Conference

"I describe a candidate for a fundamental physical theory called the causal theory of views. This describes a world constructed by a continual creation of events; where an event is a transition at which a small portion of the possible becomes actual. I first recall older results which includes the emergence of space and, with space, a non-relativistic N-body quantum dynamics. I next describe recent progress on this model including, in a different limit, a formulation of a cut off quantum field theory, which we describe in terms of an S-Matrix formulation of amplitudes. The dynamics is specified by an action principle consisting of a kinetic energy and potential energy term. The former are based on measures of how quickly components of causal change do so with respect to averaged notions. The potential energy terms measure how much local moves alter an observer's ""view"" of the universe, as seen from their perspective. These results show that quantum dynamics is restored in an N to infinity limit. Measurable non-linear corrections to quantum dynamics emerge to higher order in 1/sqrt{N}. "

Analogical reasoning has a long and distinguished history as a method for making discoveries in physics. I will discuss novel uses of formal analogies in twentieth century particle physics and condensed matter physics. I will then offer some reflections on how methodological lessons from these cases could inform the use of analogies in discoveries related to quantum gravity.

In modern cosmology there is an agreement that the seeds of structure formations resides in the quantum fluctuation of the geometry in the early universe, but there is no agreement about how these could be derived from a quantum theory of gravity. In this talk I present a proposal based on the covariant formulation of Loop Quantum Gravity. I describe how to define a wavefunction of the universe in this context, and a how we can study fluctuations and correlations between spacial regions. The results obtained so far has been made possible by recent progress in numerical computations. I discuss the current state of this research program and the possible implications for modeling the early universe.

Quantum gravitational phenomena dominate the physics of a black hole in the past of a high curvature spacelike surface. Because of the backreaction of the evaporation, this surface crosses the horizon. I describe a recent line of investigation on the possible evolution compatible with nonperturbative quantum gravity, and in particular I illustrate what can be predicted using loop quantum gravity.

I will discuss a number of theoretical, observational, and conceptual aspects of the Everpresent Λ cosmological model arising from fundamental principles in causal set theory and unimodular gravity. In this framework the value of the cosmological constant (Λ) fluctuates, in magnitude and in sign, over cosmic history. At each epoch, Λ stays statistically close to the inverse square root of the spacetime volume. Since the latter is of the order of H^2 today, this provides a way out of the cosmological constant puzzle without fine tuning. I will review the theoretical background of this idea. I will also describe a phenomenological implementation of this model, and discuss recent results on the statistics of its simulations and observational tests of it.

The nonlocality of causal sets gives us hope of solving the cosmological constant puzzle (``why is the universe so smooth, big and old if there is only one scale---the discreteness scale---in the theory?’’) On the other hand locality, , GR and local QFT, must be recovered from quantum gravity in the continuum approximation at large scales, which is a challenge. If we are lucky though (like Goldilocks, the universe gets the nonlocality ``just right’’) nonlocality may be a rich source of phenomenology. Yasaman Yazdi’s talk will be on cosmological models based on the nonlocality of causal sets. I will give a couple of examples of more astrophysical phenomenological models based on simple assumptions---randomness due to spacetime uncertainty and Lorentz invariance---and pose a research question: is there a model of ``quantum swerves’’?