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The Institute for Gravitation and the Cosmos (IGC) promotes interdisciplinary effort to create and develop fundamental theories and study their manifestations in the observable universe. The Institute is also developing new realms of inquiry that use novel types of astronomy to guide theoretical investigations.
Members of the IGC belong to one or more of its three centers. Specific information about research in each of the centers is available at these links:
- Research at the Center for Fundamental Theory
- Research at the Center for Gravitational Wave Physics
- Research at the Center for Particle Astrophysics
However, with its emphasis on interdisciplinary studies, the IGC is more than the sum of these centers. It stimulates collaborative research between centers as well as within each center. The history of physical science testifies to the constructive resonance between empirical results and advances in theory. The IGC provides bridges between different observational theaters, bridges between different theoretical paradigms, and an overarching structure to connect observations with theory.
Theoretical research at the Institute spans astroparticle physics, cosmology, general relativity, quantum gravity, string theory and the interface of geometry and physics. We seek to illuminate the dynamics that fuel the most energetic explosions in the universe, to elucidate aftermaths of black hole collisions, and to study the death dance of binary neutron stars as they spiral in an ever tightening embrace. General relativity and quantum physics, the great pillars of 20th century physics, have succeeded brilliantly in their own domains. But they provide strikingly different pictures of the physical universe. To unify them, we pursue both leading approaches — loop quantum gravity and string theory — as potential, possibly complementary, frameworks. These investigations are guided by the expertise in geometry and topology at the IGC and in turn inspire new developments in these areas.
Cosmology has developed over the past century from philosophical speculation to a science of precision measurements. With quantum cosmology, we attempt to describe the earliest instants of the universe which still elude us. Black holes appear in a multitude of ways in the cosmic riddle. They provide engines that drive extreme astronomical phenomena, they have emerged as the most promising sources of gravitational radiation and they serve to bring out some of the deepest puzzles that lie at the interface of gravity, thermodynamics and quantum mechanics. The IGC researchers use ideas and methods from geometry, astrophysics, computational science and fundamental theory to address this diverse array of challenges.
On the observational front, the IGC is unique in helping to develop new windows on the cosmos using each of the four forces of Nature:
- (1) Gravitational force
- Gravitational waves from collapsing stars, from merging black holes and neutron stars, and from the first moment of the universe are targets of study using LIGO (Laser Interferometer Gravitational-Wave Observatory) and the future LISA (Laser Interferometer Space Antenna). IGC scientists have played central roles in the development of theoretical under-pinnings for the new discipline of gravitational wave astronomy.
- (2) Electromagnetic force
- With its Mission Operation Center at Penn State, the Swift Gamma-Ray Burst Mission has been revolutionizing our knowledge of the powerful gamma ray bursts that can be detected from the edge of the observable universe. IGC scientists are leading the way in deriving new understandings from the Swift data.
- (3) Strong nuclear force
- The Pierre Auger Cosmic Ray Observatory monitors the arrivals of nature's most energetic particles through their nuclear interactions in the atmosphere. This new field of charged particle astronomy studies the extreme conditions that produce the highest energy cosmic rays, and IGC faculty are prominent members of the international Auger Collaboration.
- (4) Weak nuclear force
- The IceCube Neutrino Observatory at the South Pole studies high energy neutrinos which penetrate the earth because they are immune to electromagnetic and strong nuclear forces. The neutrinos are detected by their weak nuclear interactions in the ice. IGC members are major players in the IceCube deployment and analysis.
The Institute for Gravitation and the Cosmos is a catalyst that brings together research in different specialties where cross fertilization can produce major discoveries. The four novel windows on the cosmos are observing dynamic cosmic occurrences through different techniques. A holistic analysis of the collective observations provides insights that are not apparent using any one window by itself. Similarly, string theory and loop quantum gravity provide complementary perspectives which together are leading to new understandings and theoretical breakthroughs. The Institute is designed to develop such synergy between its complementary specialties and to foster new interdisciplinary fields of research.