# Category Archives: Uncategorized

## Mathematics in Ancient Egypt

Below is a review I wrote for a CUP journal (The Mathematical Gazette) about a recently published text on mathematics in ancient Egypt Mathematics in ancient Egypt, a contextual history by Annette Imhausen, pp 234, £21.05 (hard), ISBN 978-0-691-11713-3, Princeton … Continue reading

## Visual sheafs, presheafs, stalks and germs

Ok. I know some mathematicians are a bit squeamish about visualizing concepts. However, attached is a sheet of interrelated diagrams that I find helpful to understand sheafs.

## Blowing up singularities

Commentary and examples, including one from Hartsthorne’s Algebraic Geometry. Trusting GCHQ are not bothered by the ‘blowing up’ in the title …

## Commentary on the Diagrams in The Red Book

In particular Spec (*) …

## Commentary on Mumford’s Red Book

My notes and commentary on the first couple of chapters of David Mumford’s: The Red Book of Varieties and Schemes.

## Visualizing affine algebraic varieties

An affine algebraic variety is an irreducible closed subset of (with the induced topology) as discussed in the previous two posts. A non-constant polynomial in the variables and defines a plane curve affine variety . Below is the variety for … Continue reading

## Affine and Quasi-affine Varieties – 2

Restatement: An affine algebraic variety, the set of common zeros of a collection of polynomials, is an irreducible closed subset of (with the induced topology). An open subset of an affine variety is called a quasi affine algebraic variety. In this post … Continue reading