Quantum Gravity
Georgia Tech Physics 8823 special topics course, Fall 2019

Instructor: Tom Banks

These are recordings of the first two lectures of the course. 

This detaild introduction/overview of the course emphasizes that Quantum Gravity (QG) is a theory that doesn't exist yet, but String Theory gives us some clues. 

The course describes QG in space-times unlike that in which we live.  The striking fact about string theory is that all of its quantum variables live on a "holographic screen" that is infinitely far away from any trajectory in the bulk of the space-time.  The Holographic Spacetime Theory (HST), which is the subject of this course, is a compromise between this Extreme Holography and local Quantum Field Theory (QFT), which is not the correct theory of quantum gravity.  Given a choice of timelike trajectory in a spacetime, the quantum variables can be organized to be associated with finite "causal diamond", subregions that can be accessed during a fixed proper time interval along that trajectory.  A quantum version of Einstein's relativity principle relates the descriptions along different trajectories.  

The first two lectures, which I've divided into short segments, introduce the basic ingredients of General Relativity (GR) necessary to understand HST.  We will review more GR if the students ask for more details. 

Lectures also describe Jacobson's Principle, which when combined with the idea from QFT that variables associated with space-like separated regions should commute, translates the metric structure of a space-time into a quantum mechanical notion.

Segment 1, Chapter 1 Introduction
Segment 2, Chapter 1 Causal diamonds
Segment 1, Chapters 2 Holographic spacetime - 13 Raychaudhuri equation
Segment 3, Chapters 1 Raychaudhuri equation - 7 Outline of the rest of the course