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.
I will argue that anthropic reasoning is unnecessary or misleading when the universe/multiverse is small enough that another observer with exactly your memories is unlikely to exist. Instead, one can evaluate theories or make predictions in the standard Bayesian way, based on the conditional probability of something unknown given all that you do know. Things are not so clear when the universe is large enough that all competing theories predict that an observer with your exact memories exists with probability close to one.
TBA
We present a holographic framework for inflationary universes, in particular those that are either asymptotically de Sitter or asymptotically power-law. This framework reveals how cosmological observables, including the primordial power spectrum and non-Gaussianities, are encoded in the correlation functions of a three-dimensional non-gravitational quantum field theory. Introducing a simple yet general class of holographic models, we obtain distinctive observational predictions that are compatible with current observational data and may be either confirmed or excluded by Planck.
Problematic growths of curvature and anisotropy are found in nonsingular bouncing cosmologies that include both an ekpyrotic phase and a bouncing phase. Classically, initial curvature and anisotropy that are suppressed during the ekpyrotic phase will grow back exponentially during the nonsingular bouncing phase. Besides, curvature perturbations and anisotropy are generated by quantum fluctuations during the ekpyrotic phase. In the bouncing phase, an adiabatic curvature perturbation grows to dominate and gives rise to a blue spectrum that spoils the scale-invariance.
Einstein's theory of General Relativity and its couplings to matter in 3+1 dimensions can be slightly enlarged with the requirement of a local scale (conformal) symmetry and the corresponding gauge degrees of freedom. This form of the theory is a prediction from 2T-gravity in 4+2 dimensions. It has no dimensionful constants, not even the gravitational constant, and requires all scalar fields to be conformally coupled to gravity and to the rest of matter. The theory can be gauge fixed to the usual gravity theory in the Einstein frame, thus generating the gravitational constant.
I will briefly review the predictions of the theory of the Selection of the Initial Conditions of the Universe from the Landscape Multiverse and focus on recent and upcoming evidence. In this theory, the wavefunction of the universe propagating on the landscape is localized via Anderson localization. Decoherence of the wavefunction is triggered by the backreaction of massive superhorizon fluctuations. Thus the selection of the initial conditions is determined by the quantum dynamics of gravitational (vacuum energy) vs. matter degrees of freedom.
TBA
This talk will be a heuristic discussion of the challenges for the big bang inflationary picture and possible approaches for addressing them.
I will discuss a novel framework of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike
inflation, this scenario requires no exponential superluminal expansion of
Check back for details on the next lecture in Perimeter's Public Lectures Series