Summer Minicourses 

Ohio State University

Overview

This is the minicourse webpage for Bundles and Characteristic Classes. Tentatively, the course will break into roughly three parts. In the first part we will lay the framework for a general theory of characteristic classes by investigating the relationship between $G$-bundles and principal $G$-bundles. In the second part we will begin our investigation into characteristic classes. In the third part, time permitting, we will take a tour of one of Chern-Weil theory, characteristic classes of surface bundles or bordism.

The schedule below is subject to change based on participants' interests and background. We may take a detour into the realm of differential topology to discuss tubular neighborhoods, collar neighborhoods and transversality.

Useful references for the material discussed above will be provided below the schedule.


Tentative Schedule

Week Topics
Week 1

Day 1: Orientation and Introduction. Fiber Bundles and $G$-bundles.

Week 2

Day 1: Morphisms of $G$-bundles.

Day 2: Pullback Theorem, Fiber Bundle Construction Theorem and Associated Principal Bundle Functor.

Week 3

Day 1: The Associated Bundle Construction and the equivalence between $\mathsf{Prin}_{G}$ and $\mathsf{Bun}_{G}^{F}$. Part 1 of smooth homotopy invariance

Day 2: Part 2 of smooth homotopy invariance. Topological homotopy invariance. Classifying spaces and the universal bundle.

Week 4

Day 1: The Serre Spectral Sequence. First Computations and characteristic classes.

Day 2: More computations and the Splitting Principle.


References

Reference Comment
Milnor and Stasheff's Characteristic Classes.

This is the classic reference. It has a bit of everything. Be aware that the authors use some antiquated notation such as $\tau_{M}$ for $TM$.

Switzer's Algebraic Topology.

Switzer's book is a classic. While it is a little old-fashioned in its description of spectra and the stable homotopy category, both from the $\infty$-categorical perspective and the modern symmetric monoidal point-set definitions, it's still a useful reference. The part relevant to this minicourse is the chapter on characteristic classics and Thom classes. Switzer develops this for a general (complex oriented) cohomology theory $E$.

Bott and Tu's Differential Forms in Algebraic Topology.

Chapter IV discusses characteristic classes using de Rham cohomology. Besides this, the book has a bunch of other goodies.

Kobayashi and Nomizu's Foundations of Differential Geometry, Volumes I & II

This is another classic reference. It has a comprehensive treatment of connections in principal $G$-bundles and the curvature of such connections.

Tu's Differential Geometry: Connections, Curvature, and, Characteristic Classes.

This is an interesting book. Tu cam sometimes be imprecise with definitions but when this happens it can be cross-checked. It should be seen as an alternative to Kobayashi and Nomizu's volumes.

Spivak's A Comprehensive Introduction to Differential Geometry, Volume 2.

From chapter 7 onwards, Spivak treats all the various ways of defining connections and shows they are all equivalent.

Hirsch's Differential Topology.

This is a great book and includes a lot more than just the basic differential topology we will need. One should be wary of some of the more delicate arguments Hirsch gives, especially wherever Hirsch appeals to his so-called globalization theorem is used. An incomplete list of errata may be found here but I'm also happy to talk about anything you suspect is a misprint or simply wrong. Read carefully.

Kosinski's Differential Manifolds.

This is another book that contains all of the differential topology we will need. Besides that, this book includes a lot of great stuff and this is its strength. Just as with Hirsch, one should also be wary of incorrect arguments and typos. Many arguments in this book are simply harder than they need to be or present things in a highly non-standard way. Read carefully.


Further References

Reference Comment
Stong's Notes on Cobordism Theory.

The book doesn't have a detailed table of contents but Landweber and Ravenel have provided one here. My impression is that the book is really only for those serious about pursuing bordism but the appendix has a nice and careful treatment of some often neglected or incorrectly stated results in differential topology.

Hirzebruch's Manifolds and Modular Forms.

I can't confess to know much about this one. Genera are supposed to be important in theoretical and mathematical physics. Since genera are ring-homomorphisms from cobordism rings, it is unsurprising characteristic classes get involved.


Written Notes