Physics 8B

This semester I’m one of the GSIs for Physics 8B: Introductory Physics.  This is an undergraduate course for non-majors being taught by Profs. Mike DeWeese and Catherine Bordel.

Here’s the course description:

Introduction to electricity, magnetism, electromagnetic waves, optics, and modern physics. The course presents concepts and methodologies for understanding physical phenomena, and is particularly useful preparation for upper division study in biology and architecture.

Galaxy-Scale Strong-Lensing Tests of Gravity and Geometric Cosmology: Constraints and Systematic Limitations

The Astrophysical Journal, Volume 708, Issue 1, pp. 750-757 (2010)

Josiah Schwab, Adam Bolton and Saul Rappaport

Galaxy-scale strong gravitational lenses with measured stellar velocity dispersions allow a test of the weak-field metric on kiloparsec scales and a geometric measurement of the cosmological distance-redshift relation, provided that the mass-dynamical structure of the lensing galaxies can be independently constrained to a sufficient degree. We combine data on 53 galaxy-scale strong lenses from the Sloan Lens ACS Survey with a well-motivated fiducial set of lens-galaxy parameters to find (1) a constraint on the post-Newtonian parameter γ = 1.01 ± 0.05, and (2) a determination of ΩΛ = 0.75 ± 0.17 under the assumption of a flat universe. These constraints assume that the underlying observations and priors are free of systematic error. We evaluate the sensitivity of these results to systematic uncertainties in (1) total mass-profile shape, (2) velocity anisotropy, (3) light-profile shape, and (4) stellar velocity dispersion. Based on these sensitivities, we conclude that while such strong-lens samples can, in principle, provide an important tool for testing general relativity and cosmology, they are unlikely to yield precision measurements of γ and ΩΛ unless the properties of the lensing galaxies are independently constrained with substantially greater accuracy than at present.