## Talks: slides and videos

**Non-commutativity and the Dirac operator**

Odense May 2019 This is an introductory talk explaining how the Dirac operator in high-energy physics has the structure of a non-commutative geometry, and how I hope to use this structure to construct models of quantum gravity.

Nottingham 2017 Another talk with a similar aim. It starts with a discussion of the Planck scale and non-commutativity and ends with a brief description of the first paper with Lisa Glaser on random non-commutative geometries.

The talk in Nijmegen in April 2016 at the conference on Gauge Theory and Noncommutative Geometry explains how the axioms of non-commutative geometry can be written in as geometric moves on diagrams (in the same way as moves on spin networks express the relations in a spherical category). The talk starts with an informal explanation of how these relate to Feynman diagrams for Dirac particles.

**The spin foam lectures**

Jan 2013 UNAM Mexico version:

- Lecture 1: Introductory and spin networks. Slides
- Lecture 2: State sum models. Slides
- Lecture 3: 3d spin foam models. Slides
- Lecture 4: 4d spin foam models. Slides

The first lecture is the same as Caen (minor corrections) but the remaining ones are new.

September 2010, Caen version:

- Lecture 1: Spin networks. Slides
- Lecture 1b: Spherical categories. Slides and screencast (streaming, mp4)
- Lecture 2: Skein algebra. Slides and screencast of part 1 (streaming, mp4), and part 2 (streaming, mp4)
- Lecture 3: State sum models. Slides and screencast of part 1 (streaming, mp4)

Previously given September 2009, Corfu, except lecture 1b is new. The lecture series is supported by FQXi.

**State sum models, induced gravity and the spectral action.**

December 2009, IHES slides of the first, brief, talk

May 2010, Bayrischzell slides of a longer talk with more detail of the proposals

May 2010, Oxford: video of the latest version of the talk, with some detail of the 2-category diagrams explaining the geometry-matter interaction in 3d (currently under development with Catherine Meusburger).

**State sum models of quantum gravity.**

June 2009, Wroclaw video and slides of the talk about the 4d state sum models of quantum gravity (for video, scroll down to #6). The talk starts with a general introduction to the ideas of spin foam models.

March 2011, Queen Mary, updated version of the slides of this talk, with pictures.

**Knots and links in braided quantum field theory.**

August 2008, Oxford, video of blackboard talk. I explain some aspects of braided quantum field theory: how it is a generating function of knots and links, and also a little about the relation to 3d quantum gravity. The physics is first. If you want the mathematical part, fast-forward to where I clear the board.

[…] 2010), using Camtasia Studio. The resulting screencasts are available from his blog page page https://johnwbarrett.wordpress.com/talks/ He has also tried out Echo360 Personal Capture, and plans to record a large number of classes using […]

Camtasia Studio and Echo360 | Explaining mathematics16 December 2010 at 20:06

[…] pointed out that John Barrett is working on LQG and NCG. (I don't understand a word of this!) https://johnwbarrett.wordpress.com/talks/ […]

LQG, NCG and all that23 August 2015 at 16:36