9:00-10:00
Pawel Sobocinski:
Adhesive
categories, Van Kampen squares and bicolimits.
[slides]
In 2004 Steve Lack and myself introduced adhesive categories,
which have since been
widely used as a mathematical foundation for graph rewriting (for instance, via
the double pushout approach). Adhesive categories follow in the
tradition of extensive categories in that particular colimits
(coproducts in extensive categories, certain pushouts in adhesive
categories) "behave well" with respect to pullbacks. The colimits in
question can be characterised in an
elementary fashion: they satisfy what has become known as the Van Kampen condition. In recent
work with Tobias Heindel we have characterised
this condition as a universal property---a colimit satisfies the Van
Kampen condition exactly when it is a bicolimit when embedded into the canonical
bicategory of spans.
10:00-10:30
Jean-Guillaume Dumas:
Sequential computation and cartesian effect categories.
[slides]
Most often, in a categorical semantics for a programming
language,
the substitution of terms is expressed by composition and finite
products.
However this does not deal with the order of evaluation of arguments,
which may have major consequences when there are side-effects.
We first present a characterisation of effects and then provide a
generalization of the binary product, called the sequential product.
The universal property of this sequential product
provides the obtained Cartesian effect categories with a powerful tool
for constructions and proofs.
We illustrate the notions on several examples of effects in programming
languages: exception, partiality or state, and compare our approach
with
strong monads, Freyd-categories and Haskell's Arrows.
10:30-11:00
PAUSE
11:00-11:30
Tom Hirschowitz: Algebraic structures from shapes.
[slides]
An important part of categorical computer science, at least in
proportion, consists of extracting the algebraic essence of
computational structures. The mother of all examples of this is the
correspondence between simply-typed lambda-calculus and cartesian
closed categories.
Presenting such algebraic structures can be subtle, especially
when seeking so-called coherence, which exhibits the equivalence of
algebra with some combinatorial structure.
The talk is an introduction by example to a technique for
constructing algebraic structures from their expected combinatorial
description, bypassing the tedious work of presentation. The pattern is
as follows: (1) the combinatorial description provides a monad which
yields the expected structure (2) the Leinster-Weber theory of local
right adjoint monads generates a presentation for it.
11:30-12:00
Philippe Malbos: Homotopical methods in polygraphic rewriting.
[slides]
We survey some homotopical properties of convergent
presentations of n-categories. Using the notion of polygraph, we
introduce the homotopical property of finite derivation type for
n-categories, generalising the one introduced by Squier for word
rewriting systems. We characterise this property by using the notion of
critical branching. We generalise the notion of identities among
relations, well known for presentations of groups, to presentation of
n-categories by polygraphs. We relate identities among relation and
critical branching.
12:00-12:30
Simon Perdrix:
Categorical Quantum Computing: the necessity of Euler decomposition.
[slides]
Categorical
axiomatisation of quantum information processing has been initiated by
Abramsky and Coecke. Coecke and Duncan recently introduced a
categorical formalisation of the interaction of complementary
quantum
observables. In this framework, we consider a new equation: the Euler
decomposition of H, and demonstrate that a fundamental property of
quantum entanglement is equivalent to this new axiom. Joint work with
Ross Duncan (U. Oxford)
12:30-14:00
DEJEUNER
14:00-15:00
Pawel Sobocinski: The wire calculus.
[slides]
The wire calculus is a process algebra for modelling truly
concurrent systems with explicit network topologies. Instead of a
Dijsktra-Hoare-Milner commutative parallel operator it features a non-communicating
non-commutative parallel and an operator for synchronisation on a common
boundary. The dynamics are handled by operators inspired by
Milner's CCS and Hoare's CSP: unary prefix operation, binary choice and
a standard recursion construct. The
operational semantics is a labelled transition systems derived
using SOS rules. The
category with arrows the processes (terms modulo bisimilarity) is compact
closed.
15:00-15:30
Olivier Laurent: Modèles
catégoriques du lambda-calcul via la logique linéaire.
[slides]
L'étude de la logique linéaire a fourni plusieurs
traductions du lambda-calcul basées sur différentes
décompositions linéaires de l'implication intuitionniste.
Nous montrerons comment l'analyse catégorique permet
d'interpréter ses traductions comme des constructions de
modèles du lambda-calcul à partir de modèles de la
logique linéaire.
15:30-16:00
PAUSE
16:00-16:30
Aurélien Pardon: Variable Binding, Symmetric Monoidal
Closed Theories,
and Bigraphs.
16:30-17:00
Frédéric Prost
:
Graph rewriting with polarized cloning.
[slides]
In this talk we will investigate a novel approach to graph
transformations with a particular focus on node cloning. We propose a
graph rewriting framework
where nodes can be cloned zero, one or more times. A node can be
cloned together with all its incident edges, with only the outgoing
edges, with only the incoming edges or without any of the incident
edges. We show how pushout and pullback can be used in order to handle
subtle graph transformations. This framework subsumes previous
works
such as the sesqui-pushout, the heterogeneous pushout and the adaptive
star grammars approaches.
17:00-17:30
Florian Hatat: Un lambda-calcul pour les
catégories de
réponse libres.
[slides]
17:30-18:00
Dominique Duval: Deduction and Fractions.
[slides]
A deduction rule H/C is a fraction C/H, so that the deduction
process is the composition of fractions.
Participants
Pawel
Sobocinski
Vincent Aravantinos
Alejandro
Diaz-Caro
Jean-Guillaume
Dumas
Dominique Duval
Rachid Echahed
Florian Hatat
Pierre Hyvernat
Tom Hirschowitz
Olivier Laurent
Philippe Malbos
Alexandre Miquel
Guillaume Munch-Maccagnoni
Aurelien Pardon
Simon Perdrix
Barbara Petit
Damien Pous
Frédéric Prost
Jean-Claude Reynaud
Colin Riba
Paolo Tranquilli
Benoît Valiron