Category Theory OctoberFest is an informal meeting, covering all areas of category theory and its applications. It is traditionally held in October.

Current Meeting

Octoberfest 2019 will be hosted at Johns Hopkins University, Baltimore, Maryland, over the last weekend of October, the 26th/27th. The meeting will start on the morning of Saturday the 26th and end the following afternoon. As is tradition, we will have a plenary talk at 17h00 on Friday the 25th, joint with the Johns Hopkins Category Theory seminar. Mike Shulman will give the plenary talk on the theme of internal languages: “The science of notation: an invitation to internal languages”.

Organisers: tslil clingman, Daniel Fuentes-Keuthan, and David Jaz Myers.
Contact the organisers at:

Venue Details

All activity will occur on the Johns Hopkins Homewood campus, please refer to the campus map for specifics, and the Johns Hopkins directions website for further information.

Times and locations

Fri.: 17h-18h45, 205 Krieger Hall
Sat.: 09h-17h00, 205 Krieger Hall
Sun.: 09h-12h30, 205 Krieger Hall


The slides and videos below, except where otherwise noted by the author, are copyright their respective authors and made available under the terms of the following license: Creative Commons Attribution-ShareAlike 4.0 International License.

Friday, 205 Krieger Hall

17h00-18h45 Mike Shulman The science of notation: an invitation to internal languages (video)

For those arriving early, we will be congregating in 413 Krieger Hall before the talk.

Saturday, 205 Krieger Hall

08h30 Coffee and registration in Krieger 413
09h00 Raymond Puzio Posets, Lifting properties, and Completions (video)
09h30 Gershom Bazerman Dependency Structures, Locales, and the Idempotent Distributive Lattice Completion (video) (slides)
10h00 Simon Cho A quantalic perspective on persistent and magnitude homology (video) (slides)
10h30 Coffee break in Krieger 413
11h00 Todd Trimble An Elementary Approach to Elementary Topos Theory (video unavailable) (slides)
11h30 Steve Awodey An algebraic proof of the Frobenius condition for cubical sets (video unavailable)(slides)
12h00 Lunch break
14h00 Mathieu Anel A small object argument for unique factorization systems (video)
14h30 Andrew Swan Lifting Problems in a Grothendieck Fibration (video) (slides)
15h00 Nick Gurski Pseudofunctors and simplicial categories (video) (slides)
15h30 Coffee break in Krieger 413
16h00 Ellen Lehet The Explanatory Value of Category Theory (video) (slides)
16h30 Noah Chrein Knowledge Representation and Hierarchical Ontology (video) (slides)

Sunday, 205 Krieger Hall

08h30 Coffee and registration in Krieger 413
09h00 Brandon Shapiro Algebra on Cell Diagrams & Shape Independent Category Theory (video) (slides)
09h30 Amit Sharma The homotopy theory of coherently commutative monodical quasi-categories (video)
10h00 Michael Horst A Categorification of Group Cohomology (video) (slides)
10h30 Coffee break in Krieger 413
11h00 Steve Huntsman Functorial cluster embedding (video) (slides)
11h30 Dan Shiebler Incremental Monoidal Categories (video) (slides)

Travel and Accommodation Information

We will be competing with “Parent's Weekend” at JHU for hotel space, so attendees are urged to arrange accommodation as soon as proves convenient. Below we have some suggestions for hotels near to the Homewood Campus, or easily accessible via public or hotel transport.

Although there are several airports in surrounding areas, we urge those flying to use Baltimore Washington International as it is the closest and is a short train-journey away from the city. In particular the MARC train runs between the airport and Penn. station, and the Purple Circulator stops at the station.

Parking in official lots is possible, and information about this is available on the JHU visitor parking page. There is a flat 9$/day fee for weekend parking in the South Garage and San Martin Garage


Although registration is optional, we do encourage those wishing to attend to send an email to with subject “Registration” so that we can obtain an approximate headcount. There is no deadline for registration.

Talk submission is now closed.

Previous Meetings

  • 2018, CUNY
  • 2017, CMU
  • 2015, University of Ottawa
  • 2012, Concordia
  • 2011, University of Ottawa
  • 2010, Dalhousie
  • 2009, CMU
  • 2008, Concordia
  • 2006, University of Ottawa
  • 2005, University of Ottawa
  • 2004, McGill University
  • 1999, McGill University
  • 1995, McGill University