A5081615138- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Relativity and Gravitational Theory
- Innovative Teaching and Learning Methods
- Education and Critical Thinking Development
- Experimental Learning in Engineering
- Career Development and Diversity
- Gamma-ray bursts and supernovae
- Innovative Teaching Methods
- Astronomy and Astrophysical Research
- Online and Blended Learning
- Higher Education Research Studies
- Stellar, planetary, and galactic studies
- Photonic and Optical Devices
- Aerospace Engineering and Energy Systems
- Astrophysics and Cosmic Phenomena
- Black Holes and Theoretical Physics
- Reflective Practices in Education
- Astrophysics and Star Formation Studies
- Scientific Research and Discoveries
- Educational Strategies and Epistemologies
Bridgewater State University
2008-2024
University of Pittsburgh
1999-2002
Connecticut College
2002
Darmstadt University of Applied Sciences
1989
We propose a definition of an exact lens equation without reference to background spacetime, and construct the explicitly in case Schwarzschild spacetime. For case, we give expressions for angular-diameter distance sources as well magnification factor time arrival images. compare with standard equation, derived under thin-lens-weak-field assumption (where light rays are geodesics sharp bending plane, gravitational field is weak), verify fact that weak-field thin-lens inadequate at small...
Peer-cooperative learning has been shown in the literature to improve student success gateway science and mathematics courses. Such studies typically demonstrate impact of students' attending peer-led sessions on their or grades an individual course. In this article, we examine effects introducing a required, comprehensive peer-cooperative system across five departments simultaneously at master's public university, looking not only supported classes, but also retention within STEM fields two...
We describe the structure of a writing-intensive, chemistry first year seminar designed to support three week, research focused summer bridge program. Writing assignments in helped students understand their activities, learn conduct themselves as scientists, and reflect upon lab work. The writing intensive maintain order cohesion across multiple groups. participants program have experienced higher rates retention graduation STEM fields well participation high impact practices than peers.
We present an analysis of weak lensing observations for RXJ1347-1145 over a 43' X field taken in B and R filters on the Blanco 4m telescope at CTIO. is massive cluster redshift z=0.45. Using population galaxies with 20
The images of many distant galaxies are displaced, distorted and often multiplied by the presence foreground massive near line sight; act as gravitational lenses. Commonly, lens equation, which relates placement distortion to real source position in thin-lens scenario, is obtained extremizing time arrival among all null paths from observer (Fermat's principle). We show that construction envelopes certain families surfaces constitutes an alternative variational principle or version Fermat's...
In a previous article concerning image distortion in nonperturbative gravitational lensing theory we described how to introduce shape and parameters for small sources. We also showed they could be expressed terms of the scalar products geodesic deviation vectors source's pencil rays past light cone an observer. present work give alternative approach description their evolution along null from source observer, but now optical scalars (the convergence shear vector field observer's cone)...
In this work we investigate aspects of light cones in a Schwarzschild geometry, making connections to gravitational lensing theory and new approach general relativity, the null surface formulation. By integrating geodesics our model, obtain cone from every space-time point. We study three applications cones. First, by taking intersection each point with infinity, cut function, four parameter family cuts which is central examine singularity structure function. Second, give exact lens...
We develop an iterative approach to gravitational lensing theory based on approximate solutions of the null geodesic equations. The can be employed in any space-time which is ``close'' a equations completely integrated, such as Minkowski space-time, Robertson-Walker cosmologies, or Schwarzschild-Kerr geometries. To illustrate method, we construct lens and time arrival equation for single Schwarzschild lens. This example motivates discussion relationship between approach, standard thin...
We introduce the idea of shape parameters to describe pencil rays connecting an observer with a source lying on his past light cone. On basis these parameters, we discuss setting image distortion in generic (exact) spacetime, form three parameters. The fundamental tool our discussion is use geodesic deviation fields along null study how shapes are propagated and distorted path observer. illustrate this nonperturbative treatment case lensing by Schwarzschild black hole. conclude showing that...
We examine the accuracy of strong gravitational lensing determinations mass galaxy clusters by comparing conventional approach with numerical integration fully relativistic null geodesic equations in case weak perturbations on Robertson-Walker metrics. In particular, we study spherically symmetric, three-dimensional singular isothermal sphere models and matter distribution Navarro coworkers which are both commonly used studies. cases two different methods for mass-density truncation along...
The importance of high-tech careers has risen as the international competitiveness US students on tests science and math declined. problem is compounded by a persistent inequity in ST...
Previous research has established that peer relationships are important for student success, yet little examined connections made in the classroom, as opposed to residence life or extracurricular activities. This project utilized social network analysis two cohorts of science and mathematics majors investigate degree which students take multiple courses with same peers. Results showed (1) wide variability networks, (2) course selection by included more repeated than random selection, (3)...
A modular laboratory curriculum with exercises for students and lesson plans teachers is presented. Fundamentals of basic integrated photonic (IP) devices can be taught, first as a lecture-in-the-lab followed by "hands-on" measurements. This comprehensive utilizes data collected from the "AIM Photonics Institute PIC education chip" that was designed specifically purpose education, fabricated at AIM SUNY Poly. Training using this will performed through Academy network in New York (NY)...
Using the Newman and Penrose [E. T. R. Penrose, J. Math. Phys. (N.Y.) 3, 566 (1962).] spin-coefficient formalism, we examine full Bianchi identities of general relativity in context gravitational lensing, where matter space-time curvature are projected into a lens plane perpendicular to line sight. From one component identity, provide rigorous, new derivation Poisson equation for density source term involves second derivatives observed weak lensing shear. We also show that other components...
Predictions of the standard thin lens approximation and a new iterative approach to gravitational lensing are compared with an ``exact'' in simple test cases involving one or two lenses. We show that approaches remarkably accurate predicting time delays, source positions image magnifications for single monopole lens. However, observationally significant errors were found when method was applied configurations In these cases, remained beyond observational limits.
We consider the Bianchi identity as a field equation for distortion of shapes images produced by weak gravitational lensing. Using spin coefficient formalism Newman and Penrose (1962 J. Math. Phys. 3 566–78), we show that certain complex components Weyl Ricci curvature tensors are directly related to fundamental observables in In case fields, then provides tensor assuming known tensor. From identity, derive integral lensing presented Miralda-Escude (1996 IAU Symp. vol 173 p 131), thus making...
The light rays and wave fronts in a linear class of the Gödel-type metric are examined to reveal causality-violating features space-time. Noncausal demonstrated by development unusual front singularities shown be related nonmonotonic advance time along rays, as measured system observers at rest with respect one another synchronized clocks.
The accuracy of mass estimates by gravitational lensing using the thin-lens approximation applied to Navarro–Frenk–White models with a soft truncation mechanism recently proposed Baltz, Marshall and Oguri is studied. lens scenario considered case inference from observation Einstein rings (strong lensing). It found that error incurred simplifying assumption thin lenses below 0.5 per cent. As byproduct, optimal tidal radius be at most 10 times virial model.