253 citations
5 papers
On lax epimorphisms and the associated factorization
Fernando Lucatelli Nunes, Lurdes Sousa
We study lax epimorphisms in 2-categories, with special attention to and -. We show that any 2-category with convenient colimits has an or…
A proof of a conjecture about a symmetric system of orthogonal polynomials
K. Castillo, M. N. de Jesus, J. Petronilho
The purpose of this note is to give an affirmative answer to a conjecture appearing in [Integral Transforms Spec. Funct. 26 (2015) 90-95].
A note on orthogonal polynomials described by Chebyshev polynomials
K. Castillo, M. N. de Jesus, J. Petronilho
The purpose of this note is to extend in a simple and unified way some results on orthogonal polynomials with respect to the weight function $$\frac{|T_m(x)|^p}{\sqrt{1-x^2}}\;,\qu…
Discrete-Time Fractional Variational Problems
Nuno R. O. Bastos, Rui A. C. Ferreira, Delfim F. M. Torres
We introduce a discrete-time fractional calculus of variations on the time scale , . First and second order necessary optimality conditions are established. Exa…
Magnetic braking in young late-type stars: the effect of polar spots
A. Aibéo, J. M. Ferreira, J. J. G. Lima
The concentration of magnetic flux near the poles of rapidly rotating cool stars has been recently proposed as an alternative mechanism to dynamo saturation in order to explain the…