Centre for Mathematics, University of Coimbra

Seminars

Normed categories

2025-05-20

Speaker: Walter Tholen (York Univ., Toronto, Canada)

In this talk we explore Lawvere's notion of normed category through the lens of easily understood small and large example categories. Cauchy convergence of sequences in such categories gets presented as a natural extension of familiar concepts taught in Calculus and Functional Analysis, but...

Self-dual aspects of semi-abelian categories

2025-05-20

Speaker: Tim Van der Linden (Univ. catholique de Louvain and Vrije Univ. Brussel, Belgium)

The aim of this talk is to introduce di-exact categories [3], which are defined by a simple axiom system capturing self-dual aspects of the context of Janelidze-Márki-Tholen semi-abelian categories [2,1]. A Borceux-Bourn homological category [1] is Barr-exact if and only if it is di-exact....

TBA

2025-06-17

Speaker: Alfredo Costa (CMUC, Univ. Coimbra)

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2025-06-17

Speaker: Célia Borlido (CMUC, Univ. Coimbra)

TBA...

Classifying cubic graphs avoiding spectral gap sets

2025-06-25

Speaker: Gordon Royle (Univ. Western Australia, Australia)

Spectral graph theory is the study of the relationship between the graphical properties of a graph and the spectral properties (i.e., eigenvalues and eigenvectors) of various matrices associated with that graph, most commonly the adjacency matrix. The spectrum of the...

Drazin inverses in (dagger) categories

2025-08-19

Speaker: Jean-Simon Pacaud Lemay (Macquarie Univ., Sydney, Australia)

Drazin inverses are a special kind of generalized inverse that have been extensively studied and have many applications in ring theory, semigroup theory, and matrix theory. Drazin inverses can also be defined for endomorphisms in any category. A natural question is whether one can extend the...

A general approach to pointfree \(T_0\) spaces

2025-08-19

Speaker: Anna Laura Suarez (Univ. Western Cape, South Africa)

The classical dual adjunction between frames and spaces, given by the functors \( O\colon \mathbf{Top}\to\mathbf{Frm} \) and \( \mathsf{pt}\colon\mathbf{Frm}\to\mathbf{Top} \), restricts to a dual equivalence between sober spaces and spatial frames. Another pointfree approach to the study of...