April 1998 arXiv papers — page 18

R. A. Hyman, A. Zangwill, M. D. Stiles

We present a theoretical study of in-plane magnetization reversal for vicinal ultrathin films using a one-dimensional micromagnetic model with nearest-neighbor exchange, four-fold anisotropy at all sites, and two-fold anisotropy at step edges. A detailed "phase diagram" is presented that catalogs the possible shapes of hysteresis loops and reversal m

A. J. Ward, J. B. Pendry

In this paper we shall propose a simple scheme for calculating Green's functions for photons propagating in complex structured dielectrics or other photonic systems. The method is based on an extension of the finite difference time domain (FDTD) method, originally proposed by Yee, also known as the Order-N method, which has recently become a popular way

Maxim Skorobogatyy, Hong Guo, Martin Zuckermann

We have exactly solved the relaxational dynamics of a model protein which possesses a kinetically perfect funnel-like energy landscape. We find that the dependence of the relaxation time, $τ$, on the density of states (DOS) and the energy level spacing distributions of the model displays several main types of behavior depending on the temperature $T$. This a

Alexander A. Nersesyan, Alexander O. Gogolin, Fabian H. L. Essler

We develop a low-energy effective theory for spin-1/2 frustrated two-leg Heisenberg spin ladders. We obtain a new type of interchain coupling that breaks parity symmetry. In the presence of an XXZ-type anisotropy, this interaction gives rise to a novel ground state, characterized by incommensurate correlations. In the case of a single ladder, this state corr

Makoto Itoh

An attempt is made to simulate the homoepitaxial growth of a Si(111) surface by the kinetic Monte Carlo method in which the standard Solid-on-Solid model and the planar model of the (7x7) surface reconstruction are used in combination. By taking account of surface reconstructions as well as atomic deposition and migrations, it is shown that the effect of a c

S. Luding, M. Huthmann, S. McNamara, A. Zippelius

We investigate freely cooling systems of rough spheres in two and three dimensions. Simulations using an event driven algorithm are compared with results of an approximate kinetic theory, based on the assumption of a generalized homogeneous cooling state. For short times $t$, translational and rotational energy are found to change linearly with $t$. For larg

John H Miller,

Charge and spin density waves are highly correlated electron systems that can transport an electric current. A model is discussed in which a field E induces the creation, by quantum tunneling, of pairs of oppositely charged solitons and antisolitons in a density wave. Pair creation is blocked, for fields below a threshold value ET, because the increase in el

Sergei Maslov, Andrey Zheludev

We study the properties of one-dimensional gapped Heisenberg antiferromagnets in the presence of an arbitrary strong staggered magnetic field. For these systems we predict a universal form for the staggered magnetization curve. This function, as well as the effect the staggered field has on the energy gaps in longitudinal and transversal excitation spectra,

N. Sukumar

The properties of two-state nearest-neighbour cellular automata (CA) that are capable of density classification are discussed. It is shown that these CA actually conserve the total density, rather than merely classifying it. This is also the criterion for any CA simulation of DFT. The effect of boundary and periodicity conditions upon the evolution of such C

A. A. Cole, J. S. Gallagher, J. R. Mould, the WFPC2 IDT

We have imaged the nucleus of M32 at 1600 Angstroms (FUV) and 5500 Angstroms (V) using the Wide-Field/Planetary Camera 2 (WFPC2) aboard HST. We detected the nucleus at 1600 Angstroms using the redleak-free Woods filter on WFPC2. The FUV light profile can be fit with a Gaussian of FWHM 0.46" (4.6 pixels), but cannot be resolved into individual stars; no U

Neil Trentham

I review recent measurements of the faint end of the galaxy luminosity function in galaxy clusters. Evidence is presented that the luminosity function of galaxies in the central parts of clusters is remarkably constant between clusters and that this luminosity function is steep at bright and faint magnitudes and shallow in-between. The curvature is highly si

Azita Valinia, Francis E. Marshall

(Abridged) The diffuse X-ray emission from the thin disk surrounding the Galactic mid-plane (the so-called Galactic ridge) was measured with RXTE PCA in order to determine the spatial extent, spectral nature, and origin of the emission. Spatial examination of the diffuse emission in the central 30 deg of the plane in Galactic longitude reveals the presence o

Susan A. Lamb, Nathan C. Hearn, Yu Gao

In this paper we demonstrate for the first time the connection between the spatial and temporal progression of star formation and the changing locations of the very dense regions in the gas of a massive disk galaxy (NGC 1144) in the aftermath of its collision with a massive elliptical (NGC 1143). These two galaxies form the combined object Arp 118, a collisi

C. M. Carollo, M. Stiavelli

In this paper, the third of a series dedicated to the investigation of the nuclear properties of spiral galaxies, we have (i) modelled the WFPC2 F606W nuclear surface brightness profiles of 41 spiral galaxies presented in Carollo et al. 1997c, 1998 with the analytical law introduced by Lauer et al. 1995, and (ii) deprojected these surface brightness profiles

Priscilla C. Frisch

The interstellar cloud surrounding the solar system regulates the galactic environment of the Sun, and determines the boundary conditions of the heliosphere. Both the Sun and interstellar clouds move through space, so these boundary conditions change with time. Data and theoretical models now support densities in the cloud surrounding the solar system of n(H

Priscilla C. Frisch

The importance of understanding the current and historical galactic environments of cool stars is discussed. The penetration of interstellar gas into a stellar astrosphere is a function of the interaction of the star with the interstellar cloud surrounding the star, and this factor needs to be understood if an efficient search for life-bearing planets is to

C. M. Carollo, M. Stiavelli, J. Mack

We report the analysis of HST WFPC2 F606W images of 40 spirals belonging to the sample introduced in Carollo et al. (paper I), where 35 other targets were discussed. We describe the optical morphology of the new 40 galaxies, derive the surface brightness profiles for 25 of them, and present the results of photometric decompositions of these profiles into a `

Anuradha Koratkar, Robert Antonucci, Robert Goodrich, Alex Storrs

The Lyman edge at 912 Åis an important diagnostic region for studying quasi-stellar objects (QSOs). In particular, it reveals a great deal about the physical conditions within the atmospheres of accretion disks, a ubiquitous component of QSO theories. A robust prediction of accretion disk models is a significant polarization due to electron scattering just l

John Stauffer, Greg Schultz, J. Davy Kirkpatrick

We have obtained intermediate resolution spectra of eleven candidate brown dwarf members of the Pleiades open cluster using the Keck II telescope and LRIS spectrograph. Our primary goal was to determine the location of the "lithium depletion edge" in the Pleiades and hence to derive a precise age for the cluster. All but one of our 11 program objects

G. De Zotti, L. Toffolatti, G. L. Granato

We review estimates of small scale fluctuations due to extragalactic point sources in the Planck Surveyor frequency bands. While our undestanding of the spectral and evolutionary properties of these sources is far from complete, conservative estimates allow us to confidently conclude that, in the frequency range 100--200 GHz, their contaminating effect is we

R. L. Akeson, D. W. Koerner, E. L. N. Jensen

We present high-resolution imaging of the young binary T Tauri in 3 mm continuum emission. Compact dust emission with integrated flux density 50 +/- 6 mJy is resolved in an aperture synthesis map at 0.5" resolution and is centered at the position of the optically visible component, T Tau N. No emission above a 3 sigma level of 9 mJy is detected 0.7"