September 1998 arXiv papers — page 6

I. B. Khriplovich, A. A. Pomeransky

We consider the motion of a spinning relativistic particle in external electromagnetic and gravitational fields, to first order in the external field, but to an arbitrary order in spin. The noncovariant spin formalism is crucial for the correct description of the influence of the spin on the particle trajectory. We show that the true coordinate of a relativi

Eric Baird

Special relativity includes a concealed mechanism for reducing time-dilation effects in two mutually-receding objects. Forwarding their signals via one or more intermediate physical relay stages (a "probe chain") allows enhanced communication and propulsion efficiency. These possibilities are masked by the mathematical redefinitions of the special th

Thomas Lippert, Nikolay Petkov, Paolo Palazzari, Klaus Schilling

A novel parallel algorithm for matrix multiplication is presented. The hyper-systolic algorithm makes use of a one-dimensional processor abstraction. The procedure can be implemented on all types of parallel systems. It can handle matrix-vector multiplications as well as transposed matrix products.

Brett J. Vickers, Celio Albuquerque, Tatsuya Suda

Network architectures that can efficiently transport high quality, multicast video are rapidly becoming a basic requirement of emerging multimedia applications. The main problem complicating multicast video transport is variation in network bandwidth constraints. An attractive solution to this problem is to use an adaptive, multi-layered video encoding mecha

Madhav V. Marathe, R. Ravi, Ravi Sundaram, S. S. Ravi

We study a general class of bicriteria network design problems. A generic problem in this class is as follows: Given an undirected graph and two minimization objectives (under different cost functions), with a budget specified on the first, find a <subgraph \from a given subgraph-class that minimizes the second objective subject to the budget on the first. W

Jaihyung Cho, James Breen

In this paper, three new dynamic multicast routing algorithms based on the greedy tree technique are proposed; Source Optimised Tree, Topology Based Tree and Minimum Diameter Tree. A simulation analysis is presented showing various performance aspects of the algorithms, in which a comparison is made with the greedy and core based tree techniques. The effects

Jaihyung Cho, James Breen

In this paper, a new routing algorithm based on a flooding method is introduced. Flooding techniques have been used previously, e.g. for broadcasting the routing table in the ARPAnet [1] and other special purpose networks [3][4][5]. However, sending data using flooding can often saturate the network [2] and it is usually regarded as an inefficient broadcast

R. Jain

Explanation of ABR service in plain language.

R. Jain, D. Chiu, W. Hawe

Fairness is an important performance criterion in all resource allocation schemes, including those in distributed computer systems. However, it is often specified only qualitatively. The quantitative measures proposed in the literature are either too specific to a particular application, or suffer from some undesirable characteristics. In this paper, we have

R. Jain

In window flow controlled networks, if a packet is lost the destination has to decide whether to save (cache) subsequent out-of-order packets. Also, the source has to decide whether to send just one packet or to send all packets following it. This leads to four different types of caching schemes. Simulations show, against our immediate intuition, that regard

R. Jain

The problem of adaptively setting the timeout interval for retransmitting a packet has been discussed. A layered view of the algorithms has been presented. It is shown that a timeout algorithm consists of essentially five layers or procedures which can be independently chosen and modified. A number of timeout algorithms proposed in the literature have been d

R. Jain

During overload, most networks drop packets due to buffer unavailability. The resulting timeouts at the source provide an implicit mechanism to convey congestion signals from the network to the source. On a timeout, a source should not only retransmit the lost packet, but it should also reduce its load on the network. Based on this realization, we have devel

R. Jain, K. Ramakrishnan

Congestion is said to occur in the network when the resource demands exceed the capacity and packets are lost due to too much queuing in the network. During congestion, the network throughput may drop to zero and the path delay may become very high. A congestion control scheme helps the network to recover from the congestion state. A congestion avoidance sch

R. Jain, K. Ramakrishnan, D. Chiu

Widespread use of computer networks and the use of varied technology for the interconnection of computers has made congestion a significant problem. In this report, we summarize our research on congestion avoidance. We compare the concept of congestion avoidance with that of congestion control. Briefly, congestion control is a recovery mechanism, while conge

R. Jain

In heterogeneous networks, achieving congestion avoidance is difficult because the congestion feedback from one subnetwork may have no meaning to source on other other subnetworks. We propose using changes in round-trip delay as an implicit feedback. Using a black-box model of the network, we derive an expression for the optimal window as a function of the g

R. Jain

The size of computer networks, along with their bandwidths, is growing exponentially. To support these large, high-speed networks, it is neccessary to be able to forward packets in a few microseconds. One part of the forwarding operation consists of searching through a large address databse. This problem is encountered in the design of bridges, routers, gate

R. Jain

Popular myths that cheaper memory, high-speed links and high-speed processors will solve the problem of congestion in computer networks are shown to be false. A simple definition for congestion based on supply and demand of resources is proposed and is then used to classify various congestion schemes. The issues that make the congestion problem a difficult o

R. Jain

Fiber Distributed Data Interface (FDDI) is a 100 megabits per second fiber optic local area network (LAN) standard being developed by the American National Standard Institute (ANSI). We analyze the impact of various design decisions on the error detection capability of the protocol. In particular, we quantify frame error rate, token loss rate, and undetected

R. Jain

The performance of Fiber-Distributed Data Interface (FDDI) depends upon several workload parameters; for example; the arrival pattern, frame size, and configuration parameters, such as the number of stations on the ring, extent of the ring, and number of stations that are waiting to transmit. In addition, the performance is affected by a parameter called the

R. Jain

Weaknesses in several recently proposed ideas about congestion control and avoidance in high-speed netwroks are identified. Both sides of the debate concerning prior reservation of resources versus walk-in service, open-loop control versus feedback control, rate control versus window control, and router-based control versus source-based control are presented

R. Jain

Using a trace of address references, we compared the efficiency of several different hashing functions, such as cyclic redundancy checking (CRC) polynomials, Fletcher checksum, folding of address octets using the exclusive-or operation and bit extraction from the address. Guidelines are provided for determining the size of the hashmark required to achieve a

R. Jain

Key issues in upcoming FDDI standards including low-cost fiber, twisted-pair, SONET mapping, and FDDI follow-on LAN are discussed after a brief introduction to FDDI and FDDI-II

R. Jain

Congestion control mechanisms for ATM networks as selected by the ATM Forum traffic management group are described. Reasons behind these selections are explained. In particular, selection criteria for selection between rate-based and credit-based approach and the key points of the debate between the two approaches are presented. The approach that was finally

R. Jain

The paper begins with a discussion of current trends in networking and a historical reviews of past networking technologies some of which failed. This leads us to the discussion about what it takes for a new technology to succeed and what challenges we face in making the current dream of a seamless world-wide high-speed ATM network a reality. Issues in using

K. Siu, R. Jain

Asynchronous Transfer Mode (ATM) has emerged as the most promising technology in supporting future broadband multimedia communication services. To accelerate the deployment of ATM technology, the ATM Forum, which is a consortium of service providers and equipment vendors in the communication industries has been created to develop implementation and specifica

A. Charny, D. Clark, R. Jain

As the speed and the dynamic range of computer networks evolve, the issue of efficient traffic management becomes increasingly important. This work describes an approach to traffic management using explicit rate information provided to the source by the network. We present an asynchronous distributed algorithm for optimal rate calculation across the network,

Nina Amenta, Marshall Bern, David Eppstein

We study the problem of moving a vertex in an unstructured mesh of triangular, quadrilateral, or tetrahedral elements to optimize the shapes of adjacent elements. We show that many such problems can be solved in linear time using generalized linear programming. We also give efficient algorithms for some mesh smoothing problems that do not fit into the genera

Raj Jain, Shiv Kalyanaraman, Ram Viswanathan

An explicit rate indication scheme for congestion avoidance in computer and telecommunication networks is proposed. The sources monitor their load and provide the information periodically to the switches. The switches, in turn, compute the load level and ask the sources to adjust their rates up or down. The scheme achieves high link utilization, fair allocat

G. Dommety, Raj Jain

The main goal of this study was to survey current applications of GPS to distributed systems and networks. Detailed lists of GPS products, current applications, addresses of manufacturers, and sources for further information are included in this report.

Shiv Kalyanaraman, Raj Jain, Sonia Fahmy, Rohit Goyal

We study the buffering requirements for zero cell loss for TCP over ABR. We show that the maximum buffers required at the switch is proportional to the maximum round trip time (RTT) of all VCs through the link. The number of round-trips depends upon the the switch algorithm used. With our ERICA [erica-final] switch algorithm, we find that the buffering requi

Raj Jain, Shiv Kalyanaraman, Sonia Fahmy, Rohit Goyal

The Available Bit Rate (ABR) service has been developed to support data applications over Asynchronous Transfer Mode (ATM) networks. The network continuously monitors its traffic and provides feedback to the source end systems. This paper explains the rules that the sources have to follow to achieve a fair and efficient allocation of network resources.

Sonia Fahmy, Raj Jain, Fang Lu, Shivkumar Kalyanaraman

Satellite communication systems are the means of realizing a global broadband integrated services digital network. Due to the statistical nature of the integrated services traffic, the resulting rate fluctuations and burstiness render congestion control a complicated, yet indispensable function. The long propagation delay of the earth-satellite link further

Sonia Fahmy, Raj Jain, Shivkumar Kalyanaraman, Rohit Goyal

During the design of ABR traffic management at the ATM Forum, we performed several analyses to ensure that the ABR service will operate efficiently over satellite links. In the cases where the performance was unacceptable, we suggested modifications to the traffic management specifications. This paper describes one such issue related to the count of missing

Shiv Kalyanaraman, Raj Jain, Rohit Goyal, Sonia Fahmy

We study the buffering requirements for zero cell loss for TCP/IP over satellite links using the available bit rate (ABR) and unspecified bit rate (UBR) services of asynchronous transfer mode (ATM) networks. For the ABR service, we explore the effect of feedback delay (a factor which depends upon the position of the bottleneck), the switch scheme used, and b

Shiv Kalyanaraman, Raj Jain, Sonia Fahmy, Rohit Goyal

The Asynchronous Transfer Mode (ATM) networks are quickly being adopted as backbones over various parts of the Internet. This paper analyzes the performance of TCP/IP protocols over ATM network&#39;s Available Bit Rate (ABR) and Unspecified Bit Rate (UBR) services. It is shown that ABR pushes congestion to the edges of the ATM network while UBR leaves it ins

Shiv Kalyanaraman, Raj Jain, Sonia Fahmy, Rohit Goyal

We extend our earlier studies of buffer requirements of TCP over ABR in two directions. First, we study the performance of TCP over ABR in an ATM backbone. On the backbone, the TCP queues are at the edge router and not inside the ATM network. The router requires buffer equal to the sum of the receiver window sizes of the participating TCP connections. Second

Rohit Goyal, Raj Jain, Shiv Kalyanaraman, Sonia Fahmy

ATM-UBR switches respond to congestion by dropping cells when their buffers become full. TCP connections running over UBR experience low throughput and high unfairness. For 100% TCP throughput each switch needs buffers equal to the sum of the window sizes of all the TCP connections. Intelligent drop policies can improve the performance of TCP over UBR with l

Shivkumar Kalyanaraman, Raj Jain, Rohit Goyal, Sonia Fahmy

The Available Bit Rate (ABR) service has been developed to support 21st century data applications over Asynchronous Transfer Mode (ATM). The ABR service uses a closed-loop rate-based traffic management framework where the network divides left-over bandwidth among contending sources. The ATM Forum traffic management group also incorporated open-loop control c

Shiv Kalyanaraman, Raj Jain, Jianping Jiang, Rohit Goyal

The Available Bit Rate (ABR) service in ATM networks has been specified to allow fair and efficient support of data applications over ATM utilizing capacity left over after servicing higher priority classes. One of the architectural features in the ABR specification [tm4] is the Virtual Source/Virtual Destination (VS/VD) option. This option allows a switch t

Raj Jain, Gojko Babic

The testing group at ATM Forum is working on developing a specification for performance testing of ATM switches and networks. The emphasis is on the user perceived frame-level performance. This paper explains what is different about this new effort and gives its status.

Sonia Fahmy, Raj Jain, Shivkumar Kalyanaraman, Rohit Goyal

Asynchronous transfer mode (ATM) networks must define multicast capabilities in order to efficiently support numerous applications, such as video conferencing and distributed applications, in addition to LAN emulation (LANE) and Internet protocol (IP) multicasting. Several problems and issues arise in ATM multicasting, such as signaling, routing, connection

Rohit Goyal, Raj Jain, Shivkumar Kalyanaraman, Sonia Fahmy

We study the performance of Selective Acknowledgments with TCP over the ATM-UBR service category. We examine various UBR drop policies, TCP mechanisms and network configurations to recommend optimal parameters for TCP over UBR. We discuss various TCP congestion control mechanisms compare their performance for LAN and WAN networks. We describe the effect of s

Rita Maria Zorzenon dos Santos, Americo T. Bernardes

The immune system can be thought as a complex network of different interacting elements. A cellular automaton, defined in shape-space, was recently shown to exhibit self-regulation and complex behavior and is, therefore, a good candidate to model the immune system. Using this model to simulate a real immune system we find good agreement with recent experimen

A. Krämer, S. Doniach

Using path-integral Quantum Monte Carlo we study the low-temperature phase diagram of a two-dimensional superconductor within a phenomenological model, where vortices have a finite mass and move in a dissipative environment modeled by a Caldeira-Leggett term. The quantum vortex liquid at high magnetic fields exhibits superfluidity and thus corresponds to a {

Christian M. Dury, Gerald H. Ristow

We study the interface dynamics of a binary particle mixture in a rotating cylinder numerically. By considering only the particle motion in axial direction, it is shown that the initial dynamics can be well described by a one-dimensional diffusion process. This allows us to calculate a macroscopic diffusion constant and we study its dependence on the inter-p

C. Bennemann, J. Baschnagel, W. Paul

We present simulation results for a model polymer melt, consisting of short, nonentangled chains, in the supercooled state. The analysis focuses on the monomer dynamics, which is monitored by the incoherent intermediate scattering function. The scattering function is recorded over six decades in time and for many different wave-vectors. The lowest temperatur

Raffaella Burioni, Davide Cassi, Claudio Destri

Thirty years ago, Stanley showed that an O(n) spin model on a lattice tends to a spherical model as $n\to\infty$. This means that at any temperature the corresponding free energies coincide. This fundamental result, providing the basis for more detailed studies of continuous symmetry spin models, is no longer valid on more general discrete structures lacking

T. Hakioglu, M. Ye. Zhuravlev

The two-dimensional many-body Holstein-Hubbard model in the T=0 normal state is examined within the framework of the self-consistent coupling of charge fluctuation correlations to the vibrational ones. The parameters of our model are the adiabaticity, the electron concentration, as well as the electron-phonon and the Coulomb interaction strengths. A fluctuat

Paolo Butta`, Joel L. Lebowitz

We investigate the time evolution of a model system of interacting particles, moving in a $d$-dimensional torus. The microscopic dynamics are first order in time with velocities set equal to the negative gradient of a potential energy term $Ψ$ plus independent Brownian motions: $Ψ$ is the sum of pair potentials, $V(r)+γ^d J(γr)$, the second term has the form

Yadin Y. Goldschmidt

In this paper we consider directed walks on a tree with a fixed branching ratio K at a finite temperature T. We consider the case where each site (or link) is assigned a random energy uncorrelated in time, but correlated in the transverse direction i.e. within the shell. In this paper we take the transverse distance to be the hierarchical ultrametric distanc

Stephane Morel, Jean Schmittbuhl, Juan M. Lopez, Gerard Valentin

Scaling properties of wood fractured surfaces are obtained from samples of three different sizes. Two different woods are studied: Norway spruce and Maritime pine. Fracture surfaces are shown to display an anomalous dynamic scaling of the crack roughness. This anomalous scaling behavior involves the existence of two different and independent roughness expone

I. F. G. Parker, M. Endres, P. J. Thomas, G. Yang

Static and dynamic transport measurements on stacks of intrinsic Josephson junctions on Bi2Sr2CaCu2O8+delta single crystals, near to optimal doping, are presented. The zero bias minimum in dynamic conductance is consistent with a normal state pseudo-gap. At Tc, a critical current develops simultaneously with new features consistent with a gap in the supercon

P. Launois, R. Moret, E. Llusca, J. Hone

First single crystal X-ray diffraction studies of polymerized KC60 and RbC60 are presented. While powder diffraction studies showed no definite structural differences, the single crystal diffraction data analysis reveals different relative chain orientations in the two compounds. They are discussed in relation with semi-empirical energy calculations. The str

J. Talbot, G. Tarjus, P. Viot

We investigate, both analytically and by computer simulation, the kinetics of a microscopic model of hard rods adsorbing on a linear substrate. For a small, but finite desorption rate, the system reaches the equilibrium state very slowly, and the long-time kinetics display three successive regimes: an algebraic one where the density varies as $1/t$, a logari

P. Launois, R. Moret, J. Hone, A. Zettl

The KC60 and RbC60 polymer phases exhibit contrasting electronic properties while powder diffraction studies have revealed no definite structural difference. We have performed single crystal X-ray diffraction and diffuse scattering studies of these compounds. It is found that KC60 and RbC60 possess different chain orientations about their axes, which are des

Ikuo Ichinose, Masaomi Kimura

We study delocalization transition in a one-dimensional electron system with quenched disorder by using supersymmetric (SUSY) methods. Especially we focus on effects of nonlocal correlation of disorder, for most of studies given so far considered $δ$-function type white noise disorder. We obtain wave function of the &#34;lowest-energy&#34; state which domina

C. -H. Pao, H. -B. Schuttler

The fluctuation exchange (FLEX) approximation is applied to study the Holstein-Hubbard model. Due to the retarded nature of the phonon-mediated electron-electron interaction, neither fast Fourier transform (FFT) nor previously developed NRG methods for Hubbard-type purely electronic models are applicable, while brute force solutions are limited by the demand

Leonardo Testi, Anneila Sargent

We report the results of a millimeter interferometric survey of compact 3 mm continuum sources in the inner 5.5&#39;x5.5&#39; region of the Serpens core. We detect 32 discrete sources above 4.0 mJy/beam, 21 of which are new detections at millimeter wavelengths. By comparing our data with published infrared surveys, we estimate that 26 sources are probably pr

L. Miller, W. J. Percival

We provide a new multi-waveband compilation of the data describing the cosmological evolution of quasars, and discuss a model that attributes the evolution to variation in the rate of merging between dark halos in a hierarchical universe. We present a new Press-Schechter calculation of the expected merger rate and show that this can reproduce the principal f

R. V. E. Lovelace, H. Li, S. A. Colgate, A. F. Nelson

We find a linear instability of non-axisymmetric Rossby waves in a thin non-magnetized Keplerian disk when there is a local maximum in the radial profile of a key function ${\cal L}(r) \equiv {\cal F}(r) S^{2/Γ}(r)$, where ${\cal F}^{-1} = \hat {\bf z}\cdot ({\bf \nabla}\times {\bf v}) /Σ$ is the potential vorticity, $S = P/Σ^Γ$ is the entropy, $Σ$ is the su

Marc Kamionkowski

Much recent work on the cosmic microwave background (CMB) has focussed on the angular power spectrum of temperature anisotropies and particularly on the recovery of cosmological parameters from acoustic peaks in the power spectrum. However, there is more that can conceivably be done with CMB measurements. Here I briefly survey a few such ideas: cross-correla

Duncan Forbes, Trevor Ponman, Richard Brown

The fundamental plane (FP) has an intrinsic scatter that can not be explained purely by observational errors. Using recently available age estimates for nearby early type galaxies, we show that a galaxy&#39;s position relative to the FP depends on its age. In particular, the mean FP corresponds to ellipticals with an age of ~10 Gyr. Younger galaxies are syst

H. Krüger, E. Grün, D. P. Hamilton, M. Baguhl

Between Jan 1993 and Dec 1995 the Galileo spacecraft traversed interplanetary space between Earth and Jupiter and arrived at Jupiter on 7 Dec 1995. The dust instrument onboard was operating during most of the time. A relatively constant impact rate of interplanetary and interstellar (big) particles of 0.4 impacts per day was detected over the whole three-yea

S. B. Potter, Mark Cropper, Pasi Hakala

Modelling of the polarized cyclotron emission from magnetic cataclysmic variables (MCVs) has been a powerful technique for determining the structure of the accretion zones on the white dwarf. Until now, this has been achieved by constructing emission regions (for example arcs and spots) put in by hand, in order to recover the polarized emission. These models

Cynthia H. James, Graziella Branduardi-Raymont, Mark Cropper

The XMM satellite has a scientific payload of 3 EPIC and 2 RGS instruments which provide for both imaging and non-dispersive spectroscopy as well as medium-to-high resolution dispersive spectroscopy, in the soft to medium X-ray bands. The co-aligned OM adds the facility for simultaneous optical and UV studies. In this poster paper we describe the instrumenta

Matthew Holman, Paul Wiegert

A simple question of celestial mechanics is investigated: in what regions of phase space near a binary system can planets persist for long times? The planets are taken to be test particles moving in the field of an eccentric binary system. A range of values of the binary eccentricity and mass ratio is studied, and both the case of planets orbiting close to o

Gavin Ramsay, David Buckley, Mark Cropper, M Kate Harrop-Allin

Schwope et al (1997) suggested that the newly discovered Polar RX J2115-5840 is a near-synchronous system. We have obtained circular polarisation observations of RX J2115-5840 which show that the spin and orbital periods differ by 1.2%. We find the first direct evidence of `pole-switching&#39; in a near-synchronous Polar. Further our data requires that the a

Andrea Dieball, Eva K. Grebel

We studied in detail the binary cluster candidates SL 538 and NGC 2006 in the Large Magellanic Cloud (LMC). This cluster pair is located in the northwestern part of the large OB association LH 77 in supergiant shell LMC 4. A third star cluster, KMHK 1019, is located within 5&#39; from the cluster pair. Our study is the first age determination of SL 538 and N

R. Dominguez-Tenreiro, P. B. Tissera, A. Saiz

We report results on the formation of disk-like structures in two cosmological hydrodynamical simulations in a hierarchical clustering scenario, sharing the same initial conditions. In the first one, a simple and generic implementation of star formation has allowed galaxy-like objects with stellar bulges and extended, populated disks to form. Gas in the disk

Gavin Ramsay, Mark Cropper, Keith Mason, Pasi Hakala

Cropper et al 1998 presented X-ray observations of RX J1914+24 and claimed that the most likely interpretation of their data was that of a double degenerate Polar. Here we show the preliminary results of optical and further X-ray observations. We identify the optical counterpart and show that no other period apart from the 569 sec period seen in X-rays is id

Mark Cropper, Kinwah Wu, Gavin Ramsay

The post-shock flow in the accretion region of MCVs is considered to be a magnetically confined cooling flow. The X-ray spectrum from this hot plasma is emitted from a range of temperatures and densities. Extracting information from such spectra obtained with the next generation of X-ray satellites will rely on models for the structure of this flow which inc

Sarbani Basu, H. M. Antia, S. C. Tripathy

Ring diagram analysis of solar oscillation power spectra obtained from MDI data is carried out to study the velocity fields in the outer part of the solar convection zone. The three dimensional power spectra are fitted to a model which has a Lorentzian profile in frequency and which includes the advection of the wave front by horizontal flows, to obtain the

A. J. Lawson, I. M. McHardy

We present the results of a three-week daily monitoring campaign on the quasar 3C 279 by the X-ray satellites RXTE and ROSAT. A cross correlation provides no evidence for any time lag between the very similar soft and hard X-ray light curves, and the source shows no significant spectral variability over the observing period. There is no evidence to support t

G. H. Tovmassian, P. Szkody, J. Greiner, S. Vrielmann

We present phase-resolved spectral and multicolor CCD-photometric observations of the eclipsing polar RX J0719.2+6557 obtained with relatively high time (~600 sec/15 sec) and spectral (2.1 A) resolution when the system was in a high accretion state. The trailed spectrograms clearly reveal the presence of three different line components with different width a

G. G. Pooley, R. P. Fender, C. Brocksopp

20 months of observations of the radio emission at 15 GHz from Cygnus X-1, starting in 1996 October, show variations at the binary period of 5.6 days, but with a phase offset from those at X-ray wavelengths. There are also longer-term variations on a time-scale of 150 days which are only loosely related to the soft X-ray flux. The source was in the hard/low

Noah Brosch, Michael Shara, John MacKenty, David Zurek

We present an analysis of the deepest pure-UV observations with the highest angular resolution ever performed, a set of 12 exposures with the HST WFPC2 and F160BW filter obtained in parallel observing mode, which cover $\sim$12 square arcminutes in the LMC, North of the bar and in the ``general field&#39;&#39; regime of the LMC. The 341 independent measureme

Michael G. Richer, Grazyna Stasinska, Marshall L. McCall

We present spectroscopy of planetary nebulae in M32 and in the bulge of M31 that we obtained with the MOS spectrograph at the Canada-France-Hawaii Telescope. Our sample includes 30 planetary nebulae in M31 and 9 planetary nebulae in M32. We also observed one H II region in the disk of M31. We detected [O III]$λ$4363 in 18 of the planetary nebulae, 4 in M32 a

Michael G. Richer, Marshall L. McCall, Grazyna Stasinska

We investigate the chemical properties of M32, the bulges of M31 and the Milky Way, and the dwarf spheroidal galaxies NGC 205, NGC 185, Sagittarius, and Fornax using previously published oxygen abundances for their planetary nebulae. Our principal result is that the mean stellar oxygen abundances for all of these galaxies correlate very well with their mean

J. E. J. Lovell, D. L. Jauncey, J. E. Reynolds, M. H. Wieringa

We have measured a time delay of 26 (+4/-5) days and a magnification ratio of 1.52 +/- 0.05 in the strong radio gravitational lens PKS 1830-211. The observations were made over the 18 month period from 1997 January to 1998 July with the Australia Telescope Compact Array at 8.6 GHz, and have shown that the source started a large flux density outburst around 1

A. J. Barger, L. L. Cowie, N. Trentham, E. Fulton

We present the results of an HK&#39; wide-field survey encompassing the Hubble Deep Field and its Flanking Fields. Our wide-field survey provides uniform coverage of an area 61.8 square arcmin to a depth equivalent to K=20.1 at 5-sigma. We have also imaged the Hubble Deep Field in HK&#39;, providing uniform coverage of an area 7.8 square arcmin to a depth eq

H. -W. Chen, K. M. Lanzetta, J. K. Webb, X. Barcons

We present results of an ongoing program to study the gaseous extent of galaxies and the origin of QSO absorption line systems. For \lya absorption systems, we find that absorption equivalent width depends strongly on galaxy impact parameter and galaxy $B$-band luminosity, and that the gaseous extent of individual galaxies scales with galaxy $B$-band luminos

Noriaki Yahata, Kenneth M. Lanzetta, John K. Webb, Xavier Barcons

We present new statistical study on the origin of Lyman-alpha absorption systems that are detected in QSO fields. The primary objective is to investigate environmental dependence of the relationship between galaxies and Lyman-alpha absorption systems. We find that galaxies exhibit no environmental dependence in giving rise to Lyman-alpha absorbers in their h

S. M. Pascarelle, K. M. Lanzetta, A. Fernandez-Soto

Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star-formation rate density, of the Universe at redshifts 1<z<2. We use photometric redshifts of galaxies in the HDF to determine the comoving UV luminosity density and find that, when errors (in particula

Kenneth M. Lanzetta, Hsiao-Wen Chen, Sebastian Pascarelle, Noriaki Yahata

Here we describe our attempts to establish statistically complete samples of very high redshift galaxies by obtaining photometric redshifts of galaxies in Medium Deep Survey (MDS) fields and photometric and spectroscopic redshifts of galaxies in very deep STIS slitless spectroscopy fields. On the basis of this analysis, we have identified galaxies of redshif

Tyler J. Jarvis

This article treats various aspects of the geometry of the moduli of r-spin curves and its compactification. Generalized spin curves, or r-spin curves, are a natural generalization of 2-spin curves (algebraic curves with a theta-characteristic), and have been of interest lately because of the similarities between the intersection theory of these moduli space

F. Finelli, R. Brandenberger

We demonstrate that cosmological perturbations can undergo amplification by parametric resonance during the preheating period following inflation, even on scales larger than the Hubble radius, without violating causality. A unified description of gravitational and matter fluctuations is crucial in order to determine the strength of the instability. To extrac

James M. Gelb, S. P. Rosen

We take another look at ``Just-So'' solar neutrino oscillations, characterizing them by the energy $E_{\pi/2}$ at which the distance-varying angle is $\pi/2$, instead of the usual $\Delta m^2$. The rising spectrum recently observed by SuperKamiokande is consistent with $E_{\pi/2}\sim$ 6-9 MeV and marginally with 48 MeV. The pp neutrinos must then be reduced

Zahid Zakir

An instantaneous temperature path of a point particle in the space - temperature manifold can be represented as a string of length L=1/kT (thermostring). The thermostring swepts a surface in the space-time-temperature manyfold at its temporal evolution. The thermostring is closed, its points can be rearranged and the charge is distributed along the length. S

G. Conforto, M. Barone, C. Grimani

The LSND result is shown to fit into a minimal three-flavour neutrino-mixing scenario capable of describing all known experimental facts provided the large Delta M^2 = m_3^2 - m_2^2 \sim m_3^2 - m_1^2 lies in the range 2.5 x 10^{-1} < Delta M^2 < 3.0 eV^2. In this range the value of P_{μτ} is expected to be about 5% or larger.

Stephan J. Huber, Michael G. Schmidt

The MSSM with a light right-handed stop and supersymmetric models with a singlet whose vev is comparable to that of the SU(2)_W Higgs allow for a strongly first-order electroweak phase transition even for a mass of the lightest Higgs around 100 GeV. After a short review of the standard model situation we discuss these supersymmetric models. We also compare p

Ara Ioannisian, Apostolos Pilaftsis

We study neutrino oscillations in space within a realistic model in which both the source and the target are considered to be stationary having Gaussian-form localizations. The model admits an exact analytic solution in field theory which may be expressed in terms of complementary error functions, thereby allowing for a quantitative discussion of quantum-mec

Steven Abel, Carlos Savoy

We examine charge/colour breaking along directions in supersymmetric field space which are F and D-flat. We catalogue the dangerous directions and include some new ones which have not previously been considered. Analytic expressions for the resulting constraints are provided which are valid for all patterns of supersymmetry breaking. As an example we conside

S. Sen, N. Banerjee

In this work we check the validity of the no scalar hair theorem in charged axisymmetric stationary black holes for a wide class of scalar tensor theories.

Zhi-zhong Xing

We show that the CP-violating phases βand β&#39; can respectively be determined from the time-dependent measurements of B_d \to D^*\pmD^\mp and B_s \to D^*\pm_sD^\mp_s decays, whose final states are non-CP eigenstates. The penguin contributions to the mixing-induced interference quantities are expected to be about 4% or smaller. We also point out two observa

A. Ino, C. Kim, T. Mizokawa, Z. -X. Shen

Using angle-resolved photoemission spectroscopy (ARPES), we have observed the band structure, Fermi surface and their doping dependences in La2-xSrxCuO4. The results reveal that the Fermi surface undergoes a dramatic change: it is hole-like and centered at k=(pi,pi) in underdoped (x = 0.1) and optimally doped (x = 0.15) samples as in other cuprates while it

Gautam Bhattacharyya, Palash B. Pal

In an R-parity-violating supersymmetric theory, we derive upper bounds on all the λ&#39;&#39;_{ijk}λ_{i&#39;j&#39;k&#39;}-type combinations from the consideration of proton stability, where λ&#39;&#39;_{ijk} are baryon-number-violating couplings involving three baryonic fields and λ_{i&#39;j&#39;k&#39;} are lepton-number-violating couplings involving three l

J. S. Penttila, U. Parts, P. J. Hakonen, M. A. Paalanen

VI-curves of resistively shunted single Josephson junctions with different capacitances and tunneling resistances are found to display a crossover between two types of VI-curves: one without and another with a resistance bump (negative second derivative) at zero-bias. The crossover corresponds to the dissipative phase transition (superconductor-insulator tra

C. W. Kim, U. W. Lee

We investigate the implications of a possible excess of the electron neutrino events in the Super-Kamiokande atmospheric neutrino experiment. The excess, if real, leads to constraints on the $ν_μ\leftrightarrow ν_e$, $ν_μ\leftrightarrow ν_τ$ and $ν_e \leftrightarrow ν_τ$ oscillation parameters. Specifically, the excess impies that $ν_e - ν_μ$ and $ν_μ- ν_τ$

M. D. Lukin, S. F. Yelin, M. Fleischhauer, M. O. Scully

We predict the possibility of sharp, high-contrast resonances in the optical response of a broad class of systems, wherein interference effects are generated by coherent perturbation or interaction of dark states. The properties of these resonances can be manipulated to design a desired atomic response.

R. S. Ward

This paper studies the structure of Lax pairs associated with integrable lattice systems (where space is a one-dimensional lattice, and time is continuous). It describes a procedure for generating examples of such systems, and emphasizes the features that are needed to obtain equations which are local on the spatial lattice.