CWRU Physics Faculty

We live in an exciting time for cosmology. After decades of struggling to obtain data about the properties of our universe on the largest scales and at the earliest possible times, we now find ourselves with a wealth of data pouring in from many sources. These include in particular observations of the microwave background radiation -- the relic radiation of the early universe -- and surveys of astronomical objects -- galaxies, quasars, supernovae, gamma-ray bursters, ... -- over large fractions of the sky out to large fractions of the radius of the observable universe. This flow of data is likely to only increase -- new larger, deeper surveys, more detailed observations of the microwave background and its polarization, measurements of gravitational lensing, observations of gravity waves.

At the same time, precision tests of our fundamental theories of particle physics and of gravity continue to improve. The standard model of the strong, weak, and electromagnetic interactions of particles is a remarkable achievement; after thirty years of being tested, its predictions still agree with all known experimental data within the limits of experimental and theoretical accuracy. In all that time, the only knew twist that data has forced us to add to the theory is neutrino masses. Nevertheless, few particle theorists would contend that the Standard Model is the ultimate theory of everything (or even almost everything). For one thing, the Standard Model contains at least 20 independent parameters, for which it offers no explanation, and many of them have what we call unnatural values - they are significantly smaller than the values that one would have guessed in the absence of experiments. Our lack of understanding of various subsets of these parameters has acquired several names: the Gauge Hierarchy Problem, the Fermion Mass Problem, the Strong CP Problem. The theory also fails to incorporate any understanding of the quantum mechanical nature of gravity, which must manifest itself at high energies. For the last three decades much of the energy and attention of theoretical particle physicists has been focused on trying to address these perceived failings of the standard Model. String Theory (and other models of quantum gravity), Grand Unified Theories, Supersymmetry, Super Gravity, Technicolor, large extra dimensions, are all attempts to address some -- or all --- of the questions raised by the ad hoc nature of the Standard Model. In early 2007, the Large Hadron Collider, the latest greatest particle accelerator will turn on. This machine promises to give us some further insight into the nature of fundamental interactions and hopefully a window into physics beyond the standard model.

For a theorist, like I, this is both the best of times and the worst of times. On the one hand data constrains your imagination -- if you want to do physics (as opposed to mathematics) you must ultimately confine your interest to what is measured or measurable. On the other hand, new and future data implies the ability to make predictions and so test your theories. This is incredibly exciting.

Together with collaborators, research associates, graduate and undergraduate students I am engaged in a number of very exciting projects closely connected with current or future data. These include:

• searching for evidence of non-trivial (i.e. interesting) topology of the universe in microwave background data: We have published the most stringent limit on the smallest loop around the universe -- greater than about 75 Billion light years. We continue to search for topology near or just over the horizon.
• determining how best to search for differences between General Relativity and modified theories of gravity that try to explain the accelerating expansion of the universe or the rotation of galaxies: We have shown how modified theories of gravity will change the orbits of planets and moons in the solar system (aka Lue-Starkman precession) We have shown how large scale structure grows at a modified rate in modified gravity. We have shown that the mass as determined by motions of particles (e.g. rotation of galaxies) and the mass as determined by bending of light will differ.
• exploring the possibility that an Aether can replace either or both dark matter and dark energy (in explaining galaxy dynamics and growth on the one hand, and the accelerated expansion of the universe on the other)
• working with the ATLAS detector group to model the production and decay of mini-black holes at the Large Hadron Collider: We have developed the most complete event generator that includes black hole rotation, black hole recoil, "brane splitting" and brane tension.
• Investigating the large scale correlations of the universe: Using data from the Wilkinson Microwave Anisotropy Probe (WMAP) we have demonstrated that on large scales the microwave background is not (statistically) isotropic but rather is correlated within itself and to solar system geometry.
• Investigating the topology of extra dimensions We have shown how hyperbolic (negatively curved) extra dimensions solve many of the standard problems with large extra dimension theories
• Investigating the future of life and thought in the universe
• Arguing against the anthropic principle

Oh yeah, I almost forgot -- I also work on detecting and characterizing Earth-like planets around nearby stars.