306 citations
Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.
- Universidade do PortoPT174 papers
- University of CoimbraPT98 papers
- University of MinhoPT81 papers
- University of LisbonPT24 papers
- Centre National de la Recherche ScientifiqueFR22 papers
- Instituto Superior TécnicoPT22 papers
- UCLouvainBE13 papers
- Universidade Federal da BahiaBR13 papers
- Centro de Análise Matemática Geometria e Sistemas DinâmicosPT10 papers
- Pontifícia Universidade Católica do Rio de JaneiroBR10 papers
- Universidad de La LagunaES9 papers
- Universidade Federal do Rio de JaneiroBR9 papers
23 papers · 1 filter
Finite automata for Schreier graphs of virtually free groups
Pedro Silva, Xaro Soler-Escrivà, Enric Ventura
The Stallings construction for finitely generated subgroups of free groups is generalized by introducing the concept of Stallings section, which allows an eficient computation of t…
On a coupled PDE model for image restoration
V. B. Surya Prasath, Dmitry Vorotnikov
In this paper, we consider a new coupled PDE model for image restoration. Both the image and the edge variables are incorporated by coupling them into two different PDEs. It is sho…
Some operators that preserve the locality of a pseudovariety of semigroups
Alfredo Costa, Ana Escada
It is shown that if V is a local monoidal pseudovariety of semigroups, then K(m)V, D(m)V and LI(m)V are local. Other operators of the form Z(m)(_) are considered. In the process, r…
Explosion of smoothness for conjugacies between multimodal maps
Jose F. Alves, Vilton Pinheiro, Alberto A. Pinto
Let and be smooth multimodal maps with no periodic attractors and no neutral points. If a topological conjugacy between and is at a point in the nearby…
Spinors: a Mathematica package for doing spinor calculus in General Relativity
Alfonso García-Parrado Gómez-Lobo, José M. Martín-García
The "Spinors" software is a "Mathematica" package which implements 2-component spinor calculus as devised by Penrose for General Relativity in dimension 3+1. The "Spinors" software…
Flows near Compact Invariant Sets - Part I
Pedro Teixeira
In this paper it is proved that near a compact, invariant, proper subset of a continuous flow on a compact, connected metric space, at least one, out of twenty eight relevant dynam…
A weighted finite difference method for the fractional diffusion equation based on the Riemann-Liouville derivative
Ercília Sousa, Can Li
A one dimensional fractional diffusion model with the Riemann-Liouville fractional derivative is studied. First, a second order discretization for this derivative is presented and…
Relative Commutator Theory in Semi-Abelian Categories
Tomas Everaert, Tim Van der Linden
Basing ourselves on the concept of double central extension from categorical Galois theory, we study a notion of commutator which is defined relative to a Birkhoff subcategory B of…
The ternary commutator obstruction for internal crossed modules
Manfred Hartl, Tim Van der Linden
In finitely cocomplete homological categories, co-smash products give rise to (possibly higher-order) commutators of subobjects. We use binary and ternary co-smash products and the…
Spherical linear waves in de Sitter spacetime
Joao L. Costa, Artur Alho, Jose Natario
We apply Christodoulou's framework, developed to study the Einstein-scalar field equations in spherical symmetry, to the linear wave equation in de Sitter spacetime, as a first ste…
Einstein four-manifolds with skew torsion
Ana Cristina Ferreira
We develop a notion of Einstein manifolds with skew torsion on compact, orientable Riemannian manifolds of dimension four. We prove an analogue of the Hitchin-Thorpe inequality and…
Rank two quadratic pairs and surface group representations
Peter B. Gothen, André Oliveira
Let be a compact Riemann surface. A quadratic pair on consists of a holomorphic vector bundle with a quadratic form which takes values in fixed line bundle. We show that th…
Topological complexity and the homotopy cofibre of the diagonal map
J. Calcines, L. Vandembroucq
In this paper we analyze some relationships between the topological complexity of a space and the category of the homotopy cofibre of the diagonal map $Δ_X:X\rightar…
Comparing Perfect and 2nd Voronoi decompositions: the matroidal locus
Margarida Melo, Filippo Viviani
We compare two rational polyhedral admissible decompositions of the cone of positive definite quadratic forms: the perfect cone decomposition and the 2nd Voronoi decomposition. We…
On the generalized Feng-Rao numbers of numerical semigroups generated by intervals
M. Delgado, J. I. Farrán, P. A. García-Sánchez +1
We give some general results concerning the computation of the generalized Feng-Rao numbers of numerical semigroups. In the case of a numerical semigroup generated by an interval,…
Amalgams of inverse semigroups and reversible two-counter machines
Emanuele Rodaro, Pedro V. Silva
We show that the word problem for an amalgam of inverse semigroups may be undecidable even if we assume and (and therefore ) to have finite $\m…
Scattering of spherically symmetric d-dimensional alpha'-corrected black holes in string theory
Filipe Moura
We study scattering of minimally coupled massless scalar fields by non-extremal spherically symmetric black holes in d dimensions with string-theoretical alpha' corrections. We the…
Reduction of Poisson-Nijenhuis Lie algebroids to symplectic-Nijenhuis Lie algebroids with nondegenerate Nijenhuis tensor
Antonio De Nicola, Juan Carlos Marrero, Edith Padron
We show how to reduce, under certain regularities conditions, a Poisson-Nijenhuis Lie algebroid to a symplectic-Nijenhuis Lie algebroid with nondegenerate Nijenhuis tensor. We gene…
Characteristic-free resolutions of Weyl and Specht modules
Ana Paula Santana, Ivan Yudin
We construct explicit resolutions of Weyl modules by divided powers and of co-Specht modules by permutational modules. We also prove a conjecture of Boltje-Hartmann on resolutions…
Further results on monoids acting on trees
John Rhodes, Pedro V. Silva
This paper further develops the theory of arbitrary semigroups acting on trees via elliptic mappings. A key tool is the Lyndon-Chiswell length function L for the semigroup S which…
Higgs bundles and the real symplectic group
Peter B. Gothen
We give an overview of the work of Corlette, Donaldson, Hitchin and Simpson leading to the non-abelian Hodge theory correspondence between representations of the fundamental group…
Scaling limits of additive functionals of interacting particle systems
Patricia Gonçalves, Milton Jara
Using the renormalization method introduced in \cite{GJ}, we prove what we call the {\em local} Boltzmann-Gibbs principle for conservative, stationary interacting particle systems…
A new special class of Petrov type D vacuum space-times in dimension five
Alfonso García-Parrado Gómez-Lobo, Lode Wylleman
Using extensions of the Newman-Penrose and Geroch-Held-Penrose formalisms to five dimensions, we invariantly classify all Petrov type vacuum solutions for which the Riemann ten…