English

Lallement functor is a weak right multiadjoint

Category Theory 2025-12-23 v2

Abstract

For a plural signature Σ\Sigma and with regard to the category NPIAlg(Σ)s\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}}, of naturally preordered idempotent Σ\Sigma-algebras and surjective homomorphisms, we define a contravariant functor LsysΣ\mathrm{Lsys}_{\Sigma} from NPIAlg(Σ)s\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}} to Cat\mathsf{Cat}, the category of categories, that assigns to I\mathbf{I} in NPIAlg(Σ)s\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}} the category I\mathbf{I}-LAlg(Σ)\mathsf{LAlg}(\Sigma), of I\mathbf{I}-semi-inductive Lallement systems of Σ\Sigma-algebras, and a covariant functor (Alg(Σ)s)(\mathsf{Alg}(\Sigma)\,{\downarrow_{\mathsf{s}}}\, \cdot) from NPIAlg(Σ)s\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}} to Cat\mathsf{Cat}, that assigns to I\mathbf{I} in NPIAlg(Σ)s\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}} the category (Alg(Σ)sI)(\mathsf{Alg}(\Sigma)\,{\downarrow_{\mathsf{s}}}\, \mathbf{I}), of the coverings of I\mathbf{I}, i.e., the ordered pairs (A,f)(\mathbf{A},f) in which A\mathbf{A} is a Σ\Sigma-algebra and f ⁣:AIf\colon \mathbf{A}\longrightarrow \mathbf{I} a surjective homomorphism. Then, by means of the Grothendieck construction, we obtain the categories NPIAlg(Σ)sLsysΣ\int^{\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}}}\mathrm{Lsys}_{\Sigma} and NPIAlg(Σ)s(Alg(Σ)s)\int_{\mathsf{NPIAlg}(\Sigma)_{\mathsf{s}}}(\mathsf{Alg}(\Sigma)\,{\downarrow_{\mathsf{s}}}\, \cdot); define a functor LΣ\mathfrak{L}_{\Sigma} from the first category to the second, which we will refer to as the Lallement functor; and prove that it is a weak right multiadjoint. Finally, we state the relationship between the P{\l}onka functor and the Lallement functor.

Cite

@article{arxiv.2311.02944,
  title  = {Lallement functor is a weak right multiadjoint},
  author = {Juan Climent Vidal and Enric Cosme Llópez},
  journal= {arXiv preprint arXiv:2311.02944},
  year   = {2025}
}

Comments

31 pages. arXiv admin note: text overlap with arXiv:2305.03581

R2 v1 2026-06-28T13:12:26.780Z