Classical and Quantum Gravity - Dr. Wang, Dr. Shen, Dr. Kirsten
Gravity, Cosmology and Astroparticle Physics Group (GCAP) conducts research in classical and quantum gravity, and their applications to astrophysics and cosmology. Currently research topics include string inflation, current acceleration of the universe, the cosmological constant problem, brane worlds, black holes, their thermodynamics and formation, gravitational radiation, and nonlinear dynamics and critical phenomena at the threshold of black hole formation.
One of remarkable discoveries over the past few years in astronomical physics is that currently our universe is at accelerating expansion. In Einstein's theory of gravity, to account for such an expansion, a new component to the matter fields of the universe with a large negative pressure is needed, the so-called dark energy. Recent astronomical observations indicate that our universe is flat and currently consists of approximately 70% dark energy, 25% dark matter, and 5% baryon matter and radiation.
Another outstanding problem in gravitational and particle physics is the so-called hierarchy problem, that is, the large difference in magnitude between the Planck and electroweak scales. To solve this problem, brane-world scenarios were proposed in 1998/99, in which our four-dimensional universe is considered as a 3-brane embedded in a high dimensional bulk spacetime. An important result of such investigations is that high dimensional black holes are predicted to be produced in the next generation of colliders in laboratories.
Einstein's general theory of gravity predicts the existence of black holes and gravitational waves. Black hole physics, including thermodynamics of black holes, and gravitational collapse and formation of black holes, have been one of the main focuses in gravitational physics in the last couple of decades. These studies have further been promoted by several newly-built gravitational wave detectors, such as LIGO (USA), GE600 (Germany & England), Virgo (Italy & France), and TAM300 (Japan).
String Theory/M-Theory - Dr. Cleaver, Dr. Shen, Dr. Kirsten
The Early Universe Cosmology and Strings Group conducts research in a variety of gravitational physics, cosmology and high energy astrophysics areas. Superstring theory is presently the only known framework providing a consistent theory of quantum gravity, allowing it to probe the earliest moments of the universe. In this sense, superstring theory may be thought of as a window to the Creation itself. Members of the EUCOS group are currently examining the construction of phenomenologically realistic superstring models, their dual models, and M-theory embeddings. Such models should yield as their low energy effective field theory either the Standard Model or the Minimal Supersymmetric Standard Model.
Additionally, the 'second string revolution' has opened up numerous new directions in string/M-theory research, many of which are cosmological in nature. Cosmology and quantum gravity are only two of the exciting areas also being investigated within EUCOS. Many aspects of gravitation and quantum cosmology, including braneworld scenarios and brane cosmology, are being examined in coordination with the GCAP group, using tools from general relativity, superstring theory and M-Theory.