Daniel Murfet

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We give an introduction to computation and logic tailored for algebraists, and use this as a springboard to discuss geometric models of computation and the role of cut-elimination in these models, following Girard’s geometry of interaction program. We discuss how to represent programs in the λ-calculus and proofs in linear logic as linear maps between(More)
Abelian categories are the most general category in which one can develop homological algebra. The idea and the name “abelian category” were first introduced by MacLane [Mac50], but the modern axiomitisation and first substantial applications were given by Grothendieck in his famous Tohoku paper [Gro57]. This paper was motivated by the needs of algebraic(More)
These notes closely follow Matsumura’s book [Mat80] on commutative algebra. Proofs are the ones given there, sometimes with slightly more detail. Our focus is on the results needed in algebraic geometry, so some topics in the book do not occur here or are not treated in their full depth. In particular material the reader can find in the more elementary(More)
In this note we define cohomology of sheaves by taking the derived functors of the global section functor. As an application of general techniques of cohomology we prove the Grothendieck and Serre vanishing theorems. We introduce the Čech cohomology and use it to calculate cohomology of projective space. The original reference for this material is EGA III,(More)
Throughout this note all rings are commutative, and A is a fixed ring. If S, T are graded A-algebras then the tensor product S ⊗A T becomes a graded A-algebra in a canonical way with the grading given by (TES,Lemma 13). That is, S ⊗A T is the coproduct of the morphisms of A-modules Sd ⊗A Te −→ S ⊗A T for d, e ≥ 0. The canonical morphisms p1 : S −→ S ⊗A T,(More)
Definition 1. Let A be a ring. A graded A-algebra is an A-algebra R which is also a graded ring in such a way that if r ∈ Rd then ar ∈ Rd for all a ∈ A. That is, Rd is an A-submodule of R for all d ≥ 0. Equivalently a graded A-algebra is a morphism of graded rings A −→ R where we grade A by setting A0 = A,An = 0 for n > 0. A morphism of graded A-algebras is(More)
In the topos Sets we build algebraic structures out of sets and operations (morphisms between sets) where the operations are required to satisfy various axioms. Once we have translated these axioms into a diagrammatic form, we can copy the definition into any category with finite products. The advantage of such constructions is that many of the complicated(More)
In this note we study the higher direct image functors Rf∗(−) and the higher coinverse image functors Rf (−) which will play a role in our study of Serre duality. The main theorem is the proof that if F is quasi-coherent then so is Rf∗(F ), which we prove first for noetherian schemes and then more generally for quasi-compact quasi-separated schemes. Most(More)