42,879 research outputs found
Initial Data for Numerical Relativity
Initial data are the starting point for any numerical simulation. In the case
of numerical relativity, Einstein's equations constrain our choices of these
initial data. We will examine several of the formalisms used for specifying
Cauchy initial data in the 3+1 decomposition of Einstein's equations. We will
then explore how these formalisms have been used in constructing initial data
for spacetimes containing black holes and neutron stars. In the topics
discussed, emphasis is placed on those issues that are important for obtaining
astrophysically realistic initial data for compact binary coalescence.Comment: 50 pages, LaTeX(livrev.cls), Review article for "Living Reviews in
Relativity" (http://www.livingreviews.org/), July 200
Summer Cook Associate Professor of Kinesiology (COLA) travels to Australia
I was partially supported by a CIE International development grant to travel to Perth, Australia for one month in 2016. Dr. Timothy Fairchild, a colleague and friend, invited me to visit the Department of Psychology and Exercise Science at Murdoch University in the hopes of establishing a research relationship with the University of New Hampshire Department of Kinesiology. Over the last several years, I have had students earn Summer Undergraduate Research Fellowships (SURF) from the Hamel Center and have always wanted to give students an opportunity to apply for SURF abroad grants or to study abroad while conducting research within our field. The idea of international collaboration and the opportunity to leave the New England winter to work on the coast of Western Australia made the decision to travel very simple
Testing a Simplified Version of Einstein's Equations for Numerical Relativity
Solving dynamical problems in general relativity requires the full machinery
of numerical relativity. Wilson has proposed a simpler but approximate scheme
for systems near equilibrium, like binary neutron stars. We test the scheme on
isolated, rapidly rotating, relativistic stars. Since these objects are in
equilibrium, it is crucial that the approximation work well if we are to
believe its predictions for more complicated systems like binaries. Our results
are very encouraging.Comment: 9 pages (RevTeX 3.0 with 6 uuencoded figures), CRSR-107
Systematics and distributions of the genera Cyrtusa Erichson, Ecarinosphaerula Hatch, Isoplastus Horn, Liocyrtusa Daffner, Lionothus Brown, and Zeadolopus Broun of the United States and Canada (Coleoptera: Leiodidae: Leiodinae: Leiodini)
The following genera of Leiodini (Coleoptera: Leiodidae: Leiodinae) of the continental United States and Canada are reviewed: Cyrtusa Erichson, with two species; Isoplastus Horn, with two species (one new); Liocyrtusa Daffner, with three species; Lionothus Brown, with five species (three new), and Zeadolopus Broun, with four species (all genera are in the “Cyrtusa genus group”) and Ecarinosphaerula Hatch, with one named species (in the “Leiodes genus group”). The new species are Isoplastus floridanus Peck and Cook of Florida; Lionothus bidentatus Peck and Cook of Texas and Oklahoma, Lionothus exiguus Peck and Cook of Florida and Texas, and Lionothus parvoculus Peck and Cook of Arizona and New Mexico. Bionomic data on the species are given, and complete known distributions are mapped
Quasi-circular Orbits for Spinning Binary Black Holes
Using an effective potential method we examine binary black holes where the
individual holes carry spin. We trace out sequences of quasi-circular orbits
and locate the innermost stable circular orbit as a function of spin. At large
separations, the sequences of quasi-circular orbits match well with
post-Newtonian expansions, although a clear signature of the simplifying
assumption of conformal flatness is seen. The position of the ISCO is found to
be strongly dependent on the magnitude of the spin on each black hole. At close
separations of the holes, the effective potential method breaks down. In all
cases where an ISCO could be determined, we found that an apparent horizon
encompassing both holes forms for separations well inside the ISCO.
Nevertheless, we argue that the formation of a common horizon is still
associated with the breakdown of the effective potential method.Comment: 13 pages, 10 figures, submitted to PR
A revision of the species of Anogdus LeConte of the United States and Canada (Coleoptera: Leiodidae: Leiodinae: Leiodini)
A review of the genus Anogdus LeConte (Coleoptera: Leiodidae: Leiodinae: Leiodini) of North America finds 16 species. Ten of these were previously described and there are no new synonyms. Six are named as new species: A. alachua n. sp., of Florida; A. cochise, n. sp., of Arizona; A. huachuca n. sp., of Arizona; A. rileyi n. sp, of Texas; A. texanus n. sp., of Texas and Oklahoma; and A. tridens n. sp, of Arkansas, Arizona, Illinois, Indiana, Oklahoma, and Texas. A key is provided to aid identification of the species
Task-Specific Experience and Task-Specific Talent: Decomposing the Productivity of High School Teachers
We use administrative panel data to decompose worker performance into components relating to general talent, task-specific talent, general experience, and task-specific experience. We consider the context of high school teachers, in which tasks consist of teaching particular subjects in particular tracks. Using the timing of changes in the subjects and levels to which teachers are assigned to provide identifying variation, we show that much of the productivity gains to teacher experience estimated in the literature are actually subject-specific. By contrast, very little of the variation in the permanent component of productivity among teachers is subject-specific or level-specific. Counterfactual simulations suggest that maximizing the value of task-specific experience could produce nearly costless efficiency gains on the order of .02 test score standard deviations
- …