Gammie selected for 2015 Simons Fellowship

Siv Schwink
3/17/2015 12:00 AM

U. of I. Professor of Physics and Astronomy Charles Gammie
U. of I. Professor of Physics and Astronomy Charles Gammie
Professor Charles Gammie has been named a 2015 Simons Fellow in Theoretical Physics by the Simons Foundation.

Gammie, who has joint appointments in astronomy and physics at the University of Illinois at Urbana-Champaign, will use the fellowship to continue his leading-edge theoretical work in black hole astrophysics, while on sabbatical next academic year at the University of Oxford in the United Kingdom. While abroad, Gammie will also enjoy an appointment as a visiting fellow at All Souls College in Oxford, for the fall (Michaelmas) term. 

A major thrust of Gammie’s theoretical work at the U. of I. is investigating the gravitational field of black holes, particularly in the unexplored strong field regime near the black hole event horizon, and using that to test general relativity, one of the fundamental theories of physics.

A related research focus for Gammie is exploring the physics that govern black hole accretions. Accreting black holes are among the most luminous objects in the universe; the radiation from supermassive accreting black holes at galactic centers can outshine their entire host galaxies. Accretion disks can also affect the evolution of a galaxy. Specifically, Gammie’s team was the first to develop fully relativistic fluid models of the luminous hot plasma that surrounds black holes, elucidating emission properties of hot plasmas, and developing techniques for relativistic radiative transport that can be used to simulate observations, including inclination, spin, and accretion rate of the black hole.

Gammie’s group at the U. of I. has been active in laying the theoretical groundwork for the North American Event Horizon Telescope and the European Black Hole Cam collaborations (EHT/BHC). These collaborations are working together to create an expanded network of millimeter-wavelength telescopes that, by 2017, may provide the first-ever high-contrast image of the silhouette of the supermassive black hole at the center of the Milky Way galaxy.

Gammie’s team is currently developing new models for Sgr A* at the center of the Milky Way galaxy, known to contain the supermassive black hole. The new models take into account the physical processes present in hot, dilute (collisionless) plasmas: heat conduction, viscosity, and decoupling of the temperatures of the plasma’s constituent ions and electrons.

Because dissipative relativistic fluid theories that incorporate these effects are impossible to solve with existing numerical methods, his team is devising novel numerical techniques to solve them. Existing models also fail to account for modification of the flow by its own radiation field, a negligible effect in Sgr A* that is nonetheless important for the only other black hole candidate—in the nucleus of the galaxy M87—that will be resolved by EHT/BHC. This year, his team will complete the first models that self-consistently (relativistically) incorporate radiative effects.

While on sabbatical next year, Gammie will explore problems motivated by his teams new models of Sgr A*. Gammie is looking forward to the rich intellectual environment and new collaborations this opportunity will afford:

“Oxford has an excellent astrophysics program—one of the best in Europe—and lots of good people working in my areas of interest. I'm particularly excited about working with an old mentor of mine, Steven Balbus, who is now Savilian Professor at Oxford. I'm also excited about talking to people at Oxford who observe black hole candidates, as well as those who work in plasma astrophysics. All Souls is a postgraduate college that is focused entirely on research, and I'm told it provides a wonderful, interesting community of scholars to visiting faculty," he shares.

 

The Simons Foundation is a private foundation based in New York City, incorporated in 1994 by Jim and Marilyn Simons, with the mission of advancing the frontiers of research in mathematics and the basic sciences. The Simons Foundation Mathematics and Physical Sciences (MPS) division supports leading research efforts in mathematics, theoretical physics and theoretical computer science.

 

 

Recent News

It took two years on a supercomputer to simulate 1.2 microseconds in the life of the HIV capsid, a protein cage that shuttles the HIV virus to the nucleus of a human cell. The 64-million-atom simulation offers new insights into how the virus senses its environment and completes its infective cycle.

The findings are reported in the journal Nature Communications.

  • Accolades

The Center for Advanced Study has appointed seven new members to its permanent faculty – one of the highest forms of academic recognition the University of Illinois campus makes for outstanding scholarship. The new CAS Professors are Antoinette Burton, history; Gary Dell, psychology; Eduardo Fradkin, physics; Martin Gruebele, chemistry; Sharon Hammes-Schiffer, chemistry; Harry Liebersohn, history; and Catherine Murphy, chemistry. They join 21 other CAS Professors with permanent appointments, and they will remain full members of their home departments while also serving on the annual selection committee for the CAS Associates and Fellows program.

  • In the Media
  • Biological Physics

A common bacteria is furthering evidence that evolution is not entirely a blind process, subject to random changes in the genes, but that environmental stressors can also play a role. A NASA-funded team is the first group to design a method demonstrating how transposongs-DNA sequences that move positions within a genome-jump from place to place. The researchers saw that the jumping rate of these transposons, aptly-named "jumping genes" increases or decreases depending on factors in the environment, such as food supply.

  • Research
  • Condensed Matter Physics
  • Condensed Matter Theory
  • ICMT
  • Institute for Condensed Matter Theory

Researchers at the University of Illinois at Urbana-Champaign and Princeton University have theoretically predicted a new class of insulating phases of matter in crystalline materials, pinpointed where they might be found in nature, and in the process generalized the fundamental quantum theory of Berry phases in solid state systems. What’s more, these insulators generate electric quadrupole or octupole moments—which can be thought of roughly as very specific electric fields—that are quantized. Quantized observables are a gold standard in condensed matter research, because experimental results that measure these observables have to, in principle, exactly match theoretical predictions—leaving no wiggle room for doubt, even in highly complex systems.

The research, which is the combined effort of graduate student Wladimir Benalcazar and Associate Professor of Physics Taylor Hughes of the Institute for Condensed Matter Theory at the U. of I., and Professor of Physics B. Andrei Bernevig of Princeton, is published in the July 7, 2017 issue of the journal Science.