Michael Barr | 26 Mar 13:45 2015
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coequalizers in the category of algebras for the double powerset triple

Recently there was a question as to whether these coequalizers exist. 
Unless I have misunderstood the question, the affirmative answer is given 
in the example in the middle of p.72 of Linton's paper in TAC reprint #18.

Michael

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Richard Garner | 26 Mar 02:27 2015
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Tensor product of left exact morphisms

Dear categorists,

If G is a group, then [G,Set] is the classifying topos for right
G-torsors.

What about the classifying topos for possibly non-transitive torsors?

I'm not very adept at these calculations, but if I construct it as a
subtopos of the classifying topos for G^op-sets, it appears to come out
as [X,Set] where X is the category of finitely presentable, free,
non-empty G^op-sets.

Similarly, if G is a groupoid, the corresponding classifying topos
appears to be [X,Set], where X is the full subcategory of [G^op, Set] on
those finite coproducts of representables which have global support.

Is this correct?

Richard

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Dirk Hofmann | 25 Mar 14:22 2015
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CT 2015 (abstract submission)

Dear Colleagues,

this is just a reminder that the deadline for submitting an abstract to
CT 2015 is Friday, March 27.

We also recommend to book accommodation as soon as possible (we have
pre-reserved rooms till March 31, see our website http://ct2015.web.ua.pt/).

All the best
Dirk

On 11/29/2014 12:52 PM, Dirk Hofmann wrote:
> Dear Colleagues,
>
> recall that the
>
>             International Category Theory Conference CT2015
>
> will take place in Aveiro, Portugal, from Sunday, June 14 till Friday,
> June 19.
>
> We have now a conference website located at
>
>      ct2015.web.ua.pt.
>
> It is also my pleasure to announce the
>
> INVITED SPEAKERS
> Clemens Berger - Universit?? de Nice
> Julie Bergner - University of California, Riverside
(Continue reading)

Townsend, Christopher | 24 Mar 12:44 2015

Question about coequalizers in the category of algebras of the double power locale monad

Hello - 

I was wondering if anyone knew whether or not the category of algebras of the double power locale monad has
coequalizers? Reflexive ones will do. 

Thanks, Christopher 

From: Townsend, Christopher <Christopher.Townsend <at> rbccm.com>
Subject: RE: Colimits in the category of algebras of power locale monads
Newsgroups: gmane.science.mathematics.categories
Date: 2013-12-30 16:46:31 GMT (1 year, 11 weeks, 6 days, 12 hours and 54 minutes ago)

Hello, 

If P is the upper, lower or double power locale monad on the category of locales (Loc), does anyone know if the
corresponding category of EM algebras,  Loc^P, has (i) coequalizers; and/or, (ii) finitary coproducts? 

Thanks, Christopher  

info <at> christophertownsend.org

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Marino Gran | 19 Mar 08:39 2015
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Workshop in category theory and algebraic topology (UCL): 2nd announcement

Dear Colleagues,

This is the second announcement concerning the 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.   

There will be 8 invited talks by the following lecturers.     

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

The programme of the workshop will also include a very limited number of (25-minute) contributed talks. 
If you wish to give a talk, please send an abstract to Marino Gran (marino.gran <at> uclouvain.be
<mailto:marino.gran <at> uclouvain.be>) by May 31. 

You will be informed concerning the acceptance of your abstract by June 15.     
The final programme of the workshop will be available by the end of June on the conference website, at the
address    http://sites.uclouvain.be/ctat2015 <http://sites.uclouvain.be/ctat2015>

Online registration is now open on the conference website. 
The registration fee of 50 euros should be paid upon arrival at the conference in Louvain-la-Neuve: it will
cover the conference documentation, the coffee breaks, a welcome reception on Thursday 10, and the
conference dinner on Friday 11. 

Registration will be free for PhD students.     
(Continue reading)

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Ackermann Award 2015

ACKERMANN AWARD 2015 - THE EACSL OUTSTANDING DISSERTATION AWARD FOR
LOGIC IN COMPUTER SCIENCE
    CALL FOR NOMINATIONS

Nominations are now invited for the 2015 Ackermann Award.
PhD dissertations in topics specified by the EACSL and LICS
conferences, which were formally accepted as PhD theses at a
university or equivalent institution between 1.1.2013 and 31.12.2014
are eligible for nomination for the award. The deadline for submission
is 15 April 2015.
Submission details follow below.
Nominations can be submitted from 1 January 2015 and should be sent
to the chair of the Jury, Anuj Dawar, by e-mail:anuj.dawar <at> cl.cam.ac.uk

The Award
The 2015 Ackermann award will be presented to the recipient(s) at the
annual conference of the EACSL, 7-10 September 2015, in Berlin (Germany).
The award consists of

       * a certificate,
       * an invitation to present the thesis at the CSL/LICS conference,
       * the publication of the laudatio in the CSL/LICS proceedings,
       * travel support to attend the conference, and
       * an invitation to present the work to the Kurt G??del Society in
Vienna.

The jury is entitled to give the award to more (or less) than one
dissertation in a year.

Jury
(Continue reading)

David Yetter | 17 Mar 15:25 2015

A coherence theorem question


A question, that if it has a known answer would probably have been settled long before electronically
searchable media arose, came up in the project a  student of mine is working on for his dissertation.

Obviously the coherence theorem for symmetric monoidal categories applies to cartesian monoidal
categories.  The question is:  Is there anything better?

More specifically is anyone aware of (with a citation to where it is proved) a coherence theorem asserting a
large class of diagrams commute in any cartesian monoidal category, or giving criteria for their
commuting, when the  diagrams are made not just prolongations of the monoidal structure maps, but also
involve projections (or equivalently unique arrows to the terminal object 3D monoidal identity) or
diagonals.  (If the "or" turns out to be exclusive, I'd be happiest for a theorem including diagonals,
but not projections, since those come up more in my student's work.)

Of course I'd be happy with a modern-style coherence result, characterizing  free cartesian monoidal
categories, too, since we should be able to read off the "all-[these] diagrams commute" sort of theorem
from it.

Best Thoughts,

David Yetter

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Robin Cockett | 17 Mar 00:12 2015
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Partial functors ..

David Leduc <david.leduc6 <at> googlemail.com> writes:

> A partial functor from C to D is given by a subcategory S of C and a
> functor from S to D. What is the appropriate notion of natural
> transformation between partial functors that would allow to turn small
> categories, partial functors and those "natural transformations" into
> a bicategory? The difficulty is that two partial functors from C to D
> might not have the same definition domain.

Here is a basic and quite natural interpretation (if someone has not
already pointed this out):

One can have a n.t  F => G iff F is less defined than G and on their common
domain (which is just the domain of F) there is a natural transformation
from F => \rst{F} G.   Partial functors, of course, form a restriction
category so they are naturally partial order enriched (by restriction).
This 2-cell structure must simply respect this partial order ...

This is certainly not the only possibility, unfortunately ... for example
why not also allow partial natural transformations ... which are less
defined than the functor.   Here one does have to be a bit careful: a
natural transformation must "know" the subcategory it is working with ...
thus defining the natural transformation as a function on arrows (rather
than just objects) is worthwhile adjustment (see MacLane page 19, Excercise
5).  This then works too ....

I hope this helps.

-robin

(Continue reading)

Bob Rosebrugh | 16 Mar 17:25 2015
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Easik 3.0: (correction)

[The first link below was incorrect in the message sent earlier; it is 
corrected in this post]

Version 3.0 of the Java application Easik has been released. Previous
versions were announced on this list.

Easik is a graphical environment for database design based on the finite
limit, finite sum Entity-Attribute (EA) sketches, and also for data entry
and manipulation. EA sketches are the syntactic basis of the categorical
Sketch Data Model developed by the poster and Michael Johnson. The model
extends and considerably enhances the widely studied and implemented
Entity-Relationship-Attribute data model.

Easik supports graphical design of EA sketches and their export to SQL
database schemas. An exported schema has triggers and procedures which
enforce the graphically specified constraints, both finite limit and
finite sum. Views built from subschemas may be designed and implemented.
Easik also provides connectivity for data manipulation to the common
open-source database management system MySQL.

Version 3.0 contains the functionality of Version 2.0 and adds several new
view features. Most importantly, views can now implement constraints from
the supporting EA sketch. Some known safe view updates are permitted, and
are restricted in other cases. Constraint handling has been tested and
refined.

The application is available at

**Correction:**

(Continue reading)

Michael Winter | 16 Mar 14:07 2015
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CALL FOR PhD/MSc Contributions (RAMiCS 2015)


                            4th CALL FOR PAPERS

                         (with deadline extension)

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

            28 September to 1 October 2015, Braga, Portugal
                  URL:  http://ramics2015.di.uminho.pt
         PDF: http://ramics2015.di.uminho.pt/RAMiCS15-CFP.pdf

Scope
-----

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 disciplines.

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
(Continue reading)

Bob Rosebrugh | 12 Mar 01:45 2015
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Easik 3.0: categorical database design and manipulation

Version 3.0 of the Java application Easik has been released. Previous 
versions were announced on this list.

Easik is a graphical environment for database design based on the finite 
limit, finite sum Entity-Attribute (EA) sketches, and also for data entry 
and manipulation. EA sketches are the syntactic basis of the categorical 
Sketch Data Model developed by the poster and Michael Johnson. The model 
extends and considerably enhances the widely studied and implemented 
Entity-Relationship-Attribute data model.

Easik supports graphical design of EA sketches and their export to SQL 
database schemas. An exported schema has triggers and procedures which 
enforce the graphically specified constraints, both finite limit and 
finite sum. Views built from subschemas may be designed and implemented. 
Easik also provides connectivity for data manipulation to the common 
open-source database management system MySQL.

Version 3.0 contains the functionality of Version 2.0 and adds several new 
view features. Most importantly, views can now implement constraints from 
the supporting EA sketch. Some known safe view updates are permitted, and 
are restricted in other cases. Constraint handling has been tested and 
refined.

The application is available at

http://mathcs.mta.ca/research/rosebrugh/Easik

or follow the link from

http://www.mta.ca/~rrosebru/
(Continue reading)


Gmane