Physics Colloquium – Sarah Vigeland

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

Searching for a Gravitational Wave Background with Pulsar Timing Arrays

Sarah Vigeland, Asst. Professor, Dept. of Physics, UW-Milwaukee
Pulsar timing arrays use observations of millisecond pulsars to detect nanohertz gravitational waves. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Collaboration has recently released their 15-year data set containing observations of 68 millisecond pulsars. These data contain evidence for Hellings-Downs correlations, which are characteristic of a gravitational wave background.

Physics Colloquium – Alan Wiseman

KIRC 1150 3135 N. Maryland Ave., Milwaukee, WI, United States

The Self-force on Static and Dynamic Charges in Schwarzschild Spacetime Using the Method of Images
Alan Wiseman, Assoc. Professor, Dept. of Physics, UW-Milwaukee
One of the most basic examples of a self-force phenomenon (sometimes called the radiation reaction force) is that of a small, charged particle near a large spherical mass such as a Schwarzschild black hole. If the particle is held stationary, there are novel electrostatic forces on the particle. If the particle is orbiting the mass, the fields created by the particle back-react on the particle and cause it to depart from its otherwise free-fall motion. There are many ways to solve for the forces and motion in these circumstances, but past solutions have involved considerable technical machinery, and the results are messy and "non-intuitive".