Gravity, Cosmology, and Astroparticle Physics Group (GCAP)

Baylor Faculty - Dr. Anzhong Wang (Physics), Dr. Qin (Tim) Sheng (Math), and Dr. Yumei Wu (Physics)

Gravity, Cosmology, and Astroparticle Physics Group (GCAP), founded in 2006, is one of the theoretical research groups in Physics Department & CASPER. Currently, it consists of three Baylor faculty members, Dr. Anzhong Wang, the head of the group (Physics), Dr. Qin (Tim) Sheng (Math), and Dr. Yumei Wu (Physics); three adjunct professors, Dr. Rong-Gen Cai, from the Institute of Theoretical Physics, Chinese Academy of Science, Dr. Yungui Gong, from College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, and Dr. N. O. Santos, from Queen Mary College, London University and the Brazilian National Scientific Computation Lab (LNCC); and several graduate/undergraduate students. Recently, research topics include late cosmic acceleration of the universe, cosmology in string/M theory, the hierarchy and cosmological constant problems, Horava-Lifshitz theory of quantum gravity and its applications to cosmology and astrophysics, higher dimensional black holes, and their thermodynamics and formation from gravitational collapse.

Our Universe and Accelerating Expansion

One of the remarkable discoveries over the past decade in astronomy is that currently our universe is at its accelerating expansion. In Einstein's theory, to account for such an acceleration, a new component to the matter fields of the universe with a large negative pressure is needed, the so-called dark energy. A fundamental question now is the nature and origin of dark energy. The hierarchy and cosmological constant problems are other outstanding problems in particle physics and cosmology. To solve these problems, brane-world scenarios were proposed, in which our four-dimensional universe is considered as a brane embedded in a high dimensional bulk. An important result of such investigations is that high dimensional black holes are predicted to be produced in the TeV energy scale, which shall be explored directly by colliders in laboratories, such as LHC.

Very recently, Horava proposed a new theory of quantum gravity motivated by the Lifshitz theory in solid state physics. The Horava-Lifshitz theory is non-relativistic and power-counting ultraviolet-renormalizable, and should recover general relativity in the infrared limit. The effective speed of light diverges in the UV regime, and this potentially resolves the horizon problem without invoking the inflationary scenario. In addition, almost scale-invariant super-horizon curvature perturbations can be produced without inflation. As the theory was still in its infant time, a more complete understanding of it is highly demanded. In addition, theories of gravity, including general relativity, predict the existence of black holes and gravitational waves. Black holes, their thermodynamics and formation from gravitational collapse have been one of the main focuses in the last couple of decades. These studies have further been promoted by several gravitational wave detectors, built a couple of years ago, such as LIGO (USA), GE600 (Germany & England), Virgo (Italy & France), and TAM300 (Japan).


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