Meetings

Meeting 1:

19 November 2025, University of Nottingham 

The meeting is open to everybody. Participants from the four nodes may be offered travel reimbursement. We hope to be able to reimburse all staff and PhD students from the nodes, but if (depending on participants numbers) any budget issues arise priority will be given to PhD students and early career researchers.

Here is the Registration form, where you have the option to submit an abstract for a contributed talk.

The deadline for abstract submission is 5 November 2025.

Invited speakers:

Léonard Guetta (Utrecht University)

Nima Rasekh (University of Greifswald)

Location

• Pre lunch session: Room B13 in the Xu Yafen Building, Jubilee Campus, Google Maps

• Post lunch sessions: Lecture Theatre LT1 in the Exchange Building, Jubilee Campus, Google Maps 

Travel from Nottingham train station to campus

• By taxi: exit the station at Queens Road entrance, then call a taxi

• By bus: exit at the main station entrance, then walk to Victoria Centre, then take bus 28 or 30 to Jubilee Campus.

Programme 

• 11:00 - 11:15   Welcome

• 11:15 - 12:30   Léonard Guetta: Lax Functoriality of the higher Grothendieck construction and  Gray ω-categories

• 12:30 - 14:00   Lunch break

• 14:00 - 15:15   Nima Rasekh: Filter Quotient Models in Homotopy Type Theory

• 15:15 - 16:00   Break

• 16:00 - 17:40   Introductions and speed talks by the four network  co-organizers (Eric Finster, Nicolai Kraus, Nicola Gambino, Simona Paoli) and by Calum Hughes, Giacomo Tendas, Michele Riva, Stiéphen Pradal.

Titles and Abstracts

Leonard Guetta:

Title: Lax Functoriality of the higher Grothendieck construction and Gray ω-categories

Abstract: In this talk, I will present recent joint work with Dimitri Ara on extending the Grothendieck construction to ω-categories, with a focus on its functorial properties. I will explain how this extension naturally leads us to consider lax Gray ω-categories—a variant of ω-categories in which the interchange law holds only up to a non-invertible cell. This opens up an unexplored and exciting new direction in higher category theory. Reference: arXiv:2503.08832

Nima Rasekh:

Title: Filter Quotient Models in Homotopy Type Theory

Abstract: Since the early days of homotopy type theory (HoTT), a central goal has been to identify and classify its models, thereby clarifying the correspondence between homotopical syntax and semantics. This commenced with the simplicial model and expanded through numerous subsequent constructions, ultimately culminating in the result that every Grothendieck ∞-topos provides a model of HoTT. While this has been a significant achievement, it has long been anticipated that many potential models remain unexplored.

In this talk, I introduce a new approach to constructing models of HoTT via the filter quotient construction. Filter quotients were first introduced in category-theoretic foundations as a systematic way to construct new models, analogous to the set-theoretic forcing method. Recently, I have extended these concepts to the ∞-categorical setting, leading to the construction of filter quotient ∞-categories. I will explain how the ∞-categorical filter quotient construction preserves models of HoTT, thereby yielding an entirely new class of models. Time permitting, I will also explore how this framework can be used to produce models with tailored properties, thereby yielding new independence results.

Participants

• Aref Mohammadzadeh (University of Nottingham )

• Axel Ljungström (University of Nottingham)

• Bruno Lindan (University of Manchester)

• Calum Hughes (University of Manchester)

• Cameron Kemp (University of Nottingham)

• Eric Finster (University of Birmingham)

• Fredrik Bakke (Norwegian University of Science and Technology (NTNU))

• Giacomo Tendas (University of Manchester)

• Ieke Moerdijk (University of Sheffield/Utrecht)

• Ishan Dasgupta Samarendra (King's College, University of Cambridge)

• Jonathan Davies (University of Nottingham)

• Kunhong Du (School of Computer Science, University of Nottingham)

• Leonard Guetta (Utrecht University)

• Mark Williams (University of Nottingham)

• Martin Ray (University of Nottingham)

• Michele Riva (University of Manchester)

• Nicola Gambino (University of Manchester)

• Nicolai Kraus (University of Nottingham)

• Nima Rasekh (University of Greiswald)

• Owen Chan (University of Manchester)

• Pouya Partow (University of Birmingham)

• Reuben Hillyard (University of Birmingham)

• Saheb Mohapatra (Durham University)

• Sam Speight (University of Birmingham )

• Samuel Toth (University of Nottingham)

• Sean Moss (University of Birmingham)

• Simona Paoli (University of Aberdeen)

• Stiéphen Pradal (University of Nottingham)

• Thorsten Altenkirch (University of Nottingham)

• Till Rampe (University of Birmingham)

• Ulrik Buckholtz (University of Nottingham)

• Zhili Tian (University of Nottingham)

Lunch Options

For the lunch break (12:30-14:00), there are several options on campus. We recommend:

• Spokes Cafe (most restaurant-like option; but please order at the till, then find a table)

• The Atrium (a canteen, basic food)

• Cafe Terrazzo (light food: loaded fries, paninis, etc)

• Aspire (just below the conference room; however, most likely extremely busy)

All options with menues can be found on this university website:

https://www.nottingham.ac.uk/hospitality/cafesbars/jubileecampus.aspx