This series covers all areas of research at Perimeter Institute, as well as those outside of PI's scope.
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
Gravitational waves provide a unique way to study the Universe. From
2005 to 2007, the Laser Interferometer Gravitational-wave Observatory
Physicists have been working for banks and hedge funds on applied problems in finance for more than two decades, and recently have doing academic research as well. This talk will survey academic research by physicists and contrast it with mainstream economics. I will argue that the difference comes not from the application of alternative techniques or new mathematics, but rather from fundamental differences in what questions are considered interesting and how one should go about solving them.
According to hidden-variables theories, quantum physics is a special 'equilibrium' case of a much wider 'nonequilibrium' physics. We describe the search for that wider physics in a cosmological context. The hypothesis that the universe began in a state of quantum nonequilibrium is shown to have observable consequences. In de Broglie-Bohm theory on expanding space, relaxation to quantum equilibrium is shown to be suppressed for field modes whose quantum time evolution satisfies a certain inequality, resulting in a 'freezing' of early nonequilibrium for these particular modes.