## Visiting Assistant Professor

### Physics

Bill Hirsch received his BS from the Pennsylvania State University in Astrophysics and performed computational nuclear physics research when earning his MS at the Indiana University of Pennsylvania. He received his Ph.D. from Wake Forest University for theoretical research concerning general relativity’s interplay with quantum field theory. This research was an exploration of an approximation to a quantum theory of gravity in which quantum fields interact with a space-time of extreme curvature. He examined quantum effects created by the presence of a fermion field (electrons, neutrinos, etc.) in blackhole and worm hole space-times. The nature of these effects may predict the non-existence of astrophysical objects that produce extreme space-time curvature.

### Courses Taught

- Introductory physics for scientists and engineers
- Introductory physics for the health professions
- General relativity
- Particle physics
- Honors seminars

### Research Interests

- Solutions to the Einstein field equations
- Neutron star and magnetar structure
- Quantum fields in space-times with large curvature
- Plausibility of wormholes in the framework of semi-classical general relativity
- Mathematical physics

### Publications

**Related papers coauthored by Hirsch:**

**Other related paper:**

- Method to compute the stress-energy tensor for the massless spin 1/2 field in a general static spherically symmetric spacetime

Recently, Bill has become interested in the modeling of the interior of magnetars, neutron stars with enormous magnetic fields. These magnetic fields are on the order of 1000 trillion times the Earth’s (about 10^{15} Gauss!) and their origin is not well understood. The most refined, current models consider the neutron star to be non-rotating and constructed of a relativistic perfect fluid. Bill’s current project involves solving the Einstein field equations for a rotating neutron star with a more realistic equation of state for its interior. The goal is to more accurately describe the space-time geometry inside the neutron star to gain insight into the dynamics within and perhaps find clues to the nature of the large magnetic fields.