Cosmology & Gravity Research Progress
The Quantum Gravity program was established in 1986 to address Big Questions such as, “What is the nature of gravity and its relationship to quantum physics?” and “How has the universe evolved from the moment of the Big Bang?” The program strategically strengthened Canada’s effort in theoretical cosmology, with CIFAR working with several universities to hire and retain researchers who provided the intellectual leadership for this effort.
The program expanded its scope 10 years later to include observational cosmology, numerical relativity, string theory and experimental astrophysics. Eleven members from five universities were added to the program universities to support this expansion. Renamed Cosmology & Gravity, the program become home to leaders in international efforts to measure and model the cosmic microwave background (CMB) radiation, tackle the question of how large-scale structure evolved in our universe, and explore the nature of string theory and its applicability as a “theory of everything.”
CIFAR’s CMB work, starting with early contributions to a theoretical framework and closely related observational campaigns, has led to a detailed understanding of the nature of the universe from the moment of the Big Bang through its first several hundred thousand years. Program members have also been using large-scale supernovae surveys to measure the geometry and expansion of the universe. This has led to the conclusion that the universe appears to be flat geometrically and that is expanding at an ever increasing rate. This theory, known as the Concordance Model, provides a comprehensive theoretical framework that has created new hypotheses and enabled the field of cosmology to advance rapidly. (Program members are now involved in next-generation CMB measurements, using advanced observational tools such as the European Space Agency’s Planck satellite and a balloon-borne telescope project known as Spider.)
The work of this program eventually led CIFAR to collaborate with the Natural Sciences and Engineering Council and the University of Toronto in support of a new national centre, the Canadian Institute for Theoretical Astrophysics (CITA). CITA provided both a physical centre and a national resource for theoretical astrophysical research.
In its current five-year cycle, the Cosmology & Gravity program’s core focus remains physical cosmology, covering the theory, as well as experiment and observation of the early, middle and late Universe. It also has nodes in high-energy astrophysics, numerical relativity, string theory and particle astrophysics.
The continued CMB studies are complemented by projects such as the Canada-France-Hawaii Legacy Survey, the aim of which is to amass one of the world’s largest set of supernovae observations. Efforts to understand structure formation build on projects like the Millennium Simulation, an international effort with strong Canadian involvement, which in 2005 made the most ambitious hydrodynamic simulation of the universe to date.
String theory remains a second focus of the program, and one of the most exciting sources of new ideas for an underlying theory of particles and forces. Program members continue to grapple with how to make connections between this model and our world.
The areas of high-energy astrophysics and particle astrophysics constitute the third major thrust of the program. This work involves studies of compact objects such as neutron stars, quasars (which are understood to be massive black holes) and exotic objects such as “magnetars,” which appear to be highly magnetized neutron stars. These studies are one of the few ways of testing general relativity in the regime where gravity dominates the structure of space-time. Numerical relativity, with a particular focus on black-hole dynamics, provides the theoretical framework for the observational effort of the astrophysical components of the program.