Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA). PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
It is a standard axiom of quantum mechanics that the Hamiltonian H must be Hermitian because Hermiticity guarantees that the energy spectrum is real and that time evolution is unitary. In this talk we examine an alternative formulation of quantum mechanics in which the conventional requirement of Hermiticity is replaced by the more general and physical condition of space- time reflection (PT) symmetry. We show that if the PT symmetry of H is unbroken, Then the spectrum of H is real. Examples of PT-symmetric non-Hermitian Hamiltonians are $H=p^2+ix^3$ and $H=p^2-x^4$.
This is an introduction to background independent quantum theories of
gravity, with a focus on loop quantum gravity and related approaches.
Basic texts:
-Quantum Gravity, by Carlo Rovelli, Cambridge University Press 2005 -Quantum gravityy with a positive cosmological constant, Lee Smolin,
hep-th/0209079
-Invitation to loop quantum gravity, Lee Smolin, hep-th/0408048 -Gauge fields, knots and gravity, JC Baez, JP Muniain
Prerequisites:
This is an introduction to background independent quantum theories of
gravity, with a focus on loop quantum gravity and related approaches.
Basic texts:
-Quantum Gravity, by Carlo Rovelli, Cambridge University Press 2005 -Quantum gravityy with a positive cosmological constant, Lee Smolin,
hep-th/0209079
-Invitation to loop quantum gravity, Lee Smolin, hep-th/0408048 -Gauge fields, knots and gravity, JC Baez, JP Muniain
Prerequisites:
Globular proteins, which act as enzymes, are a key component of the network of life. Over many decades, much experimental data has been accumulated yet theoretical progress has been somewhat limited. We argue that the key results accumulated over the years inexorably lead to a unified framework for understanding proteins. Our framework yields predictions on the existence of a fixed menu of folds determined by geometry, the role of the amino acid sequence in selecting the native state structure from this menu and the propensity for amyloid formation.
I discuss the backreaction of inhomogeneities on the expansion of the universe. The average behaviour of an inhomogeneous spacetime is not given by the Friedmann-Robertseon-Walker equations. The new terms in the exact equations hold the possibility of explaining the observed acceleration without a cosmological constant or new physics. In particular, the coincidence problem may be solved by a connection with structure formation.
We express the total equation of state parameter of a spatially flat Friedman-Robertson-Walker universe in terms of derivatives of the red-shift dependent spin-weighted angular moments of the two-point correlation function of the three dimensional cosmic shear. In the talk I will explain all the technical terms in the first sentence, I will explain how such an expression is obtained and highlight its relevance for determining the expansion history of the universe.
We express the total equation of state parameter of a spatially flat Friedman-Robertson-Walker universe in terms of derivatives of the red-shift dependent spin-weighted angular moments of the two-point correlation function of the three dimensional cosmic shear. In the talk I will explain all the technical terms in the first sentence, I will explain how such an expression is obtained and highlight its relevance for determining the expansion history of the universe.
From at least the fifth century B.C.E., music became a way of knowing the world, when Pythagoras discovered the mathematics of musical beauty. Proclaiming that certain simple ratios produce the most pleasing harmonies, he offered them as one element in the structure of an orderly universe. Yet, right from the beginning, vexing paradoxes arose. When multiplied to higher and higher frequencies, the very formulas that form what seem to be covenants under heavens watchful gaze produce tones that are antagonistic, refusing to merge peacefully. The structure of musical space appears to warp.