August 1995 arXiv papers — page 11

K. Refson, R. A. Wogelius, D. G. Fraser, M. C. Payne

The observed reactivity of MgO with water is in apparent conflict with theoretical calculations which show that molecular dissociation does not occur on a perfect (001) surface. We have performed ab-initio total energy calculations which show that a chemisorption reaction involving a reconstruction to form a (111) hydroxyl surface is strongly preferred with

Kenneth A. Ribet

We discuss the equation $a^p + 2^\a b^p + c^p =0$ in which $a$, $b$, and $c$ are non-zero relatively prime integers, $p$ is an odd prime number, and $\a$ is a positive integer. The technique used to prove Fermat's Last Theorem shows that the equation has no solutions with $\a>1$ or $b$ even. When $\a=1$ and $b$ is odd, there are the two trivial solutions

Joerg Wenzel

The concept of Rademacher type $p$ ($1\leq p\leq2$) plays an important role in the local theory of Banach spaces. In \cite{mas88} Mascioni considers a weakening of this concept and shows that for a Banach space $X$ weak Rademacher type $p$ implies Rademacher type $r$ for all $r<p$. As with Rademacher type $p$ and weak Rademacher type $p$, we introduce the co

Lisa Randall, Csaba Csa&#39;ki

The doublet-triplet splitting problem is probably the most significant challenge to supersymmetric GUT theories. In this talk, we review potential solutions and their problematic aspects. We also present a complete consistent realization of our preferred solution, higgses as pseudogoldstone bosons, and discuss some distinctive aspects of its phenomenology.

V. M. Belyaev, A. V. Radyushkin

We use local quark-hadron duality to estimate the purely nonperturbative soft contribution to the $γ^* p \to Δ$ form factors. Our results are in agreement with existing experimental data. We predict that the ratio $G_E^*(Q^2)/G_M^*(Q^2)$ is small for all accessible $Q^2$, in contrast to the pQCD expectations that $G_E^*(Q^2) \to -G_M^*(Q^2)$.

E. L. Gubankova, Yu. A. Simonov

Confined and deconfined phases are defined through nonperturbative correlators and nonperturbative background perturbation theory is used to compute the critical temperature $T_c$ and spatial string tension. Taking evolution along one of the spatial axes the set of Hamiltonians $H(n_1,n_2)$ with different Matsubara frequencies is obtained. Meson and glueball

W. Melnitchouk, A. W. Thomas

We investigate the possibility of identifying an explicit pionic component of the nucleon through measurements of polarized $Δ^{++}$ baryon fragments produced in deep-inelastic leptoproduction off polarized protons, which may help to identify the physical mechanism responsible for the breaking of the Gottfried sum rule. The pion-exchange model predicts highl

Gerhard Ecker, Martin Mojzis

The renormalized pion-nucleon Lagrangian is calculated to O(p^3) in heavy baryon chiral perturbation theory. By suitably chosen transformations of the nucleon field, the Lagrangian is brought to a standard form.

G. Miele

A novel approach to parton distributions parameterization in terms of quantum statistical functions is here outlined. The description, already proposed in previous publications, is here improved by adding to the statistical distributions an unpolarized {\it liquid} component. This new contribution to fermion partons is able to reproduce the expected low $x$

Bo-Qiang Ma, Tao Huang

We analyse the perturbative contributions from the higher helicity ($λ_{1}+λ_{1}=\pm 1$) components, which should be naturally contained in the light-cone wave function for the pion as a consequence of the Wigner rotation, in the QCD calculation of the pion form factor. It is pointed out that the contributions may provide the other fraction needed to fit the

S. Abachi, D0 collabolation

We present measurements of the production cross sections times leptonic branching fractions and the transverse momentum distributions of $W$ and $Z$ bosons in $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV using data collected with the DØdetector at the Fermilab Tevatron $p\bar{p}$ collider. A preliminary measurement of the $W$ charge asymmetry is also presente

CLEO Collaboration, J. Gronberg et al

Using data collected with the CLEO~II detector, we have observed the isospin-violating decay $D_s^{*+}\to D_s^+π^0$. The decay rate for this mode, relative to the dominant radiative decay, is found to be $Γ(D_s^{*+}\to D_s^+π^0)/Γ(D_s^{*+}\to D_s^+γ)= 0.062^{+0.020}_{-0.018}\pm0.022$.

Gregory A. Burnett, Alan D. Rendall

We prove that the maximal development of any spherically symmetric spacetime with collisionless matter (obeying the Vlasov equation) or a massless scalar field (obeying the massless wave equation) and possessing a constant mean curvature $S^1 \times S^2$ Cauchy surface also contains a maximal Cauchy surface. Combining this with previous results establishes t

Marc A. Rieffel

We have previously shown how to construct a deformation quantization of any locally compact space on which a vector group acts. Within this framework we show here that, for a natural class of Hamiltonians, the quantum evolutions will have the classical evolution as their classical limit.

C. G. Giraud-Carrier, T. R. Martinez

Learning and reasoning are both aspects of what is considered to be intelligence. Their studies within AI have been separated historically, learning being the topic of machine learning and neural networks, and reasoning falling under classical (or symbolic) AI. However, learning and reasoning are in many ways interdependent. This paper discusses the nature o

Q. Zhao, T. Nishida

Identifying inaccurate data has long been regarded as a significant and difficult problem in AI. In this paper, we present a new method for identifying inaccurate data on the basis of qualitative correlations among related data. First, we introduce the definitions of related data and qualitative correlations among related data. Then we put forward a new conc

Takashi Yamamoto, Norio Kawakami, Sung-Kil Yang

Critical properties of the Calogero-Sutherland model of $BC_N$-type ($BC_N$-CS model) are studied. Using the asymptotic Bethe-ansatz spectrum of the $BC_N$-CS model, we calculate finite-size corrections in the energy spectrum. Since the $BC_N$-CS model does not possess translational invariance, the finite-size spectrum acquires the contributions coming from

H. M. Cataldo, C. F. Tejero

The stability of the hard-sphere icosahedral quasilattice is analyzed using the differential formulation of the generalized effective liquid approximation. We find that the icosahedral quasilattice is metastable with respect to the hard-sphere crystal structures. Our results agree with recent findings by McCarley and Ashcroft [Phys. Rev. B {\bf 49}, 15600 (1

Anton Bovier, Christof Kulske

We prove that in dimension $d\leq 2$ translation covariant Gibbs states describing rigid interfaces in a disordered solid-on-solid (SOS) cannot exist for any value of the temperature, in contrast to the situation in $d\geq 3$. The prove relies on an adaptation of a theorem of Aizenman and Wehr. Keywords: Disordered systems, interfaces, SOS-model

Zhu-Pei Shi, Rajiv R. P. Singh

The $T=0$ spin stiffness $ρ_{s}$ and the transverse susceptibility $χ_{\perp }$ of the square lattice half-filled Hubbard model are calculated as a function of the Hubbard parameter ratio $U/t$ by series expansions around the Ising limit. We find that the calculated spin-stiffness, transverse susceptibility, and sublattice magnetization for the Hubbard model

L. L. Bonilla, F. G. Padilla, G. Parisi, F. Ritort

In this note we present an exact solution of the Monte Carlo dynamics of the spherical Sherrington-Kirkpatrick spin-glass model. We obtain the dynamical equations for a generalized set of moments which can be exactly closed. Only in a certain particular limit the dynamical equation of the energy coincides with that of the Langevin dynamics.

Siegfried Clar, Barbara Drossel, Franz Schwabl

We introduce a nonequilibrium percolation model which shows a self-organized critical (SOC) state and several periodic states. In the SOC state, the correlation length diverges slower than the system size, and the corresponding exponent depends non universally on the parameter of the model. The periodic states contain an infinite cluster covering only part o

P. W. Leung, Ngar-wing Lam

We study the spin-$1\over2$ Heisenberg antiferromagnet with an antiferromagnetic $J_3$ (third nearest neighbor) interaction on a square lattice. We numerically diagonalize this ``$J_1$-$J_3$&#39;&#39; model on clusters up to 32-sites and search for novel ground state properties as the frustration parameter $J_3/J_1$ changes. For ``larger&#39;&#39; $J_3/J_1$

Géza Ódor

In the stochastic cellular automaton of rule 18 defined by S. Wolfram [Rev.\ Mod.\ Phys.\ {\bf 55}, 601 (1983)] the crossover of the critical behaviour induced by nonlocal site exchange was investigated using the coherent anomaly method. The continuous variation of the critical $β$ exponent was confirmed.

Vladimir N. Kostur

It is shown that a correlation between the positions of the $c$-axis longitudinal optic ($LO_c$) phonons and ``notch&#39;&#39;-like structures in the $a$-$b$ plane conductivity of high-$T_c$ superconductors results from phonon-mediated interaction between electrons in different layers. It is found that the relative size of the notches depends on $λ_{ph}(Ω_{p

K. Z. Stanek, M. Mateo, A. Udalski, M. Szymanski

The color-magnitude diagrams of $\sim 1 \times 10^6$ stars obtained for 19 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We found that the distributions of the extinction-adjusted apparent magnitudes of red clump stars in fields lying at $l=\pm5°$ in galactic longitude differ by $\sim 0.4\;

Moshe Elitzur

General solutions of the maser polarization problem are presented for arbitrary absorption coefficients. The results are used to calculate polarization for masers permeated by magnetic fields with arbitrary values of \xB, the ratio of Zeeman splitting to Doppler linewidth, and for anisotropic pumping. The $\xb \to 0$ limit of the magnetic solution reproduces

Bohdan Paczynski

A high optical depth to gravitational microlensing towards the galactic bulge is consistent with current models of the galactic bar. The low optical depth towards the LMC can probably be accounted for by the ordinary stars in our galaxy and in the LMC itself. No conclusive evidence is available yet for the presence or absence of a large number of brown dwarf

David A. Buote, Claude R. Canizares

We have analyzed ROSAT PSPC X-ray data of the optically elongated S0 galaxy NGC 1332 with the purposes of constraining the intrinsic shape of its underlying mass and presenting a detailed investigation of the uncertainties resulting from the assumptions underlying this type of analysis. The X-ray isophotes are elongated with ellipticity $0.10 - 0.27$ (90% co

S. R. Cranmer, S. P. Owocki

We present two-dimensional hydrodynamical simulations of corotating stream structure in the wind from a rotating O star, together with resulting synthetic line profiles showing discrete absorption components (DACs). An azimuthal variation is induced by a local increase or decrease in the radiative driving force, as would arise from a bright or dark ``star sp

Kim A. Venn, David L. Lambert, Michael Lemke

Boron abundances in A- and B-type stars may be a successful way to track evolutionary effects in these hot stars. The light elements -- Li, Be, and B -- are tracers of exposure to temperatures more moderate than those in which the H-burning CN-cycle operates. Thus, any exposure of surface stellar layers to deeper layers will affect these light element abunda