@TechReport{ it:2018-009, author = {Carlo Garoni and Mariarosa Mazza and Stefano Serra-Capizzano}, title = {Block Generalized Locally Toeplitz Sequences: From the Theory to the Applications}, institution = {Department of Information Technology, Uppsala University}, department = {Division of Scientific Computing}, year = {2018}, number = {2018-009}, month = may, abstract = {The theory of generalized locally Toeplitz (GLT) sequences is a powerful apparatus for computing the asymptotic spectral distribution of matrices $A_n$ arising from virtually any kind of numerical discretization of differential equations (DEs). Indeed, when the mesh fineness parameter $n$ tends to infinity, these matrices $A_n$ give rise to a sequence $\{A_n\}_n$, which often turns out to be a GLT sequence or one of its ``relatives'', i.e., a block GLT sequence or a reduced GLT sequence. In particular, block GLT sequences are encountered in the discretization of systems of DEs as well as in the higher-order finite element or discontinuous Galerkin approximation of scalar DEs. Despite the applicative interest, a solid theory of block GLT sequences has been developed only recently, in 2018. The purpose of the present paper is to illustrate the potential of this theory by presenting a few noteworthy examples of applications in the context of DE discretizations.} }