Black Hole-Neutron Star Mergers in Globular Clusters

We model the formation of black hole-neutron star (BH-NS) binaries via dynamical interactions in globular clusters. We find that in dense, massive clusters, 16-61% of the BH-NS binaries formed by interactions with existing BH binaries will undergo mergers driven by the emission of gravitational radiation. If the BHs are retained by the cluster after merging with a NS, the BHs acquire subsequent NS companions and undergo several mergers. Thus, the merger rate depends critically upon whether or not the BH is retained by the cluster after the merger. Results from numerical relativity suggest that kick imparted to a ~7 M_sun BH after it merges with a NS will greatly exceed the cluster's escape velocity. In this case, the models suggest that the majority of BH-NS mergers in globular clusters occur within 4 Gyrs of the cluster's formation and would be unobservable by Advanced LIGO. For more massive BHs, on the other hand, the post merger kick is suppressed and the BH is retained. Models with 35 M_sun BHs predict Advanced LIGO detection rates in the range 0.04 - 0.7 per year. On the pessimistic end of this range, BH-NS mergers resulting from binary-single star interactions in globular clusters could account for an interesting fraction of all BH-NS mergers. On the optimistic end, this channel may dominate the rate of detectable BH-NS mergers.Comment: 13 pages, 7 figures, 3 tabels, accepted for publication in MNRA

Dynamically formed black hole+millisecond pulsar binaries in globular clusters

The discovery of a binary comprising a black hole (BH) and a millisecond pulsar (MSP) would yield insights into stellar evolution and facilitate exquisitely sensitive tests of general relativity. Globular clusters (GCs) are known to harbor large MSP populations and recent studies suggest that GCs may also retain a substantial population of stellar mass BHs. We modeled the formation of BH+MSP binaries in GCs through exchange interactions between binary and single stars. We found that in dense, massive clusters most of the dynamically formed BH+MSP binaries will have orbital periods of 2 to 10 days, regardless of the mass of the BH, the number of BHs retained by the cluster, and the nature of the GC's binary population. The size of the BH+MSP population is sensitive to several uncertain parameters, including the BH mass function, the BH retention fraction, and the binary fraction in GCs. Based on our models, we estimate that there are $0.6\pm0.2$ dynamically formed BH+MSP binaries in the Milky Way GC system, and place an upper limit on the size of this population of $\sim 10$. Interestingly, we find that BH+MSP binaries will be rare even if GCs retain large BH populations.Comment: 15 pages, 5 figures, 2 tables, accepted for publication in MNRAS, updated to match published versio

Interpolating compact binary waveforms using the singular value decomposition

Compact binary systems with total masses between tens and hundreds of solar masses will produce gravitational waves during their merger phase that are detectable by second-generation ground-based gravitational-wave detectors. In order to model the gravitational waveform of the merger epoch of compact binary coalescence, the full Einstein equations must be solved numerically for the entire mass and spin parameter space. However, this is computationally expensive. Several models have been proposed to interpolate the results of numerical relativity simulations. In this paper we propose a numerical interpolation scheme that stems from the singular value decomposition. This algorithm shows promise in allowing one to construct arbitrary waveforms within a certain parameter space given a sufficient density of numerical simulations covering the same parameter space. We also investigate how similar approaches could be used to interpolate waveforms in the context of parameter estimation.Comment: 5 pages, 3 figures, presented at the joint 9th Edoardo Amaldi Conference on Gravitational Waves and 2011 Numerical Relativity - Data Analysis (NRDA) meetin

Does the Community Reinvestment Act influence lending? an analysis of changes in bank low-income mortgage activity

Anecdotal evidence that the Community Reinvestment Act (CRA) influences the lending behavior of financial institutions has not been uniformly supported by empirical research. We revisit this issue by evaluating changes in low-income mortgage lending at commercial banks over the 1992-96 period. Our empirical results fail to support a hypothesis that banks respond to public and regulatory pressure exerted as a result of a downgrade in CRA rating by increasing low-income mortgage lending. The findings are consistent with the contention that during this period regulators stressed adjustments in the lending process of banks (e.g., documentation of lending program and efforts directed at targeted markets) more than lending performance. The findings underscore the importance of regulatory efforts made later in the decade to more closely link enforcement of the CRA to lending outcomes.Community Reinvestment Act of 1977 ; Mortgages ; Bank loans ; Financial institutions

Identifying Opportunities and Priorities for Energy Extension

An online survey was administered to all educators and specialists within the University of Maryland Extension to assess client-driven opportunities and priorities for energy-related programming, while in-service training evaluations were used to further assess programmatic needs. Results indicate the need for information related to energy conservation and clean energy technology for agricultural and residential clientele. Primary barriers were perceived as the insufficient understanding and high costs associated with clean energy, while experiential participation and firsthand observation were reported as preferred learning methods. These results provide an understanding of how energy-related programming can expand the role and relevancy of Extension

A Structural Approach to the Analysis of Rock Music

This dissertation situates itself in the middle of an ongoing debate about the applicability of Schenkerian analytical techniques to the analysis of pop and rock music. In particular, it investigates ways in which the standard conceptions of voice leading, harmonic function, and counterpoint may be updated to better apply to this new repertoire. A central claim is that voice-leading structure is intimately related to formal structure such that the two domains are mutually informing. Part I of the dissertation focuses on harmonic and melodic theory. Chapter 2, Harmonic Syntax, advocates for a conception of harmonic function based on syntax and form rather than the identity of specific chords. In this conception, chords other than V, such as IV, II, flat-VII, or even some versions of I, can often be said to function syntactically as the dominant. Chapter 3, The Melodic-Harmonic Divorce, explores contrapuntal paradigms in which the domains of melody and harmony seem to be operating independently. This chapter outlines three types of melodic-harmonic divorce: hierarchy divorce, rotation divorce, and syntax divorce. Part II of the dissertation aims to devise voice-leading models for full song forms. Chapter 4 focuses on AABA form, Chapter 5 on verse-prechorus-chorus, and Chapter 6 on verse-chorus forms. These chapters demonstrate that these common forms are associated with general voice-leading structures that act in dialog with the specific voice-leading structures of songs that exhibit these forms. This part of the dissertation is largely analytical, and has the secondary goal of demonstrating a Schenkerian analytical methodology applied to rock music

An evaluation of personal-use typewriting programs in selected secondary schools throughout New England

Thesis (M.A.)--Boston University, 1948. This item was digitized by the Internet Archive