1 Aug 2007 13:45

### last PhD thesis from Bangor

The very last PhD thesis from Bangor (for the foreseeable future) is now
available on the website. In it Richard Lewis looks at the problem of the
interpretation of the formal maps to a crossed module introduced by
Porter and Turaev and using a simplicial analogue of etale spaces gets a
representation in terms of locally constant stacks.

http://www.informatics.bangor.ac.uk/public/mathematics/research/preprints/0=
7/cathom07.html#07.09

All for now,

Tim

PS.  The abstract follows

Stacks and formal maps of crossed modules
Abstract:
If X is a topological space then there is an equivalence between the
category \pi_1(X)-Set, of actions of the fundamental group of X on sets,
and the category of covering spaces on X. Moreover the latter is also
equivalent to the category of locally constant sheaves on X.
Grothendieck has conjectured that this should be the 'n=3D1' case of a
result which is true for all n, and it is the 'n=3D2' case we look at in
this thesis.
The desired generalisation should replace actions of the group \pi_1(X)
(which is an algebraic model for the 1-type of X) by actions of a crossed
module (i.e., by an algebraic model for the 2-type) on groupoids; 'locally
constant sheaves of sets' by 'locally constant stacks of groupoids'; and
'covering space' by a locally trivial object whose fibres are groupoids.


1 Aug 2007 10:26

### Answers to: definition of parsimony

Dear List Members,

two days ago I posted a message asking whether there is a formal
definition of parsimony for fundamental scientific theories, perhaps
using category theory.

Ralph Wojtowicz recommended to have a look at Part D in Volume II of
Johnstone's "Sketches of an Elephant", which as he wrote contains
discussions of constructions involving translations between formal
systems and their semantic categories.

As an example for parsimony in category theory, Eduardo Ochs suggested
the have a look at the relationships between set theory, local set
theories, and elementary toposes.

The paper by F. Wiedijk, "Is ZF a hack? Comparing the complexity of
some (formalist interpretations of) foundational systems for
mathematics", Journal of Applied Logic 4, 622-645, 2006 ps.gz pdf dvi
via http://www.cs.ru.nl/~freek/pubs/index.html also was recommended.

Many thanks to all respondents and also to Vaughan Pratt for his
refreshing critical remarks!

The answer to the question appears to be more difficult than I had
expected.  As often in philosophy, this may be to a good extent due to
difficulties in explaining what the question is.  One important point
which I failed to clarify is the difference between fundamental
mathematical theories and fundamental scientific theories.


4 Aug 2007 13:14

### Coalgebraic and Categorical Quantum Logic in Oxford

The programs for:

* COALGEBRAIC LOGIC, August 10-11, Oxford, UK
* CATEGORICAL QUANTUM LOGIC, August 11-12, Oxford, UK

are now available at:

* http://se10.comlab.ox.ac.uk:8080/FOCS/COQL_en.html

Sincerely, Bob Coecke.


6 Aug 2007 15:00

### PEPM 2008

                  PEPM 2008
ACM SIGPLAN Workshop on
Partial Evaluation and Program Manipulation
January 7-8, 2008, San Francisco
Keynotes by Ras Bodik (Berkeley) and Monica Lam (Stanford)
Co-located with POPL

http://www.program-transformation.org/PEPM08/WebHome

PEPM is a leading venue for the presentation of
cutting-edge research in program analysis, program
generation and program transformation. Its proceedings
scope, submission process, and program committee
can be found at the above URL.

The program committee would particularly welcome
submissions from

category theorists

on any topic relating to

categorical justification of program fusion rules

Abstracts are due on October 12, and the deadline for
full paper submission is October 17.

Prospective authors are welcome to contact the program
chairs, Robert Glueck (glueck <at> acm.org) and Oege de Moor


7 Aug 2007 13:19

### Editorial Board of 'K-Theory' has resigned

Dear Categories,

Thanks,

Tim Porter

-------------------------------------

OPEN LETTER from the Board of Editors of the Journal of K-theory

Dear fellow mathematicians,

The Editorial Board of 'K-Theory' has resigned. A new journal titled
'Journal of K-theory' has been formed, with essentially the same Board
of Editors. The members are A.Bak, P.Balmer, S.J.Bloch, G.E.Carlsson,
A.Connes, E.Friedlander, M.Hopkins, B.Kahn, M.Karoubi, G.G.Kasparov, A.S.
Merkurjev, A.Neeman, T.Porter, D.Quillen, J.Rosenberg, A.A.Suslin, G.Tang,
B.Totaro, V.Voevodsky, C.Weibel, and Guoliang Yu.

The new journal is to be distributed by Cambridge University Press. The
price is 380 British pounds, which is significantly less than half that of
the old journal. Publication will begin in January 2008. We ask for your
continued support, in particular at the current time. Your submissions
are welcome and may be sent to any of the editors.

Board of Editors
Journal of K-theory



7 Aug 2007 15:06

### Re: Editorial Board of 'K-Theory' has resigned

Congratulations, Tim.  This is something to celebrate.  Mathematicians
and librarians the world over should be grateful to you and the other
editors: you're both saving us money and bringing another journal back
under the full control of academics.

Of course, the pattern of naming now established (Topology becomes
Journal of Topology, K-Theory becomes Journal of K-Theory) presents a
problem: what's JPAA going to do?

Tom

On Tue, 2007-08-07 at 12:19 +0100, tporter <at> informatics.bangor.ac.uk
wrote:
> Dear Categories,
>
> Please note this open letter.
>
> Thanks,
>
> Tim Porter
>
> -------------------------------------
>
>
>   OPEN LETTER from the Board of Editors of the Journal of K-theory
>
>  Dear fellow mathematicians,
>
>  The Editorial Board of 'K-Theory' has resigned. A new journal titled
>  'Journal of K-theory' has been formed, with essentially the same Board


8 Aug 2007 04:06

### Re: Editorial Board of 'K-Theory' has resigned

Of course, it will become Pure and Applied Algebra.  Not that I much care.
It started as the flagship journal of category theory, but has long since
escaped our grasp.  At any rate, it is about time, the editors resigned.

Michael

On Tue, 7 Aug 2007, Tom Leinster wrote:

> Congratulations, Tim.  This is something to celebrate.  Mathematicians
> and librarians the world over should be grateful to you and the other
> editors: you're both saving us money and bringing another journal back
> under the full control of academics.
>
> Of course, the pattern of naming now established (Topology becomes
> Journal of Topology, K-Theory becomes Journal of K-Theory) presents a
> problem: what's JPAA going to do?
>
> Tom
>
>
> On Tue, 2007-08-07 at 12:19 +0100, tporter <at> informatics.bangor.ac.uk
> wrote:
> > Dear Categories,
> >
> > Please note this open letter.
> >
> > Thanks,
> >
> > Tim Porter
> >


8 Aug 2007 14:03

### Re: Editorial Board of 'K-Theory' has resigned

PAA?

jim

On Aug 7, 2007, at 9:06 AM, Tom Leinster wrote:

> Congratulations, Tim.  This is something to celebrate.  Mathematicians
> and librarians the world over should be grateful to you and the other
> editors: you're both saving us money and bringing another journal back
> under the full control of academics.
>
> Of course, the pattern of naming now established (Topology becomes
> Journal of Topology, K-Theory becomes Journal of K-Theory) presents a
> problem: what's JPAA going to do?
>
> Tom
>


14 Aug 2007 18:36

### Preprint: Derived semidistributive lattices

Dear Category Theorists,

a preprint of my Nice-PSSL talk on "Derived semidistributive lattices"
is now available through arXiv:
http://arxiv.org/abs/0708.1695

Any of your comment will be very much appreciated.

Best wishes,

Luigi

--

--
Luigi Santocanale

LIF/CMI Marseille  				Tél: 04 91 11 35 74
http://www.cmi.univ-mrs.fr/~lsantoca/		Fax: 04 91 11 36 02


14 Aug 2007 23:23

### Topology and Groupoids , by Ronald Brown

This is now available printed in the UK through amazon.co.uk RRP £15.99 but currently £10.49

The e-version may be bought using credit cards or other ways via Kagi at
https://store.kagi.com/cgi-bin/store.cgi?storeID=6FEPD_LIVE
for £5. This version has some colour and hyperref.

Ronnie Brown
ww.bangor.ac.uk/r.brown



Gmane