Summer 2013, Central Lecture of the Graduiertenkolleg 1150 (Homotopy and Cohomology). Thur 11-13:00 (SemR 0.011) (University link). First lecture: April 11th.

**Lecture Notes and Exercises**

Full lecture notes (in one pdf, last update July 17, 2013)

- Course Syllabus
- Lecture 1: Overview (April 11, 2013)
- Exercises 1 (pdf)
- Does anyone have a link to a good video of the “belt-trick” or something equivalent?

- Lecture 2: Pontryagin’s Construction (April 18,2013)
- Exercises 2 (pdf) (29.4.2013 – begining of exercise 2.1 corrected)
- Addendum (pdf) on the relationship between stable tangential framings and stable normal framings. (there are still some errors in this. 29.4.2013)

- Lecture 3: Introduction to Jet Transversality. (April 25, 2013) (update: 29.4.2013)
- Exercises 3 (pdf) (exercise 3.2 corrected)

- Lecture 4: The Pontryagin-Thom Construction (May 2, 2013)
- Exercises 4 (pdf) (There are some really fun ones this time!)

- (No Lecture 9.5.2013)
- Lecture 5: A General Proof of Density Theorems (May 16, 2013) (like Thom’s Jet Transversality Theorem) (update 16.5.2013: Incorrect Lemma 5.1.8 stricken, proof of Globalization Thm 5.2.3 altered slightly to avoid using the faulty lemma).
- (No Lecture 23.5.2013 or 30.5.2013)
- Lecture 6: End of Proof of Jet Transversality (June 6, 2013) (see previous week for lecture notes) No exercises this week.
- Lecture 7: The h-principle, part I. (June 13,2013)
- Lecture 8: The h-principle, part II: (June 20, 2013)
- Lecture 9: The h-principle, part III (June 27, 2013)
- Lecture 10: The h-principle , part IV (July 4, 2013)
- Lecture 11: The h-principle, part V (July 11, 2013)
- Lecture 12: The h-principle, part VI (July 18, 2013)

##### Abstract

A basic problem in topology is to gain an understanding of the structure of both manifolds and maps between them. A powerful tool for this is the theory of bordism, as initiated in the mid-20th century by René Thom and Lev Pontryagin. This theory provides a powerful feedback loop between manifolds on the one hand and maps between them, on the other.

Topological field theories are a modern extension of bordism invariants. They provide a further bridge linking topology and algebra together. The classification of topological field theories, which combines methods and ideas from differential topology, homotopy theory, and higher category theory, has lead to a greater understanding of this back-and-forth interplay.

In this lecture course we will take stroll along these bridges. We will focus on some of the techniques and ideas which play a part in the classification of TFTs, beginning with the classical theory of bordism and progressing into more modern developments.

**Prerequisites**: Algebraic topology (homology, cohomology, and homotopy theory). Smooth manifolds, tangent bundles. Classifying spaces. Exposure to characteristic classes, spectra, or spectral sequences would be helpful.

**Homework:** The best way to learn is by doing, and so I will provide (optional) homework problems every week.

**Text**: There is no single text. I will give some references and I am hoping to provide lecture notes. I am drawing from lectures given by:

- Dan Freed, Bordism Old and New (UT Austin, Fall ’12). Yes, I stole his title.
- John Francis, The h-Principle in Topology (Northwestern, winter ’10/’11)
- Michael Weiss, Immersion Theory for Homotopy Theorists (U. of Aberdeen, winter ’04/’05)

#### A Preliminary List of Topics/Lectures… subject to change

- Overview
- Morse Theory and Handles, the second stable stem.
- Thom Transversality, “Transversality unlocks the secrets of manifolds”
- The Pontryagin-Thom construction
- Weak fibrations and h-principles (Segal categories?)
- The Hirsch-Smale theorem (a.k.a. Immersion theory)
- Configuration Spaces, scanning, and more.
- The third stable stem, via geometry.
- The Cobordism Hypothesis, part 1: ideas and statements
- The Galatius-Madsen-Tillmann-Weiss theorem
- The Cobordism Hypothesis, part 2: overview of the proof
- leftovers and applications.