Theoretical Particle Physics, Astrophysics, and Cosmology

Faculty: Thomas W. Kephart and Thomas J. Weiler

Research Associate: Arjun Berera Graduate Students: Doris J. Wagner, Stuart Wick, and Rob Cutler, and Steve Jacobson

Professors Weiler and Kephart work on interpreting, explaining, and modeling some of the most exotic phenomena known to exist, or theorized to exist, in nature. The language of nature is mathematics, and so their research is intrinsically mathematical. This research ranges from the very small (the elementary quark and lepton building blocks of matter) to the very large (the distributions of matter throughout the universe), and from the lowest of energies (the 2K neutrino relic radiation left over from the first second after the big bang) to the highest of energies (the "Planck energy" of 1028 eV, where even the weak force of gravity becomes strong). The interests of Kephart and Weiler overlap considerably, and so some of their research is carried out together. However, most of their efforts are independent.

Dr. Weiler's research concentration includes modeling the symmetry breaking of the electroweak (EW) theory with scalar "Higgs" sectors, and identifying search strategies to seek these exotic Higgs particles at the world's highest energy accelerators; looking for the effects of physics beyond what is now known (i.e. beyond the "Standard Model") in the quantum loop corrections to the EW interaction; investigating possible origins and signatures of CP-violation; seeking and modeling the properties of the elusive neutrino particle; using neutrino extragalactic cosmic rays to ask and answer several questions about the content and evolution of the universe as a cosmological system. Another way to characterize these research interests would be TeV physics (which includes symmetry breaking in gauge-field theory, supersymmetry physics, EW radiative corrections, Higgs physics, the top quark, and the fundamental origin of the experimentally tiny CP-violation); neutrino physics and astrophysics (as it hints at the origin of mass and mixing of fundamental quanta, as a probe into the sun's center, and as a cosmic ray window on the hottest astrophysical sources - supernovae, gamma-ray bursters, quasars- and on cosmology itself); and other particle physics aspects of astrophysics (the Hawking radiation spectrum) and cosmology (the nature of the mysterious "dark matter" that seems to comprise most of the universe). Dr. Weiler's interests are driven by surprises in recent data, or by the prospects of new data in unexplored regimes of physics. He expects to continue to focus his research on the areas of elementary particle physics and astrophysics/cosmology where the prospects for continued experimental surprises remain bright.

One set of topics studied in Professor Kephart's recent work includes the quantum physics of black holes and cosmic wormholes. It is deduced that the very early universe (soon after the big bang) was in thermal equilibrium, which is in contradiction to what is predicted by Einstein's equations if the universe is expanding as a relativistic gas. Professor Kephart and a collaborator have shown that the equilibrium can be restored if a more complicated universe containing cosmic wormholes is considered. Wormholes in space-time act like bridges between vastly separated locations in space. Black holes can also arise in the early universe and may contribute to the generation of the structure like galaxies, clusters of galaxies, and cosmic voids we see today.

The group has graduated four Ph.D. students and one M.S. student. The Ph.D. students went on to postdocs at Texas A&M University (Pois) and at Tsing Hua University in Taiwan (Ng), and to faculty positions in Hungary (Forisz) and at Cumberland University (Farris). The M.S. student (Strobl) went to the University of Cambridge in England where he completed his Ph.D. Four postdoctoral fellows have formerly held two or three year appointments with the group. Subsequently, they left here for other postdoctoral positions at Northwestern University (Yuan), University of Valencia in Spain (Hochberg), University of Southampton in England (Diaz), and University of Hawaii (Ter Veldhuis).

Recent publications include:

1. "Wormhole Cosmology and the Horizon Problem," D. Hochberg and T. W. Kephart, Physical Review Letters 70, 2665 (1993).

2. "Effective Potential of a Black Hole in Thermal Equilibrium with Quantum Fields," D. Hochberg, T. W. Kephart and J. W. York, Jr., Physical Review D49, 5257 (1994).

3. "Magnetic Monopoles as the Highest-Energy Cosmic Ray Primaries, T.W. Kephart and T.J. Weiler, Astroparticle Phys. 4, 27 (1996).

4. "Higgs Boson Mass as the Discriminator of Electroweak Models," M. A. Diaz, T. A. ter Veldhuis, and T. J. Weiler, Physical Review Letters 74, 2876 (1995).