Diese Arbeit befasst sich mit der unimodularen Überdeckung und Triangulierung von Gitterpolytopen. Zentral ist in diesem Zusammenhang die Angabe einer möglichst guten oberen Schranke c0, so dass die Vielfachen cP eines Polytopes P für alle c>c0 eine unimodulare Überdeckung besitzen. Bruns und Gubeladze haben erstmals die Existenz einer solchen Schranke nachgewiesen und konnten sogar explizit eine solche in Abhängigkeit von der Dimension des Polytopes angeben. Allerdings war diese Schranke super-exponentiell. In dieser Arbeit wird nun u.a. eine polynomielle obere Schranke hergeleitet.

The aim of this thesis is to introduce the reader to the theory of affine monoids and, thereby, to present some results. We therefore start with some auxiliary sections, containing general introductions to convex geometry, affine monoids and their algebras, Hilbert functions and Hilbert series. One central part of the thesis then is the description of an algorithm for computing the integral closure of an affine monoid. The algorithm has been implemented, in the computer program `normaliz´; it outputs the Hilbert basis and the Hilbert function of the integral closure (if the monoid is positive). Possible applications include: finding the lattice points in a lattice polytope, computing the integral closure of a monomial ideal and solving Diophantine systems of linear inequalities. The other main part takes up the notion of multigraded Hilbert function: we investigate the effect of the growth of the Hilbert function along arithmetic progressions (within the grading set) on global growth. This study is motivated by the case of a finitely generated module over a homogeneous ring: there, the Hilbert function grows with a degree which is well determined by the degree of the Hilbert polynomial (and the Krull dimension).