ISSN 1201-561X

             THEORY AND APPLICATIONS OF CATEGORIES 

                    Volume 2, 1996


Editorial Notice 
Robert W. Thomason 1952-1995                                            1


Computing crossed modules induced by an inclusion 
of a normal subgroup, with applications to homotopy 2-types
Ronald Brown and Christopher D. Wensley                                 3


The Chu construction
Michael Barr                                                           17

A counterexample to a conjecture of Barr
Sarah Whitehouse                                                       36

An algebraic description of locally multipresentable categories
Jiri Adamek and Jiri Rosicky                                           40


Finiteness of a non-abelian tensor product of groups
N. Inassaridze                                                         54

On quantic conuclei in orthomodular lattices
Leopoldo Roman and Rita E.ZuaZua                                       62

Combinatorics of curvature and the Bianchi identity
Anders Kock                                                            69


Remarks on quintessential and persistent localizations
Peter T. Johnstone                                                     90

Glueing Analysis for Complemented Subtoposes
Anders Kock and Till Plewe                                            100

A note on free regular and exact completions 
and their infinitary generalizations
Hongde Hu and Walter Tholen                                           113


Copyright: The Editors of Theory and Applications of Categories


THEORY AND APPLICATIONS OF CATEGORIES (ISSN 1201-561X) will disseminate 
articles that significantly advance the study of categorical algebra or 
methods, or that make significant new contributions to mathematical 
science using categorical methods. The scope of the journal includes: 
all areas of pure category theory, including higher dimensional categories; 
applications of category theory to algebra, geometry and topology and 
other areas of mathematics; applications of category theory to computer 
science, physics and other mathematical sciences; contributions to 
scientific knowledge that make use of categorical methods.
 
Articles appearing in the journal have been carefully and critically
refereed under the responsibility of members of the Editorial Board.
Only papers judged to be both significant and excellent are accepted for
publication.
 
The method of distribution of the journal is via the Internet tools
WWW/ftp. The journal is archived electronically and in
printed paper format.
 
Subscription information:
Individual subscribers receive (by e-mail) abstracts of articles
as they are published. Full text of published articles is available
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address.

For institutional subscription, send enquiries to the Managing Editor,
Robert Rosebrugh, rrosebrugh@mta.ca.
 
Information for authors:
The typesetting language of the journal is TeX, and LaTeX is the
preferred flavour. TeX source of articles for publication should
be submitted by e-mail directly to an appropriate Editor.
They are listed below. Please obtain detailed information on 
submission format and style files from the journal's WWW server at URL 
http://www.tac.mta.ca/tac/
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You may also write to tac@mta.ca to receive details by e-mail.
 
Editorial board:
John Baez, University of California, Riverside: 
baez@math.ucr.edu
Michael Barr, McGill University: 
barr@triples.math.mcgill.ca
Lawrence Breen, Universite de Paris 13: 
breen@math.univ-paris13.fr
Ronald Brown, University of North Wales: 
r.brown@bangor.ac.uk
Jean-Luc Brylinski, Pennsylvania State University: 
jlb@math.psu.edu
Aurelio Carboni, University of Genoa: 
carboni@vmimat.mat.unimi.it
P. T. Johnstone, University of Cambridge: 
ptj@pmms.cam.ac.uk
G. Max Kelly, University of Sydney: 
kelly_m@maths.su.oz.au
Anders Kock, University of Aarhus: 
kock@mi.aau.dk
F. William Lawvere, State University of New York at Buffalo: 
wlawvere@acsu.buffalo.edu
Jean-Louis Loday, Universite de Strasbourg: 
loday@math.u-strasbg.fr
Ieke Moerdijk, University of Utrecht: 
moerdijk@math.ruu.nl
Susan Niefield, Union College: 
niefiels@gar.union.edu
Robert Pare, Dalhousie University: 
pare@cs.dal.ca
Andrew Pitts, University of Cambridge: 
ap@cl.cam.ac.uk
Robert Rosebrugh, Mount Allison University: 
rrosebrugh@mta.ca
Jiri Rosicky, Masaryk University: 
rosicky@math.muni.cz
James Stasheff, University of North Carolina: 
jds@charlie.math.unc.edu
Ross Street, Macquarie University: 
street@macadam.mpce.mq.edu.au
Walter Tholen, York University: 
tholen@mathstat.yorku.ca
Myles Tierney, Rutgers University: 
tierney@math.rutgers.edu
Robert F. C. Walters, University of Sydney: 
walters_b@maths.su.oz.au
R. J. Wood, Dalhousie University: 
rjwood@cs.da.ca