English

Automata and coalgebras in categories of species

Category Theory 2026-01-14 v4 Formal Languages and Automata Theory

Abstract

We study generalized automata (in the sense of Ad\'amek-Trnkov\'a) in Joyal's category of (set-valued) combinatorial species, and as an important preliminary step, we study coalgebras for its derivative endofunctor \partial and for the "Euler homogeneity operator" LL\circ\partial arising from the adjunction LRL\dashv\partial\dashv R. The theory is connected with, and in fact provides relatively nontrivial examples of, "differential 2-rigs", a notion recently introduced by the author putting combinatorial species on the same relation a generic (differential) semiring (R,d)(R,d) has with the (differential) semiring N[ ⁣[X] ⁣]\mathbb N[\![ X]\!] of power series with natural coefficients. The desire to study categories of "state machines" valued in an ambient monoidal category (K,)(\mathcal K,\otimes) gives a pretext to further develop the abstract theory of differential 2-rigs, proving lifting theorems of a differential 2-rig structure from (R,)(\mathcal R,\partial) to the category of \partial-algebras on objects of R\mathcal R, and to categories of Mealy automata valued in (R,)(\mathcal R,\otimes), as well as various constructions inspired by differential algebra such as jet spaces and modules of differential operators. These theorems adapt to various "species-like" categories such as coloured species, kk-vector species (both used in operad theory), linear species (introduced by Leroux to study combinatorial differential equations), M\"obius species, and others.

Keywords

Cite

@article{arxiv.2401.04242,
  title  = {Automata and coalgebras in categories of species},
  author = {Fosco Loregian},
  journal= {arXiv preprint arXiv:2401.04242},
  year   = {2026}
}

Comments

Hom. Il. 18.371-376; extended version of the note published in the proceedings of CMCS2024