Centre for Mathematics, University of Coimbra

Seminars

Open multiplication in relatively free profinite semigroupoids

2025-06-17

Speaker: Alfredo Costa (CMUC, Univ. Coimbra)

We study when a relatively free profinite semigroupoid, generated by a finite-vertex graph, has open multiplication. This leads to extensions of published results about finitely generated relatively free profinite semigroups. We highlight some applications that motivated our research, namely...

A variety of co-quasivarieties

2025-06-17

Speaker: Maria Manuel Clementino (CMUC, Univ. Coimbra)

It is shown that the duals of several categories of topological flavour, like the categories of ordered sets, generalised metric spaces, probabilistic metric spaces, topological spaces, approach spaces, are quasivarieties, presenting a common proof for all such results. This talk is based...

Keys, virtual keys and applications

2025-06-18

Speaker: Olga Azenhas (CMUC, Univ. Coimbra)

Demazure atoms are core components in the description of Demazure crystals. It is natural to ask to which Demazure atom a given vertex of a crystal belongs. The answer to this question is provided by the right key map (respectively left key for opposite Demazure atoms)....

Numerical techniques for reducing the ill conditionining in the method of fundamental solutions

2025-06-20

Speaker: Pedro Antunes (GFM/IST, Univ. Lisboa)

The method of fundamental solutions (MFS) is a numerical method for solving boundary value problems involving linear partial differential equations. It is well known that it can be very effective assuming regularity of the domain and boundary conditions. The main drawback of the MFS is that...

Generalized product formula for Whittaker's functions and a novel class of index transforms

2025-06-24

Speaker: Semyon Yakubovich (Univ. Porto)

Generalized product formulas and index transforms involving products of Whittaker functions with different indices are established and investigated. The corresponding inversion formulas are derived. Particular cases include index transforms with products of modified Bessel and Whittaker...

Closure of Riemannian foliations

2025-06-25

Speaker: Mateus Moreira de Melo (Univ. Fed. Espírito Santo, Brazil)

The Molino-Alexandrino-Radeschi Theorem establishes the smoothness of the leaf closure of a Riemannian foliation, that is, the partition of a manifold obtained by taking the closures of the leaves of a Riemannian foliation is itself a Riemannian foliation. In this talk, I will present this...

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...

Large random tilings of a hexagon

2025-09-15

Speaker: Arno Kuijlaars (KU Leuven, Belgium)

TBA...

Quasi-orthogonal polynomials and positive quadrature on the unit circle

2025-09-18

Speaker: Ruymán Cruz Barroso (University of La Laguna, Spain)

TBA...