Nov 26 2013
Scientists at Rochester Institute of Technology are on the hunt for gravitational waves and clues about the early universe. Their simulations of black holes colliding—and the gravitational waves produced from the impact—will be the blueprints for detecting actual gravity waves and verifying Einstein's theory of general relativity—an event that could occur within the decade.
Astrophysicists in RIT's Center for Computational Relativity and Gravitation will simulate extreme black holes with support from a $525,000 grant from the National Science Foundation. Their contributions will help advance the international effort to confirm the existence of gravitational waves and black holes, and anticipate the new field of gravitational wave astronomy.
Manuela Campanelli and Carlos Lousto—fellows of the American Physical Society and founding members of RIT's Center for Computational Relativity and Gravitation—and Yosef Zlochower are known for one of the first simulations to merge two black holes on a supercomputer. Their method solved the 10 interrelated equations for strong field gravity that comprise Albert Einstein's famous theory of general relativity, connecting matter, space and time.
Campanelli and Lousto belong to the international collaboration supporting the Advanced Laser Interferometer Gravitational Wave Observatory. Advanced LIGO is a series of ground-based detectors working in unison to identify and measure gravitational wave forms for the first time. Advanced LIGO will start operation in 2015. The detectors will collect data for one to two years before the information is analyzed to increase the probability of capturing several black-hole mergers. Direct observation of gravity waves could occur as early as 2017, according to Lousto.
"It will be a historic moment," says Lousto, associate professor in RIT's School of Mathematical Sciences. "The theory of general relativity will be 100 years old in December 2015, and we're trying to verify one of its boldest predictions. Gravitational waves don't exist in Newton's theory. This is a genuine prediction of general relativity, the theory of gravity."
Gravitational waves are created by the impact of massive bodies like black holes or neutron stars and can pass through matter. In contrast, photons—or units of light—in the electromagnetic spectrum are created when stars break apart. Matter blocks the movement of photons and disperses them into clouds of electrons.
"With gravitational wave astronomy, we can reach areas of the universe that cannot be reached by any other means," Lousto says. "Some people call it the dark side of the universe because of the black holes and because we can get much closer to the Big Bang and to much earlier times. With electromagnetic waves you can only see what happened 300,000 years later."
Faint signals of gravitational waves, weakened by time and space, reach Earth undetected. Highly sensitive detectors were developed for Advanced LIGO to perceive what has gone unnoticed. RIT's simulation-blueprints will help other scientists in the collaboration identify actual gravitational waves from the "noise" drawn down from space.
Access to supercomputers at the Texas Advanced Computing Center at the University of Texas at Austin and at the San Diego Supercomputer Center will enable Lousto and his colleagues at RIT to model more complex systems with certain mass ratios and spins. The Extreme Science and Engineering Discovery Environment, an NSF-funded cyberinfrastructure for sharing computing resources, recently awarded the center a large amount of time on these facilities.
These allocations are essential for simulating how the universe formed from the Big Bang; the role black holes may have played in creating galaxies; and whether black holes at the early stages of the universe formed with small or large masses. The scientists will extend their results to generate statistical distributions to model the structure of the universe.
Another aspect of research the NSF funding supports compares different gravitational waves. New simulations will allow Lousto and his colleagues at RIT to single out different signatures of gravitational waves predicted in alternative theories of general relativity. A comparative wave or signature study will discern wave patterns that are unique in one theory and cannot be reproduced in another.
Einstein wasn't content with general relativity, Lousto says. He thought there should be a grand unifying theory.
"We know general relativity has problems," Lousto says. "Combining general relativity and quantum theory is not compatible. We know we have to move one step forward from general relativity, but we don't know what it is. Hopefully, gravitational waves will give us clues on how general relativity has to be generalized or if it must be changed completely. We are in the search of a unifying theory. The theory of everything."