Gravity from the Quantum Dynamics of Shape

What can we measure if not the ratios of lengths of objects in our local neighborhood and the angles between them? Take a group of objects. Change their overall orientation and size. Move their origin. None of these operations can ever effect anything that is measurable in the system. Only the fundamental shape of the objects has any empirical significance. Yet, all of our physical theories of Nature assume more structure than this. The theory that assumes the least is Einstein's theory of gravity but, even in this elegantly simple theory, the global size of the universe is thought to have physical significance. I believe this to be a defect of the theory: a defect which has led to many difficulties in understanding how to develop a quantum theory of gravity. Instead, I propose that Einstein's theory is just a special limit of a new theory in which only the shape of the universe evolves. Though this approach is still early in its development, there are strong clues that this new theory may be free of some of the problems that plague the quantum version of Einstein's theory. Other clues suggest that the scale appearing in Einstein's theory will emerge naturally out of this new theory as a kind of phase transition similar to what happens when water turns into ice. In this talk, I will explain some of the problems with Einstein's theory and describe how shape dynamics might help to eliminate them.

Sean Gryb is a PhD candidate working under the supervision of Lee Smolin at the University of Waterloo and the Perimeter Institute (PI) for Theoretical Physics. He received his Bachelor of Science at the University of Western Ontario and his Masters of Science from the University of Waterloo, both in physics. His research interests involve understanding the nature of quantum spacetime. He has several years of experience teaching physics in the lab and in the classroom at the undergraduate level, and has contributed dozens of public talks to an international audience of students, teachers, and science buffs. Most notably, he gave lectures as part of PI’s Physica Phantastica tour and Black Hole sessions. He has been a science advisor for PI’s film The Mystery of Dark Matter and has appeared in PI’s film The Challenge of Quantum Reality. Finally, he is actively involved in collaborations with artists and has participated in a round table discussion between artists and physicists as part of the Universal Code exhibition at the Power Plant in Toronto.