Research Highlights / Full Story

Computational Relativity and Gravitation

Research conducted at the center is tied to Einstein’s Theory of General Relativity, first published in 1915. His ideas redefined gravity and foresaw contemporary astrophysics. Einstein envisioned gravity as the geometry of space-time—the fabric of the universe—instead of as the Newtonian concept of force. 

Center Director Manuela Campanelli and her colleagues are celebrating the centennial year of Einstein’s famous theory with invited talks and a conference and workshop at RIT in May, among other activities. 

The Center for Computational Relativity and Gravitation (CCRG)—a research hub and an RIT Research Center of Excellence in the College of Science—has won nearly $7 million in federal grants since it formed in 2007. The center consists of 26 members, including 10 faculty, administrative staff, postdoctoral researchers, and Ph.D. students. Last year, assistant professors Richard O’Shaughnessy and Jason Nordhaus joined the team.

Faculty members affiliated with the center hold positions in three different colleges at RIT: the School of Mathematical Sciences and the School of Physics and Astronomy in the College of Science; the Department of Computer Science in the Golisano College of Computing and Information Sciences; and the Department of Science and Mathematics in the National Technical Institute for the Deaf. 

Likewise, the center is affiliated with the astrophysical sciences and technology Ph.D. program and MS graduate programs—applied and computational mathematics, computer science, and data science. Future affiliations will draw upon two programs pending approval, a Ph.D. in mathematical modeling and an MS in physics.

“When it was created it was one of only a few centers of its kind,” said Campanelli, professor of mathematics and program faculty in astrophysical sciences and technology. “It’s a model that has been repeated at other universities. The CCRG is now one of the largest and most renowned research groups in gravitational physics in the world.”

 

 

 

 
A New Era for Astrophysics

Einstein’s prediction of gravitational waves and the black holes that produce them still impacts and inspires new fields of research, Campanelli said. 

General relativity led to numerical relativity, a specialized field of study that involves solving Einstein’s equations with sophisticated mathematics and supercomputers, and further offshoots like computational relativistic astrophysics, gravitational wave astrophysics and observations, and galactic and stellar dynamics. Solving Einstein’s equations draws upon mathematics, astrophysics, and computer programming, requiring expertise in mathematical modeling, high-performance advanced computation, data analysis and statistics in connection with big data and scientific visualization. 

Contributions from Campanelli and professors Carlos Lousto and Yosef Zlochower have advanced numerical relativity over the last decade. In 2005, while at the University of Texas at Brownsville, the team, led by Campanelli, made a scientific breakthrough that computationally solved Einstein’s strong field equations to describe the merger of two black holes and the resulting gravitational waves.

Simulations of gravitational waves are the blueprints other scientists will use to observe actual gravitational waves at observatories in Hanford, Wash., and Livingston, La., and other advanced detectors in the world. Campanelli, Lousto, O’Shaughnessy, and professors John Whelan and Hans-Peter Bischof belong to the international LIGO Scientific Collaboration, along with several Ph.D. students and postdoctoral researchers. Hundreds of scientists analyze data taken by the Laser Interferometer Gravitational Wave Observatory (LIGO) and other detectors searching for gravity waves emitted by the violent collisions of massive astrophysical systems. Contributions of LIGO scientists have advanced gravitational physics with the anticipation of direct observations of gravitational waves by the end of the decade. The CCRG’s gravitational wave data analysis group, led by Whelan and O’Shaughnessy, works within the LIGO Scientific Collaboration to develop and implement methods to detect and interpret gravitational wave signals in the advanced detector data.

“So far, in astronomy, we’re looking at the universe with electromagnetic waves, signals that come to us from the stars traveling at the speed of light,” Campanelli said. “Gravitational waves, which also travel at the speed of light, are a completely new form of radiation. It’s not the same spectrum. The shape of the gravitational waves—the way the energy is distributed—will tell us what the source was. They can even help us probe the universe fractions of a second after the Big Bang.” 

The center’s signature projects simulate the inspiral and merger of binary black holes using various permutations of mass and spin. Campanelli, Lousto, and Zlochower are authors of numerous papers that have led to the famous discovery of large gravitational-radiation recoils (up to 5000 km/s) from merging spinning supermassive black holes, the study of spin dynamics effects, such as spin-flips, precession and hang-up orbits, and extreme mass-ratio binaries. 

More recently, a focus on extreme pairs of spinning binaries of black holes, led by Lousto and postdoctoral researcher James Healy, revealed a new discovery, dubbed the “spin flip-flop” effect. The work, which was recently accepted by Physical Review Letters, demonstrates that a pair of spinning black holes under certain conditions can completely reverse their spins in just a few hundreds of orbits, possibly producing shocks and electromagnetic signatures
in their surrounding accretion disks.

In a departure from her gravitational-wave studies, Campanelli is exploring electromagnetic emissions resulting from black holes and their accretion disks at the centers of quasars—the cores of primitive galaxies—and the surrounding magnetized gas. She and her Ph.D. students, Dennis Bowen and Brennan Ireland, are collaborating with a large team of scientists both at RIT and at other universities such as Johns Hopkins University, the University of Tulsa, and the University of Kyoto.

In a related project, professors Nordhaus and Joshua Faber are working to solve the equations of magneto-hydrodynamics to learn what happens
when stars are tidally disrupted by supermassive black holes residing at the center of galaxies.

 

 

Black Hole Lab

At the heart of the center is the Black Hole Lab and its advanced computer clusters NewHorizons and BlueSky.

The facility showcases the center’s research and its commitment to green computing. Opticool Technologies, an in-rack green cooling solution installed in 2012, has a 60-ton cooling capacity. It is more efficient than traditional HVAC solutions and safer than water-based solutions that could develop faulty cooling lines, Campanelli noted.

BlueSky Linux is a 1040 processor cluster with more than four terabytes of onboard DDR3 RAM and 200 terabytes of high-speed Lustre-based storage interconnected with a QDR InfiniBand network. NewHorizons is a 736 processor Linux cluster with 3 TB of onboard RAM and over 100 TB of storage. 

Scientists at the center supplement the Black Hole Lab with supercomputing resources at the National Center for Supercomputer Applications. Some of their largest simulations are done at the peta-scale Blue Waters system at the Illinois’ National Center for Supercomputer Applications (NCSA) and XSEDE resources. “This is one of the most powerful supercomputers in the world available for open scientific research,” said Campanelli. “Our resources, combined with CCRG's key experts in the field, are why we are one of the main contributors to the rapid growth of gravitational physics.”