Subject: categories: New and old preprint available

From: kock <[email-masked]>
Date: Wed, 7 Jan 2004 13:07:13 +0100

A new and an old preprint available.

The new preprint is: "Envelopes - notion and definiteness",
Aarhus Preprint Series No. 12 (2003),
http://www.imf.au.dk/publications/matppt/2003/12.pdf

Abstract: We examine critically some of the existing descriptions of the
envelope of a 1-parameter family of surfaces in 3-space. Using the
formalism of Synthetic Differential Geometry, the characteristic curves
(which make up the envelope) can be described as intersections of 1st order
neighbour surfaces. In the classical literature, such a description is
presented as having "heuristic" value, only.

The old preprint is: "Postulated colimits and left exactness of
Kan-extensions",
Aarhus Preprint Series 1989/90 No. 9. It has never been published, but due
to some recent interest in the results, I have digitalized this preprint;
it can be obtained from
http://home.imf.au.dk/kock/postulated.pdf

My Home Page has been improved, and contains now links AND short abstracts
for other of my recent articles, including the 2002 version of "Algebra of
Principal Fibre Bundles, and Connections"
http://www.imf.au.dk/publications/matppt/2003/13.pdf
The address of the home page is
http://home.imf.au.dk/kock/

Anders Kock