Semi-invariants of tubular algebras

The focus of this thesis is on the rings of semi-invariants of the representation spaces of tubular algebras. These rings reflect the cyclic nature of the structure of the modules of the tubular algebras. The main theorem gives the generators and relations of the rings of semi-invariants SI(Q/I, d) where d is a dimension vector of a module in the tubes of an algebra where certain conditions hold. The theorem can be directly applied to Euclidean algebras and Tubular algebras since they have separating tubular families. The results reflect the work of Skowronski and Weyman on semi-invariants of Euclidean Algebras. Also, in the case of tubular algebras, applications of shrinking functors to the rings of semi-invariants are explored.