Marino Gran | 23 Oct 14:18 2014

Workshop in Category Theory and Algebraic Topology

Dear Colleagues,

This is the first announcement for a "Workshop in Category Theory and Algebraic Topology," which will take
place at the UCL in Louvain-la-Neuve, Belgium, from 
Thursday 10 to Saturday 12 September 2015. 

The following invited speakers have accepted to give a talk at the workshop:

Joachim Kock (Universitat Autònoma de Barcelona)
Steve Lack (Macquarie University)
Tom Leinster (University of Edinburgh)
Sandra Mantovani (Università degli Studi di Milano)
Ieke Moerdijk (Radboud Universiteit Nijmegen)
Fernando Muro (Universidad de Sevilla)
Emily Riehl (Harvard University)
Tim Van der Linden (Université catholique de Louvain)

(see the webpage of the conference at the address  for more information).

Some practical information concerning registration will be sent in a second announcement at the
beginning of 2015.

We look forward to seeing you in Louvain-la-Neuve!

Best wishes,

Kathryn Hess, Marino Gran, Jérôme Scherer and Enrico Vitale

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Michael Winter | 20 Oct 21:19 2014

CFP: Relational and Algebraic Methods in Computer Science (RAMiCS 2015)

                            CALL FOR PAPERS

                   15th International Conference on
     Relational and Algebraic Methods in Computer Science (RAMiCS 2015)

             28 September to 1 October 2015, Braga, Portugal


  We invite submissions in the general area of Relational and Algebraic
  Methods  in Computer Science. Special focus will lie on formal methods
  for software engineering, logics of programs and links with neighbouring

  Particular topics of interest for the conference cover,
  but are not limited to:

  * Algebraic approaches to
    - specification, development, verification, and analysis of programs
      and algorithms
    - computational logic, in particular logics of programs, modal and
      dynamic logics, interval and temporal logics
    - semantics of programming languages

  * Applications in fields such as
    - relational formal methods such as B or Z, tabular methods
    - information systems
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Michael Barr | 19 Oct 13:40 2014

Journal pricing

Dear Colleagues:

I would like to call your attention to this:

If even Harvard cannot keep up with the cost of journals, who can?  As we 
know, during the 90s, there were two sharp trends: the cost of publishing 
mathematics dropped precipitously as more and more mathematicians were 
using tex to typeset their own papers, and the price of journals rose 
equally precipitously.  As you all know, the first trend led to the 
founding of TAC about 20 years ago which is a cost-free journal.

It is also interesting to look at the linked story:

about how the Fields medalist Tim Gowers has reacted to journals pricing.

Bob has given me permission to post this on the categories list, but NOT 
to start a general discussion there.  Any comments should therefore be 
addressed to me.


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Vladimir Voevodsky | 18 Oct 20:02 2014

non-unital monads


I am trying to find some information about non-unital monads (gadgets with \mu but without \eta).

In particular I am interested in the following two questions:

1. Given a non-unital monad can it have two different "unitality" structures?

2. Is there a concept of a free non-unital monad? For example, I can think of
the "free" non-unital monad generated by the functor X |-> X^2 on sets as the monad
that sends a set X into the set of "homogeneous" expressions made with one binary operation
s such that there is s(x1,x2) and s(s(x1,x2),s(x3,x4)) but no x1 itself and no s(x1,s(x2,x3)). 
But what is the universal characterization of it? 


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Tim Van der Linden | 14 Oct 14:18 2014

PSSL97 - First announcement

Dear Colleagues,

We are pleased to announce that the 97th Peripatetic Seminar on Sheaves
and Logic will be held on the weekend of 31st January–1st February 2015 in
Louvain-la-Neuve, Belgium.

We will take the occasion to celebrate Rudger Kieboom's 65th birthday.

The website of the conference can be found at the address

In order to register, please complete the Registration Form here below,
and send it to any of the organisers before the 15th of December. Saturday's
lunch will be offered to those PSSL participants who register by then.

If you wish to book a room at the hotel Ibis Style (ex-Mercure, the only hotel in
Louvain-la-Neuve), please do contact us by the 30th of November, so that we can make
a booking at the UCL special rate (90€ for a single room, breakfast included).

Lecture slots will be attributed on a first come-first serve basis. If you wish to give
a talk, please let us know as soon as possible, preferably before the end of October.

We are looking forward to seeing you in Louvain!

Best regards,

The organisers

Philippe Cara
Tomas Everaert
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Andrzej Murawski | 11 Oct 13:02 2014

LICS 2015 - First Call for Papers

                         CALL FOR PAPERS

                Thirtieth Annual ACM/IEEE Symposium on

                   July 6–10, 2015, Kyoto, Japan



LICS 2015 will be hosted in Kyoto, Japan during the week 6-10 July
2015 and will be colocated with ICALP 2015.


The LICS Symposium is an annual international forum on theoretical and
practical topics in computer science that relate to logic, broadly
construed. We invite submissions on topics that fit under that rubric.

Suggested, but not exclusive, topics of interest include: automata
theory, automated deduction, categorical models and logics,
concurrency and distributed computation, constraint programming,
constructive mathematics, database theory, decision procedures,
description logics, domain theory, finite model theory, formal aspects
of program analysis, formal methods, foundations of computability,
higher-order logic, lambda and combinatory calculi, linear logic,
logic in artificial intelligence, logic programming, logical aspects
of bioinformatics, logical aspects of computational complexity,
logical aspects of quantum computation, logical frameworks,  logics of
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Jamie Vicary | 10 Oct 19:55 2014

Coherence for tricategories


The usual argument that not all tricategories can be strictified appeals to
the existence of nontrivially braided monoidal categories. But this leaves
open the possibility that a tricategory can be strictified completely aside
from interchangors for endomorphisms of unit 1-morphisms, or something
similar. Are results along these lines known?

There are of course the results of Joyal and Kock that it is possible to
put all the weak structure in the unitors. One could see this as mildly in
support of the above proposal, where also the weak structure is closely
related to unit morphisms.

In the absence of hard facts, reasoned speculation would also be good to

Best wishes,

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José Pedro Magalhães | 10 Oct 15:57 2014

Mathematics of Program Construction (MPC 2015): first call for papers

Apologies for multiple copies.


12th International Conference on Mathematics of Program Construction, MPC 2015
Königswinter, Germany, 29 June - 1 July 2015


The MPC conferences aim to promote the development of mathematical principles
and techniques that are demonstrably practical and effective in the process
of constructing computer programs, broadly interpreted.

The 2015 MPC conference will be held in Königswinter, Germany, from 29th June
to 1st July 2015. The previous conferences were held in Twente, The
Netherlands (1989), Oxford, UK (1992), Kloster Irsee, Germany (1995),
Marstrand, Sweden (1998), Ponte de Lima, Portugal (2000), Dagstuhl, Germany
(2002), Stirling, UK (2004, colocated with AMAST), Kuressaare, Estonia (2006,
colocated with AMAST), Marseille, France (2008), Québec City, Canada (2010,
colocated with AMAST), and Madrid, Spain (2012).


Papers are solicited on mathematical methods and tools put to use in program
construction. Topics of interest range from algorithmics to support for
program construction in programming languages and systems. The notion of
"program" is broad, from algorithms to hardware. Some typical areas are type
systems, program analysis and transformation, programming-language semantics,
security, and program logics. Theoretical contributions are welcome, provided
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Thomas Streicher | 2 Oct 09:37 2014

a note on sources of my text of fibered categories

> Renewed study of these ideas, in light of the later exposition by
> Thomas Streicher, should lead to further applications (for example
> to the solution of problems posed in my 1972 Perugia Notes.)

Thanks for mentioning this text. But since I think ownership of ideas
is an important issue I want to point out that the aim of this text
was to exhibit part of the ideas and results of Jean B'enabou's almost
single handed approach to Fibered Categories as a foundation of
Category Theory over most general base categories. I also tried to explain
some work by J.-L. Moens (his 1982 Thesis) where I think I have added
a bit of additional material. As far as B'enabou's work is concerned
my sources were Roisins notes from B'enabou's 1980 Louvain-la-Neuve
lectures. My exposition evolved over the years and I have integrated
additional material and made corrections as I learnt from Jean for
which I am very grateful to him.

At one place I have referred to a fibred version of the Special
Adjoint Functor Theorem which one can find in Par'e and Schumacher's
text or alternatively in J.Celeyrette's These d'Etat from 1974 under
supervision of B'enabou.

The references in my text are not exhaustive at all. It's certainly a
mistake not to have formally referred to work by Grothendieck and Giraud.
But I was not using too much these original sources.

Moreover, I have used results from a paper by Mamuka Jibladze. I have
not given the precise reference but made clear in the title of the
appendix that it is Mamuka's result.

The aim of these notes was not to document precisely who did
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wlawvere | 25 Sep 20:00 2014

Dietmar Schumacher

I am very sad to learn about the passing of Dietmar Schumacher. I remember 
him as a student from Walter Felscher's classroom in Freiburg im Breisgau. 
It was 50 years ago on my first visit to Germany. In the classroom Walter 
publicly referred to Dietmar and praised him, and the tall, shy student 
replied:  'mich?'

I served on his doctoral committee and over the years continued to be 
impressed by the seriousness of his approach to mathematics. He was an 
important contributor to the Canada-UK collaboration that published in 
1978 major advances in the application of Grothendieck's 1961 fibered 
categories. To facilitate those applications Pare' and Schumacher devised 
a flexible presentation of the basic theory in terms of what they called 
indexed categories.

Renewed study of these ideas, in light of the later exposition by Thomas 
Streicher, should lead to further applications (for example to the 
solution of problems posed in my 1972 Perugia Notes.)  The serene spirit 
of Dietmar Schumacher will continue to inspire those who strive to develop 
such unifying applications.

My heartfelt condolences go to his family.

Bill Lawvere

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Aleks Kissinger | 25 Sep 19:31 2014

Soundness of commutative diagram proofs

A common style of proof in CT papers is to draw a huge commutative
diagram, number some subset of the faces, and justify why each of
these faces commute. However, such an argument alone doesn't imply
that the overall diagram commutes. Consider for example a triangle of
arrows with three additional arrows connecting each of the corners to
a fourth object in the centre. It is very easy to find examples where
the three little triangles commute, but not the big outside triangle.
E.g. take the three inward-pointing arrows to be 0 morphisms, then we
can take f,g,h to be arbitrary on the outside.

So, my question is:

Is there a simple way of judging soundness for a commutative diagram proof?

One answer is to determine what constitutes a legal pasting of
diagrams, then only admit those which were obtained inductively by
legal pastings of commuting faces. However, its not immediately
obvious that, given a diagram without such a decomposition into legal
pastings, we can obtain the decomposition efficiently. Has this
problem been studied formally somewhere?



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