# Gravitational Physics

Gravitational Physics is a broad discipline with connections to diverse fields, from GPS technology to astrophysics and cosmology and pure mathematics. A large-scale goal of contemporary research in gravitational physics is to implement gravitational wave astronomy, by observing and interpreting the gravitational radiation of astrophysical sources. While there are different aspects of gravitational physics research - classical or quantum, general relativity or alternative - and different methodologies - theoretical, computational or experimental - the thrust at Duquesne is in classical general relativity with a theoretical methodology and the focus is on the Einstein equations themselves as a system of nonlinear partial differential equations. The immediate impact of this research is on computational methodology for the simulation of gravitational waves, otherwise known as numerical relativity.

**Members**

Simonetta Frittelli, PhD, Associate Professor.

**Collaborations**

Roberto Gomez, PhD, Senior Computational Science Consultant, Pittsburgh Supercomputing Center, Carnegie Mellon University.

Thomas P. Kling, PhD, Professor, Department of Physics, Bridgewater State University.

**Past members***Undergraduate Students*

Eric Sinagra, BS 2011, Duquesne University, Physics.

Robert Leonard, BS 2008, West Virginia University, Physics.

Paul Stumpf, BS 2002, Duquesne University, Physics.

Thomas E. Oberst, BS 2001, Duquesne University, Physics.

Amanda Mazzoni, BS 1999, Duquesne University, Physics.

**Representative publications with relevance to numerical relativity**

A framework for large-scale relativistic simulations in the characteristic approach, R. Gómez, W. Barreto and S. Frittelli, Physical Review D 76, 124029 (2007)

Initial-value-problem of the self-gravitating scalar field in the Bondi-Sachs gauge, S. Frittelli and R. Gómez, Physical Review D 75, 044021 (2007)

Well-posed ADM equivalent of the Bondi-Sachs problem, S. Frittelli, Physical Review D 73, 124001 (2006)

Einstein boundary conditions for the Einstein equations in the conformal-traceless decomposition, S. Frittelli and R. Gómez, Physical Review D 70, 064008 (2004)

**Representative publications with relevance to gravitational lensing**

Accuracy of the thin lens approximation in strong lensing by smoothly truncated dark matter haloes, S. Frittelli and T. P. Kling, Monthly Notices of the Royal Astronomical Society 415, 3599-3608 (2011)

Study of errors in strong gravitational lensing, T. P. Kling and S. Frittelli, Astrophysical Journal 675, 115-125 (2008)

Wavefronts, caustic sheets and caustic surfing in gravitational lensing, S. Frittelli and A. O. Petters, Journal of Mathematical Physics 43, 5578-5611 (2002)

Dynamics of Fermat potentials in nonperturbative gravitational lensing, S. Frittelli and E. T. Newman, Physical Review D 65, 123006 (2002)

Image distortion by thick lenses, S. Frittelli and T. E. Oberst, Physical Review D 65, 023005 (2002)

**National Science Foundation**

Grant PHY-0555218: "Theoretical questions of Analysis and Astrophysics in the Einstein equations", August 1, 2006 through July 31, 2011, $90,130.

Grant PHY-0244752: "Properties of the Einstein equations and gravitational lensing in relativity", August 1, 2003 through July 31, 2006, $75,000.

Grant PHY-0070624: "Issues in Theoretical General Relativity", August 1, 2000 through July 31, 2003, $54,519.

Grant PHY-9803301: "Prescription of initial data with small radiation content for characteristic evolution", August 1, 1998 through July 31, 2000, $38,457.