Block rational Krylov methods for matrix equations and matrix functions

In this thesis, we describe block rational Krylov subspaces, highlighting their correspondence with rational matrices and generalizing important properties that apply to the non-block case. We develop procedures based on block rational Krylov subspaces for solving Sylvester and tensor Sylvester equations, computing functions of Hermitian hierarchically semiseparable (HSS) matrices, and applying functions of Hermitian matrices to block vectors.In the context of Sylvester equations with low-ran...

Peasants prefiguring agroecology, critical pedagogy and peasant feminism: a participatory action research project with the Kenyan Peasants League

Essays on International Migration using Big Data Analytics

How can social big data help to understand issues related to international migration? Official data such as census, survey and administrative data have been traditionally the main data source to study migration. However, these data have some limitations. They are inconsistent across different nations because countries employ different definitions of international migration and characterisations of migrants. Moreover, collecting traditional data is costly and time consuming, thus tracking...

Fibering Hyperbolic Manifolds and Hyperbolic Groups

In this thesis, we present new results regarding hyperbolic manifolds that fiber over the circle, and some consequences these have on hyperbolic groups. In particular, we construct a 5-dimensional hyperbolic manifold that fibers over the circle, and other hyperbolic manifolds ranging from dimension 4 to 8 that algebraically fiber. Our method, inspired by the work of Jankiewicz, Norin, and Wise, and relying on Bestvina-Brady theory, begins with a hyperbolic right-angled polytope. It involves a...