* For potential new students!* I have openings for possible research projects in the following areas:

**Testing a new theoretical model for intergalactic dust.**The goal is to take a model for the opacity of the intergalactic medium (IGM) that I have devised with previous student Nathan Prins and combine it with information about galaxy spectra and cosmological expansion to arrive at a theoretical prediction for EBL intensity as observed on Earth. We will compare this with observational data and work backward to constrain the properties of dust grains in the IGM. This project would suit a student who has taken ASTR 162 (General Astronomy II), has taken (or plans to take) ASTR 371 (Stellar Astrophysics), and is comfortable with*Mathematica.***Limits on higher-dimensional dark matter from gamma-ray background radiation.**Working with previous student Jack Mitcham, I have calculated that candidates for dark matter within certain higher-dimensional “braneworld scenarios” can be ruled out because they produce excessive amounts of gamma-ray background radiation. These results depended on a rough approximation and were never published. The project is to improve the model and present or publish the results. It would suit a student who has taken PHYS 307 (Mathematical Physics), has an interest in relativity and cosmology, and is comfortable with (or willing to learn)*Mathematica*and*LaTeX.***Testing a symbolic code to solve Einstein’s equations in higher dimensions.**Building on work with previous student Ryan Everett, I have developed a suite of symbolic*Mathematica*routines that can solve Einstein’s field equations of General Relativity in arbitrary dimensions and characterize the results in various ways. I am particularly interested in applying this code to a theory known as Space-Time-Matter, in which matter and energy in the four-dimensional Universe are “induced” from pure geometry in higher dimensions. The project is to test the code using known solutions, and then apply it to a new wavelike solution to see whether it has physically acceptable properties. This is a challenging project for a student who has done well in PHYS 307 (Mathematical Physics), is interested in the philosophical side of physics, and is comfortable with*Mathematica*.**Exotic spacetime topology as an alternative to dark matter and/or energy.**Together with a colleague at Johns Hopkins University, Dr. Richard Henry, I am interested in the idea that what we have taken as evidence for dark matter and/or energy may instead be a manifestation of exotic spacetime topology. The four-dimensionality of our Universe is very special: it turns out that*n*= 4 is the only dimension for which there are manifolds that are differentiable (i.e., one can “do calculus” on them) but not diffeomorphic to*R*^4. These are called “exotic”. Not only do exotic spaces exist, and only in*n*= 4, but it is now known that there are infinitely many of them! If spacetime in the real Universe is described by one of these geometries, rather than*R*^4, then we might expect gravitational consequences, since the identification of gravity with geometry is the very essence of General Relativity. This is a challenging project for a student who has done well in PHYS 307 (Mathematical Physics) and has taken or will be taking MATH 477 (Topology) concurrently.

If you are interested in pursuing any of these opportunities, or if you have some other project idea that you’d like to discuss, feel free to contact me directly.