# Quantum Gravity

This series consists of talks in the area of Quantum Gravity.

## Seminar Series Events/Videos

Oct 4 2018 - 2:30pm
Room #: 400
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Oct 11 2018 - 2:30pm
Room #: 400
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Oct 18 2018 - 2:30pm
Room #: 400
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Oct 25 2018 - 2:30pm
Room #: 400
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Nov 1 2018 - 2:30pm
Room #: 400
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Thursday Sep 20, 2018
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I will discuss certain irrelevant operator deformations of holographic conformal field theories that define a one parameter family of quantum field theories which are thought to be dual to quantum gravity in finite regions.
Some examples include the "$T\bar{T}$ deformation of two dimensional holographic CFTs, its generalisations and higher dimensional cousins.

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Thursday Aug 02, 2018
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Despite being broadly accepted nowadays, temperature gradients in thermal equilibrium states continue to cause confusion, since they naively seem to contradict the laws of classical thermodynamics. In this talk, we will explore the physical meaning behind this concept, specifically discussing the role played by the university of free fall. We will show that temperature, just like time, is an observer dependent quantity and discuss why gravity is the only force capable of causing equilibrium thermal gradients without violating any of the laws of thermodynamics.

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## Boundary contributions to (holographic) entanglement entropy

Thursday Jun 28, 2018
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The entanglement entropy, while being under the spotlight of theoretical physics for more than ten years now, remains very challenging to compute, even in free quantum field theories, and a number of issues are yet to be explored.

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## Towards the top quark mass from asymptotic safety

Friday Jun 08, 2018
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I will discuss a proposed mechanism to fix the value of the top quark mass from asymptotic safety of gravity and matter, and will review the status of the proposal.

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## Beyond isotropic & homogeneous loop quantum cosmology: theory and predictions

Thursday Jun 07, 2018
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In this talk I will discuss several recent advances in loop quantum cosmology and its extension to inhomogeneous models. I will focus on spherically symmetric spacetimes and Gowdy cosmologies with local rotational symmetry in vacuum. I will discuss how to implement a quantum Hamiltonian evolution on these quantizations. Then, I will focus on how we can extract predictions from those quantum geometries, and finally analyze a concrete example: cosmological perturbations on Bianchi I spacetimes in LQC.

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## The shape of a more fundamental theory?

Thursday May 31, 2018
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I suggest a minimal practical formal structure for a more fundamental theory than the Standard Model + GR and review a mechanism that produces such a structure.  The proposed mechanism has possibilities of producing non-canonical phenomena in SU(2) and SU(3) gauge theories which might allow conditional predictions that can be tested.

The slides and other writings are posted on my web page

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## BMS current algebras in three and four dimensions

Thursday May 24, 2018
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The Bondi mass loss formula has been central in the context of early research on gravitational waves. We show how it can be understood as a particular case of BMS current algebra and discuss the associated central extension. We then move down to three dimensions where a more complete picture emerges.

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## Effective line-elements in loop quantum gravity

Thursday May 10, 2018
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Canonical quantization schemes often suggest modifications to classical dynamics, such as in an effective Friedmann equation. However, although often ignored, they also necessarily imply new effects for quantum space-time leading to new (quantum) symmetries. The invariant line-element, corresponding to  new geometrical structures emerging in the presence of holonomy modifications in loop quantum gravity, shall be consistently derived in this talk. We shall use black-hole models to illustrate new features of this quantum space-time, going beyond standard Riemannian manifolds.

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## On the New Large D Limit of Matrix Models and Phases of Matrix Quantum Mechanics and SYK Models

Thursday May 03, 2018
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In the first part of the talk, I will describe the new large N limit of tensor models, based on the “index” of graphs (in contrast to the standard large N expansion  based on the “degree”), and the associated new large D limit of matrix models. This new limit sheds an interesting light on the relation between disordered models à la SYK, tensor models and black holes. In the second part of the talk, I will apply these ideas to discuss the phase diagrams of some strongly coupled matrix quantum mechanics.

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## Spin Foams: a numerical revolution

Thursday Apr 26, 2018
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In this talk, I will summarize the status of the numerical evaluation of spin foam amplitudes focusing on the Lorentzian EPRL-FK model. I will illustrate how numerical methods can lift some limitations of the theory helping us understand better its continuum and semi-classical limit.

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## LECTURES ON-DEMAND

### Roger Melko: Perimeter Institute and University of Waterloo

Speaker: Roger Melko