## Welcome

IRIF, the Research Institute on the Foundations of Computer Science, is a research laboratory of CNRS and Université de Paris, also hosting two Inria project-teams.

The research conducted at IRIF is based on the study and understanding of the foundations of all computer science, in order to provide innovative solutions to the current and future challenges of digital sciences.

IRIF hosts about 200 people. Six of its members have been distinguished by the European Research Council (ERC), five are members of the Institut Universitaire de France IUF), and two are members of the Academia Europæa.

## Notion of the day

## News

*27.1.2020*

The ANR PPS kick-off meeting will take place from **Feb 26 to Feb 28, 2020** at IRIF (Paris) and will be joined with the 3rd edition of the PIHOC workshop series initiated by Ugo Dal Lago in 2018 and with Dal Lago's DIAPASoN ERC project kick-off meeting. Register by **Jan 31**: registration is free but mandatory.

*7.2.2020*

IRIF will finance one or two additional **Master scholarships** in Foundations of Computer Science within the PGSM program of FSMP for **female students** who have completed a bachelor’s degree or the first year masters in one of the universities of the FSMP network. Apply by **May 8th**.

*30.1.2020*

Yann Régis-Gianas (IRIF) is the vice-president of the “Journées Francophones des Langages Applicatifs” that will take place at Gruissan from the **29th of January to the 1st of February**.

*6.2.2020*

Sylvain Périfel from IRIF, together with Damiano Mazza and Thomas Seiller, organize the Caleidoscope Research School in Computational Complexity, to be held in Paris, **15-19 June 2020**.

(These news are displayed using a randomized-priority ranking.)

## Events

Verification

Monday February 24, 2020, 11AM, Salle 1007

**James Worrell** (University of Oxford) *Termination of linear constraint loops*

Automata

Tuesday February 25, 2020, 2PM, Salle 3052

**Georg Zetsche** (MPI SWS) *Extensions of $\omega$-Regular Languages*

(Joint work with Mikołaj Bojańczyk, Edon Kelmendi, and Rafał Stefański)

Note the unusual time (14:00).

Enumerative and analytic combinatorics

Thursday February 27, 2020, 2PM, Salle 1007

**Sandro Franceschi** (Université Paris-sud) *Invariants de Tutte et Brownien réfléchi dans un cône*

Higher categories, polygraphs and homotopy

Thursday February 27, 2020, 2PM, Salle 1012

**Michael Batanin** (IHES) *Comparing symmetric operads and operadic categories*

In my talk I will show that the category of symmetric operads in Set (variation of colours is allowed) is a reflective subcategory of the category of operadic categories. The inclusion is given by (operadic) Grothendieck construction and the reflection is given by evaluation of the left Kan extension along arity functor on the terminal operad. Thus the notion of operadic category can be considered as a flexible extension of the notion of symmetric operad.

Moreover, there is yet another functor from operadic categories to symmetric operads which sends an operadic category O to a symmetric operad in Set whose algebras are exactly O-operads. These three functors (Grothendieck construction, its left adjoint and free operad functor) fit in a nice picture with a universal property. In particular, they various composites generate the Baez-Dolan +-constructions for both symmetric operads and operadic categories.

***Attention : date et salle inhabituelles !***

Higher categories, polygraphs and homotopy

Friday February 28, 2020, 2PM, Salle 1007

**Sebastian Posur** (Universität Siegen) *Methods of constructive category theory*

Automata

Friday February 28, 2020, 2:30PM, Salle 3052

**Marie Van Den Bogaard** (ULB) *Subgame Perfect Equilibria in Quantitative Reachability Games*