March 2015 - Categories - categories.org.au

coequalizers in the category of algebras for the double powerset triple
by Michael Barr 31 Mar '15

31 Mar '15

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 [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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FMCS 2015 - Second Announcement
by Phil Mulry 31 Mar '15

31 Mar '15

FMCS 2015 23rd Workshop on Foundational Methods in Computer Science Colgate University, Hamilton, NY, USA June 4-7, 2015 http://cs.colgate.edu/~phil/FMCS2015.html SECOND ANNOUNCEMENT Foundational Methods in Computer Science is an annual workshop bringing together researchers in mathematics and computer science with a focus on the application of category theory in computer science. Location This year's meeting will be hosted in the Department of Computer Science at Colgate University located in Hamilton, NY. Program There will be an informal welcoming reception on the evening of June 4. The scientific program starts on June 5, and consists of tutorials, invited talks, and contributed talks. There will be an excursion on one of the afternoons. The meeting ends midday on June 7th. Information on submission of abstracts for contributed talks can be found on the workshop website. Research Talks There will be some invited presentations, but the majority of the talks are solicited from the participants. If you wish to give a talk please indicate on the registration form by May 1. Student support Graduate student participation is particularly encouraged at FMCS. Students will pay a reduced registration fee. Limited financial support may also be available to students. Those interested should email the local organizer as soon as possible and no later than May 1. Registration, Housing & Travel Details on registration, housing and directions can be found on the workshop website. Anyone interested in attending or contributing a talk can also email the local organizer at pmulry at colgate dot edu. The workshop website can be found at http://cs.colgate.edu/~phil/FMCS2015.html Organizing committee: Robin Cockett (Calgary) Geoff Cruttwell (Mount Allison) Pieter Hofstra (Ottawa) John MacDonald (UBC) Phil Mulry (Colgate) Dorette Pronk (Dalhousie) Bob Rosebrugh (Mount Allison) Robert Seely (McGill) Local Arrangements: Philip Mulry [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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cubical homotopy
by Ronnie Brown 31 Mar '15

31 Mar '15

Does anyone by chance have a copy of Evrard, M. ???Homotopie des complexes simpliciaux et cubiques???. Preprint (1976). to be made available? There has been some discussion of varieties of cubical categories on http://nforum.mathforge.org/discussion/6528/cubes-with-diagonals/#Item_2 Ronnie -- [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Re: Tensor product of left exact morphisms
by Richard Garner 28 Mar '15

28 Mar '15

Thanks, André, that's helpful. This: > In general, if a topos $mathcal{E}$ > classifies the models of a geometric theory T, there is > another topos $mathcal{E}$ which classifies variable families > of models of T: it is the *bagdomain* of $mathcal{E}$ > introduced by Johnstone. See the Elephant vol. I Proposition 4.4.16. is particularly good. I knew about the bagdomain, but didn't connect it to my question. However, I think I want a non-transitive torsor to be a right G-set with a free action, but which is also inhabited. This means passing to a subtopos of [X, Set], where X is as before the category of finitely generated free G^op sets. Looking at the calculation I made before, I think I got it wrong. I must pass to the topology generated by making 0 ----> G into a cocover in X. But then I must also make every pushout of this into a cocover, and every composite of such pushouts into a cocover. So, in the end, I think the classifying topos should be Sh(X^op) for the topology whose cocovers are the coproduct injections in X. In other words, I take the Lawvere theory of G^op-sets, and take sheaves on it for the topology given by the project projections. Richard [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Tensor product of left exact morphisms
by Richard Garner 27 Mar '15

27 Mar '15

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 [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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CT 2015 (abstract submission)
by Dirk Hofmann 25 Mar '15

25 Mar '15

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 > Gabriella B??hm - Wigner Research Centre for Physics, Budapest > Richard Garner - Macquarie University, Sydney > Henning Krause - Bielefeld University > Diana Rodelo - University of Algarve > > as selected by the Scientific Committee. > > IMPORTANT DATES: > Abstract Submission: 27 of March > Acceptance: 25 of April > Early registration: 1 of May > > A further announcement with information about accommodation, > registration and abstract submission will follow soon (probably in > January). > > PLEASE TAKE NOTE: > > Directly preceding CT2015 there will be the 2015 AMS-EMS-SPM > International Meeting of the American Mathematical Society, the European > Mathematical Society and the hosting Portuguese Mathematical Society > > http://aep-math2015.spm.pt, > > which will take place in Porto (some 50 km from Aveiro) from Wednesday, > June 10, to Saturday, June 13. At this meeting, Gon??alo Gutierres and I > are organising a special session on "Categorical Methods in Algebra and > Topology" which will be held on Friday and Saturday (12/13 June) at the > Mathematics Department of the Faculty of Sciences of the University of > Porto. If you are interested in participating in this special session, > please contact me (dirk(a)ua.pt) or Gon??alo (ggutc(a)mat.uc.pt) For a > schedule of all special sessions see > > http://aep-math2015.spm.pt/ListOfSessions. > > I hope to see you in Portugal next June! > > Best regards > Dirk (for the organising committee) [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Question about coequalizers in the category of algebras of the double power locale monad
by Townsend, Christopher 25 Mar '15

25 Mar '15

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 [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Workshop in category theory and algebraic topology (UCL): 2nd announcement
by Marino Gran 19 Mar '15

19 Mar '15

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(a)uclouvain.be <mailto:marino.gran@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. The deadline for registering is June 30. We are looking forward to seeing you in Louvain-la-Neuve, Best regards, Kathryn Hess and Marino Gran [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Partial functors ..
by Robin Cockett 19 Mar '15

19 Mar '15

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 [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Ackermann Award 2015
by European Association of Computer Science Logic 19 Mar '15

19 Mar '15

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@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 The jury consists of: * Thierry Coquand (Chalmers University of Gothenburg); * Anuj Dawar (University of Cambridge), the president of EACSL; * Dexter Kozen (Cornell University), ACM SigLog representative; * Orna Kupferman (Hebrew University of Jerusalem); * Daniel Leivant (Indiana University, Bloomington); * Luke Ong (University of Oxford); * Jean-Eric Pin (CNRS and University of Paris 7); * Simona Ronchi Della Rocca (University of Torino), the vice-president of EACSL; How to submit The candidate or his/her supervisor should submit 1. the thesis (ps or pdf file); 2. a detailed description (not longer than 20 pages) of the thesis in ENGLISH (ps or pdf file); 3. a supporting letter by the PhD advisor and two supporting letters by other senior researchers (in English); supporting letters can also be sent directly to Anuj Dawar (anuj.dawar(a)cl.cam.ac.uk) 4. a short CV of the candidate; 5. a copy of the document asserting that the thesis was accepted as a PhD thesis at a recognized University (or equivalent institution) and that the candidate has received his/her PhD within the specified period. The submission should be sent by e-mail as attachments to the chairman of the jury, Anuj Dawar: anuj.dawar(a)cl.cam.ac.uk With the following subject line and text: * Subject: Ackermann Award Submission * Text: Name of candidate, list of attachments Submission can be sent via several e-mail messages. If this is the case, please indicate it in the text. Letters of support and documents can also be faxed to: Anuj Dawar Ackermann Award +44 1223 334678 The Jury has the right to declare submissions to be out of scope or not to meet the requirements. The Award is sponsored by the Kurt G??del Society. [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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