravindran

The importance of polarised gluons fragmenting into $Λ$ in the polarised $e^+ e^-$ annihilation is discussed using the Altarelli-Parisi evolution equations satisfied by the quark and gluon fragmentation functions. In this context, the polarised fragmentaion function $\hat g_1^Λ(x,Q^2)$ appearing in the cross section is discussed within the parton model. We r

V. Ravindran

We discuss the polarised fragmentation functions of quarks and gluons in Perturbative Quantum Chromodynamics. The Altarelli-Parisi evolution equations governing these fragmentation functions are presented. We find that the first moment of the polarised gluon fragmentation function to order $α_s$ is as important as that of the quark and anti-quark fragmentati

Chong Sheng Li, Hong Yi Zhou, Yun Lun ZhU, Jin Min Yang

The supersymmetric QCD corrections to top quark pair production by $q\bar q$ annihilation in $p\bar p$ collisions are calculated in the minimal supersymmetric model. We consider effects of the mixing of the scalar top quarks on the corrections to the total $t\bar t$ production cross section at the Fermilab Tevatron. We found that such correction is less sens

Stefano Moretti

Within the framework of the Standard Model, integrated and differential distributions are given for Higgs production via the $WW$-fusion mechanism and decay via the channels $H\ar b\bar b$ and $H\ar WW\ar {jjjj}$, with and without photon radiation, at Next Linear Collider energies. Calculations are carried out at tree-level and rates of the leading processes

R. Kirschner, L. Mankiewicz, A. Schäfer, L. Szymanowski

The small $x$ behaviour of the structure function $h_1(x,Q^2)$ is studied within the leading logarithmic approximation of perturbative QCD. There are two contributions relevant at small $x$. The leading one behaves like $(\frac{1}{x})^0$ i.e. it is just a constant in this limit. The second contribution, suppressed by one power of $x$, includes the terms summ

A. D. Dolgov

Deviations from kinetic equilibrium of massive particles caused by the universe expansion are calculated analytically in the Boltzmann approximation. For the case of an energy independent amplitude of elastic scattering, an exact partial differential equation is derived instead of the usual integro-differential one. A simple perturbative solution of the form

D. de Florian, C. Garcia Canal, S. Joffily, R. Sassot

We analyse the phenomenological consequences of target and current fragmentation contributions at next to leading order in semi-inclusive spin dependent deep inelastic scattering asymmetries.

A. Leike

The present status of calculations of four fermion final states is reviewed. Higher order problems arising there are pointed out. Special attention is paid to results obtained in the semi-analytical approach and their limitations and perspectives.

V. A. Bednyakov, S. G. Kovalenko, H. V. Klapdor-Kleingrothaus, Y. Ramachers

We performed a combined analysis of the parameter space of the Minimal Supersymmetric Standard Model (MSSM) taking into account cosmological and accelerator constraints including those from the radiative $b\rightarrow sγ$ decay measured by the CLEO collaboration. Special attention is paid to the event rate, $R$, of direct dark matter neutralino detection. We

Malek Zareyan

An exact solution of the source-free Kaluza-Klein field equations is presented. It is a 5D generalization of the Robinson-Trautman quasi-spherical gravitational wave with a cosmological constant. The properties of the 5D solution are briefly described.

D. V. Gal'tsov, O. V. Kechkin

Four--dimensional Einstein--Maxwell--dilaton--axion system restricted to space--times with one non--null Killing symmetry is formulated as the three--dimensional gravity coupled sigma--model. Several alternative representations are discussed and the associated hidden symmetries are revealed. The action of target space isometries on the initial set of (non--d

O. Iguchi, H. Ishihara, J. Soda

We study how the initial inhomogeneities of the spatial curvature affect the onset of inflation in the closed universe. We consider a cosmological model which contains a radiation and a cosmological constant. In order to treat the inhomogeneities in the closed universe, we improve the long wavelength approximation such that the non-small spatial curvature is

Lian Zheng, S. Das Sarma

We comment on the theoretical interpretations applied to a recent experiment on electron lifetime in graphite. We point out that the acoustic-plasmon excitations in a layered two-dimensional electron system do not produce a linear energy dependence for the Coulomb scattering rate.

Cz. Oleksy, J. Lorenc

We consider a lattice-gas model with an infinite range pairwise noncovex interaction. It might be relevant, for example, for adsorption of alkaline elements on W(112) and Mo(112). We study a competition between the effective dipole-dipole and indirect interactions. The resulting ground state phase diagrams are analysed (numerically) in detail. We have found

Gunter M. Schütz

We study the dynamics of an exactly solvable lattice model for inhomogeneous interface growth. The interface grows deterministically with constant velocity except along a defect line where the growth process is random. We obtain exact expressions for the average height and height fluctuations as functions of space and time for an initially flat interface. Fo

M. Capone, M. Grilli, W. Stephan

We investigate the conditions leading to polaron formation for a single electron interacting with dispersionless optical phonons within the Holstein and the Su-Schrieffer-Heeger models. Both from analytic perturbation theory and exact numerical diagonalization of small clusters, we find different criteria for the model parameters ruling the setting in of the

J. T. Chalker, Igor V. Lerner, Robert A. Smith

We establish a new approach to calculating spectral statistics in disordered conductors, by considering how energy levels move in response to changes in the impurity potential. We use this fictitious dynamics to calculate the spectral form factor in two ways. First, describing the dynamics using a Fokker-Planck equation, we make a physically motivated decoup

R. Hayn, A. F. Barabanov, J. Schulenburg

The dispersion of one hole in an extended $t$-$J$ model with additional hopping terms to second and third nearest neighbours and a frustration term in the exchange part has been investigated. Two methods, a Green's function projection technique describing a magnetic polaron of minimal size and the exact diagonalization of a $4*4$ lattice, have been appli

Bernard Derrida, Reuven Zeitak

For the zero temperature Glauber dynamics of the $q$-state Potts model, we calculate the exact distribution of domain sizes by mapping the problem on an exactly soluble one-species coagulation model ($A+A\rightarrow A$). In the long time limit, this distribution is universal and from its (complicated) exact expression, we extract its behavior in various regi

J. Ambjorn, Y. Makeenko, K. Zarembo

We solve a supersymmetric matrix model with a general potential. While matrix models usually describe surfaces, supersymmetry enforces a cancellation of bosonic and fermionic loops and only diagrams corresponding to so-called branched polymers survive. The eigenvalue distribution of the random matrices near the critical point is of a new kind.

M. Bulenda, F. Schwabl, U. C. Täuber

Static and dynamical properties of elastic phase transitions under the influence of short--range defects, which locally increase the transition temperature, are investigated. Our approach is based on a Ginzburg--Landau theory for three--dimensional crystals with one--, two-- or three--dimensional soft sectors, respectively. Systems with a finite concentratio

Ruihong Yue, Tetsuo Deguchi

We found the eigenvalues of the transfer matrices for the 1-D Hubbard model and for the coupled XY model with twisted boundary condition by using the analytic Bethe Ansatz method. Under a particular condition the two models have the same Bethe Ansatz equations. We have also proved that the periodic 1-D Hubbard model is exactly equal to the coupled XY model w

C. Huscroft, R. T. Scalettar

The half-filled attractive Hubbard model exhibits simultaneous charge density wave and superconducting order in its ground state. In this paper we explore the effect of disorder in the site energies on this degeneracy. We find that superconducting order survives randomness out to a critical amount of disorder, but charge ordering is immediately reduced. We e

Eneko Agirre, German Rigau

This paper presents a method for the resolution of lexical ambiguity of nouns and its automatic evaluation over the Brown Corpus. The method relies on the use of the wide-coverage noun taxonomy of WordNet and the notion of conceptual distance among concepts, captured by a Conceptual Density formula developed for this purpose. This fully automatic method requ

Anoop Sarkar, Aravind Joshi

In this paper we show that an account for coordination can be constructed using the derivation structures in a lexicalized Tree Adjoining Grammar (LTAG). We present a notion of derivation in LTAGs that preserves the notion of fixed constituency in the LTAG lexicon while providing the flexibility needed for coordination phenomena. We also discuss the construc

Werner M. Vieira, Alfredo M. O. de Almeida

We use Moser's normal forms to study chaotic motion in two-degree hamiltonian systems near a saddle point. Besides being convergent, they provide a suitable description of the cylindrical topology of the chaotic flow in that vicinity. Both aspects combined allowed a precise computation of the homoclinic interaction of stable and unstable manifolds in the

A. Z. Gorski, R. Botet, S. Drozdz, M. Ploszajczak

Scaling analysis of nuclear giant resonance transition probabilities with increasing level of complexity in the background states is performed. It is found that the background characteristics, typical for chaotic systems lead to nontrivial multifractal scaling properties.

Laura Cayon, Joseph Silk, Stephane Charlot

In order to explain the small scale-lengths detected in the recent deep field observations performed from large ground-based telescopes and from the Hubble Space Telescope, we investigate the predictions at high redshifts for disk galaxies that formed by infall. Changes with redshift in the observed properties of field galaxies are directly related to the ev

E. E. Falco, J. Lehar, R. A. Perley, J. Wambsganss

We report observations of the four-image gravitational lens system Q2237+0305 with the VLA at 20 cm and 3.6 cm. The quasar was detected at both frequencies (\approx 0.7 mJy) with a flat spectrum. All four lensed images are clearly resolved at 3.6 cm, and the agreement of the radio and optical image positions is excellent. No radio emission is detected from t

Juan Garcia-Bellido, David Wands

We study the amplitude and spectral tilt of density perturbations in the simplest hybrid inflation models. We give an exact expression for the amplitude of quantum fluctuations on all scales in the limit where we can neglect the backreaction on the metric. This is a very good approximation for values of the inflaton field well below the Planck scale and our

Andrea Ferrara, Simone Bianchi, Ralf-Juergen Dettmar, Carlo Giovanardi

We present results from Monte Carlo simulations describing the radiation transfer of $Hα$ line emission, produced both by HII regions in the disk and in the diffuse ionized gas (DIG), through the dust layer of the galaxy NGC891. This allows us to calculate the amount of light originating in the HII regions of the disk and scattered by dust at high $z$, and c

M. H. van Kerkwijk, P. Bergeron, S. R. Kulkarni

We report on spectroscopy of the white-dwarf companion of the millisecond radio pulsar PSR J1012+5307. We find strong Balmer absorption lines, as would be expected for a cool DA white dwarf. The profiles are much narrower than usual, however, and lines are seen up to H12, indicating that the companion has a low gravity and hence a low mass. This is consisten

Limin Lu, Wallace L. W. Sargent, Thomas A. Barlow

Damped Lyman-alpha absorption systems found in the spectra of high redshift quasars are believed to trace the interstellar gas in high redshift galaxies. In this paper, we study the elemental abundances of C, N, O, Al, Si, S, Cr, Mn, Fe, Ni, and Zn in a sample of 14 damped Lyman-alpha systems using high quality echelle spectra of quasars obtained with the 10

M. Cvetic, A. A. Tseytlin

We present non-extreme generalisations of intersecting p-brane solutions of eleven-dimensional supergravity which upon toroidal compactification reduce to non-extreme static black holes in dimensions D=4, D=5 and 5<D<10, parameterized by four, three and two charges, respectively. The D=4 black holes are obtained either from non-extreme configuration of three

Joerg Huefner, Boris Kopeliovich

Our main observations are: (i) The effective path length of the $c\bar c$ wave packet, which is produced in the nucleus, grows with the energy of the produced charmonium. The variation is controlled by the coherence length $l_c=2E_{\Psi}/M^2_{\Psi}$. (ii) A colorless $c\bar c$ wave packet produced in $pp$-interaction is a specific linear combination of the $

A. Bartl, W. Porod, M. A. Garcia-Jareno, M. B. Magro

In a class of supersymmetric models with R-parity breaking the lightest stop can have new decay modes into third generation fermions, $\tilde{t}_1 \rightarrow b + τ$. We show that this decay may be dominant or at least comparable to the ordinary R-parity conserving mode $\tilde{t}_1 \rightarrow c + \tildeχ_1^0$, where $\tildeχ_1^0$ denotes the lightest neutr

J. G. Russo

We investigate the conformal string $σ$-model corresponding to a general five-dimensional non-extremal black hole solution. In the horizon region the theory reduces to an exactly solvable conformal field theory. We determine the modular invariant spectrum of physical string states, which expresses the Rindler momentum operator in terms of three charges and s

T. Sato, T-. S. H. Lee

An effective Hamiltonian consisting of bare $\Delta \leftrightarrow\pi N$, $\gamma N$ vertex interactions and energy-independent meson-exchange $\pi N \leftrightarrow \pi N, \gamma N$ transition operators is derived by applying a unitary transformation to a model Lagrangian with $N,\Delta,\pi$, $\rho$, $\omega$, and $\gamma$ fields. With appropraite phenomen

David Dean, David Lancaster

We define a replica field theory describing finite dimensional site disordered spin systems by introducing the notion of grand canonical disorder, where the number of spins in the system is random but quenched. A general analysis of this field theory is made using the Gaussian variational or Hartree Fock method, and illustrated with several specific examples

Francesca M. Borzumati, Yuval Grossman, Enrico Nardi, Yosef Nir

We study neutrino masses and mixing in Supersymmetric Models without $R$ parity and with generic soft Supersymmetry breaking terms. Neutrinos acquire mass from various sources: tree level neutrino--neutralino mixing, loop effects and non--renormalizable operators. Abelian horizontal symmetries (invoked to explain the smallness and hierarchy in quark paramete

David Saltzberg

The CHORUS experiment is searching for nu-mu to nu-tau oscillations using an 800 kilogram emulsion target and an electronic detector. Two of four years of running have been completed. The experiment will probe small mixing angles for squared neutrino mass differences greater than 10 eV^2, at least one order of magnitude better than previous limits.

Paul Biran

We discuss closed symplectic 4-manifolds which admit full symplectic packings by $N$ equal balls for large $N$&#39;s. We give a homological criterion for recognizing such manifolds. As a corollary we prove that ${\Bbb C}P^2$ can be fully packed by $N$ equal balls for every $N\geq 9$.

Limin Lu, Wallace L. W. Sargent, Donna S. Womble, Masahide Takada-Hidai

This paper describes a study of the Lyman-alpha forest absorption clouds along the quasar sightline Q0000-26 (zem=4.1). The spectrum was obtained with the High Resolution Spectrometer on the 10m Keck telescope. We derive accurate H I column density and Doppler width distributions for the clouds from Voigt profile fitting. We also analyze simulated Lyman-alph

Randall D. Kamien

Recent experiments on aligned DNA show hexatic order with no sign of macroscopic chirality. I make the analogy between smectic liquid crystals and chiral hexatics and show how the absence of chirality cannot occur in a thermodynamic phase of chiral molecules. In addition, I discuss the microscopic origin of chiral mesophases in liquid crystals and show that,

Adrian Alscher, Kai Hencken, Dirk Trautmann, Gerhard Baur

We calculate the cross sections for the production of one and more electron-positron pairs due to the strong electromagnetic fields in relativistic heavy ion collisions. Using the generating functional of fermions in an external field we derive the N-pair amplitude. Neglecting the antisymmetrisation in the final state we find that the total probability to pr

C. R. Fernandez-Pousa, M. V. Gallas, T. J. Hollowood, J. L. Miramontes

Two series of integrable theories are constructed which have soliton solutions and can be thought of as generalizations of the sine-Gordon theory. They exhibit internal symmetries and can be described as gauged WZW theories with a potential term. The spectrum of massive states is determined.

I. Bakas

Several gravitational string backgrounds can be interpreted as 2-dim soliton solutions of reduced axion-dilaton gravity. They include black-hole and worm-hole solutions as well as cosmological models with an exact conformal field theory description. We illustrate the use of gravisolitons for the particular example of Nappi-Witten universe which is thus &#34;

Mark de Wild Propitius

A detailed analysis of Chern-Simons (CS) theories in which a compact abelian direct product gauge group U(1)^k is spontaneously broken down to a direct product H of (finite) cyclic groups is presented. The spectrum features global H charges, vortices carrying flux labeled by the elements of H and dyonic combinations. Due to the Aharonov-Bohm effect these par

R. Z. Zhdanov

We develop an algebraic approach to studying the spectral properties of the stationary Schrödinger equation in one dimension based on its high order conditional symmetries. This approach makes it possible to obtain in explicit form representations of the Schrödinger operator by $n\times n$ matrices for any $n\in {\bf N}$ and, thus, to reduce a spectral probl

Ch. Devchand, V. Ogievetsky

We show that the self-dual Yang-Mills equations afford supersymmetrisation to systems of equations invariant under global N-extended super-Poincaré transformations for arbitrary values of N, without the limitation (N\le 4) applicable to standard non-self-dual Yang-Mills theories. These systems of equations provide novel classically consistent interactions fo

N. G. Deshpande, Xiao-Gang He, Sandip Pakvasa

We study partial rate asymmetry in decays with single isospin final state. For K meson or hyperon decays, the partial rate asymmetries are always zero if the final states are single isospin states. In B decays the situation is dramatically different and partial rate asymmetries can be non-zero even if the final states are single isospin states. We calculated

Vladimir M. Dubovik, Valentin E. Kuznetsov

If neutrino is the Majorana particle it can possess only one electromagnetic characteristic, the toroid dipole moment (anapole) in the static limit and nothing else. We have calculated the diagonal toroid moment (form factor) of the Majorana neutrino by the dispersion method in the one-loop approximation of the Standard Model and found it to be different fro

S. Veseli, M. G. Olsson

We present an analysis which uses Regge structure and the Bjorken and Voloshin HQET sum rules to restrict the choice of parameters of a relativistic quark model.

B. Kerbikov, S. V. Bashinsky

We develop a new formalism to study $K\bar{K}$ threshold phenomena with resonances $f_0$, $a_0$ and $K^+K^-$ atom (kaonium) included. The approach provides two possible scenarios for $f_0-a_0$ mixing. Drastic interference patterns can be observed in $K^+K^-$electroproduction at CEBAF, $pd\to ~^3HeX$ reaction, and $N\bar N$ annihilation.

J. Blümlein, A. Vogt

The resummation of $O(α_s^{l+1} \ln^{2l} x)$ terms in the evolution equation of the singlet part of $g_1(x,Q^2)$ is carried out. The corresponding singlet evolution kernels are calculated explicitely. The leading small-$x$ contribution to the three-loop splitting function matrix is determined in the $\overline{\rm MS}$ scheme. Relations are derived for the c

K. Sridhar

Theoretical analyses of the results on quarkonium production at large transverse momentum ($p_T$) in $p\bar p$ collisions, at the Tevatron have revealed two novel features of the physics of quarkonium production : 1) the contribution of fragmentation of gluons and charm quarks to the cross-section at large $p_T$, and 2) the importance of colour octet compone

M. Wakamatsu

Using the standard auxiliary field method, we derive from the extended Nambu-Jona-Lasinio model an effective meson action containing vector and axial-vector mesons in addition to Goldstone bosons. The vector and axial-vector mesons in this effective action transform as gauge fields of hidden local symmetry $G_{local} = {[U(n)_L \times U(n)_R]}_{local}$. Here

M. Welling

In this paper we describe the matter-free toroidal spacetime in &#39;t Hooft&#39;s polygon approach to 2+1-dimensional gravity (i.e. we consider the case without any particles present). Contrary to earlier results in the literature we find that it is not possible to describe the torus by just one polygon but we need at least two polygons. We also show that t

Thomas W. Baumgarte, Gregory B. Cook, Mark A. Scheel, Stuart L. Shapiro

Locating apparent horizons is not only important for a complete understanding of numerically generated spacetimes, but it may also be a crucial component of the technique for evolving black-hole spacetimes accurately. A scheme proposed by Libson et al., based on expanding the location of the apparent horizon in terms of symmetric trace-free tensors, seems ve

M. Karplus, E. Shakhnovich

We argue that that the folding criterion suggested by Klimov and Thirumalai is similar to the one published earlier and that their conclusion of invalidity of the ``gap criterion&#39;&#39; is due to misunderstanding of previous work

M. R. Evans

A disordered version of the one dimensional asymmetric exclusion model where the particle hopping rates are quenched random variables is studied. The steady state is solved exactly by use of a matrix product. It is shown how the phenomenon of Bose condensation whereby a finite fraction of the empty sites are condensed in front of the slowest particle may occ

Serge Galam

Competing bimodal coalitions among a group of actors are discussed. First, a model from political sciences is revisited. Most of the model statements are found not to be contained in the model. Second, a new coalition model is built. It accounts for local versus global alignment with respect to the joining of a coalition. The existence of two competing world

D. B. Saakian

The $P\to\infty$ limit was considered in the spherical P-spin glass. It is possible to store information in the vacuum configuration of ferromagnetic phase. Maximal allowed level of noise was calculated in ferromagnetic phase.

B. C. den Hertog, M. P. Das

We examine various aspects of the normal state phase of ${\rm CuO_{2}}$ planes in the high Tc superconductors. In particular, within the context of the three band Hubbard model, we study as a function of doping the competition between a charge density wave phase induced by oxygen breathing modes, antiferromagnetic order and paramagnetism. To account for the

Federico Bonetto, Giovanni Gallavotti, Guido Gentile, Vieri Mastropietro

Under suitable conditions a flow on a torus $C^{(p)}$--close, with $p$ large enough, to a quasi periodic diophantine rotation is shown to be conjugated to the quasi periodic rotation by a map that is analytic in the perturbation size. This result is parallel to Moser&#39;s theorem stating conjugability in class $C^{(p&#39;)}$ for some $p&#39;<p$. The extra c

Blas Echebarria, Dario Krmpotić, Carlos Pérez-García

Convection in a cylindrical container of small aspect ratio is studied. It is known that when, in addition to buoyancy forces, thermocapillarity effects are taken into account, resonant interactions of two modes may appear. In the case of 1:2 resonance amplitude equations are derived, showing the existence of a stable heteroclinic orbit and rotating waves, u

P. Meszaros, M. J. Rees

We discuss the evolution of cosmological gamma-ray burst remnants, consisting of the cooling and expanding fireball ejecta together with any swept-up external matter, after the gamma-ray event. We show that significant optical emission is predicted which should be measurable for timescales of hours after the event, and in some cases radio emission may be exp

Daniel Schaerer

We demonstrate that it is crucial to account for the evolution of the starburst population in order to derive reliable numbers of O stars from integrated spectra for burst ages t > 2 - 3 Myr. In these cases the method of Vacca & Conti (1992) and Vacca (1994) systematically underestimates the number of O stars. Therefore the current WR/O number ratios in Wolf