1,984,063 research outputs found
Higher-dimensional categories with finite derivation type
We study convergent (terminating and confluent) presentations of
n-categories. Using the notion of polygraph (or computad), we introduce the
homotopical property of finite derivation type for n-categories, generalizing
the one introduced by Squier for word rewriting systems. We characterize this
property by using the notion of critical branching. In particular, we define
sufficient conditions for an n-category to have finite derivation type. Through
examples, we present several techniques based on derivations of 2-categories to
study convergent presentations by 3-polygraphs
Repetitive higher cluster categories of type A_n
We show that the repetitive higher cluster category of type A_n, defined as
the orbit category D^b(mod kA_n)/(tau^{-1}[m])^p, is equivalent to a category
defined on a subset of diagonals in a regular p(nm+1)-gon. This generalizes the
construction of Caldero-Chapoton-Schiffler, which we recover when p=m=1, and
the work of Baur-Marsh, treating the case p=1, m>1. Our approach also leads to
a geometric model of the bounded derived category D^b(mod kA_n)
The univalence axiom for elegant Reedy presheaves
We show that Voevodsky's univalence axiom for intensional type theory is
valid in categories of simplicial presheaves on elegant Reedy categories. In
addition to diagrams on inverse categories, as considered in previous work of
the author, this includes bisimplicial sets and -spaces. This has
potential applications to the study of homotopical models for higher
categories.Comment: 25 pages; v2: final version, to appear in HH
Towards a directed homotopy type theory
In this paper, we present a directed homotopy type theory for reasoning
synthetically about (higher) categories, directed homotopy theory, and its
applications to concurrency. We specify a new `homomorphism' type former for
Martin-L\"of type theory which is roughly analogous to the identity type former
originally introduced by Martin-L\"of. The homomorphism type former is meant to
capture the notions of morphism (from the theory of categories) and directed
path (from directed homotopy theory) just as the identity type former is known
to capture the notions of isomorphism (from the theory of groupoids) and path
(from homotopy theory). Our main result is an interpretation of these
homomorphism types into Cat, the category of small categories. There, the
interpretation of each homomorphism type hom(a,b) is indeed the set of
morphisms between the objects a and b of a category C. We end the paper with an
analysis of the interpretation in Cat with which we argue that our homomorphism
types are indeed the directed version of Martin-L\"of's identity types
Higher-dimensional normalisation strategies for acyclicity
We introduce acyclic polygraphs, a notion of complete categorical cellular
model for (small) categories, containing generators, relations and
higher-dimensional globular syzygies. We give a rewriting method to construct
explicit acyclic polygraphs from convergent presentations. For that, we
introduce higher-dimensional normalisation strategies, defined as homotopically
coherent ways to relate each cell of a polygraph to its normal form, then we
prove that acyclicity is equivalent to the existence of a normalisation
strategy. Using acyclic polygraphs, we define a higher-dimensional homotopical
finiteness condition for higher categories which extends Squier's finite
derivation type for monoids. We relate this homotopical property to a new
homological finiteness condition that we introduce here.Comment: Final versio
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