Cosmology, Relativity, and Gravity Commons^™

Sensitivity Curves For Spaceborne Gravitational Wave Interferometers, Shane L. Larson, William A. Hiscock, Ronald W. Hellings

All Physics Faculty Publications

To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic …

Superstring Cosmology: An Investigation Into Low Temperature Effective Gauss-Bonnet Corrections To The Einstein Field Equations In An Inflationary Scenario, David Dressel

Masters Theses

Several problems with the inflationary cosmological model and the force coupling constants are addressed in the context of superstring theory. In order to simplify the field equations slightly, vacuum solutions are attempted. The solutions for several field equations are analyzed in order to obtain an inflationary universe that leads to a nearly static internal space. A solution is found when Gauss-Bonnet terms, as well as the Einstein terms, are used in the field equations, along with an exponential radii function for a ten dimensional product space. The solutions lead to a three-phase universe that might describe our very early universe. …

Characterization Of Cosmic Microwave Background Temperature Fluctuations For Cosmological Topologies Specified By Topological Betti Numbers, Troy Gobble

Masters Theses

The cosmic microwave background explorer, COBE, and the Balloon Observations of Millimetric Extragalactic Radiation and Geophysics, BOOMERanG, have collected data from the universe and detected relic anisotropies indicative of one of the earliest events of the universe, decoupling. Hidden in the correlation between these temperature fluctuations is the signature of the global shape, or topology, of the early universe. It is possible to calculate the temperature fluctuations as due to primeval adiabatic density temperature fluctuations from the Sachs-Wolfe effect, which contains a topological term. Here we investigate some of the spaces and how they affect the microwave background.

A large …

Book Review: The Birth Of Time: How Astronomers Measured The Age Of The Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Birth of Time : How Astronomers Measured the Age of the Universe by John Gribbin. Yale, 2000 237p, 0-300-08346-7 $22.50.

Peculiar Velocities Of Nonlinear Structure: Voids In Mcvittie Spacetime, Sakai, Nobuyuki, Haines, Paul

Dartmouth Scholarship

As a study of peculiar velocities of nonlinear structure, we analyze the model of a relativistic thin-shell void in the expanding universe. (1) Adopting McVittie (MV) spacetime as a background universe, we investigate the dynamics of an uncompensated void with negative MV mass. Although the motion itself is quite different from that of a compensated void, as shown by Haines & Harris (1993), the present peculiar velocities are not affected by MV mass. (2) We discuss how precisely the formula in the linear perturbation theory applies to nonlinear relativistic voids, using the results in (1) as well as the previous …

A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

A quantum field theory warm inflation model is presented that solves the horizon and flatness problems. The model obtains, from the elementary dynamics of particle physics, cosmological scale factor trajectories that begin in a radiation dominated regime, enter an inflationary regime, and then smoothly exit back into a radiation dominated regime, with non-negligible radiation throughout the evolution.

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.

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 …

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 …

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) 15^h10^m-16^h10^m; (2) 20^h30^m-21^h50^m; (3) 00^h10^m-01^h30^m. New R-band CCD photometry and spectroscopic data for the galaxies are used. The fundamental plane distance-indicator …

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. …

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 …

How To Count Kinks. From The Continuum To The Lattice And Back, Marcelo Gleiser, Hans-Reinhard Muller

Dartmouth Scholarship

We investigate the matching between (1+1)-dimensional nonlinear field theories coupled to an external stochastic environment and their lattice simulations. In particular, we focus on how to obtain numerical results which are lattice-spacing independent, and on how to extract the correct effective potential which emerges from the simulations. As an application, we study the thermal production of kink-antikink pairs, obtaining a number density of pairs which is lattice-spacing independent and the

A New Approach To Probing Large-Scale Power With Peculiar Velocities, Hume A. Feldman, Richard Watkins

Dartmouth Scholarship

We propose a new strategy for probing the power spectrum on large scales using galaxy peculiar velocities. We explore the properties of surveys that cover only two small fields in opposing directions on the sky. Surveys of this type have several advantages over those that attempt to cover the entire sky; in particular, by concentrating on galaxies in narrow cones, these surveys are able to achieve the density needed to measure several moments of the velocity field with only a modest number of objects, even for surveys designed to probe scales >∼100h⁻¹Mpc. We construct mock surveys with this …

Stellar Populations And The White Dwarf Mass Function: Connections To Supernova Ia Luminosities, Ted Von Hippel, G. D. Bothum, R. A. Schommer

Publications

We discuss the luminosity function of SNe Ia under the assumption that recent evidence for dispersion in this standard candle is related to variations in the white dwarf mass function (WDMF) in the host galaxies. We develop a simple parameterization of the WDMF as a function of age of a stellar population and apply this to galaxies of different morphological types. We show that this simplified model is consistent with the observed WDMF of Bergeron et al. (1992) for the solar neighborhood. Our simple models predict that WDMF variations can produce a range of more than 1.8 mag in MB(SN …

Using Fundamental Plane Distances To Estimate The Total Binding Mass In Abell 2626, Joseph J. Mohr, Gary Wegner

Dartmouth Scholarship

We use fundamental plane (FP) distance estimates to the components of the double cluster A2626 (cz ~ 17,500 km/s) to constrain cluster kinematics and estimate total binding mass. We employ deep R band CCD photometry, multi-object spectroscopy, and software designed to account for seeing effects to measure the FP parameters R_e, sigma , and for 24 known early type and S0 cluster members. The FP coefficients from this sample (alpha =1.30+/-0.36 and beta =0.31+/-0.06) are consistent with others reported in the literature. We examine the Mg_b equivalent width distributions within both subclusters and find them to be indistinguishable. Lacking evidence …

The Tully-Fisher Relation And H0, Riccardo Giovanelli, Martha P. Haynes, Luiz N. Da Costa, Wolfram Freudling, John Salzer, Gary Wegner

Dartmouth Scholarship

The use of the Tully-Fisher (TF) relation for the determination of H₀ relies on the availability of an adequate template TF relation and of reliable primary distances. Here we use a TF template relation with the best available kinematical zero point, obtained from a sample of 24 clusters of galaxies extending to cz ~ 9000 km s^-1, and the most recent set of Cepheid distances for galaxies fit for TF use. The combination of these two ingredients yields H₀ = 69 ± 5 km s^-1 Mpc^-1. The approach is significantly more accurate than …

Astrophysical Bounds On Global Strings, Shane L. Larson, William A. Hiscock

All Physics Faculty Publications

Global topological defects produce nonzero stress energy throughout spacetime, and as a result can have observable gravitational influence on surrounding matter. Gravitational effects of global strings are used to place bounds on their cosmic abundance. The minimum separation between global strings is estimated by considering the defects' contribution to the cosmological energy density. More rigorous constraints on the abundance of global strings are constructed by examining the tidal forces such defects will have on observable astrophysical systems. The small number of observed tidally disrupted systems indicates there can be very few of these objects in the observable Universe.

Semiclassical Effects In Black Hole Interiors, William A. Hiscock, Shane L. Larson, Paul R. Anderson

All Physics Faculty Publications

First-order semiclassical perturbations to the Schwarzschild black hole geometry are studied within the black hole interior. The source of the perturbations is taken to be the vacuum stress-energy of quantized scalar, spinor, and vector fields, evaluated using analytic approximations developed by Page and others (for massless fields) and the DeWitt-Schwinger approximation (for massive fields). Viewing the interior as an anisotropic collapsing cosmology, we find that minimally or conformally coupled scalar fields, and spinor fields, decrease the anisotropy as the singularity is approached, while vector fields increase the anisotropy. In addition, we find that for massless fields of all spins, the …

Lower And Upper Bounds On Internal-Wave Frequencies In Stratified Rotating Fluids, Benoit Cushman-Roisin

Dartmouth Scholarship

According to classical theories, the frequencies of internal-gravity waves in stratified rotating fluids must lie between the Brunt-Väisälä frequency (a measure of the vertical density stratification) and the Coriolis frequency (equal to twice the rotation rate about the vertical axis). It is shown here that, in the case of the Earth's rotation where the pole-to-pole axis of rotation is almost everywhere not parallel to the local vertical, the range of realizable frequencies is broader. New formulas are derived for the lower and upper bounds of the frequencies.

The Mass Distribution In The Nearby Universe, Luiz N. Da Costa, Wolfram Freudling, Gary Wegner, Riccardo Giovanelli

Dartmouth Scholarship

We present a new reconstruction of the mass density and the peculiar velocity fields in the nearby universe using recent measurements of Tully-Fisher distances for a sample of late spirals. We find significant differences between our reconstructed fields and those obtained in earlier work: overdensities tend to be more compact while underdense regions, consisting of individual voids, are more abundant. Our results suggest that voids observed in redshift surveys of galaxies represent real voids in the underlying matter distribution. While we detect a bulk velocity of ~300 km s^-1, within a top-hat window 6000 km s^-1 in …

New Promise For Electron Bulk Energization In Solar Flares: Preferential Fermi Acceleration Of Electrons Over Protons In Reconnection-Driven Magnetohydrodynamic Turbulence, Ted La Rosa, Ronald L. Moore, James A. Miller, Steven N. Shore

Faculty Articles

The hard X-ray luminosity of impulsive solar flares indicates that electrons in the low corona are bulk energized to energies of order 25 keV. LaRosa & Moore pointed out that the required bulk energization could be produced by cascading MHD turbulence generated by Alfvénic outflows from sites of strongly driven reconnection. LaRosa, Moore, & Shore proposed that the compressive component of the cascading turbulence dissipates into the electrons via Fermi acceleration. However, for this to be a viable electron bulk energization mechanism, the rate of proton energization by the same turbulence cannot exceed the electron energization rate. In this paper …

A Test Of The Lauer-Postman Bulk Flow, Riccardo Giovanelli, Martha P. Haynes, Gary Wegner, Luiz N. Da Costa

Dartmouth Scholarship

We use Tully-Fisher distances for a sample of field late spiral galaxies to test the Lauer & Postman result suggestive of a bulk flow with respect to the cosmic microwave background reference frame, of amplitude of +689 km s^-1 in the direction l = 343°, b = +52°. A total of 432 galaxies are used, subdivided between two cones, of 30° semiaperture each and pointed toward the apex and antapex of the LP motion, respectively. The peculiar velocities in the two data sets are inconsistent with a bulk flow of the amplitude claimed by Lauer & Postman. When combined …

Is The Universe Expanding?: An Historical And Philosophical Perspective For Cosmologists Starting Anew, David A. Vlosak

Masters Theses

This study addresses the problem of how scientists ought to go about resolving the current crisis in big bang cosmology. Although this problem can be addressed by scientists themselves at the level of their own practice, this study addresses it at the meta-level by using the resources offered by philosophy of science.

There are two ways to resolve the current crisis. Either cosmologists can continue working on big bang theory or they can start anew. For those who choose to start anew, this study argues it would be a mistake for them to assume any new cosmological theory would have …

Absence Of Open Strings In A Lattice-Free Simulation Of Cosmic String Formation, Julian Borrill

Dartmouth Scholarship

Lattice-based string formation algorithms can, at least in principle, be reduced to the study of the statistics of the corresponding aperiodic random walk. Since in three or more dimensions such walks are transient, this approach necessarily generates a population of open strings. To investigate whether open strings are an artifact of the lattice we develop an alternative lattice-free simulation of string formation. Replacing the lattice with a graph generated by a minimal dynamical model of a first-order phase transition we obtain results consistent with the hypothesis that the energy density in string is due to a scale-invariant Brownian distribution of …

Ion Viscosity Mediated By Tangled Magnetic Fields: An Application To Black Hole Accretion Disks, P. Subramanian, P. A. Becker, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We examine the viscosity associated with the shear stress exerted by ions in the presence of a tangled magnetic field. As an application, we consider the effect of this mechanism on the structure of black hole accretion disks. We do not attempt to include a self-consistent description of the magnetic field. Instead, we assume the existence of a tangled field with coherence length λcob• which is the average distance between the magnetic "kinks" that scatter the particles. For simplicity, we assume that the field is self-similar, and take λcob to be a fixed fraction ξ of the local disk height …

Basic Astronomy Labs, Terry L. Smith, Michael D. Reynolds, Jay S. Huebner

Physics Faculty Research and Scholarship

Providing the tools and know-how to apply the principles of astronomy first-hand, these 43 laboratory exercises each contain an introduction that clearly shows budding astronomers why the particular topic of that lab is of interest and relevant to astronomy. About one-third of the exercises are devoted solely to observation, and no mathematics is required beyond simple high school algebra and trigonometry.Organizes exercises into six major topics—sky, optics and spectroscopy, celestial mechanics, solar system, stellar properties, and exploration and other topics—providing clear outlines of what is involved in the exercise, its purpose, and what procedures and apparatus are to be used. …

Using Geant To Model Calrimeter Response For Electromagnetic Cascades From Nucleus-Nucleus Interactions In A Cosmic Ray Detector, Kazuhiko Murai, Carlos A. Sanchez, Donald C. Wold

Journal of the Arkansas Academy of Science

Ascintillating optical fiber calorimeter (SOFCAL) is being developed by NASA/Marshall Space Flight Center for use in balloon-borne experiments to study the spectrum of high-energy cosmic rays and gamma rays. SOFCAL will not saturate for long exposures and the calorimeter willbe useful in emulsion chambers to study primary cosmic-ray nuclei with energies from 100 GeV to 1,000 TeV. The event generator FRITIOF was used to model the collision of a cosmic-ray projectile with a target nucleus inan emulsion chamber. The measurements of charged particles from the interaction in the emulsions are related to the energy of the primary cosmic ray nucleus-nucleus …

Using Fritiof To Model Nucleus-Nucleus Interactions In A Cosmic Ray Detector, Carlos A. Sanchez, Kazuhiko Murai, Donald C. Wold

Journal of the Arkansas Academy of Science

Ascintillating optical fiber calorimeter (SOFCAL) isbeing developed by NASA/Marshall Space Flight Center for use in experiments to study the spectrum of high-energy cosmic rays and gamma rays from 100 GeV to 1,000 TeV. SOFCAL willnot saturate for long exposures and this calorimeter inthese balloon-borne emulsion chambers willbe helpful for the study of the composition of primary cosmic-ray nuclei. For primary nuclei with energies much greater than 1014 eV, nucleus-nucleus interactions are likely to exhibit characteristics of a quark-gluon plasma (QGP). Aparticle event generator was used tomodel the collision of a cosmic-ray nucleus with a target nucleus inan emulsion chamber. FRITIOF …

Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The isothermal shocks and their stabilities in fully relativistic accretion wedge flows onto black holes are studied. The jump condition across the shock is modified by the relativistic effects when the sound speed is comparable to the speed of light. With a new kind of instability analysis, it is found that only one of the two possible shocks is stable. The results are applied to the QPO behavior in galactic black hole candidates such as Cygnus X-1.