This series covers all areas of research at Perimeter Institute, as well as those outside of PI's scope.
Viscosity is a very old concept which was introduced to physics by Navier in the 19th century. However, in strongly coupled systems, the viscosity is usually difficult to compute. In this talk I will describe how gauge/gravity duality, a by-product of string theory, allows one to compute the viscosity for a class of strongly interacting fluids not too dissimilar to the quark gluon plasma. I will also describe efforts to measure the viscosity and other physical properties of the quark gluon plasma at the Relativistic Heavy Ion Collider.
We will review the definitions of spin foam models for quantum gravity and the recent advances in this field, such as the "graviton propagator", the definition of coherent states of geometry and the derivation of non-commutative field theories as describing the effective dynamics of matter coupled to quantum gravity. I will insist on the role of group field theories as providing a non-perturbative definition of spinfoams and their intricate relation with non-commutative geometry and matrix models.
Last May, NASA astronauts performed a challenging and flawless Space Shuttle servicing mission to the orbiting Hubble Space Telescope. With science instruments repaired on board and incredible new ones installed, the observatory is more powerful now than ever before. I will show the dramatic highlights of the mission, and present some of the first results from the refurbished telescope.
Ever since there's been money, there have been people trying to counterfeit it, and governments trying to stop them. In 1969, the physicist Stephen Wiesner raised the remarkable possibility of money whose authenticity would be guaranteed by the laws of quantum mechanics. However, the question of whether one can have secure quantum money that anyone (not only the bank) can verify has remained open for forty years. In this talk, I'll tell you about progress on the question over the last two years.
The graph isomorphism (GI) problem plays a central role in the theory of computational complexity and has importance in physics and chemistry as well. While no general efficient algorithm for solving GI is known, it is unlikely to be NP-complete; in this regard it is similar to the factoring problem, for which Shor has developed an efficient quantum algorithm.
I will describe a new connection between supersymmetry, geometry and computer science. An exploration of the equations of supersymmetry has revealed a geometrical sub-structure whose classification depends on self-dual error correcting codes.
Of all four forces only the weak interaction has experimentally exhibited parity violation. At the same time observations suggest that general relativity may require modification to account for dark matter and dark energy. Could it be that this modification involves gravitational parity violation? Many of the dominant approaches to quantum gravity, such as string theory and loop quantum gravity, point to an effective parity violating extension to general relativity known as Chern-Simons General Relativity (CSGR).
Is there a theory yet to be discovered that underlies quantum theory and explains its structure? If there is such a theory, one of the features it will have to explain is the central role of complex numbers as probability amplitudes. In this talk I explore the physical meaning of the statement “probability amplitudes are complex” by comparing ordinary complex-vector- space quantum theory with the real-vector-space theory having the same basic structure.
In 1981 Bill Unruh showed that the equation of motion for sound waves in a
convergent fluid flows is given by a wave equation in an acoustic metric
geometry. More importantly it is possible to set up sonic horizons in
transsonic flows, and thus in principle to mimic experimentally the