June 1995 arXiv papers — page 12

Alan H. Durfee

Let $f(x,y)$ be a real polynomial of degree $d$ with isolated critical points, and let $i$ be the index of $grad f$ around a large circle containing the critical points. An elementary argument shows that $|i| \leq d-1$. In this paper we show that $ i \leq max \{1, d-3 \}$. We also show that if all the level sets of $f$ are compact, then $i = 1$, and otherwis

K. Moulopoulos, S. Roche

We have studied the influence of a particular kind of phason-defect on the Landauer resistance of a Fibonacci chain. Depending on parameters, we sometimes find the resistance to decrease upon introduction of defect or temperature, a behavior that also appears in real quasicrystalline materials. We demonstrate essential differences between a standard tight-bi

A. E. Allakhverdyan, D. B. Saakian

We consider paramagnetic, spin-glass and ferromagnetic phases. At $T=0$ model gives for the some values of connectivity (near the critical) extremal suppression of finite size effects (decoding error probability).

M. Persic, P. Salucci, F. Stel

We use a homogeneous sample of about 1100 rotation curves (RCs) and relative surface photometry to investigate (out to 2 optical radii and over 6 mag) the main mass structure properties of spirals. We confirm the strong dependence on luminosity for both the profile and the amplitude of RCs. Spiral RCs show the striking feature that a single parameter, the lu

Edward Malec

The weak cosmic censorship hypothesis can be understood as a statement that there exists a global Cauchy evolution of a selfgravitating system outside an event horizon. The resulting Cauchy problem has a free null-like inner boundary. We study a selfgravitating spherically symmetric nonlinear scalar field. We show the global existence of a spacetime with a n

Stefano Borgani, Francesco Lucchin, Sabino Matarrese, Lauro Moscardini

Recent data on the high--redshift abundance of damped Ly$α$ systems are compared with theoretical predictions for `blue' (i.e. $n>1$) Mixed Dark Matter models. The results show that decreasing the hot component fraction $Ω_ν$ and/or increasing the primordial spectral index $n$ implies an earlier epoch of cosmic structure formation. However, we also show

C. Alexandrou, A. Borrelli, Ph. de Forcrand, A. Galli

We investigate Lüscher's method of including dynamical Wilson fermions in a lattice simulation of QCD with two quark flavours. We measure the accuracy of the approximation by comparing it with Hybrid Monte Carlo results for gauge plaquette and Wilson loops. We also introduce an additional global Metropolis step in the update. We show that the complexity

N. Armesto, C. Pajares, Yu. M. Shabelski

Production of charmed and beauty mesons and baryons in hadron-nucleon collisions at not very high energy is considered in the framework of the Quark-Gluon String Model. We take into account the possible corrections to the model which disappear at asymptotically high energies but could be important at comparatively low energies, essentially in the case of hea

V. A. Khoze, W. J. Stirling

One of the most powerful methods for obtaining a precision measurement of M_W at LEP2 is from direct reconstruction of the invariant mass distribution of W bosons produced in e+e- --> W+W-. We investigate the effects on the W line shape, and in particular on the average invariant mass, of phase-space and first-order Coulomb corrections. The latter are shown

M. Hatsuda, M. Sato, S. Yahikozawa, T. Hatsuda

Adiabatic effective action for vortices in neutral and charged superfluids at zero temperature are calculated using the topological Landau-Ginzburg theory recently proposed by Hatsuda, Yahikozawa, Ao and Thouless, and vortex dynamics are examined. The Berry phase term arising in the effective action naturally yields the Magnus force in both neutral and charg

G. M. Kavoulakis, Gordon Baym, J. P. Wolfe

Recent experiments on high density excitons in Cu$_2$O provide evidence for degenerate quantum statistics and Bose-Einstein condensation of this nearly ideal gas. We model the time dependence of this bosonic system including exciton decay mechanisms, energy exchange with phonons, and interconversion between ortho (triplet-state) and para (singlet-state) exci

Matt Greenwood, Xiao-Song Lin

We prove that the knot invariant induced by a $\Bbb Z$-homology 3-sphere invariant of order $\leq k$ in Ohtsuki's sense, where $k\geq 4$, is of order $\leq k-2$. The method developed in our computation shows that there is no $\Bbb Z$-homology 3-sphere invariant of order 5. This result agrees with a conjecture of Rozansky based on physical predictions abo

Peter W. Michor

The assumption in the main result of [Peter W. Michor: Basic Differential Forms for Actions of Lie Groups, Proc. AMS 124, 5 (1996) 1633-1642] is removed. Thus: A section of a Riemannian $G$-manifold $M$ is a closed submanifold $\Si$ which meets each orbit orthogonally. It is shown that the algebra of $G$-invariant differential forms on $M$ which are horizont

D. M. Gitman, A. E. Gonçalves

A pseudoclassical model to describe Weyl particle in 10 dimensions is proposed. In course of quantization both the massless Dirac equation and the Weyl condition are reproduced automatically. The construction can be relevant to Ramond-Neveu-Schwarz strings where the Weyl reduction in the Ramond sector has to be made by hand.

Vicente Pleitez

We consider an extension of the ordinary four dimensional Minkowski space by introducing additional dimensions which have their own Lorentz transformation. Particles can transform in a different way under each Lorentz group. We show that only quark interactions are slightly modified and that color confinement is automatic since these degrees of freedom run o

Stefano De Leo

We derive an appropriate definition of transpose for quaternionic matrices and give a new panoramic review of the quaternionic groups. We aim to analyse possible quaternionic groups for GUTs.

R. Carroll, Y. Kodama

The dispersionless differential Fay identity is shown to be equivalent to a kernel expansion providing a universal algebraic characterization and solution of the dispersionless Hirota equations. Some calculations based on D-bar data of the action are also indicated.

J. Fuchs

The geometric description of Yang-Mills theories and their configuration space M is reviewed. The presence of singularities in M is explained and some of their properties are described. The singularity structure is analyzed in detail for structure group SU(2).

B. J. Schroers

The scale invariance of the $O(3)$ sigma model can be broken by gauging a $U(1)$ subgroup of the $O(3)$ symmetry and including a Maxwell term for the gauge field in the Lagrangian. Adding also a suitable potential one obtains a field theory of Bogomol'nyi type with topological solitons. These solitons are stable against rescaling and carry magnetic flux

Kazuo Fujikawa

A recent application of an index relation of the form, $dim\ ker\ M - dim\ ker\ M^{\dagger} = ν$, to the generation of chiral fermions in a vector-like gauge theory is reviewed. In this scheme the chiral structure arises from a mass term with a non-trivial index.The essence of the generalized Pauli-Villars regularization of chiral gauge theory, which is base

Neil Marcus

We present the alternative topological twisting of N=4 Yang-Mills, in which the path integral is dominated not by instantons, but by flat connections of the COMPLEXIFIED gauge group. The theory is nontrivial on compact orientable four-manifolds with nonpositive Euler number, which are necessarily not simply connected. On such manifolds, one finds a single to

Keith R. Dienes, Moshe Moshe, Robert C. Myers

We demonstrate that the spectrum of any consistent string theory in $D$ dimensions must satisfy a number of supertrace constraints: $ Str~M^{2n}=0 $ for $0 \leq n < D/2-1$, integer $n$. These results hold for a large class of string theories, including critical heterotic strings. For strings lacking spacetime supersymmetry, these supertrace constraints will

Keith R. Dienes

We discuss one of the generic spacetime consequences of having (1,0) worldsheet supersymmetry in tachyon-free string theory, namely the appearance of a ``misaligned supersymmetry&#39;&#39; in the corresponding spacetime spectrum. Misaligned supersymmetry is a universal property of (1,0) string vacua which describes how the arrangement of bosonic and fermioni

Yoshihisa Kitazawa

We prove the renormalizability of quantum gravity near two dimensions. The successful strategy is to keep the volume preserving diffeomorphism as the manifest symmetry of the theory. The general covariance is recovered by further imposing the conformal invariance. The proof utilizes BRS formalism in parallel with Yang-Mills theory. The crucial ingredient of

Davison E. Soper

The main topics covered in this summary talk are the Large Hadron Collider, heavy ion collisions, renormalons, parton distribution functions, measurements of the strong coupling and the top quark. Of special interest this year was the discovery of the top quark by the CDF and D0 groups at Fermilab. I conclude that the evidence is compelling and that the best

X. Wang, J. Lopez, D. Nanopoulos

We compute the supersymmetric contribution to $R_{b}\equiv Γ(Z\to b{\bar b})/Γ(Z\to {\rm hadrons})$ in a variety of supersymmetric models. In the context of supergravity models with universal soft-supersymmetry-breaking and radiative electroweak breaking we find $R^{\rm susy}_b\lsim0.0004$, which does not shift significantly the Standard Model prediction ($R

Xiangdong Ji

Because of the infrared renormalons, it is difficult to get power accuracy in the traditional approach to the Wilson&#39;s operator product expansion. Based on a new perturbative renormalization scheme for power-divergent operators, I propose a practical version of the OPE that allows to calculate power corrections to desired accuracy. The method is applied

L. M. A. Bettencourt, T. S. Evans, R. J. Rivers

We develop winding number correlation functions that allow us to assess the role of field fluctuations on vortex formation in an Abelian gauge theory. We compute the behavior of these correlation functions in simple circumstances and show how fluctuations are important in the vicinity of the phase transition. We further show that, in our approximation, the e

B. Margolis, S. Punch, ; C. Hamzaoui

We study a class of quark mass matrix models with the $\cal CP$-violating phase determined through making the $\cal CP$-violating parameter $J$ an extremum. These models assume that $m_u \ll m_c \ll m_t$ and that $m_d \ll m_s \ll m_b$. They have $\left|{V_{ub}\over{V_{cb}}}\right|\approx{\sqrt{m_u \over{m_c}}}$, $\left|{V_{td}\over{V_{ts}}}\right|\approx{\sq

M. Phipps

In this paper, the semileptonic decays of heavy mesons are treated fully relativistically. By means of an effective vertex, the effect of Fermi momentum are included both at the inclusive and at the exclusive levels, and the spin of both parent and daughter particles are taken into account. The differential decay rates with respect to the lepton energy and m

Jogesh C. Pati

This talk is dedicated to honor the memory of Professor S.N. Bose. I survey the crucial roles played by Bose-Fermi symmetry in all recent attempts at higher unification, which include the ideas of (i) the conventional approach to grand unification; (ii) the preonic approach; and (iii) superstrings.

G. Montagna, O. Nicrosini, F. Piccinini

The Monte Carlo program {\tt WWGENPV}, designed for computing distributions and generating events for the four-fermion process $e^+ e^- \to W^+ W^- \to 4f$, is described. It is based on the calculation of the exact tree-level matrix element of the four-fermion reaction and includes initial-state radiation in the leading-log approximation within the structure

P. Colangelo, F. De Fazio, N. Di Bartolomeo, R. Gatto

We compute the strong coupling constant $G_{B^{**} B π} \; (G_{D^{**} D π})$, where $B^{**}$ ($D^{**}$) is the $0^+$ $P-$wave $b \bar q \; (c \bar q)$ state, by QCD sum rules and by light-cone sum rules. The two methods give compatible results in the limit $m_Q \to \infty$, with a rather large value of the coupling constant. We apply the results to the calcu

D. R. Timothy Jones

Recent work on the use of dimensional reduction for the regularisation of non--supersymmetric theories is reviewed. It is then shown that there exists a class of theories for which a universal form of the soft supersymmetry breaking terms is invariant under renormalisation. It is argued that this universal form might be approached as an infra--red fixed poin

John F. Donoghue

I describe the methodology for the use of dispersion relations in connection with chiral perturbation theory. The conditions for matching the two formalisms are given at $O(E^2)$ and $O(E^4)$. The two have several complementary features, as well as some limitations, and these are described by the use of examples, which include chiral sum rules related to the

V. Bernard, N. Kaiser, Ulf-G. Meißner

We evaluate the S-wave pion--nucleon scattering length $a^-$ in the framework of heavy baryon chiral perturbation theory up--to--and--including terms of order $M_π^4$. We show that the order $M_π^4$ piece of the isovector amplitude at threshold, $T^-_{\rm thr}$, vanishes exactly. We predict for the isovector scattering length, $0.088 \, M_{π^+}^{-1} \le a^-

C. S. Kim, Jae Kwan Kim, Yeong Gyun Kim, Kang Young Lee

We developed the new parton model approach for exclusive semileptonic decays of $B$-meson to $D,~D^*$ by extending the inclusive parton model, and by combining with the results of the HQET, motivated by Drell-Yan process. Without the nearest pole dominance ansätze, we {\bf derived} the dependences of hadronic form factors on $q^2$. We also calculated numeric

A. Yu. Ignatiev, G. C. Joshi

We analyze the role played by the gauge invariance for the existence of Dirac monopole. To this end, we consider the electrodynamics with massive photon and ask if the magnetic charge can be introduced there. We show that the derivation of the Dirac quantization condition based on the angular momentum algebra cannot be generalized to the case of massive elec

R. Rattazzi, U. Sarid

The consequences of assuming the third-generation Yukawa couplings are all large and comparable are studied in the context of the minimal supersymmetric extension of the standard model. General aspects of the RG evolution of the parameters, theoretical constraints needed to ensure proper electroweak symmetry breaking, and experimental and cosmological bounds

Dong Chen

We study the chiral phase transition with staggered fermions on the lattice at finite temperature in the strong coupling limit. The thermodynamic potential is derived in the large $d$ approximation where $d+1$ is the dimension of space time. Our calculation is simpler than the conventional method and leads to a simple physical interpretation for the approxim

A. Patrascioiu, E. Seiler

We reply to David&#39;s comment (hep-lat/9504017) on our paper Phys.Rev.Lett. 74(1995)1920.

M. Campostrini, A. Pelissetto, P. Rossi, E. Vicari

The renormalized zero-momentum four-point coupling $g_r$ of O(N)-invariant scalar field theories in $d$ dimensions is studied by applying the 1/N expansion and strong coupling analysis. The O(1/N) correction to the $β$-function and to the fixed point value $g_r^*$ are explictly computed. Strong coupling series for lattice non-linear sigma models are analyzed

Robert Graham, Andras Csordas

Spatially homogeneous models in quantum supergravity with a nonvanishing cosmological constant are studied. A class of exact nontrivial solutions of the supersymmetry and Lorentz constraints is obtained in terms of the Chern-Simons action on the spatially homogeneous 3-manifold, both in Ashketar variables where the solution is explicit up to reality conditio

U. Bunke, M. Olbrich

We compute the cohomology of a Fuchsian group of the second kind with coefficients in the hyperfunction vectors of the principal series representations of $SL(2,R)$ supported on the limit set.

R. J. Mooney, M. E. Califf

This paper presents a method for inducing logic programs from examples that learns a new class of concepts called first-order decision lists, defined as ordered lists of clauses each ending in a cut. The method, called FOIDL, is based on FOIL (Quinlan, 1990) but employs intensional background knowledge and avoids the need for explicit negative examples. It i

M. Veloso, P. Stone

There has been evidence that least-commitment planners can efficiently handle planning problems that involve difficult goal interactions. This evidence has led to the common belief that delayed-commitment is the &#34;best&#34; possible planning strategy. However, we recently found evidence that eager-commitment planners can handle a variety of planning probl

Whitney Mason, S. V. Kravchenko, G. E. Bowker, J. E. Furneaux

We have studied the resistivity, $ρ$, of a two-dimensional electron system in silicon in the temperature range 200 mK < T < 7.5 K at zero magnetic field at low electron densities, when the electron system is in the insulating regime. Our results show that at an intermediate temperature range $ρ=ρ_0 exp[(T_0/T)^{1/2}]$ for at least four orders of magnitude up

S L A de Queiroz

The two-dimensional site percolation problem is studied by transfer-matrix methods on finite-width strips with free boundary conditions. The relationship between correlation-length amplitudes and critical indices, predicted by conformal invariance, allows a very precise determination of the surface decay-of-correlations exponent, $η_s = 0.6664 \pm 0.0008$, c

Kikuo Harigaya

Exciton effects on conjugated polymers are investigated in soliton lattice states. We use the Su-Schrieffer-Heeger model with long-range Coulomb interactions. The Hartree-Fock (HF) approximation and the single-excitation configuration- interaction (single-CI) method are used to obtain optical absorption spectra. The third-harmonic generation (THG) at off-res

Daniele Balboni, Pierre-Antoine Rey, Michel Droz

A class of $d$-dimensional reaction-diffusion models interpolating continuously between the diffusion-coagulation and the diffusion-annihilation models is introduced. Exact relations among the observables of different models are established. For the one-dimensional case, it is shown how correlations in the initial state can lead to non-universal amplitudes f

Michael E. Flatté, Martin Holthaus

We investigate the correspondence between classical and quantum mechanics for periodically time dependent Hamiltonian systems, using the example of a periodically forced particle in a one-dimensional triangular well potential. In particular, we consider quantum mechanical Floquet states associated with resonances in the classical phase space. When the classi

H. P. Fangi, L. Y. Cao

In principle, all the natural systems such as biological, ecological and economical systems are structure-variable systems (in which some environment parameters are not fixed). In this Letter we show that data sequences from many structure-variable systems are short-term predictable. We also argue how to characterize the data sequences from structure-variabl

Brigitte Grote, Nils Lenke, Manfred Stede

In order to generate cohesive discourse, many of the relations holding between text segments need to be signalled to the reader by means of cue words, or {\em discourse markers}. Programs usually do this in a simplistic way, e.g., by using one marker per relation. In reality, however, language offers a very wide range of markers from which informed choices s

James Geddes, Theodore C. Quinn, Robert M. Wald

We investigate the injection spectrum of ultra-high-energy (>10^{15} eV) cosmic rays under the hypotheses that (1) these cosmic rays are protons and (2) the sources of these cosmic rays are extra-galactic and are homogeneously distributed in space. The most puzzling aspect of the observed ultra-high-energy cosmic ray spectrum is the apparent nonexistence of

C. A. Scharf, K. Jahoda, E. Boldt

If gamma-ray bursts are cosmological or in a halo distribution their properties are expected to be isotropic (at least to 1st order). However, our motion with respect to the burst parent population (whose proper frame is expected to be that of the Cosmic Microwave Background (CMB), or that of a static halo) will cause a dipole effect in the distribution of b

Enrique Gaztañaga

We analyze the uncertainties in the amplitudes of the spatial correlation functions estimated from angular correlations in a sample from the APM Galaxy Survey, with $b_J=17-20$. We model the uncertainties in the selection function and in the evolution of clustering. In particular we estimate $σ_8^{APM}$, the rms galaxy number fluctuations in spheres of radiu

Paolo Padoan

The role played by velocity fields in the fragmentation of a cold medium and in the formation of protostars is studied. The velocity field is modeled with a compressible turbulent flow. A supersonic turbulent velocity field can fragment the medium into clumps of mass smaller than a local Jeans&#39; mass, and therefore stabilize the medium against the formati

G. Bono, F. Caputo, V. Castellani, M. Marconi

A solution to the old Oosterhoff controversy is proposed on the basis of a new theoretical pulsational scenario concerning RR Lyrae cluster variables (Bono and coworkers). We show that the observed constancy of the lowest pulsation period in both Oosterhoff type I (OoI) and Oosterhoff type II (OoII) prototypes (M3, M15) can be easily reproduced only by assum

Dean C. Hines, Beverley J. Wills

We present IUE spectrophotometry and optical spectropolarimetry of the ultraluminous, extreme FeII-emitting QSO IRAS 07598+6508. We find broad absorption troughs from high- and low-ionization species, showing that this object is a member of the class of rare low-ionization BAL QSOs. Compared with non-BAL QSOs, the spectral energy distribution is reddened by

Edward Bierstone, Pierre D. Milman, Wieslaw Pawlucki

We introduce a new point of view towards Glaeser&#39;s theorem on composite $C^\infty$ functions [Ann. of Math. 1963], with respect to which we can formulate a ``$C^k$ composite function property&#34; that is satisfied by all semiproper real analytic mappings. As a consequence, we see that a closed subanalytic set $X$ satisfies the $C^\infty$ composite funct

Dan Abramovich

A common practice in arithmetic geometry is that of generalizing rational points on projective varieties to integral points on quasi-projective varieties. Following this practice, we demonstrate an analogue of a result of L. Caporaso, J. Harris and B. Mazur, showing that the Lang - Vojta conjecture implies a uniform bound on the number of stably integral poi