June 2017 - Categories - categories.org.au

Is there a standard name?
by Michael Barr 01 Jul '17

01 Jul '17

It is well known that the homotopy relation on maps of simplicial sets is not symmetric nor transitive (it is reflexive). Is there a standard name for its symmetric, reflexive closure. I have been calling it wide homotopy, but I don't want to introduce a new term if there is a standard one. Michael [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Full-Time Postdoctoral Research Fellow and Researcher/Research Engineer
by Ehresmann 24 Jun '17

24 Jun '17

Moreno Andreatta has asked me to transmit the following information which could interest young category researchers. Yours Andree Full-Time Postdoctoral Research Fellow and Researcher/Research Engineer in Computational Musicology, University of Strasbourg, France Applications are invited for a one-year post-doctoral Research position and a one-year Researcher/Research Engineer position, both based at the Institute of Advanced Mathematical Research (IRMA) of the University of Strasbourg. The two positions are available within the SMIR (Structural Music Information Research) Project supported by USIAS (University of Strasbourg Institute for Advanced Study), in collaboration with IRCAM (Institut de Recherche et Coordination Acoustique/Musique). The project investigates the use of structural mathematical methods based on algebra, topology and category theory in the field of MIR (Music Information Research) and aims to build bridges between different musical genres, ranging from contemporary art music to popular music, including rock, pop, jazz and chanson. Applicants should have (or be about to receive) a PhD in mathematics or computer-science with a significant musical background. Strong skills in programming (e.g. Java, C/C++, Python, Matlab/Mathematica) are essential. A knowledge of algebraic models in computational music analysis and other symbolic approaches in MIR is an advantage. Applicants will need to demonstrate a record of research success and the ability to work independently and in a creative way. While French language skills are not mandatory, a fluency in English is required. The two one-year posts are available, respectively, from 1st September 2017 and from 1st January 2018. For further details about the SMIR Project, including the list of institutional collaborations, please visit: http://repmus.ircam.fr/moreno/smir Applications must include a detailed CV with a list of publications and a motivation letter. Please do not hesitate to contact me for informal Inquiries, Best regards, Moreno ANDREATTA CNRS Director of Research IRCAM - CNRS UMR 9912 (STMS) - UPMC e-mail: Moreno.Andreatta[at]ircam.fr USIAS Fellow and Invited Researcher at the University of Strasbourg CNRS IRMA UMR 7501 e-mail: andreatta[at]math.unistra.fr > [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Re: Functors arising from a relational Grothendieck construction
by Thomas Streicher 24 Jun '17

24 Jun '17

> a variant of the one in (Nielsen 2004, TAC 12(7), pp 248???261), but > consider You mean Niefield and not Nielsen. This paper makes clear the relation to Giraud-Conduch'e functors. But they just study the Weak Factorization Lifting Property (WFLP) which in terms of distributors means that all components of the natural transformation corresponding to lax preservation of composition are surjective. Faithful functors to B reflecting identities correspond to "relational variable sets" on B as described in the Niefield paper. But they are NOT Conduch'e fibrations since they just validate WFLP and not FLP. p : E -> B is a Conduch'e fibration (i.e. validatates FLP) iff it is exponentiable in Cat/B but p validates WLFP iff it is exponentiable in Cat_f/B (Cor.4.2 in Niefield paper). What Niefield calls Grothendieck construction is an instance of the transition from a lax normalised functor from B^op to Dist to a functor to B (due to Benabou). But this has nothing to do with what you describe as Grothendieck construction which rather is chanke of base along a functor B* -> B. Thomas [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Functors arising from a relational Grothendieck construction
by Luc Pellissier 23 Jun '17

23 Jun '17

Dear Category Theorists, with my adviser Damiano Mazza and his other student Pierre Vial, we are looking for a name – or even better, a reference – for the following kind of functors: Let C and B be two categories, F : C ---> D a functor satisfying, for all morphisms f:c -> c' in C: - if Ff = g \circ h, then there exists two morphisms k,l such that + f = k \circ l + Fk = g + Fl = h - if Ff = id_a for a certain object a, then f itself is an identity. These functors arise when applying the Grothendieck construction to relational presheaves: P : B ---> Rel. Indeed, the category of relational presheaves on B is equivalent (through the Grothendieck construction) to a category whose objects are such functors over B. If anyone could point us in a right direction, it would be much appreciated. Best, — Luc [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Charles Wells
by Michael Barr 21 Jun '17

21 Jun '17

Could you post an announcement that Charles Wells died on Saturday, June 17. It was sudden and unexpected. Mike [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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List delay
by Bob Rosebrugh 21 Jun '17

21 Jun '17

Note from moderator: >>From June 22-27, 2017 I will not have reliable access to email. Posts for the list sent during that period will be forwarded later. Best to all, Bob Rosebrugh [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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HDRA 2017: Deadline extension
by Samuel Mimram 19 Jun '17

19 Jun '17

============================================= CALL FOR PAPERS Higher-Dimensional Rewriting and Applications (HDRA 2017) ============================================= Dear everybody, The deadline for submitting to HDRA has been extended by one week: you still have until *Sunday, June 25* in order to submit or update papers! ------------------------------------------------------------------------------- Third edition of the workshop on Higher-Dimensional Rewriting and Applications September 8-9 2017, Oxford, United Kingdom http://hdra.gforge.inria.fr/ Satellite workshop of FSCD 2017, co-located with STRING 2017. ------------------------------------------------------------------------------- Rewriting consists in orienting equalities. This seemingly simple point of view has given rise to a rich theory, which was first developped in computer science for handling strings and terms, and was then extended over the recent years to many other settings (operads, monoidal categories, higher categories, etc.), allowing it to have applications in algebra, homotopy theory and physics. All these generalizations fit into the general scope of higher-dimensional rewriting theory, which has emerged as a unifying algebraic framework. The aim of the workshop is to gather people interested in pushing further rewriting theory, using (higher) categories as a common language. It is open to all topics concerning higher-dimensional generalizations and applications of rewriting theory, including - higher-dimensional rewriting: extensions of rewriting theory to higher-dimensional settings (operads, opetopes, polygraphs/computads, parity complexes, augmented directed complexes, etc.), generalizations of string/term/graph rewriting systems, etc. - higher categorical structures: weakening, combination and comparison of categorical structures (monoids, bialgebras, Frobenius algebras, Lie algebras, etc.), coherence theorems, etc. - applications of rewriting to algebraic topology: construction of resolutions, homotopical and homological invariants, linear rewriting (Gr??bner bases, applications to algebras and operads), Koszul duality theory, etc. - applications and interactions with other fields: calculi for quantum computations, proof nets, algebraic lambda-calculi, topological models for concurrency, homotopy type theory, combinatorial group theory, etc. - implementations: the workshop will also be interested in implementation issues in higher-dimensional rewriting and will allow demonstrations of prototypes of existing and new tools in higher-dimensional rewriting. HDRA 2017 will be co-located with the first edition of the STRING workshop (http://string2017.cs.ru.nl/) Invited speakers ================ * Dimitri Ara (Aix-Marseille Universit??) * Marcelo Fiore (University of Cambridge) * Paul-Andr?? Melli??s (CNRS and Paris Diderot) Submission ========== Important dates --------------- * Submission: June 25, 2017 * Notification: July 2, 2017 * Final version: July 9, 2017 * Conference: September 8-9, 2017 Submitting ---------- Submissions should consist in an extended abstract, in pdf format, approximatively 6 pages long, in standard article format. The page for uploading those is https://easychair.org/conferences/?conf=hdra2017 Proceedings ----------- The accepted extended abstracts will be made available electronically before the workshop. Program committee ================= * Yves Guiraud (INRIA / Universit?? Paris 7) * Philippe Malbos (Universit?? Claude Bernard Lyon 1) * Paul-Andr?? Melli??s (Universit?? Paris 7) * Samuel Mimram (??cole Polytechnique) * Tim Porter (University of Wales, Bangor) * Femke van Raamsdonk (VU University, Amsterdam) * Pawel Sobocinski (University of Southampton) * Jamie Vicary (University of Oxford) Organizers ========== * Yves Guiraud (INRIA / Universit?? Paris 7) * Philippe Malbos (Universit?? Claude Bernard Lyon 1) * Samuel Mimram (??cole Polytechnique) [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Is there a name for this?
by Harley D. Eades III 16 Jun '17

16 Jun '17

Hi, everyone. Take associativity away from the definition of a monoidal category. So we have a bi-functor, tensor, and the unitors, but nothing else. Is there a name for this? Of course, when we remove the associator, then we no longer have the diagrams. I have been thinking that maybe a magma category would work which only has the tensor product, and a magma category with units would add the unitors back in, etc. I’m sure someone has a name for this already, though. Thanks, Harley [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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Re: History of CT meetings
by Peter Johnstone 14 Jun '17

14 Jun '17

Dear Robert, Yes, I was aware of the 1974 Montreal seminar. But I think it falls outside my self-imposed restriction of including only meetings held during the summer months (June to September). So too do the Aarhus `Open House' meetings of 1973 and 1977, since they were both in May; and the Dalhousie meeting of 1971 which produced SLN 274, since that was in January. I've added to the list the earlier Oberwolfach meetings quoted by Walter, the La Jolla meeting (7-12 June 1965), the Z\"urich meeting of the Midwest Category Seminar (24-30 August 1970), and the l'Aquila workshop on categorical topology (31 August-4 September 1994) which I had overlooked because I didn't attend it. Best regards, Peter On Tue, 13 Jun 2017, Robert Seely wrote: > Thanks Peter, and now Walter too, for this list - there cannot be a lot of entries still to add, but there's one I'd like to see. > > I was going to add mention myself of the Séminaire de Mathématiques Supérieures (Université de Montréal) meeting in spring-early summer 1974, entitled "Méthodes catégoriques en logique mathématique et en théorie des automates", under the nominal direction of S. Takahashi. At this meeting important series of talks (virtually summer-school-type introductions, combined with state-or-the-art research talks) by Benabou, Joyal, Freyd, Reyes, and many others, made this meeting ground-breaking I think - one might regard it as the "coming of age" of the marriage of logic and categories begun by Bill Lawvere (who I am pretty sure was there too, but my memory is poor after all this time!) less than a decade earlier. (Much as the Boulder meeting was often regarded in a similar light for the connections between categories and computer science.) > > But sadly, I cannot give the exact dates (May or June '74?) for that meeting. I kept a student's diary at the time, but seem to have lost it, so have no records myself to base this information on. Surely someone can help with this? > > -= rags =- > > ----- Original Message ----- > From: tholen(a)mathstat.yorku.ca > To: "Peter Johnstone" <ptj(a)dpmms.cam.ac.uk> > Cc: "Categories mailing list" <categories(a)mta.ca>, tholen(a)mathstat.yorku.ca > Sent: Monday, June 12, 2017 3:45:46 PM > Subject: categories: Re: History of CT meetings > > Thanks, Peter, for compiling this list, this is great! > > There were also "Kategorien" meetings at Oberwolfach in 1972 and 1973, > organized by John Gray and Horst Schubert, which were probably > instrumental in establishing the tradition of summer conferences in > category theory: > > Oberwolfach, 23-29 July, 1972, > Oberwolfach, 22-28 July, 1973. > > When leafing through the Oberwolfach archives (to recall the dates > above), to my surprise, I saw that there was also a summer conference > on "Kategorien und Funktoren" in 1966, organized by Albrecht Dold and > Saunders Mac Lane(!): > > Oberwolfach, 17-23 July, 1966. > > This was just one year after the 1965 La Jolla meeting, probably to be > considered the first major international conference on category theory > ever. In Aveiro (CT2015) we acknowledged the 50th anniversary of that > pivotal conference. > > With the help of all readers of the list (and perhaps by leafing > through old Springer Lecture Notes), it should be possible to close the > information gap in the open interval (1966,1972). > > Walter > > > > > > > Quoting Peter Johnstone <ptj(a)dpmms.cam.ac.uk>: > >> When the 100th PSSL meeting was held in Cambridge last year, I made >> public the (almost) complete list of speakers and titles of talks at >> PSSL meetings, which I've been keeping since they started. A number >> of people suggested that it would be interesting to have a similar >> list for the summer CT meetings. I'm afraid that compiling a full >> list of speakers at such meetings would be beyond my resources, but >> I thought it might be of interest to make a list of the dates and >> locations of the meetings. So here is my first attempt at compiling >> it; it's in the form of a plain TeX document, but should be easily >> readable as text. At present it begins with the first Isle of Thorns >> meeting in 1974, simply because that was the first such meeting that >> I attended; information on earlier meetings, and corrections to the >> information below, are very welcome. >> >> Peter Johnstone >> >> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% >> [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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History of CT meetings
by Peter Johnstone 14 Jun '17

14 Jun '17

When the 100th PSSL meeting was held in Cambridge last year, I made public the (almost) complete list of speakers and titles of talks at PSSL meetings, which I've been keeping since they started. A number of people suggested that it would be interesting to have a similar list for the summer CT meetings. I'm afraid that compiling a full list of speakers at such meetings would be beyond my resources, but I thought it might be of interest to make a list of the dates and locations of the meetings. So here is my first attempt at compiling it; it's in the form of a plain TeX document, but should be easily readable as text. At present it begins with the first Isle of Thorns meeting in 1974, simply because that was the first such meeting that I attended; information on earlier meetings, and corrections to the information below, are very welcome. Peter Johnstone %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \centerline{\bf Category Theory Summer Conferences} \bigskip The following is intended to be a list of (mostly week-long) international conferences organized by, and attended mainly or exclusively by, category-theorists during the (northern) summer months (which I have interpreted broadly as June to September, inclusive). Dates quoted are arrival and departure dates: in most cases there were no lectures on the arrival date, and in some there were none on the departure date. Unless otherwise indicated, the official topic of the meeting was simply `Category Theory' or something equivalent; the meetings with other subjects are included because they were attended by a large proportion of `the usual suspects'. For meetings organized under the aegis of a body not solely devoted to category theory (MFI Oberwolfach, the London Mathematical Society, MSRI etc.) the meeting venue is shown in square brackets. \bigskip {\settabs\+worraw & worraworraworrawo & worraworrawo & worra\cr \+Year & Place & Dates & Subject if not CT \cr \+ & & \cr \+1974 & Isle of Thorns & 27/7--2/8 & \cr \+1974 & [Oberwolfach] & 3/8--9/8 & \cr \+1975 & [Oberwolfach] & 29/6--5/7 & \cr \+1976 & Isle of Thorns & 25/6--31/6 & \cr \+1977 & [Durham] & 9/7--21/7 & Applications of Sheaves\cr \+1977 & [Oberwolfach] & 31/7--6/8 & \cr \+1979 & [Oberwolfach] & 8/7--14/7 & \cr \+1980 & Amiens & 6/7--12/7 & (In memory of Ch.~Ehresmann)\cr \+1980 & Ottawa & 10/8--16/8 & Categorical Topology \cr \+1981 & Gummersbach & 5/7--10/7 & \cr \+1981 & Cambridge & 19/7--25/7 & \cr \+1982 & Isle of Thorns & 11/7--16/7 & \cr \+1983 & [Oberwolfach] & 18/9--24/9 & \cr \+1984 & Murten & 23/7--28/7 & \cr \+1985 & Isle of Thorns & 14/7--19/7 & \cr \+1985 & Bangor & 21/7--25/7 & Algebraic Homotopy Theory\cr \+1986 & Cambridge & 20/7--26/7 & \cr \+1987 & [Boulder] & 14/7--20/7 & Categories in Computer Science \&\ Logic\cr \+1987 & Louvain-la-Neuve & 26/7--1/8 & \cr \+1988 & Isle of Thorns & 10/7--15/7 & \cr \+1988 & Praha & 21/8--27/8 & Categorical Topology\cr \+1989 & Bangor & 3/7--7/7 & \cr \+1990 & Como & 22/7--28/7 & \cr \+1991 & [Durham] & 20/7--30/7 & Applications of Categories in Computer Science\cr \+1992 & Isle of Thorns & 12/7--17/7 & \cr \+1993 & [MSRI] & 11/7--24/7 & Universal Algebra \&\ Category Theory \cr \+1994 & Tours & 24/7--29/7 & \cr \+1995 & Halifax & 9/7--15/7 & \cr \+1995 & [Cambridge] & 6/8--12/8 & (part) Category Theory \&\ Computer Science \cr \+1996 & Isle of Thorns & 7/7--12/7 & \cr \+1996 & Cape Town & 14/7--20/7 & (B.~Banaschewski 70th birthday) \cr \+1997 & Vancouver & 13/7--19/7 & \cr \+1999 & Coimbra & 18/7--24/7 & \cr \+2000 & Como & 16/7--22/7 & \cr \+2002 & Haute-Bodeux & 7/9--12/9 & (European meeting)\cr \+2003 & [Toronto] & 22/9--28/9 & Categorical Structures for Descent \cr \+2004 & Vancouver & 18/7--24/7 & \cr \+2005 & Macquarie & 10/7--16/7 & (R.~Street 60th birthday)\cr \+2006 & White Point & 25/6--1/7 & \cr \+2007 & Carvoeiro & 17/6--23/6 & \cr \+2008 & Calais & 22/6--28/6 & \cr \+2009 & Cape Town & 28/6--4/7 & \cr \+2010 & Genova & 20/6--26/6 & \cr \+2011 & Vancouver & 17/7--23/7 & \cr \+2012 & Coimbra & 8/7--14/7 & (G.~Janelidze 60th birthday) \cr \+2013 & Macquarie & 7/7--13/7 & \cr \+2014 & Cambridge & 29/6--5/7 & \cr \+2015 & Aveiro & 14/6--20/6 & \cr \+2016 & Halifax & 7/8--13/8 & \cr \+2017 & Vancouver & 16/7--22/7 & \cr } \end [For admin and other information see: http://www.mta.ca/~cat-dist/ ]

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