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palmgren | 8 Feb 16:30
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Call for Papers: 8th SCANDINAVIAN LOGIC SYMPOSIUM 20-21 August 2012 at Roskilde University, DENMARK

8th SCANDINAVIAN LOGIC SYMPOSIUM 20-21 August 2012 at Roskilde University,
DENMARK

First Announcement and Call for Papers

The 8th Scandinavian Logic Symposium will be held at Roskilde University,
Trekroner, Denmark, 20-21 August 2012.

After a gap of fifteen years, the Scandinavian Logic Symposium is back.
The Symposium is the first major initiative of the newly revived
Scandinavian Logic Society (SLS, http://scandinavianlogic.org/) and will
be held at Roskilde University (RUC), Denmark.

As with previous editions of this conference, the aim of the programme is
to reflect current activity in logic in our part of the world. So we hope
that participants from Scandinavia, the Baltic countries and Northwestern
Russia will take the opportunity to contribute a talk and to meet with
fellow logicians from the area. But needless to say, we also extend a warm
welcome to logicians from further afield and plan to present a varied and
interesting collection of invited and contributed talks.

Related events:

A post-SLS tutorial day will be organized on August 22

Also note that Advances in Modal Logic (AiML) will be held on 22-25 August
2012, Copenhagen, Denmark. URL: http://hylocore.ruc.dk/aiml2012/ .

TOPICS
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Ohad Kammar | 8 Feb 21:29
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Pullbacks of a family of arrows

What is the standard name for the limit of the diagram consisting of a morphism
f : A --> C
and an I-indexed family of morphisms
g_i : B_i --> C
where I is a set?

This is a slight generalisation of pullbacks. I am really interested
in the terminology for the following notion:

A class of morphisms M is stable under such generalised pullbacks if,
for all such limiting cones
a : P --> A
b_i : P --> B_i
if g_i are all in M, then so is the morphism a : P --> A

(This is a slight generalisation of stability of M under pullbacks.)

Thanks,
Ohad.

--

-- 
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.

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Andrej Bauer | 6 Feb 16:28
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Announcement: Fourth Workshop on Formal Topology (4WFTop) and Workshop on higher dimensional algebra, categories and types (HDACT)

  FOURTH WORKSHOP ON FORMAL TOPOLOGY (4WFTop)

                            June 15-19 2012

                                  and

HIGHER DIMENSIONAL ALGEBRA, CATEGORIES AND TYPES (HDACT)

                              June 20 2012

                          Ljubljana (Slovenia)

                       http://4wft.fmf.uni-lj.si/

FOURTH WORKSHOP ON FORMAL TOPOLOGY (4WFTop)
===========================================

The workshop on formal topology is an international meeting dedicated
to formal topology and related topics, including constructive and
computable topology, point-free topology, and other generalizations of
topology.

This is the fourth of a series of successful meetings on the
development of Formal Topology and its connections with related
approaches. The first three have been held in Padua (1997), Venice
(2002), and Padua (2007).

IMPORTANT DATES

May 2      - deadline for abstract submissions
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Joyal, André | 5 Feb 22:43
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about to go up in smoke?

Information: 

http://www.forbes.com/sites/timworstall/2012/01/28/elseviers-publishing-model-might-be-about-to-go-up-in-smoke/

Cheers, ---André

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ams | 4 Feb 13:52
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CMCS 2012: Call for Participation and Short Contributions

------------------------------------------------------------------------------
           CMCS 2012 call for participation and short contributions
------------------------------------------------------------------------------

The 11th International Workshop on Coalgebraic Methods in Computer Science
                31 March - 1 April 2012, Tallinn, Estonia
                        co-located with ETAPS 2012
                           www.coalg.org/cmcs12

Aims and scope
--------------

In more than a decade of research, it has been established that a wide
variety of state-based dynamical systems, like transition systems,
automata (including weighted and probabilistic variants), Markov
chains, and game-based systems, can be treated uniformly as
coalgebras. Coalgebra has developed into a field of its own interest
presenting a deep mathematical foundation, a growing field of
applications, and interactions with various other fields such as
reactive and interactive system theory, object-oriented and concurrent
programming, formal system specification, modal and description
logics, artificial intelligence, dynamical systems, control systems,
category theory, algebra, analysis, etc. The aim of the CMCS workshop
series is to bring together researchers with a common interest in the
theory of coalgebras, their logics, and their applications.

The topics of the workshop include, but are not limited to:

   * the theory of coalgebras (including set theoretic and categorical
     approaches);
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David Spivak | 2 Feb 06:51
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Re: question about discrete op-fibrations

Hi Mark,

Nice work; thank you for the simple answer and good explanation.

I hope this isn't annoying, but what if I change the problem somewhat
and take DOF(C) to be the full subcategory of Cat_{C/} spanned by the
discrete opfibrations C-->D? Again I want to know whether DOF(C) has a
terminal object. Under this definition, by setting C=empty-category we
get DOF(C)=Cat, which does have a terminal object.

Thanks,
David

On Wed, Feb 1, 2012 at 5:29 PM, Mark Weber
<mark.weber.math <at> googlemail.com> wrote:
> Dear David
>
> I'll assume by the coslice DOF_{C/} you mean the category whose objects are discrete opfibrations C --> D,
and whose arrows are strictly commuting triangles under C.
>
> In that case the answer to your question is no. When C is empty, DOF_{C/}  is just your category DOF, of small
categories and discrete opfibrations between them, and DOF lacks a terminal object. For suppose that D is
terminal in DOF. Then for any set X, there is a discrete opfibration I(X) --> D, where I(X) is the category
obtained from X by freely adding an initial object. That is, the objects of I(X) are the elements of X
together with one additional object 0, and one has a unique arrow 0 --> x for all x in X.
>
> If F:I(X) --> D is a discrete opfibration, then F(0) is an object of D such that the cardinality of the set of
all arrows with source F(0) is that of X. Thus since D is terminal in DOF, for any set X there is an object x of  D
such that the cardinality of the set of all arrows with source x is that  of X. This contradicts the smallness
of D.
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David Spivak | 1 Feb 01:03
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question about discrete op-fibrations

Hi all,

Here's a quick question perhaps someone here can answer easily.

Let DOF denote the category whose objects are small categories C,D,
etc. and in which Hom(C,D) is the set of discrete op-fibrations C-->D.
For a category C, let DOF_{C/} denote the coslice over C.

Question: Does there exist a terminal object in DOF_{C/}?

Thanks!
David

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Eduardo J. Dubuc | 31 Jan 00:14
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Re: the cost of knowledge

Registration for library.nu is no longer possible.  See:

https://www.facebook.com/pages/librarynu/115557691886871

e.d.

Library.nu is closed on registration. I have no control over this. Main
reason is Library.nu ranked 7th in the world for usage of its type. Now
they have legal maters to deal with. They are trimming back there usage
by closing registration. However this has not only happening to
Library.nu. Its happening all over the web. SOPA and collages are trying
to shut down free software sites. SOPA never passed, But is being done
under stealth. Next few months you will see less and less of the web
free. Government of the United States is after file sharing host.
Passing DNS blocks on many countries. The ending goal is the end of the
internet as we know it. A move to a internet 2 type system ran by
governments of the world. Once there is more using internet 2 and all
major search providers switch.(Google, Bing, Aol, Yahoo, Facebook and
twitter) They will shut down Internet 1. New system will be a cloud
based system where the government can track every file on the web. (Bot
AI) Before a file goes to your pc. it must pass threw a cloud system.
Before a user can connect to the internet, They will have to go threw
valid ID checks on the cloud system. This is a move to control media and
the world in the end. We will lose the last freedom we have. Political
members of our governments don't work for us. They work for a global
agenda to control us all. They must play there parts in censoring the
web if they want there power and money in return. (Just greed)

If Library.nu ever opened back up registration it will be a miracle.
Legal maters is the main key why there can be no invites. If you have an
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Eduardo J. Dubuc | 29 Jan 22:46
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Re: cost of knowledge


Please Moderator, let this come across. The subject seems to me 
pertinent to all mathematicians, including category theorists.

In private mail I was told there is already a kind of math-megaupload, 
the following:  <http://library.nu/>. The problem is that to get an 
account on should be invited.

e.d.

On 28/01/12 19:27, Joyal, André wrote:
> Dear Eduardo,
>
> Supporting the boycott is probably easier for an established
> mathematician like myself
> than for a young mathematician without a permanent position.
>
> On the other hand, solving this problem is important for the young
> generation,
> since it concerns the scientific life of the future.
>
> I agree that there are other modes of action,
> like putting our papers on the arXiv. I am strongly supporting that.
> But it does not address the problem of our libraries which are forced to
> spend huge sums of money
> to buy knowledges produced by universities, not by publishing houses.
>
> http://www.guardian.co.uk/commentisfree/2011/aug/29/academic-publishers-murdoch-socialist
>
> http://www.guardian.co.uk/science/2012/jan/16/academic-publishers-enemies-science?CMP=twt_fd
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David Chemouil | 29 Jan 13:04
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Re: Gowers petition against Elsevier

[ Note from moderator: While interesting, this thread is off-topic and 
list policy does not allow for discussion. Posts sent after tomorrow will 
not be forwarded. Thanks. ]

Dear colleagues,

although this petition may be useful, I think there is much more to be 
done here.

For the time being, it is quite difficult to boycott any commercial 
publisher unless you are an experienced sommité in your domain. For 
instance, PhD students need to publish in highly-rated journals or 
conferences, which are almost always associated to a publisher like 
Elsevier or Springer. To fight this situation, and as in the case of the 
free software movement, the best strategy is in my view to develop a 
high-quality alternative to commercial scientific publishing. For 
instance, the said sommités could join (or create) programme and editing 
committees of journals and conferences publishing only under a 
totally-open access scheme (i.e gratis for authors and readers, as well 
as under a "free" licence, such as the Creative Commons - Attribution - 
Share-Alike licence). As a matter of fact, as most know, this is already 
the case with publications such as TAC or LMCS and with conferences 
relying on the EPTCS proceedings. Besides, it is easy to setup a site as 
an ArXiv overlay to rely on the long-lastingness of this publication 
platform. In ten years or so, with such committees and a good editing 
policy, such journals or conferences will be as well ranked as 
commercial ones.

However the subscription to the Elsevier or Springer electronic library 
will be needed for a long time, just to be able to get digitized
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Joyal, André | 28 Jan 23:27
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Re: the cost of knowledge

Dear Eduardo,

Supporting the boycott is probably easier for an established mathematician like myself
than for a young mathematician without a permanent position.

On the other hand, solving this problem is important for the young generation,
since it concerns the scientific life of the future.

I agree that there are other modes of action,
like putting our papers on the arXiv. I am strongly supporting that.
But it does not address the problem of our libraries which are forced to spend huge sums of money
to buy knowledges produced by universities, not by publishing houses.

http://www.guardian.co.uk/commentisfree/2011/aug/29/academic-publishers-murdoch-socialist

http://www.guardian.co.uk/science/2012/jan/16/academic-publishers-enemies-science?CMP=twt_fd

Best,
André

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Gmane