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Physical Sciences and Mathematics Commons™

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1998

Dartmouth College

Articles 1 - 30 of 40

Full-Text Articles in Physical Sciences and Mathematics

Gravitational Waves From Collapsing Vacuum Domains, Marcelo Gleiser, Ronald Roberts Dec 1998

Gravitational Waves From Collapsing Vacuum Domains, Marcelo Gleiser, Ronald Roberts

Dartmouth Scholarship

The breaking of an approximate discrete symmetry, the final stages of a first order phase transition, or a postinflationary biased probability distribution for scalar fields are possible cosmological scenarios characterized by the presence of unstable domain wall networks. Combining analytical and numerical techniques, we show that the nonspherical collapse of these domains can be a powerful source of gravitational waves. We compute their contribution to the stochastic background of gravitational radiation and explore their observability by present and future gravitational wave detectors.

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Hey, You Got Your Language In My Operating System!, Jon Howell, Mark Montague Dec 1998

Hey, You Got Your Language In My Operating System!, Jon Howell, Mark Montague

Computer Science Technical Reports

Several projects in the operating systems research community suggest a trend of convergence among features once divided between operating systems and languages. We describe how partial evaluation and transformational programming systems apply to this trend by providing a general framework for application support, from compilation to run-time services. We contend that the community will no longer think of implementing a static collection of services and calling it an operating system; instead, this general framework will allow applications to be flexibly configured, and the ``operating system'' will simply be the application support that is supplied at run-time.

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Snowflake: Spanning Administrative Domains, Jon Howell, David Kotz Dec 1998

Snowflake: Spanning Administrative Domains, Jon Howell, David Kotz

Computer Science Technical Reports

Many distributed systems provide a ``single-system image'' to their users, so the user has the illusion that they are using a single system when in fact they are using many distributed resources. It is a powerful abstraction that helps users to manage the complexity of using distributed resources. The goal of the Snowflake project is to discover how single-system images can be made to span administrative domains. Our current prototype organizes resources in namespaces and distributes them using Java Remote Method Invocation. Challenging issues include how much flexibility should be built into the namespace interface, and how transparent the network …

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The Motions Of Clusters Of Galaxies And The Dipoles Of The Peculiar Velocity Field, Riccardo Giovanelli, Martha P. Haynes, John J. Salzer, Gary Wegner Dec 1998

The Motions Of Clusters Of Galaxies And The Dipoles Of The Peculiar Velocity Field, Riccardo Giovanelli, Martha P. Haynes, John J. Salzer, Gary Wegner

Dartmouth Scholarship

In preceding papers of this series, TF relations for galaxies in 24 clusters with radial velocities between 1000 and 9200 km s-1 (SCI sample) were obtained, a Tully-Fisher (TF) template relation was constructed, and mean offsets of each cluster with respect to the template were obtained. Here, an estimate of the line-of-sight peculiar velocities of the clusters and their associated errors are given. It is found that cluster peculiar velocities in the cosmic microwave background reference frame do not exceed 600 km s-1 and that their distribution has a line-of-sight dispersion of 300 km s-1, suggesting …

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Cluster Versus Field Elliptical Galaxies And Clues On Their Formation, Mariangela Bernardi, Alvio Renzini, Luiz N. Da Costa, Gary Wegner Dec 1998

Cluster Versus Field Elliptical Galaxies And Clues On Their Formation, Mariangela Bernardi, Alvio Renzini, Luiz N. Da Costa, Gary Wegner

Dartmouth Scholarship

Using new observations for a sample of 931 early-type galaxies, we investigate whether the Mg2-σ0 relation shows any dependence on the local environment. The galaxies have been assigned to three different environments depending on the local overdensity (clusters, groups, and field); we used our complete redshift database to guide the assignment of galaxies. It is found that cluster, group, and field early-type galaxies follow almost identical Mg2-σ0 relations, with the largest Mg2 zero-point difference (clusters minus field) being only 0.007±0.002 mag. No correlation of the residuals is found with the morphological type or …

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Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos Nov 1998

Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective evolution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdamped regime, the dissipative kernel in the field equation of motion is closely related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a time-dependent Ginzburg-Landau description of the approach to equilibrium …

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Flows On Scales Of 150 Mpc?, K. R. Müller, W. Freudling, R. Watkins, G. Wegner Nov 1998

Flows On Scales Of 150 Mpc?, K. R. Müller, W. Freudling, R. Watkins, G. Wegner

Dartmouth Scholarship

In order to investigate the reality of large-scale streaming motion on scales of up to 150 Mpc, we have studied the peculiar motions of ~200 early-type galaxies in three directions of the South Equatorial Strip at distances out to ~20,000 km s-1. The new Automatic Plate Measuring Facility South Equatorial Strip Catalog (-175<δ<+25) was used to select the sample of field galaxies in three directions: (1) 15h10m-16h10m; (2) 20h30m-21h50m; (3) 00h10m-01h30m. New R-band CCD photometry and spectroscopic data for the galaxies are used. The fundamental plane distance-indicator …

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A Photometric And Kinematic Study Of Awm 7, Daniel M. Koranyi, Margaret Geller, Joseph J. Mohr, Gary Wegner Nov 1998

A Photometric And Kinematic Study Of Awm 7, Daniel M. Koranyi, Margaret Geller, Joseph J. Mohr, Gary Wegner

Dartmouth Scholarship

We have measured redshifts and Kron-Cousins R-band magnitudes for a sample of galaxies in the poor cluster AWM 7. We have measured redshifts for 172 galaxies; 106 of these are cluster members. We determine the luminosity function (LF) from a photometric survey of the central 1.2 × 1.2 h-1 Mpc. The LF has a bump at the bright end and a faint-end slope of α = -1.37 ± 0.16, populated almost exclusively by absorption-line galaxies. The cluster velocity dispersion is lower in the core (~530 km s-1) than at the outskirts (~680 km s-1), …

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Utility Driven Mobile-Agent Scheduling, Jonathan Bredin, David Kotz, Daniela Rus Oct 1998

Utility Driven Mobile-Agent Scheduling, Jonathan Bredin, David Kotz, Daniela Rus

Computer Science Technical Reports

Mobile agents are programs capable of migrating from one host machine to another. We propose that mobile agents purchase resource access rights from host machines thereby establishing a market for computational resources and giving agents a metric to evenly distribute themselves throughout the network. Market participation requires quantitative information about resource consumption to define demand and calculate utility. We create a formal utility model to derive user-demand functions, allowing agents to efficiently plan expenditure and deal with price fluctuations. By quantifying demand and utility, resource owners can precisely set a value for a good. We simulate our model in a …

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Abstractions For Simplifying Planning In Self-Reconfigurable Robotic Systems, Craig Mcgray, Daniela Rus Oct 1998

Abstractions For Simplifying Planning In Self-Reconfigurable Robotic Systems, Craig Mcgray, Daniela Rus

Computer Science Technical Reports

In [KVRM], we described a three-dimensional self-reconfiguring robot module called the Molecule Robot. In this paper, we provide a system of abstractions for modules in self-reconfigurable robotic systems, and show how this system can be used to simplify the motion planning of the Molecule Robot system.

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Hubble Space Telescope Images And Spectra Of The Remnant Of Sn 1885 In M31, Robert A. Fesen, Christopher L. Gerardy, Kevin M. Mclin, Andrew J. S. Hamilton Oct 1998

Hubble Space Telescope Images And Spectra Of The Remnant Of Sn 1885 In M31, Robert A. Fesen, Christopher L. Gerardy, Kevin M. Mclin, Andrew J. S. Hamilton

Dartmouth Scholarship

Near-UV Hubble Space Telescope images of the remnant of SN 1885 (S And) in M31 show a 070±005 diameter absorption disk silhouetted against M31's central bulge, at SN 1885's historically reported position. The disk's size corresponds to a linear diameter of 2.5±0.4 pc at a distance of 725±70 kpc, implying an average expansion velocity of 11,000±2000 km s-1 over 110 yr. Low-dispersion Faint Object Spectrograph spectra over 3200-4800 Å reveal that the absorption arises principally from Ca II H and K (equivalent width 215 Å), with weaker absorption features of Ca I 4227 Å and Fe I 3720 Å. The …

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Peculiar Velocity Dipoles Of Field Galaxies, Riccardo Giovanelli, Martha P. Haynes, Wolfram Freudling, Luiz N. Da Costa, John J. Salzer, Gary Wegner Oct 1998

Peculiar Velocity Dipoles Of Field Galaxies, Riccardo Giovanelli, Martha P. Haynes, Wolfram Freudling, Luiz N. Da Costa, John J. Salzer, Gary Wegner

Dartmouth Scholarship

The Tully-Fisher (TF) relation is applied to obtain peculiar velocities of field spiral galaxies and to calculate dipoles of the peculiar velocity field to cz8000 km s-1. The field galaxy sample is spatially coextensive with and completely independent of a cluster sample, for which dipole characteristics are given in a separate paper. Dipoles of the peculiar velocity field are obtained separately by applying (1) an inverse version of the TF relation and selecting galaxies by redshift windowing and (2) a direct TF relation, with velocities corrected for the inhomogeneous Malmquist bias and windowing galaxies by TF distance. …

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Comparison Of The Sfi Peculiar Velocities With The Iras 1.2-Jy Gravity Field, L. N. Da Costa, A. Nusser, W. Freudling, R. Giovanelli, M. P. Haynes, J J. Salzer, G. Wegner Sep 1998

Comparison Of The Sfi Peculiar Velocities With The Iras 1.2-Jy Gravity Field, L. N. Da Costa, A. Nusser, W. Freudling, R. Giovanelli, M. P. Haynes, J J. Salzer, G. Wegner

Dartmouth Scholarship

We present a comparison between the peculiar velocity fields measured from a recently completed I-band Tully-Fisher survey of field spirals (SFI) and that derived from the IRAS 1.2-Jy redshift survey galaxy distribution. The analysis is based on the expansion of these data in redshift space using smooth orthonormal functions, and is performed using low- and high-resolution expansions, with an effective smoothing scale which increases almost linearly with redshift. The effective smoothing scales at 3000 km s−1 are 1500 and 1000 km s−1 for the low- and high-resolution filters. The agreement between the high- and low-resolution SFI velocity …

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Applications Of Parallel I/O, Ron Oldfield, David Kotz Aug 1998

Applications Of Parallel I/O, Ron Oldfield, David Kotz

Computer Science Technical Reports

Scientific applications are increasingly being implemented on massively parallel supercomputers. Many of these applications have intense I/O demands, as well as massive computational requirements. This paper is essentially an annotated bibliography of papers and other sources of information about scientific applications using parallel I/O. It will be updated periodically.

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Hot White Dwarfs In The Extreme ‐ Ultraviolet Explorer Survey. Iv. Da White Dwarfs With Bright Companions, Stephane Vennes, Damian J. Christian, John R. Thorstensen Aug 1998

Hot White Dwarfs In The Extreme ‐ Ultraviolet Explorer Survey. Iv. Da White Dwarfs With Bright Companions, Stephane Vennes, Damian J. Christian, John R. Thorstensen

Dartmouth Scholarship

We present an analysis of optical, ultraviolet, and X-ray spectral properties of a sample of 13 hot hydrogen-rich (DA) white dwarfs, each paired with a luminous unresolved companion. Using low-dispersion International Ultraviolet Explorer spectra, ROSAT photometry, and Extreme-Ultraviolet Explorer photometry and spectroscopy, we estimate the effective temperature, mass, and distance of the white dwarfs. Additionally, we examine the question of their atmospheric composition. We establish orbital properties for most binaries by means of high-dispersion optical spectroscopy obtained with the Hamilton echelle spectrograph at Lick Observatory; the same data help uncover evidence of activity in some of the secondary …

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Multiple Media Correlation: Theory And Applications, Charles B. Owen Jun 1998

Multiple Media Correlation: Theory And Applications, Charles B. Owen

Dartmouth College Ph.D Dissertations

This thesis introduces multiple media correlation, a new technology for the automatic alignment of multiple media objects such as text, audio, and video. This research began with the question: what can be learned when multiple multimedia components are analyzed simultaneously? Most ongoing research in computational multimedia has focused on queries, indexing, and retrieval within a single media type. Video is compressed and searched independently of audio, text is indexed without regard to temporal relationships it may have to other media data. Multiple media correlation provides a framework for locating and exploiting correlations between multiple, potentially heterogeneous, media streams. The goal …

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Multiscouting: Guiding Distributed Manipulation With Multiple Mobile Sensors, Michael G. Ross Jun 1998

Multiscouting: Guiding Distributed Manipulation With Multiple Mobile Sensors, Michael G. Ross

Dartmouth College Undergraduate Theses

This thesis investigates the use of multiple mobile sensors to guide the motion of a distributed manipulation system. In our system, multiple robots cooperatively place a large object at a goal in a dynamic, unstructured, unmapped environment. We take the system developed in [Rus, Kabir, Kotay, Soutter 1996], which employs a single mobile sensor for navigational tasks, and extend it to allow the use of multiple mobile sensors. This allows the system to perform successful manipulations in a larger class of spaces than was possible in the single scout model. We focus on the development of a negotiation protocol that …

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Distributed Route Planning Using Partial Map Building, Christine J. Alvarado Jun 1998

Distributed Route Planning Using Partial Map Building, Christine J. Alvarado

Dartmouth College Undergraduate Theses

Our goal is to manipulate and guide an object across an unknown environment toward a goal in a known location in space. Our tools include a system of manipulation robots, which are "blind" and one mobile scout robot who relies on a series of sonar sensors for information about the environment. Previous solutions to this problem have taken a simultaneous guiding and manipulating approach, moving the whole system under the scout's guidance. My approach, however, presents a separate scouting algorithm that can return a series of coordinates through which the manipulation system can safely pass to reach the goal in …

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Boosting A Simple Weak Learner For Classifying Handwritten Digits, Matthew P. Carter Jun 1998

Boosting A Simple Weak Learner For Classifying Handwritten Digits, Matthew P. Carter

Dartmouth College Undergraduate Theses

A weak PAC learner is one which takes labeled training examples and produces a classifier which can label test examples more accurately than random guessing. A strong learner (also known as a PAC learner), on the other hand, is one which takes labeled training examples and produces a classifier which can label test examples arbitrarily accurately. Schapire has constructively proved that a strong PAC learner can be derived from a weak PAC learner. A performance boosting algorithm takes a set of training examples and a weak PAC learning algorithm and generates a strong PAC learner. Our research attempts to solve …

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The Effects Of Singular Value Decomposition On Collaborative Filtering, Michael H. Pryor Jun 1998

The Effects Of Singular Value Decomposition On Collaborative Filtering, Michael H. Pryor

Dartmouth College Undergraduate Theses

As the information on the web increases exponentially, so do the efforts to automatically filter out useless content and to search for interesting content. Through both explicit and implicit actions, users define where their interests lie. Recent efforts have tried to group similar users together in order to better use this data to provide the best overall filtering capabilities to everyone. This thesis discusses ways in which linear algebra, specifically the singular value decomposition, can be used to augment these filtering capabilities to provide better user feedback. The goal is to modify the way users are compared with one another, …

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Avoiding Conflicts Dynamically In Direct Mapped Caches With Minimal Hardware Support, Peter N. Desantis Jun 1998

Avoiding Conflicts Dynamically In Direct Mapped Caches With Minimal Hardware Support, Peter N. Desantis

Dartmouth College Undergraduate Theses

The memory system is often the weakest link in the performance of today's computers. Cache design has received increasing attention in recent years as increases in CPU performance continues to outpace decreases in memory latency. Bershad et al. proposed a hardware modification called the Cache Miss Lookaside buffer which attempts to dynamically identify data which is conflicting in the cache and remap pages to avoid future conflicts. In a follow-up paper, Bershad et al. tried to modify this idea to work with standard hardware but had less success than with their dedicated hardware. In this thesis, we focus on a …

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An Implementation Of External-Memory Depth-First Search, Christopher S. Leon Jun 1998

An Implementation Of External-Memory Depth-First Search, Christopher S. Leon

Dartmouth College Undergraduate Theses

In many different areas of computing, problems can arise which are too large to fit in main memory. For these problems, the I/O cost of moving data between main memory and secondary storage (for example, disks) becomes a significant bottleneck affecting the performance of the program. Since most algorithms do not take into account the size of main memory, new algorithms have been developed to optimize the number of I/O's performed. This paper details the implementation of one such algorithm, for external-memory depth-first search. Depth-first search is a basic tool for solving many problems in graph theory, and since graph …

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A V And I Ccd Mosaic Survey Of The Ursa Minor Dwarf Spheroidal Galaxy, J. T. Kleyna, M. J. Geller, S. J. Kenyon, M. J. Kurtz, J. R. Thorstensen Jun 1998

A V And I Ccd Mosaic Survey Of The Ursa Minor Dwarf Spheroidal Galaxy, J. T. Kleyna, M. J. Geller, S. J. Kenyon, M. J. Kurtz, J. R. Thorstensen

Dartmouth Scholarship

We discuss a Johnson-Cousins V- and I-band CCD mosaic survey of the Ursa Minor dwarf spheroidal galaxy (dSph) to V ~ 22. We covered UMi with 27 105 × 105 overlapping CCD frames, each frame consisting of two 300 s exposures in each of V and I. We also observed several regions ~3° from UMi to obtain an estimate of contamination by galaxies and Galactic stars. We report the first H-R diagram of an entire dSph. Separation of dwarf stars from foreground stars by color allows a robust estimation of the structural parameters of UMi. We examine …

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A Basis Theorem For Perfect Sets, Marcia J. Groszek, Theodore A. Slaman Jun 1998

A Basis Theorem For Perfect Sets, Marcia J. Groszek, Theodore A. Slaman

Dartmouth Scholarship

We show that if there is a nonconstructible real, then every perfect set has a nonconstructible element, answering a question of K. Prikry. This is a specific instance of a more general theorem giving a sufficient condition on a pair M ⊂ N of models of set theory implying that every perfect set in N has an element in N which is not in M.

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Aquila X-1: A Low-Inclination Soft X-Ray Transient, T. Shahbaz, J. R. Thorstensen, P. A. Charles, N. D. Sherman Jun 1998

Aquila X-1: A Low-Inclination Soft X-Ray Transient, T. Shahbaz, J. R. Thorstensen, P. A. Charles, N. D. Sherman

Dartmouth Scholarship

We have obtained I-band photometry of the neutron star X-ray transient Aql X-1 during quiescence. We find a periodicity at 2.487 cycles d−1, which we interpret as twice the orbital frequency (19.30±0.05 h). Folding the data on the orbital period, we model the light-curve variations as the ellipsoidal modulation of the secondary star. We determine the binary inclination to be 20°–30° (90 per cent confidence) and also determine the 95 per cent upper limits to the radial velocity semi-amplitude and rotational broadening of the secondary star to be 117 and 50 km s−1, respectively.

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C Compiler Targeting The Java Virtual Machine, Jack Pien May 1998

C Compiler Targeting The Java Virtual Machine, Jack Pien

Dartmouth College Undergraduate Theses

One of the major drawbacks in the field of computer software development has been the inability for applications to compile once and execute across many different platforms. With the emergence of the Internet and the networking of many different platforms, the Java programming language and the Java Platform was created by Sun Microsystems to address this "Write Once, Run Anywhere" problem. What sets a compiled Java program apart from programs compiled from other high level languages is the ability of a Java Virtual Machine to execute the compiled Java program on any platform, as long as the Java Virtual Machine …

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Straightforward Java Persistence Through Checkpointing, Jon Howell May 1998

Straightforward Java Persistence Through Checkpointing, Jon Howell

Computer Science Technical Reports

Several techniques have been proposed for adding persistence to the Java language environment. This paper describes a scheme based on checkpointing the Java Virtual Machine, and compares the scheme to other techniques. Checkpointing offers two unique advantages: first, the implementation is independent of the JVM implementation, and therefore survives JVM updates; second, because checkpointing saves and restores execution state, even threads become persistent entities.

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An Implementation Of The Vesta Parallel File System Api On The Galley Parallel File System, Matthew P. Carter, David Kotz Apr 1998

An Implementation Of The Vesta Parallel File System Api On The Galley Parallel File System, Matthew P. Carter, David Kotz

Computer Science Technical Reports

To demonstrate the flexibility of the Galley parallel file system and to analyze the efficiency and flexibility of the Vesta parallel file system interface, we implemented Vesta's application-programming interface on top of Galley. We implemented the Vesta interface using Galley's file-access methods, whose design arose from extensive testing and characterization of the I/O requirements of scientific applications for high-performance multiprocessors. We used a parallel CPU, parallel I/O, out-of-core matrix-multiplication application to test the Vesta interface in both its ability to specify data access patterns and in its run-time efficiency. In spite of its powerful ability to specify the distribution of …

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Pg 1002+506: A Be Star Apparently At Z > +10 Kiloparsecs, F. A. Ringwald, W. R. J. Rolleston, R. A. Saffer, John R. Thorstensen Apr 1998

Pg 1002+506: A Be Star Apparently At Z > +10 Kiloparsecs, F. A. Ringwald, W. R. J. Rolleston, R. A. Saffer, John R. Thorstensen

Dartmouth Scholarship

PG 1002+506 is found to be a Be star, one of three found so far by the Palomar-Green survey. Its spectrum is classified as a B5 ± 1 Ve, with Teff = 14,900 ± 1200, log g = 4.2 ± 0.2, and v sin i = 340 ± 50 km s-1. At b = +51°, its height above the Galactic plane would therefore be z = +10.8 kpc, putting this apparently young, rapidly rotating star well into the Galactic halo. Its heliocentric radial velocity is found to be -2 ± 15 km s-1, consistent with …

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Semilocal String Formation In Two Dimensions, Ana Achúcarro, Julian Borrill, Andrew R. Liddle Mar 1998

Semilocal String Formation In Two Dimensions, Ana Achúcarro, Julian Borrill, Andrew R. Liddle

Dartmouth Scholarship

We present a toy model for the investigation of the formation of semilocal strings, where a planar symmetry is employed to reduce the system to two dimensions. We approximate the symmetry breaking using an extension of the Vachaspati-Vilenkin algorithm, where we throw down random phases for the scalar fields and then find the gauge field configuration which minimizes gradient energy in this fixed scalar background. We show this procedure reproduces the standard estimate for the formation rate of cosmic strings. For semilocal strings the configurations generated by this method are ambiguous, and we numerically evolve the configurations forward in time …

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