Astrophysics and Space Science Theory Group (ASSTG) - Dr. Hyde, Dr. Matthews, Dr. Kong, Dr. Qiao
Members within the Astrophysics and Space Science Theory Group (ASSTG) conduct research in a variety of areas with current research topics including complex (dusty) plasmas, gravitoelectrodynamics, protoplanetary / protostellar evolution, grain charging in dense and tenuous dusty plasmas, grain coagulation in nebular clouds, ordered grain lattice formation within dusty plasmas, wave propagation through ordered and disordered dusty plasmas as well as numerical modeling of shock (low and hypervelocity impact) physics.
Specific areas of current interest include:
Coagulation of charged micron-sized dust. The coagulation of micron-sized dust plays an early role in the process of protoplanetary formation. Protoplanets are formed from the gas and dust left in the circumstellar disk of a newly formed star. This gas and dust must coalesce on a relatively short time scale. The dust is immersed in a plasma environment and thus becomes charged. Depending on the plasma conditions and the dust size distribution, the dust particles may become oppositely charged, which would enhance coagulation rates. The dust also forms fluffy fractal aggregates as the particles collide and stick. This also enhances the coagulation rate as the fluffy aggregates have a larger cross-sectional area for future collisions.
Micro-, Meso- and Nanoscale Formation in Complex Plasmas. The formation of micro-, meso- or nanoscale crystals, clusters and balls in low temperature plasmas is a recent (and very interesting) problem in complex plasmas. In a Yukawa system, charged microparticles interact with one another through a screened Coulomb potential allowing system ordering ranging from gas->liquid->solid phases. These particles self assemble into structured formations depending on the specific boundary conditions. This research area is of great interest in nanofabrication and manipulation and is on the cutting edge of nanoscience research.
Dynamics of charged grains in Saturn's F Ring. Saturn's F Ring is a dynamic system with Voyager pictures revealing braids, kinks, and clumps that evolve in a matter of weeks or months. The plasma conditions in the F Ring are unknown, but it is likely that the micron sized dust in the ring is weakly charged. Saturn's magnetic field can impart a significant perturbation to the orbits of of these grains, while having negligible effect on the larger grains. This leads to a size-sorting mechanism which may influence the formation of braids and clumps.
Relativistic Astrophysics - Dr. Wang, Dr. Cleaver, Dr. Shen, Dr. Kirsten
The Gravity, Cosmology and Astroparticle Physics Group (GCAP) and the Early Universe Cosmology and Strings Group (EUCOS) conduct research in classical and quantum gravity and string and M-theory 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).