Dark Matter in the Cosmic Context
Katherine Mack, University of Melbourne
Fri., Feb. 24, 2017, 12:30 PM in Science Center 199
Dark matter forms the foundation for all cosmic structure, and its fundamental nature is one of science's most pressing enigmas. As we search for the most distant galaxies in the universe with radio and infrared observations, we are in a position to explore the particle physics of dark matter — the possibility of annihilation, decay, or other particle interactions — through its effects on early stars and galaxies. I will give an update on the quest to identify dark matter both in the lab and in the sky, major unsolved problems in dark matter theory, and how upcoming observations of the epoch of the first cosmic structures can be used to open a new window on the dark universe.
The First Observations of Gravitational Waves from Merging Black Holes
Geoffrey Lovelace, California State University, Fullerton
Fri., Mar. 17, 2017, 12:30 PM in Science Center 199
The Laser Interferometer Gravitational-Wave Observatory (LIGO) has made the first direct observations of gravitational waves - ripples of curved spacetime - a century after Einstein predicted their existence. Each gravitational-wave signal originated from a pair of merging black holes over a billion light years away. In this talk, I will discuss LIGO's observations, the methods that made it possible, and the implications for the dawning age of gravitational-wave astronomy. I will also highlight contributions from student and faculty researchers in California State University, Fullerton’s Gravitational-Wave Physics and Astronomy Center, including comparisons of the LIGO observations with numerical calculations of the merging black holes and the gravitational waves they emitted. Near the time of merger, the gravitational waves from merging black holes can only be predicted by numerically solving Einstein's equations of general relativity. I will present new numerical-relativity simulations of merging black holes targeting LIGO's observations, and I will discuss how these and other simulations are helping to maximize our understanding of gravitational waves' astronomical sources.
Critical Gravitational Collapse to Rotating Black Holes
Thomas Baumgarte, Bowdoin College
Fri., Mar. 31, 2017, 12:30 PM in Science Center 199
Critical phenomena, i.e. the appearance of universal scaling laws and self-similarity in the vicinity of phase transitions, appear in different fields of physics and beyond. Critical phenomena in the gravitational collapse to black holes were first observed by Matt Choptuik about 25 years ago - a seminal discovery that launched a whole new field of research. Until recently, however, much of this research was restricted to spherical symmetry, and therefore could not account for effects that break this symmetry, in particular rotation. In this talk I will review the appearance of scaling laws and self-similarity close to the onset of black hole formation. I will then present new numerical relativity simulations of the gravitational collapse of rotating perfect fluids, in the absence of spherical symmetry. These simulations inform perturbative treatments of the problem, leading to the formulation of generalized scaling laws that take into account the role of angular momentum in the critical collapse to black holes.
Searching for the Secrets of the Non-Linear Universe
Tom Giblin, Kenyon College
Fri., Apr. 14, 2017, 12:30 PM in Science Center 199
We have no evidence that general relativity is wrong; every precision test is a resounding confirmation of this elegant and powerful mathematical model. Trouble is: the greatest cosmological problems of our time (likely require) us to abandon general relativity. About 95% of the Universe remains a mystery whose solution evades our abilities. I will talk about how there may still be places in general relativity that have, until now, gone unexplored. Numerical simulations are a powerful tool that can model the complex non-linear issues of general relativity on cosmological scales. I will present progress that we have made toward modeling the late Universe in its full splendor and outline where there’s hope that we can start to tackle these great questions.