ISSN 1201-561X
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THEORY AND APPLICATIONS OF CATEGORIES
Volume 21, 2008-2009
The Tholen Festscrift:
A special volume dedicated to
Walter Tholen
on the occasion of his 60’th birthday.
Foreword
The guest editors
1
A convenient category for directed homotopy
L. Fajstrup and J. Rosicky
7
Limit preserving full embeddings
V. Trnkova and J. Sichler
21
Protolocalisations of exact Mal’cev categories
Francis Borceux, Marino Gran, Sandra Mantovani
37
Doubles for monoidal categories
Craig Pastro and Ross Street
61
Completions in biaffine sets
Elisabetta Felaco and Eraldo Giuli
76
The Editors of TAC wish to thank Maria Manuel Clementino, George Janelidze, Jiri Rosicky and Robert Rosebrugh who acted as guest editors for this special volume.
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Theory and Applications of Categories,Vol. 21 ii
Weakly Mal’cev categories
N. Martins-Ferreira
91
Extensions in the theory of lax algebras
Christoph Schubert and Gavin J. Seal
118
Approximate Mal’tsev operations
Dominique Bourn and Zurab Janelidze
152
Notes on effective descent and projectivity in quasivarieties of universal algebras
Ana Helena Roque
172
Descent for compact 0-dimensional spaces
George Janelidze and Manuela Sobral
182
Analytic functors and weak pullbacks
J. Adamek and J. Velebil
191
Relative injectivity as cocompleteness for a class of distributors
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 contribu-tions 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.
Full text of the journal is freely available in .dvi, Postscript and PDF from the journal’s server at
http://www.tac.mta.ca/tac/and by ftp. It is archived electronically and in printed paper format.
Subscription information.
Individual subscribers receive by e-mail abstracts of articles bye-mail as they are published. To subscribe, send e-mail [email protected] a full name and postal address. For institutional subscription, send enquiries to the Managing Editor.
Information for authors.
The typesetting language of the journal is TEX, and LATEX 2ε isstrongly encouraged. Articles should be submitted by e-mail directly to a Transmitting Editor. Please obtain detailed information on submission format and style files fromhttp://www.tac.mta.ca/tac/.
Managing editor.
Robert Rosebrugh, Mount Allison University: [email protected]TEXnical editor.
Michael Barr, McGill University: [email protected]Assistant TEX editor.
Gavin Seal, McGill University: gavin [email protected]Transmitting editors.
Richard Blute, Universit´e d’ Ottawa: [email protected]
Lawrence Breen, Universit´e de Paris 13: [email protected]
Ronald Brown, University of North Wales: ronnie.profbrown (at) btinternet.com
Aurelio Carboni, Universit`a dell Insubria: [email protected]
Valeria de Paiva, Cuill Inc.: [email protected]
Ezra Getzler, Northwestern University: getzler(at)northwestern(dot)edu
Martin Hyland, University of Cambridge: [email protected]
P. T. Johnstone, University of Cambridge: [email protected]
Anders Kock, University of Aarhus: [email protected]
Stephen Lack, University of Western Sydney: [email protected]
F. William Lawvere, State University of New York at Buffalo: [email protected]
Jean-Louis Loday, Universit´e de Strasbourg: [email protected]
Ieke Moerdijk, University of Utrecht: [email protected]
Susan Niefield, Union College: [email protected]
Robert Par´e, Dalhousie University: [email protected]
Jiri Rosicky, Masaryk University: [email protected]
Brooke Shipley, University of Illinois at Chicago: [email protected]
James Stasheff, University of North Carolina: [email protected]
Ross Street, Macquarie University: [email protected]
Walter Tholen, York University: [email protected]
Myles Tierney, Rutgers University: [email protected]
Robert F. C. Walters, University of Insubria: [email protected]
