Tight Closure and Its Applications (Cbms Regional Conference Series in Mathematics)

This monograph deals with the theory of tight closure and its applications. The contents are based on ten talks given at a CBMS conference held at North Dakota State University in June 1995. Tight closure is a method to study rings of equicharacteristic by using reduction to positive characteristic. In this book, the basic properties of tight closure are covered, including various types of singularities, e.g. F-regular and F-rational singularities. Basic theorems in the theory are presented including versions of the Briancon-Skoda theorem, various homological conjectures, and the Hochster-Roberts/Boutot theorems on invariants of reductive groups. Several applications of the theory are given. These include the existence of big Cohen-Macaulay algebras and various uniform Artin-Rees theorems. Features: The existence of test elements. A study of F-rational rings and rational singularities. Basic information concerning the Hilbert-Kunz function, phantom homology, and regular base change for tight closure. Numerous exercises with solutions.