Research Highlights

For decades, black holes have fascinated scientists and nonscientists alike. Their ominous voids, like an open pair of jaws, has inspired a whole wave of science-fiction featuring the phenomenon. Physicists have also been similarly inspired, specifically to understand the dynamics of what is happening inside of the black hole, especially for objects thatmay fall in. The historical theories about black holes are closely linked to those within quantum physics and they suggest interesting phenomena. “The best models of black holes we have in general relativity, like the Kerr metric or the Reissner-Nordström metric, actually make some pretty crazy predictions,” explained JILA graduate student Tyler McMaken. “After you fall in, you eventually reach a spot, called the inner horizon, where we can enter into a wormhole, see a naked singularity [A region in space-time at which matter is infinitely dense], time-travel, and do a bunch of things that go against what we think should be physically possible.” To better understand the quantum mechanics of these black hole models, McMaken and JILA Fellow Andrew Hamilton and looked into the quantum effects that may be happening around and inside a black hole. From their research, they found that there was a divergence of energy into multiple levels at the inner horizon of the black hole, suggesting that quantum effects play a crucial role in how to model realistic black holes. “The exciting part of this research is the discovery that quantum effects save the day—as you approach the inner horizon, you're met with a wall of diverging energy from Hawking radiation, so that any weird, causality-violating parts of the spacetime are completely blocked off and replaced with a singularity,” McMaken added. This diverging energy split the radiation into multiple levels. “Without a full theory of quantum gravity, we won’t know exactly what happens at this singularity, but we do know that just like the Big Bang singularity, or the singularity we might find in simpler spherical black holes, it marks the end of spacetime as we know it as the curvature exceeds the Planck scale.” The results of the study have been submitted by McMaken and Hamilton for publication in the journal Physical Review D.

Long, long ago galaxies now far away formed around ravenous black holes scattered throughout the Universe. Some 12.5 billion years later, JILA scientist Gayler Harford and Fellow Andrew Hamilton have identified the superhighways that funneled gas into some of the nascent galaxies. These thruways not only routed gas to feed the monster black holes, but also supplied raw materials for the billions and billions of stars that have illuminated those galaxies ever since.

The "dark ages" of the early Universe drew to a close with the appearance of enough stars to strip electrons off most of the hydrogen atoms in the gas clouds between galaxies. By a billion years after the Big Bang, these reionized atoms had rendered the Universe transparent to light. About 12.7 billion years later, visiting JILA member Gayler Harford, Fellow Andrew Hamilton, and Nickolay Gnedin of the Kavli Institute for Cosmological Physics decided to investigate the structures formed by ordinary matter (baryons) and dark matter soon after the reionization process was complete.

Graduate student Robyn Levine, Fellow Andrew Hamilton, and colleagues from the University of Chicago’s Kavli Institute for Cosmological Physics are working on modeling how supermassive black holes grow inside galaxies.

Fellow Andrew Hamilton recently confirmed a prediction he made 10 years ago of the location of a reverse shock wave slowing the expansion of the debris from a supernova that occurred in 1006 AD. SN1006 was (and still is) the brightest supernova observed in recorded history; it was visible from Earth (without telescopes) for three years.

Understanding dark matter's role in the distribution of galaxies in the Universe is a central question in cosmology. Dark matter pervades the universe. Haloes of dark matter surround galaxies and galaxy clusters. Dark matter also forms filamentary structures that connect these haloes, forming a cosmic web, as illustrated on the right. Until recently, cosmologists tried to understand the distribution of galaxies with theoretical analyses using different-sized dark matter haloes containing zero, one, or more galaxies.

What really happens inside black holes? Andrew Hamilton and Scott Pollack, a graduate student in the Physics Department, recently decided to investigate the answer to this question. In the process, they developed a model using realistic physics that they believe better describes the internal structure of black holes.

Andrew Hamilton and Jason Lisle, who received his Ph.D. in astrophysical and planetary sciences in 2004, have proposed a new model for the flow of matter into stationary and rotating black holes. In their "river model of black holes," space flows like a river through a flat background, while objects (like light rays) that move through the river abide by the rules of special relativity.