From MAILER-DAEMON Fri Oct 14 17:14:14 2005 Date: 14 Oct 2005 17:14:14 -0300 From: Mail System Internal Data Subject: DON'T DELETE THIS MESSAGE -- FOLDER INTERNAL DATA Message-ID: <1129320854@mta.ca> X-IMAP: 1125581369 0000000034 Status: RO This text is part of the internal format of your mail folder, and is not a real message. It is created automatically by the mail system software. If deleted, important folder data will be lost, and it will be re-created with the data reset to initial values. From rrosebru@mta.ca Thu Sep 1 09:30:55 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 01 Sep 2005 09:30:55 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EAo82-0003nb-NY for categories-list@mta.ca; Thu, 01 Sep 2005 09:25:14 -0300 Date: Thu, 1 Sep 2005 07:53:54 -0400 (EDT) From: Peter Freyd Message-Id: <200509011153.j81BrsJ4002446@saul.cis.upenn.edu> To: categories@mta.ca, tl@maths.gla.ac.uk Subject: categories: Re: Preprint: A simple description of Thompson's group F Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 1 There's a good chance that the characterization of Thompson's group F (not to mention its name) was set forth in the paper reviewed below (the authors of which became aware of R.J.Thompson's priority via this review). Freyd, Peter; Heller, Alex Splitting homotopy idempotents. II. J. Pure Appl. Algebra 89 (1993), no. 1-2, 93--106. A preliminary version of this paper was in the reviewer's hands in 1979 and was then of uncertain age. The authors have done a service in publishing it (in somewhat revised form) belatedly. The object of study is a free homotopy idempotent $f \colon X \to X$; this means that $f$ is freely (base point not necessarily preserved during the homotopy) homotopic to $f^2 \equiv f \circ f$. This $f$ is said to split if there are maps $d \colon X \to Y$ and $u \colon Y \to X$ such that $d \circ u \simeq \text{id}_Y$ and $u \circ d \simeq f$, where $\simeq$ denotes free homotopy. They construct a group $F$ and an endomorphism $\phi \colon F \to F$ such that, for a certain $\alpha_0 \in F$, $\phi^2(7) = \alpha^{-1}_0\phi(7)\alpha_0$. The induced map $g \colon K(F,1) \to K(F,1)$ is a homotopy idempotent which does not split; and it is universal in the sense that it maps "canonically" into any homotopy idempotent, and the corresponding homomorphism $F \to \pi_1(X)$ is monic if and only if $f$ does not split. This group $F$ is shown to be finitely presentable, has simple commutator subgroup, is a totally ordered group and contains a copy of its own infinite wreath-product. Every abelian subgroup is free abelian, and every subgroup is either finite-rank free abelian or contains an infinite-rank free abelian subgroup. \{Reviewer's remarks: (1) While the authors acknowledge that some of the above is due independently to J. Dydak \ref[Bull. Acad. Polon. Sci. Ser. Sci. Math. Astronom. Phys. 25 (1977), no. 1, 55--62; MR0442918 (56 \#1293)], they fail to mention that priority for this group is generally given to R. J. Thompson \ref[R. J. Thompson and R. McKenzie, in Word problems (Irvine, CA, 1969), 457--478, North-Holland, Amsterdam, 1973; MR0396769 (53 \#629)], who introduced $F$ and seemed to know many of its properties in the late 1960s. Closely related to $F$ are Thompson's finitely presented infinite simple groups. (2) Subsequently, as acknowledged by the authors, much more became known about this extraordinary group. To help the reader know what we are discussing, we mention that $F$ is often known as "the Richard Thompson group"; also as the "Freyd-Heller group", the "Dydak-Minc group" and (incorrectly, but because of later work on $F$) as the "Brown-Geoghegan group". (3) The origin of the curious name "$F$" was explained to the reviewer by one of the authors as standing for "free", as in "free homotopy idempotent".\} Reviewed by Ross Geoghegan From rrosebru@mta.ca Fri Sep 2 09:36:31 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Fri, 02 Sep 2005 09:36:31 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EBAaW-0001AN-6P for categories-list@mta.ca; Fri, 02 Sep 2005 09:24:08 -0300 Date: Thu, 1 Sep 2005 10:56:18 -0700 (PDT) From: Joseph Goguen Message-Id: <200509011756.j81HuIrM019218@fast.ucsd.edu> To: categories@mta.ca Subject: categories: Preprint: Information integration in institutions Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 2 The paper whose abstract is given below is available at http://www.cs.ucsd.edu/~goguen/pps/ifi04.pdf and will appear in a memorial volume for Jon Barwise sometime in 2006, edited by Larry Moss. Information Integration in Institutions Joseph A Goguen Department of Computer Science and Engineering University of California at San Diego, USA This paper unifies and/or generalizes several approaches to information, including the information flow of Barwise and Seligman, the formal conceptual analysis of Wille, the lattice of theories of Sowa, the categorical general systems theory of Goguen, and the cognitive semantic theories of Fauconnier, Turner, Gardenfors, and others. Its rigorous approach uses category theory to achieve independence from any particular choice of representation, and institutions to achieve independence from any particular choice of logic. Corelations and colimits provide a general formalization of information integration, and Grothendieck constructions extend this to several kinds of heterogeneity. Applications include modular programming, Curry-Howard isomorphism, database semantics, ontology alignment, cognitive semantics, and more. From rrosebru@mta.ca Fri Sep 2 09:36:32 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Fri, 02 Sep 2005 09:36:32 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EBAZu-00018B-H5 for categories-list@mta.ca; Fri, 02 Sep 2005 09:23:30 -0300 Date: Thu, 1 Sep 2005 12:17:45 -0400 (EDT) From: Peter Freyd Message-Id: <200509011617.j81GHj1q020427@saul.cis.upenn.edu> To: categories@mta.ca, tl@maths.gla.ac.uk Subject: categories: Re: Preprint: A simple description of Thompson's group F Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 3 Marcelo and Tom write We show that Thompson's group F is the symmetry group of the "generic idempotent". That is, take the monoidal category freely generated by an object A and an isomorphism A \otimes A --> A; then F is the group of automorphisms of A. Tom has pointed out to me that the review of the old Freyd/Heller I posted give no hint of its relevance. Therefor this: F was defined (40 years ago) as the initial model for a group with an endomorphism that's conjugate to its square. More formally: consider the equational theory that adds to the theory of groups a constant, s, and a unary operator e, subject to two further equations: e(xy) = (ex)(ey) "e is a endomorphism" s(ex) = (e(ex))s "e is a conjugacy-idempotent" The initial algebra for this theory is the group F. (If one insists on removing the type-error in the last sentence, then try "the initial algebra for this theory when subjected to the forgetful functor back to groups is F.") If one defines a sequence of elements s_n = e^n(s) they clearly generate F (as a group) and it isn't hard to see that a complete set of relations for F (as a group) is the doubly-infinite family s_a s_b = s_{b+1} s_a one such equation for each a < b. (It took me ten years to find a proof that just two of these equations imply all the others.) From rrosebru@mta.ca Mon Sep 5 17:14:04 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 05 Sep 2005 17:14:04 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1ECNCE-0007gY-Pk for categories-list@mta.ca; Mon, 05 Sep 2005 17:04:02 -0300 Date: Mon, 05 Sep 2005 20:44:10 +0100 From: cie06@swansea.ac.uk To: categories@mta.ca Subject: categories: CiE 2006, Call for Papers Message-ID: <431CA00A.mailD9R11ASIW@swansea.ac.uk> User-Agent: nail 10.3 11/29/02 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 4 CiE 2006 Computability in Europe 2006 : Logical Approaches to Computational Barriers 30 June - 5 July 2006 Swansea University http://www.cs.swansea.ac.uk/cie06/ CALL FOR PAPERS Deadline: DECEMBER 15, 2005 CiE 2006 is the second of a new conference series on Computability Theory and related topics which started in Amsterdam in 2005. CiE 2006 will focus on (but not be limited to) logical approaches to computational barriers: - practical and feasible barriers, e.g., centred around the P vs. NP problem; - computable barriers connected to models of computers and programming languages; - hypercomputable barriers related to physical systems. Tutorials will be given by: Samuel R. Buss (San Diego) Julia Kempe (Paris) Invited Speakers include: Jan Bergstra (Amsterdam) Luca Cardelli (Microsoft Cambridge) Jan Krajicek (Prague) Elvira Mayordomo Camara (Zaragoza) Istvan Nemeti (Budapest) Helmut Schwichtenberg (Munich) Andreas Weiermann (Utrecht) The Programme Committee cordially invites all researchers (European and non-European) in the area of Computability Theory to submit their papers (in PDF-format, at most 10 pages) for presentation at CiE 2006. We particularly invite papers that build bridges between different parts of the research community. Since women are underrepresented in mathematics and computer science, we emphatically encourage submissions by female authors. The proceedings are intended to be published within Springer's LNCS series. Important dates are: Submission Deadline: December 15th, 2005. Notification of Authors: February 15th, 2006. Deadline for Final Version: March 15th, 2006. Programme Committee: Samson Abramsky (Oxford) Klaus Ambos-Spies (Heidelberg) Arnold Beckmann (Swansea, co-chair) Ulrich Berger (Swansea) Olivier Bournez (Nancy) Barry Cooper (Leeds) Laura Crosilla (Firenze) Costas Dimitracopoulos (Athens) Abbas Edalat (London) Fernando Ferreira (Lisbon) Ricard Gavalda (Barcelona) Giuseppe Longo (Paris) Benedikt Loewe (Amsterdam) Yuri Matiyasevich (St.Petersburg) Dag Normann (Oslo) Giovanni Sambin (Padova) Uwe Schoening (Ulm) Andrea Sorbi (Siena) Ivan Soskov (Sofia) Leen Torenvliet (Amsterdam) John Tucker (Swansea, co-chair) Peter van Emde Boas (Amsterdam) Klaus Weihrauch (Hagen) Confirmed sponsors: British Logic Colloquium (BLC) Kurt Goedel Society (KGS) Welsh Development Agency (WDA) For more information about the conference please check the CiE conference series http://www.illc.uva.nl/CiE/ and our web page http://www.cs.swansea.ac.uk/cie06/. From rrosebru@mta.ca Mon Sep 5 17:14:04 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 05 Sep 2005 17:14:04 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1ECNDM-0007lG-Hd for categories-list@mta.ca; Mon, 05 Sep 2005 17:05:12 -0300 Date: Mon, 05 Sep 2005 15:53:32 +0100 From: Philip Wadler User-Agent: Mozilla Thunderbird 0.9 (X11/20050217) X-Accept-Language: en-us, en MIME-Version: 1.0 To: categories@mta.ca Subject: categories: Eighth International Symposium on Functional and Logic Programming Sender: cat-dist@mta.ca Precedence: bulk Message-Id: Status: O X-Status: X-Keywords: X-UID: 5 [FLOPS benefits from an eclectic mix of FP and LP papers, one of the few venues where the two communities get together. It should be a congenial meeting, situated under Mt Fuji. Do come! -- P] First Call For Papers Eighth International Symposium on Functional and Logic Programming FLOPS 2006 April 24--26 Fuji Susono, JAPAN Submission deadline: November 11 http://hagi.is.s.u-tokyo.ac.jp/FLOPS2006 FLOPS is a forum for research on all issues concerning declarative programming, including functional programming and logic programming, and aims to promote cross-fertilization between the two paradigms. Previous FLOPS meetings were held in Fuji Susono (1995), Shonan Village (1996), Kyoto (1998), Tsukuba (1999), Tokyo (2001), Aizu (2002), and Nara (2004). TOPICS FLOPS solicits original papers in all areas of functional and logic programming, including (but not limited to): Declarative Pearls: new and excellent declarative programs with illustrative applications; Language issues: language design and constructs, programming methodology, integration of paradigms, interfacing with other languages, type systems, constraints, concurrency and distributed computing; Foundations: logic and semantics, rewrite systems and narrowing, type theory, proof systems; Implementation issues: compilation techniques, memory management, program analysis and transformation, partial evaluation, parallelism; Applications: case studies, real-world applications, graphical user interfaces, internet applications, XML, databases, formal methods, and model checking. For 2006, we wish to particularly encourage papers on new application areas, including security, bioinformatics, and quantum computation. The proceedings will be published as a LNCS volume. The proceedings of the previous meeting (FLOPS2004) were published as LNCS2998. SUBMISSION Submissions must be unpublished and not submitted for publication elsewhere. Work that already appeared in unpublished or informally published workshops proceedings may be submitted. Submissions should fall into one of the following categories: Regular research papers: they should describe new results and will be judged on originality, correctness and significance. System descriptions: they should contain a link to a working system and will be judged on originality, usefulness and design. All submissions must be written in English and can be up to 15 proceedings pages long. Authors are strongly encouraged to use LaTeX2e and the Springer llncs class file, available at http://www.springer.de/comp/lncs/authors.html Regular research papers should be supported by proofs and/or experimental results. In case of lack of space, this supporting information should be made accessible otherwise (e.g. a link to a web page, or an appendix). Submission is Web-based and under preparation. Please visit http://hagi.is.s.u-tokyo.ac.jp/FLOPS2006/ INVITED SPEAKERS Peter Van Roy (Louvain, Belgium) other speakers to be decided CO-CHAIRS Philip Wadler (Edinburgh, UK) Masami Hagiya (Tokyo, Japan) PC MEMBERS Peter Selinger (Dalhousie, Canada) Manuel Hermenegildo (New Mexico & Madrid, US & Spain) Eijiro Sumii (Tohoku, Japan) Konstantinos Sagonas (Uppsala, Sweden) Jacques Garrigue (Nagoya, Japan) Peter Thiemann (Freiburg, Germany) David Warren (Stony Brook, US) Gabrielle Keller (UNSW, Sydney, Australia) Alain Frisch (INRIA Roquencourt, France) Veronica Dahl (Simon Fraser, Canada) Ken Satoh (NII, Tokyo, Japan) Naoyuki Tamura (Kobe, Japan) Michael Rusinowitch (INRIA Lorraine, France) Vincent Danos (Paris, France) IMPORTANT DATES Submission deadline: November 11 Author notification: January 6 Camera-ready copy: January 20 PLACE The meeting will be held at Fuji Institute of Education and Training (http://www.fujiken.gr.jp/) located in Fuji Susono, JAPAN, where the first FLOPS was held. It is famous of its view to Mt. Fuji. Previous FLOPS: FLOPS 2004, Nara: http://logic.is.tsukuba.ac.jp/FLOPS2004/ FLOPS 2002, Aizu: http://www.ipl.t.u-tokyo.ac.jp/FLOPS2002/ FLOPS 2001, Tokyo: http://www.ueda.info.waseda.ac.jp/flops2001/ SPONSOR University of Tokyo IN COOPERATION (pending) ACM SIGPLAN Japan Society for Software Science and Technology (JSSST) Association for Logic Programming (ALP) Asian Association for Foundation of Software (AAFS) INQUIRIES to Masami Hagiya hagiya@is.s.u-tokyo.ac.jp From rrosebru@mta.ca Wed Sep 7 07:19:50 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 07 Sep 2005 07:19:50 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1ECwst-0005Es-6Y for categories-list@mta.ca; Wed, 07 Sep 2005 07:10:27 -0300 Date: Tue, 6 Sep 2005 16:21:36 -0400 (EDT) From: Peter Freyd Message-Id: <200509062021.j86KLanB027117@saul.cis.upenn.edu> To: categories@mta.ca Subject: categories: Memorial service for John Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 6 On August 10 I received the following information about John Isbell's death. A memorial service is now being planned and will most likely occur at Forest Lawn on Saturday, September 10. No other details are available now; an obituary should appear in the Buffalo News today or later this week. No obit has appeared (paid or ortherwise) and I have not succeeded in finding any further information about the service. Does anyone know? Peter From rrosebru@mta.ca Wed Sep 7 19:56:19 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 07 Sep 2005 19:56:19 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1ED8lc-0003Yw-5z for categories-list@mta.ca; Wed, 07 Sep 2005 19:51:44 -0300 Date: Wed, 7 Sep 2005 18:46:01 -0400 (EDT) From: Robert Seely To: Categories List Subject: categories: News from Tulane? Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 7 Just wondering if anybody here has had any news from our collegues from Tulane (eg Mike Mislove)? Are they safe, did they evacuate before the hurricane, what's in store for them now? (I know the university is shut - and I guess probably for the forseeable future, though that's also a question.) Obviously one wishes them all the best in this impossibly difficult time. -= rags -= -- From rrosebru@mta.ca Thu Sep 8 16:34:07 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 08 Sep 2005 16:34:07 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EDS1B-0006oQ-0r for categories-list@mta.ca; Thu, 08 Sep 2005 16:25:05 -0300 From: Colin McLarty To: categories@mta.ca Message-ID: <503ca6503bb9.503bb9503ca6@cwru.edu> Date: Thu, 08 Sep 2005 07:52:34 -0400 X-Mailer: iPlanet Messenger Express 5.2 HotFix 2.05 (built Mar 3 2005) MIME-Version: 1.0 Content-Language: en Subject: categories: Noether and fast thinking X-Accept-Language: en Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 8 Somewhere MacLane published a part of a letter he sent his mother from Goettingen where he said that Fraulein Noether "thought fast and spoke faster" or something like that. I have looked at every mention of Noether by him that I can think of without re-locating this one. Does anyone know where it is? thanks, Colin From rrosebru@mta.ca Thu Sep 8 16:34:07 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 08 Sep 2005 16:34:07 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EDS67-00078f-VO for categories-list@mta.ca; Thu, 08 Sep 2005 16:30:11 -0300 Date: Thu, 08 Sep 2005 00:44:47 -0400 From: Fred E.J.Linton To: Subject: categories: Re: Memorial service for John X-Mailer: USANET web-mailer (CM.0402.7.32) Mime-Version: 1.0 Message-ID: <442JiHeSv3168S03.1126154687@uwdvg003.cms.usa.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 9 Hello, Peter, and all Categories readers, Googling "Buffalo News obituary John Isbell" today brought this up: > John R. Isbell Ph.D. = > = > August 6, 2005 age 74. Dear father of Margaret M. Thornborough of = > Bristol, England, John C. Isbell of Bloomington, IN, and Brecht W. = > Isbell of Los Angeles, CA.; grandfather of Zelie Thornborough and = > Alexander L. L. Thornborough both of England; brother of Frances W. = > Isbell of Weslaco, TX and the late Robert O. Isbell. There will be no = > prior visitation. A Memorial Service will be held Saturday, September = > 10, 2005 at 4 PM at the Chapel of Forest Lawn Cemetery. Friends = > invited. Mr. Isbell was a Math Professor at SUNY @ Buffalo from 1969- > 1999. Arrangements by AMIGONE FUNERAL HOME INC. Online guest register = > at www.Amigone.com = > > Published in the Buffalo News on 8/28/2005. = [URL (all one line; best turn off Active-X): http://legacy.com/BuffaloNews/LegacySubPage2.asp?Page=3DLifeStory&PersonI=d=3D14948085 ] ------ Original Message ------ Received: Wed, 07 Sep 2005 06:25:08 AM EDT From: Peter Freyd To: categories@mta.ca Subject: categories: Memorial service for John > On August 10 I received the following information about John Isbell's > death. > = > A memorial service is now being planned and will most likely occur > at Forest Lawn on Saturday, September 10. No other details are > available now; an obituary should appear in the Buffalo News today > or later this week. > = > No obit has appeared (paid or ortherwise) and I have not succeeded in > finding any further information about the service. > = > Does anyone know? > = > Peter > = > = > = From rrosebru@mta.ca Thu Sep 8 16:34:07 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 08 Sep 2005 16:34:07 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EDS0O-0006lP-M9 for categories-list@mta.ca; Thu, 08 Sep 2005 16:24:16 -0300 Date: Wed, 07 Sep 2005 16:13:17 -0700 From: Todd Wilson Subject: categories: Follow-ups to [HP89]? To: categories@mta.ca Message-id: <431F740D.6000201@csufresno.edu> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7BIT Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 10 In the introduction to their 1989 article, JME Hyland & AM Pitts, "The Theory of Constructions: Categorical Semantics and Topos-Theoretic Models", Contemp. Math. 92 (1989), 137 - 199, the authors say, "Clearly this paper is only a beginning." Can someone recommend follow-ups to this paper published in the intervening 15 years? Todd Wilson Department of Computer Science California State University, Fresno From rrosebru@mta.ca Thu Sep 8 16:38:17 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 08 Sep 2005 16:38:17 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EDSDV-0007hM-IN for categories-list@mta.ca; Thu, 08 Sep 2005 16:37:49 -0300 Message-ID: <431F79DC.3000703@math.upenn.edu> Date: Wed, 07 Sep 2005 19:38:04 -0400 From: jim stasheff User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Categories List Subject: categories: Re: News from Tulane? References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 11 [Note from moderator: Thanks to the many who replied, several answers are combined below.] Robert Seely wrote: >Just wondering if anybody here has had any news from our collegues from >Tulane (eg Mike Mislove)? Are they safe, did they evacuate before the >hurricane, what's in store for them now? (I know the university is shut - >and I guess probably for the forseeable future, though that's also a >question.) Obviously one wishes them all the best in this impossibly >difficult time. > >-= rags -= > Some Tulane students have been accepted here at Penn and we have picked up 2 post-docs who would've been there. jim Date: Wed, 7 Sep 2005 16:57:46 -0700 (PDT) From: Dominic Hughes Subject: Re: categories: News from Tulane? I know second-hand that Mike Mislove and James (aka Ben) Worrell got away safely. Dominic From: Michael Fourman Subject: Re: News from Tulane? Date: Thu, 8 Sep 2005 06:06:16 +0100 I checked this a few days ago. Google search for Mislove Tulane Katrina turns up the following http://atgdev.elsevier.com/blogs/cleonard/?p=3D34 Katrina and Tulane September 2nd, 2005 I=92ve just had an email from Mike Mislove, editor of Electronic Notes =20= in Theoretical Computer Science. He is usually based in New Orleans =20 at Tulane University, but is currently safe in Memphis having =20 evacuated before the hurricane hit land. Apparently it will be some =20 time before Tulane will be back to normal - daily updates on the =20 situation can be found on a special website. As a result of the recent devastation, the usual Tulane mail servers =20 are not working. If you wish to contact Mike, please use his gmail =20 account. From: Don Sannella Date: Thu, 8 Sep 2005 08:57:19 +0100 Subject: Re: News from Tulane? I recently heard from Chris Leonard at Elsevier -- where Mike Mislove is editor-in-chief of Electronic Notes in Theoretical Computer Science -- that Mike got out before the hurricane hit, is safe in Memphis, and can be reached at michael.mislove@gmail.com. I don't know anything about anybody else at Tulane. Don Sannella From: Martin Escardo Date: Thu, 8 Sep 2005 09:39:29 +0100 Subject: Re: News from Tulane? I know that Mike Mislove and Karl Hofmann safely rellocated themselves before the hurricane. Because Mike didn't mention, I assume that all other colleagues are safe, but I don't really know. Date: Thu, 08 Sep 2005 02:46:21 -0700 From: Dusko Pavlovic Subject: Re: categories: News from Tulane? mike mislove is in a hotel in memphis, tn. they evacuated before the hurricane, but times are difficult. we hope that he and his family will visit palo alto as soon as the circumstances allow. ben worrell was in canada, scheduled to return to new orleans on the morning of katrina. he was to start at oxford soon, so i hope that he is now in UK. i have no idea about the others. -- dusko From rrosebru@mta.ca Mon Sep 12 17:01:04 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 12 Sep 2005 17:01:04 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EEuKa-0006fF-ND for categories-list@mta.ca; Mon, 12 Sep 2005 16:51:08 -0300 To: categories Subject: categories: John Isbell Memorial Date: Mon, 12 Sep 2005 15:37:56 -0400 From: Samuel D. Schack Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: cat-dist@mta.ca Precedence: bulk Message-Id: Status: RO X-Status: X-Keywords: X-UID: 12 Hi, Please post the following note from the UB Mathematics Department (not me). Since postings on the catnet have sought further information on the memorial for John Isbell, the Mathematics Department of the University at Buffalo, SUNY would like to assure the community that the service and announcements were handled according to the wishes of the family. The service itself was held on Saturday afternoon and remarks about John's remarkable intellectual breadth and extensive mathematical accomplishments were made by Professors J. Duskin, F.W. Lawvere, S. Schanuel, and S. Williams. The family is preparing an obituary, with more detail than the death notice copied to the catnet by F. Linton, and we will forward it to the catnet when it appears. From rrosebru@mta.ca Fri Sep 16 11:48:29 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Fri, 16 Sep 2005 11:48:29 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EGHLT-0004We-Va for categories-list@mta.ca; Fri, 16 Sep 2005 11:37:44 -0300 From: Martin Escardo MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17194.47166.149464.378158@gargle.gargle.HOWL> Date: Fri, 16 Sep 2005 13:19:10 +0100 To: categories@mta.ca Subject: categories: stable flatness and exponentiation Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 13 I have three questions: Question 1: Is there an intrinsic characterization of the stably flat maps of locales, i.e., those continuous maps f: X->Y such that id_Z x f: Z x X -> Z x Y is flat for all Z? (Recall that f: X->Y is flat iff the right adjoint f_*: OX -> OY of f^*: OY -> OX preserves finite joins. Preservation of merely the empty join amounts to density, and hence flatness is a rather strong form of density. For example, the embedding of a completely regular locale into its Stone-Cech compactification is strongly dense in this sense.) I don't think all flat maps are stably flat, but I may be mistaken. Specifically, for a locale X let JX denote the spectral locale defined by OJX = ideals of OX. Then there is a sublocale embedding eta: X->JX defined by eta^*(I) = join I, which is known to be flat. Question 2: Is eta: X->JX stably flat for every X? If so, then compact Hausdorff locales would be exponentiating. Here a locale Y is called exponentiating iff the exponential Y^X exists for every X. Recall also that X is exponentiable iff the exponential Y^X exists for every Y, and that this is the case iff the frame OX is a continuous lattice. Now, JX is exponentiable because OJX is an algebraic lattice. We claim that if eta_X were stably flat, then for every compact Hausdorff locale Y, the exponential Y^JX would have the universal property of an exponential Y^X with respect to a suitably defined evaluation map and a suitable construction of exponential transposition. Define e: Y^JX x X -> Y as the restriction of the original evaluation map ev: Y^JX x JX -> Y, that is id x eta ev Y^JX x X ----------> Y^JX -> JX -------> Y. ------------------------------> e Now, to show that the pair (Y^JX,e) has the universal property of an exponential Y^X, given f: Z x X -> Y, we have to construct a transpose f': Z -> Y^JX such that e(f' x id_X) = f. Consider the diagram id_Z x eta_X Z x X --------------> Z x JX \ . \ . \ . \ . \ . f \ . f'' \ . \ . \ . v v Y. If eta_X were stably flat, then, by "Joyal's Lemma", which says that compact Hausdorff locales are orthogonal to flat embeddings, there would be a unique f'' making the diagram commute. Then its Y^JX-transpose f': Z -> Y^JX with respect to the original evaluation map would give the unique required Y^X-transpose of our given f: Z x X -> Y with respect to our constructed evaluation map, as an easy calculation shows, using the universal property of Y^JX with respect to the original evaluation map. This shows that if Question 2 had a positive answer then compact Hausdorff locales would be exponentiating. Question 3. But surely compact Hausdorff locales cannot possibly be exponentiating, can they? (These questions make sense for topological spaces too. ) MHE From rrosebru@mta.ca Sun Sep 18 10:27:21 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Sun, 18 Sep 2005 10:27:21 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EGz3e-0003RP-6Z for categories-list@mta.ca; Sun, 18 Sep 2005 10:18:14 -0300 Date: Sat, 17 Sep 2005 10:30:53 -0400 (EDT) From: Peter Freyd Message-Id: <200509171430.j8HEUraX013068@saul.cis.upenn.edu> To: categories@mta.ca Subject: categories: Ronnie in the news Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 14 Copyright 2005 TSL Education Limited The Times Higher Education Supplement September 16, 2005 SECTION: LETTER; No.1709; Pg.17 LENGTH: 448 words HEADLINE: Allow Beautiful Minds To Thrive BYLINE: Ronnie Brown BODY: The British Association for the Advancement of Science warns that the research assessment exercise does not recognise the importance of the public communication of science ("Scientists want time to talk", September 9). Experience in the mathematics faculty at Bangor was that the Teaching Quality Assessment did not recognise it either. This is a kind of travesty. Exploration, exposition and communication have for centuries been recognised as essential to the progress of science. Where would we be without Euclid's marvellous compilation of the geometry of his day? Galileo, Faraday, Poincare, Klein, Hilbert, Einstein, Hoyle and Feynman have all made public communication, and often disagreement with authority, an important part of their work. Our aim for the popularisation of mathematics has been, to modify Science Minister Lord Sainsbury's words in the same issue of The Times Higher, to show the public, students and the Government not only the important role that mathematics plays in society, but also how it evolves. Mathematics progresses partly through the solution of problems, but also through clarification and good exposition, providing a developing language for description, verification, deduction and calculation. It makes the difficult easy. It works over a long timescale. It shows new possibilities through gradual conceptual advance. It formulates new problems. So mathematics is a foundation of the modern technological society. It is a considerable challenge to try to show advanced mathematics from an elementary viewpoint. Some results of our work in popularisation of mathematics at Bangor over the past 20 years may be seen on our website www.popmath.org.uk. We have had strong support from, among others, the patrons of the sculptor John Robinson, for promoting his Symbolic Sculptures. An unplanned consequence has been sculptures by Robinson at, for example, Bangor, Cambridge, Durham and Macquarie universities. This supports the aim of associating mathematics and science with art, and demonstrates art as a mode of symbolising an idea. Work in communicating to children and the general public ideas in mathematics has helped us to analyse and express our programme, to communicate mathematical concepts to fellow scientists and students, and so to interdisciplinary collaboration. For the future of the UK, the public communication of science and mathematics should be supported financially and in career structure, and be part of the assessment of the success of a university and of the vitality of research and teaching teams. Ronnie Brown Emeritus professor of mathematics University of Wales, Bangor From rrosebru@mta.ca Sun Sep 18 10:27:21 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Sun, 18 Sep 2005 10:27:21 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EGz2T-0003P2-Ds for categories-list@mta.ca; Sun, 18 Sep 2005 10:17:01 -0300 From: Martin Escardo MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17195.20567.468764.582196@gargle.gargle.HOWL> Date: Sat, 17 Sep 2005 00:08:07 +0100 To: categories@mta.ca Subject: categories: Re: stable flatness and exponentiation In-Reply-To: <17194.47166.149464.378158@gargle.gargle.HOWL> References: <17194.47166.149464.378158@gargle.gargle.HOWL> Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 15 Martin Escardo writes: > Question 3. But surely compact Hausdorff locales cannot possibly be > exponentiating, can they? > > (These questions make sense for topological spaces too. ) Clarification: Alex Simpson points out, in a reply not sent to the list, that in the ambient category of topological spaces, compact Hausdorff spaces are not exponentiating. For example the exponential 2^(N^N) doesn't exist, where 2 is the two-point discrete space and N is the discrete space of natural numbers, and, of course, the exponential N^N does exist. In fact, Alex emphasized this years ago, when I subjected him to the ideas presented in the previous message. The point is that the locale product of two (sober) topological spaces doesn't coincide with the topological product, and hence exponentials are potentially different, as they are defined with respect to products. You may say: well, in any case, it is a fact that a sober space is exponentiable in Top iff it is exponentiable in Loc, so Alex's counter-example should work in Loc too. But then I reply: this coincidence has to do with the fact that the locale product coincides with the topological product if one of the factors is locally compact. In our case, because the exponent is NOT necessarily locally compact, this coincidence fails. We are considering exponentiating rather than exponentiable spaces. So, in principle, it may be that compact Hausdorff locales are exponentiating in Loc - although I very much doubt that this would be the case, as should be clear from the previous message. The point is that I just don't know, and I am looking forward to be enlightened after my failed attempts to decide the question either way. In light of Alex's observation, my conclusion to the previous message should have been: > Question 3. But surely compact Hausdorff locales cannot possibly be > exponentiating, can they? > It would be rather amazing if they were, because compact Hausdorff > spaces are not exponentiating in the category of topological > spaces. But the known arguments in the case of topological spaces > don't seem to apply here. One further comment: it is plausible that eta: X->JX is stably flat for X exponentiable. If Alex's topological counter-example applies to locales, then eta_X is not stably flat for X=N^N. MHE From rrosebru@mta.ca Mon Sep 19 13:28:58 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 19 Sep 2005 13:28:58 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EHOMj-0001Eh-J2 for categories-list@mta.ca; Mon, 19 Sep 2005 13:19:37 -0300 Mime-Version: 1.0 (Apple Message framework v734) Content-Transfer-Encoding: 7bit Message-Id: <1CA464D6-E03A-4E8C-94D5-36DB9980EC81@maths.adelaide.edu.au> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed To: categories@mta.ca From: David Roberts Subject: categories: Question re lax crossed modules Date: Mon, 19 Sep 2005 12:44:30 +0930 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 16 I have been looking at categorical groups a little and was wondering what a lax crossed module is. A search through various databases has turned up nothing. It would seem that they should be like crossed modules but only satisfy a weakened equivariance property. Any pointers toward a definition would be great. ------------------------------------------------------------------------ -- David Roberts School of Mathematical Sciences University of Adelaide SA 5005 ------------------------------------------------------------------------ -- droberts@maths.adelaide.edu.au www.maths.adelaide.edu.au/~droberts From rrosebru@mta.ca Tue Sep 20 08:15:07 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 20 Sep 2005 08:15:07 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EHg1s-0001Gu-TP for categories-list@mta.ca; Tue, 20 Sep 2005 08:11:16 -0300 Date: Mon, 19 Sep 2005 14:33:50 -0400 (EDT) From: Richard Blute To: categories@mta.ca Subject: categories: Final Octoberfest Announcement Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 17 Hi everyone, This is a brief final reminder for Octoberfest 2005, to be held October 22nd and 23rd at the University of Ottawa. If you have not already booked a room, you should do so right away. Also we will be finalizing the speaker's list this week. So we will need a title and abstract by Friday. Since we are receiving many submissions, this deadline will be strict. All details can be found at the Octberfest website at http://aix1.uottawa.ca/~scpsg/Octoberfest05/Octoberfest.final1.htm We look forward to seeing you soon, Rick Blute Phil Scott -- From rrosebru@mta.ca Tue Sep 20 08:15:07 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 20 Sep 2005 08:15:07 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EHg4n-0001SV-Iv for categories-list@mta.ca; Tue, 20 Sep 2005 08:14:17 -0300 Message-ID: <001d01c5bd6b$adea7020$94a24e51@brown1> From: "Ronald Brown" To: Subject: categories: lax crossed modules Date: Mon, 19 Sep 2005 23:43:36 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mx1.mta.ca X-Spam-Level: X-Spam-Status: No, score=0.1 required=5.0 tests=FORGED_RCVD_HELO autolearn=disabled version=3.0.4 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 18 reply to here Vaughan, David An interesting question! It raises several possible red herrings. 1) What is a lax action of a group (or groupoid) G on a group (or groupoid) A? There is a paper by Brylinski in Cahier on this, with applications to K-theory, if I remember rightly. Another interpretation of this seems to be as a Schreier cocycle (factor set). A relevant paper is 97. (with T. PORTER), ``On the Schreier theory of non-abelian extensions: generalisations and computations''. {\em Proceedings Royal Irish Academy} 96A (1996) 213-227. It is a useful exercise (which I meant to write down, but ...) to translate Brylinski into the terms of a map of a free crossed resolution, and so put this into nonabelian cohomology terms, and potentially allow for calculation using a small free crossed resoution when possible .... This suggests what might be a lax action, but does not complete in an obvious way into a lax crossed module. 2) Another way is to go to 2-crossed modules (Daniel Conduche), which brings in relations with simplicial groups (Tim Porter) and higher Peiffer elements. See also the relations with braided crossed modules and other things in 59. (with N.D. GILBERT), ``Algebraic models of 3-types and automorphism structures for crossed modules'', {\em Proc. London Math. Soc.} (3) 59 (1989) 51-73. 3) There are equivalences of categories crossed modules of groupoids <--> 2-groupoids <--> double groupoids with connections <--> double groupoids with thin elements. I have long found the cubical approach easier to follow and to use than the globular, but it turns out one needs also the globular to define commutative cubes in cubical omega-categories with connections (see a recent paper by Philip Higgins in TAC). This raises the question of "lax cubical omega-categories with connections". What do you laxify, to get an equivalence with one or other notion of weak globular (or other?) omega-category??!! Quite an amusing step, and more do-able, would be to generalise Gray categories to: cubical omega-categories C with an algebra structure C \otimes C \to C, generalising Brown-Gilbert, and using the monoidal closed structure given in 116. (with F.A. AL-AGL and R. STEINER), `Multiple categories: the equivalence between a globular and cubical approach', Advances in Mathematics, 170 (2002) 71-118 A nice point about such algebra structures is that they allow for a failure of the interchange law, with a measure of that failure, similar to the way 2-crossed modules give a measure of the failure of the Peiffer law for a crossed module by using a map { , }: P_1 \times P_1 \to P_2. Is this related to Sjoerd Crans' teisi? I have a gut feeling that these strengthened sesquicategories (with a *measure* of the failure of the interchange law) will crop up in a variety of situations, e.g. in rewriting, 2-dimensional holonomy, ...., since the interchange law makes things too abelian, sometimes. This brings in automorphism structures for crossed modules, I guess (Brown-Gilbert again, and of course derived from JHC Whitehead, who first studied such automorphisms). Another thought: the non abelian tensor product of groups derives from properties of the commutator map on groups. Why not develop the corresponding theory for the Peiffer commutator map? Hope that helps Ronnie ------------------------------------------------- *Date:* Mon, 19 Sep 2005 09:41:44 -0700 *From:* Vaughan Pratt *To:* Ronnie Brown *Reply-to:* pratt@cs.stanford.edu *Subject:* [Fwd: categories: Question re lax crossed modules] I'd be interested in knowing this too, in particular what the geometric significance of laxness is. Presumably laxness only enters in the passage from pre-crossed to crossed. Vaughan -------- Original Message -------- Subject: categories: Question re lax crossed modules Date: Mon, 19 Sep 2005 12:44:30 +0930 From: David Roberts To: categories@mta.ca I have been looking at categorical groups a little and was wondering what a lax crossed module is. A search through various databases has turned up nothing. It would seem that they should be like crossed modules but only satisfy a weakened equivariance property. Any pointers toward a definition would be great. ------------------------------------------------------------------------ -- David Roberts School of Mathematical Sciences University of Adelaide SA 5005 ------------------------------------------------------------------------ -- droberts@maths.adelaide.edu.au www.maths.adelaide.edu.au/~droberts From rrosebru@mta.ca Tue Sep 20 08:15:22 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 20 Sep 2005 08:15:22 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EHg5l-0001VP-9Y for categories-list@mta.ca; Tue, 20 Sep 2005 08:15:17 -0300 Message-ID: <432FD17B.3000207@bangor.ac.uk> Date: Tue, 20 Sep 2005 10:08:11 +0100 From: Tim Porter User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: fr, en, en-us MIME-Version: 1.0 To: categories@mta.ca Subject: categories: Re: Question re lax crossed modules References: <1CA464D6-E03A-4E8C-94D5-36DB9980EC81@maths.adelaide.edu.au> In-Reply-To: <1CA464D6-E03A-4E8C-94D5-36DB9980EC81@maths.adelaide.edu.au> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 19 Dear All, There is an interesting old result on fibrations that may shed light on this. It is well known that if $F\to E\to B$ is a fibration of pointed spaces then $\pi_1 F \to \pi_1 E$ is a crossed module and in fact any crossed module can be given in this form. Now one tries to prove it. First the action: take a loop g in E and another a in F. concatentate to get gag^{-1}. This is a loop in E whose image in the base,B, is null homotopic. Pick a null homotopy that does this. Lift it to a homotopy in E starting at gag^{-1} using the homotopy lifting property of the fibration. Evaluate the other end of the lift. This is a loop in F. The corresponding element of \pi_1 F is the result of acting on the class of a by the class of g. Note the way the action is determined up to homotopy. The verification that the rules work up to homotopy is left as an exercise. I learnt this from a paper by Eric Friedlander, who attributed it to Deligne. I suspect it is already essentially in Whitehead's Combinatorial Homotopy II paper or Peter Hilton's lovely little book on Homotopy Theory. It suggests a `homotopy everything' version of crossed module, not just a lax one. Its advantage is that it clearly links up the structure with the quite classical topological version of fibrations and so should be adaptable to other situations. Hope this helps. Tim David Roberts wrote: > I have been looking at categorical groups a little and was wondering > what a lax crossed module is. A search through various databases has > turned up nothing. It would seem that they should be like crossed > modules but only satisfy a weakened equivariance property. > > Any pointers toward a definition would be great. > > > ------------------------------------------------------------------------ > -- > David Roberts > School of Mathematical Sciences > University of Adelaide SA 5005 > ------------------------------------------------------------------------ > -- > droberts@maths.adelaide.edu.au > www.maths.adelaide.edu.au/~droberts > > > From rrosebru@mta.ca Tue Sep 20 08:16:08 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 20 Sep 2005 08:16:08 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EHg6X-0001YF-7c for categories-list@mta.ca; Tue, 20 Sep 2005 08:16:05 -0300 X-ME-UUID: 20050920105437331.50D0B1C00086@mwinf3104.me.freeserve.com Message-ID: <005d01c5bdd1$592a8320$94a24e51@brown1> From: "Ronald Brown" To: Subject: categories: More fancies on lax crossed modules and cubical ideas Date: Tue, 20 Sep 2005 11:51:30 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 20 To pursue some ideas suggested by David Robert's queries on lax crossed modules and Vaughan Pratt's interest: As said in the previous contribution: crossed modules (over groupoids) are equivalent to (edge symmetric) double groupoids with connections or thin structures, and the latter generalise easily to all dimensions. Why use crossed modules? For the work with Higgins, the aim was (a) to relate to classical invariants (relative homotopy groups) , and (b) for calculations. One thinks of calculation as serial, so the `linear' crossed modules are appropriate. But for theory, one wants the clear 2-dimensional compositions, particularly to get `algebraic inverses to subdivisions' for applications to `local-to-global problems'. Now multiple groupoids arose from considering the structure held by the singular cubical complex of a space, SC(X), which in dimension n consists of maps I^n --> X. So SC(X) has some claim to be a model of a weak omega-groupoid. Now for a filtered space X_* one can consider also R(X_*) which in dimension n is filtered maps I^n --> X_*. This again is a weak omega-groupoid, at least as much as SC(X) is. But an advantage is there is Kan fibration p:R(X_*) --> \rho(X_*) where the latter is a strict omega-groupoid. 32. (with P.J. HIGGINS), ``Colimit theorems for relative homotopy groups'', {\em J. Pure Appl. Algebra} 22 (1981) 11-41. (except that now we would modify the definition to take homotopies rel vertices of the cubes, and avoid the J_0-condition, and the theorems still work). So this suggests that a `controlled lax omega-groupoid' R should come with a Kan fibration R->G where G is a strict omega-groupoid and where R has lots of lax multiple compositions, [a_{(r)}], as considered in [32]. (why not?) This would allow for liftings of multiple compositions from G to R (loc cit), which should be helpful. An advantage of cubical over globular or simplicial is the ease of formulating multiple compositions. Notice that SC(X) has strict interchange for a 2 x 2 composition, and the connections have strict transport laws (2 x 2 again) but lax cancellation of \Gamma^-_i with \Gamma^+_i (in the terms of Al-Agl/Brown/Steiner). To backtrack a bit: \mu : M \to P is a crossed module (of groups!) if and only if there is a pointed fibration F \to E \to B such that \mu is \pi_1 F \to \pi_1 E. (Loday) The lax version of this is that given such a fibration, then \Omega F \to \Omega E may be given the structure of lax crossed module, where I cheat by saying lax means the structure that this has -- `crossed module up to homotopy'. (I am not sure if this has been written down somewhere!) This is related to an old paper of Philip R. Heath on, if I remember correctly, `Groupoid Operations and fibre homotopy equivalences'. Presumably there is also a recognition principle involved. This should answer Vaughan's question on the geometry (here topology) related to lax crossed modules. Ronnie www.bangor.ac.uk/r.brown r.brown@bangor.ac.uk From rrosebru@mta.ca Wed Sep 21 14:45:14 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 21 Sep 2005 14:45:14 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EI8Vn-0003Io-Qe for categories-list@mta.ca; Wed, 21 Sep 2005 14:36:03 -0300 Message-ID: <433014C2.30500@math.upenn.edu> Date: Tue, 20 Sep 2005 09:55:14 -0400 From: jim stasheff User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: categories@mta.ca Subject: categories: Re: lax crossed modules References: <001d01c5bd6b$adea7020$94a24e51@brown1> In-Reply-To: <001d01c5bd6b$adea7020$94a24e51@brown1> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.36 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mx1.mta.ca X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled version=3.0.4 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 21 Ronnie, I don't see these words below but `lax functor' is what came to mind. As a monoid is a category with one object, what is the many object version of an ordinary crossed module? jim From rrosebru@mta.ca Wed Sep 21 14:45:14 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 21 Sep 2005 14:45:14 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EI8X8-0003QX-H1 for categories-list@mta.ca; Wed, 21 Sep 2005 14:37:26 -0300 Message-ID: <4330190F.5000302@math.upenn.edu> Date: Tue, 20 Sep 2005 10:13:35 -0400 From: jim stasheff User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: categories@mta.ca Subject: categories: Re: Question re lax crossed modules References: <1CA464D6-E03A-4E8C-94D5-36DB9980EC81@maths.adelaide.edu.au> <432FD17B.3000207@bangor.ac.uk> In-Reply-To: <432FD17B.3000207@bangor.ac.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.36 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mx1.mta.ca X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled version=3.0.4 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 22 Tim Porter wrote: > Dear All, > There is an interesting old result on fibrations that may shed light on > this. It is well known that if $F\to E\to B$ is a fibration of pointed > spaces then $\pi_1 F \to \pi_1 E$ is a crossed module and in fact any > crossed module can be given in this form. Now one tries to prove it. > First the action: take a loop g in E and another a in F. concatentate > to get gag^{-1}. This is a loop in E whose image in the base,B, is > null homotopic. Pick a null homotopy that does this. Lift it to a > homotopy in E starting at gag^{-1} using the homotopy lifting property > of the fibration. Evaluate the other end of the lift. This is a loop > in F. The corresponding element of \pi_1 F is the result of acting on > the class of a by the class of g. > Note the way the action is determined up to homotopy. The verification > that the rules work up to homotopy is left as an exercise. > > I learnt this from a paper by Eric Friedlander, who attributed it to > Deligne. I suspect it is already essentially in Whitehead's > Combinatorial Homotopy II paper or Peter Hilton's lovely little book on > Homotopy Theory. > > It suggests a `homotopy everything' version of crossed module, not just > a lax one. There is a closely related homotopy everything version which I bet can be adapted to this problem. Consider \Omega B, the based loop space and F as the fibre over that base point. Then an argument like that above gives and action of \Omega B on F which satisfies the usual rules for an actin only up to homotopy Easiest way to say it is the adjoint map \MOmega B --> Aut F meaning the self homotopy equivalences of F is a strongly homotopy associative map of monids (if you use Moore loops) or of A_\infty spaces. It should be in "Parallel transport in fibre spaces," Bol. Soc. Mat. Mexicana (1968), 68-86. or "Associated fibre spaces," Michigan Math. Journal 15 (1968), 457-470. Hope that helps jim > Its advantage is that it clearly links up the structure with > the quite classical topological version of fibrations and so should be > adaptable to other situations. > > Hope this helps. > > Tim > From rrosebru@mta.ca Wed Sep 21 14:45:14 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 21 Sep 2005 14:45:14 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EI8as-0003mB-UY for categories-list@mta.ca; Wed, 21 Sep 2005 14:41:18 -0300 Message-ID: <1127237168.43304630dabc2@webmail.u-picardie.fr> Date: Tue, 20 Sep 2005 19:26:08 +0200 From: Andree Ehresmann To: categories@mta.ca Subject: categories: Conference Charles Ehresmann: 100 ans MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 User-Agent: Internet Messaging Program (IMP) 3.2.6 X-Originating-IP: 193.248.82.228 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 23 Conference and papers for Charles Ehresmann's centenary I recall that we organize an International Conference "Charles Ehresmann 100 ans" to commemorate the 100th anniversary of Charles' birth. It will take place at the Universite de Picardie Jules Verne in Amiens, from October 7 to 9, 2005. The first day will consist in general lectures on the life and works of Charles, and their prolongations. The 2 other days, there will be 2 parallel sessions: Category theory, Topology and Geometry, including the 82nd session of the PSSL "Peripatetic Seminar on Sheaves and Logic" and a session of the SIC (Seminaire Itinerant de Categories), Multidisciplinary applications with a Symposium ECHO V. The complete program can be found on the Internet site dedicated to Charles: http://perso.wanadoo.fr/vbm-ehr/ChEh which also contains some photos and documents on Charles, and papers dedicated to him. The abstracts of the lectures presented to the Conference will appear in Volume XLVI-3 of the "Cahiers de Topologie et Geometrie Differentielle Categoriques". The participation to the Conference is free. If you want to participate, please contact me by sending your name and address to ehres@u-picardie.fr Same address if you want to send a paper to be posted on the site. Sincerely Andree C. Ehresmann From rrosebru@mta.ca Wed Sep 21 14:45:14 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 21 Sep 2005 14:45:14 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EI8cP-0003vm-SE for categories-list@mta.ca; Wed, 21 Sep 2005 14:42:53 -0300 Message-ID: <012001c5bece$ca12fe70$2846a8c0@acerorzjm7qpwt> From: "Urs Schreiber" To: References: <001d01c5bd6b$adea7020$94a24e51@brown1> Subject: categories: Re: lax crossed modules Date: Wed, 21 Sep 2005 19:06:21 +0200 MIME-Version: 1.0 Content-Type: text/plain;format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 24 Ronald Brown wrote, in response to David Roberts: > I have a gut feeling that these strengthened sesquicategories (with a > *measure* of the failure of the interchange law) will crop up in a variety > of situations, e.g. in rewriting, 2-dimensional holonomy, ...., since the > interchange law makes things too abelian, sometimes. One can have a 2-holonomy for nonabelian gerbes if a funny condition holds, called the "fake flatness condition", which is a differential version of the exchange law, appearing when one realizes a 2-holonomy in a gerbe as a 2-functor from 2-paths to 2-group 2-torsors. Some people working on bundle gerbes feel that this constraint, which is derived in the context of strict 2-groups (crossed modules) is "too strong". While there are straightforward ways to relax conditions in the formalism, for instance by passing to weak (coherent) structure 2-groups (I guess these are essentially "the same" as lax crossed modules?) this does not seem to really address these people's concerns, because after weakening one no longer deals with Lie groups and Lie algebras, which is what they do. Hence I'd be extremely interested if somebody came up with a nice weakened version of crossed modules that would allow to realize 2-holonomy in non-fake flat gerbes. Best regards, Urs Schreiber From rrosebru@mta.ca Wed Sep 21 14:48:45 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 21 Sep 2005 14:48:45 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EI8hD-0004jY-GZ for categories-list@mta.ca; Wed, 21 Sep 2005 14:47:51 -0300 Date: Wed, 21 Sep 2005 13:38:15 -0400 (EDT) From: Peter Freyd Message-Id: <200509211738.j8LHcFF4007790@saul.cis.upenn.edu> To: categories@mta.ca Subject: categories: Bill on John (and his adequate subcats) Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 26 John Isbell's Adequate Subcategories F. W. Lawvere Submitted to the Topology Atlas (in response to Mel Henriksen's request) For mathematicians of my age, the theory of rings of continuous functions was one of the first exciting research topics we encountered. Many results of that theory have appeared, but its ramifications for category theory are still not fully worked out. A crucial link was provided by John Isbell's contributions around 1960 on the theme of adequate subcategories. Briefly, a subcategory A of a larger category is adequate if every object X of the larger category is canonically the colimit of the category A/X of objects of A equipped with structural maps to X; John's equivalent definition was that the truncated Yoneda embedding of the whole category into the category of set-valued contravariant functors on A is actually a full embedding. The following language is suggestive: (a) The objects of A are figure-types, (b) the objects of A/X are particular figures in X, and (c) the morphisms of A/X (commutative triangles in the big category) are incidence relations between figures. Thus adequacy means that the large category in question consists of objects entirely determined by their A-figures and incidence relations, and that (d) the morphisms in the whole category are nothing but the "geometrically continuous" ones in the sense that they map figures to figures without tearing the incidence relations. For example, if A is the category of countable compact spaces then A is adequate in many large categories constructed in attempts to capture the notion of topological space; in this case a morphism can be identified as a mapping that preserves sequential limits. That example is one of many illustrating that typical large categories of mathematics often have quite small adequate subcategories; it had been studied by Fox in 1945 at the instigation of Hurewicz, who sought a rational notion of function space for use in algebraic topology and functional analysis. In fact, for any A, each space of A-continuous morphisms has its own cohesion, described again by A-figures. The dual notion of a co-adequate subcategory C leads to a contravariant representation of the larger category that can be described in terms of (a) quantity-types, (b) functions, and (c) algebraic operations on functions. The dual of the notion of geometric continuity (that is, a name for naturality of maps of covariant functors instead of contravariant ones) is (d) "algebraic homomorphism" These ideas of John Isbell became fused with the conceptions of Kan, Grothendieck, and Yoneda (emerging in the same period 1958-1960), to form a basic method of analyzing and constructing mathematical categories. That method was used in the early 60's by Freyd, Gabriel, Lawvere, Mitchell, and by Isbell himself, and became as natural as breathing to many algebraists and topologists during the following decades. What does adequacy have to do with rings of continuous functions? The theory of rings of continuous functions springs from a basic philosophical hope to the effect that there should be a near-perfect duality between space and quantity. Such duality questions can be investigated for a great many different categories, but categorical considerations suggest that they need to be brought down to earth in certain respects. John Isbell was also one of the main developers of the theory of locales. This theory revealed that the traditional notion of topological space is algebraic rather than geometric (in the sense of the above analysis) with the infinitary algebras (frames) of open sets playing the dominant role; this merely means that the Sierpinski space, together with "all" its powers, constitutes a coadequate subcategory of the category of sober spaces. John's insistent quest for smallness (as a further requirement on co-adequate subcategories C) brought this analysis qualitatively nearer to real mathematics. If a small co-adequate subcategory is available, it can often be reduced to a single object (for example by taking the product of its objects; or more concretely, the Euclidean plane as a topological object will often serve the purpose of co-adequacy). The endomorphisms of that object then parameterize the unary operations whose preservation by C-homomorphisms serves to exclude ghosts from among detected points and figures. Even among those operations a few may be co-adequate, as the Stone-Weierstrass theorem had shown: addition, multiplication, and conjugation can replace the monoid of all continuous operations for that particular task, and there are many variations on that theme. But apart from such details of presentation, the implicit insight of Czech and Stone, of Hewitt and Nachbin, apparently includes smallness of the algebraic theory C in terms of which spaces are to be (co) analyzed. There was a seeming barrier to the realization of that concrete insight: set theory, in its striving for larger and larger cardinals, had neglected to emphasize that all of the cardinals arising in geometry and analysis in fact satisfy a useful smallness condition: the category of countable sets is co-adequate in the category of all small sets. That is essentially John Isbell's formulation; he proved that it is equivalent to the condition that no small set has the kind of ghost elements called Ulam measures. John knew full well that his formulation for abstract sets would imply that many categories having small adequate subcategories also have small co-adequate subcategories, thus making possible the desired sort of dualities between space and quantity. The ideas of John Isbell contributed to the enlightened understanding of mathematics by lifting some dark clouds of confusion, and they continue to be actively developed and diffused. From rrosebru@mta.ca Thu Sep 22 17:31:06 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 22 Sep 2005 17:31:06 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EIXaG-0007Ko-Sg for categories-list@mta.ca; Thu, 22 Sep 2005 17:22:20 -0300 Message-Id: <200509211842.j8LIgt423375@math-cl-n03.ucr.edu> Subject: categories: Re: lax crossed modules To: categories@mta.ca (categories) Date: Wed, 21 Sep 2005 11:42:55 -0700 (PDT) From: "John Baez" X-Mailer: ELM [version 2.5 PL6] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 27 Urs Schreiber wrote: > [...] weak (coherent) structure 2-groups (I guess these > are essentially "the same" as lax crossed modules?) [...] Since not everyone will understand this remark by my esteemed coauthor, let me elaborate. There's a nice way to weaken the concept of crossed module. A crossed module is just another way of looking at a group object in Cat - otherwise known as a "categorical group" or "strict 2-group". But, starting with the concept of group object in Cat, one can then weaken the usual group axioms to natural isomorphisms and impose suitable coherence laws, obtaining the notion of "gr-category" or "coherent 2-group". One could then backtrack and formulate this concept so that it resembles the concept of crossed module as closely as possible. I guess this would deserve to be called a "weak crossed module" or something like that. All this stuff except the last paragraph is well-known and summarized here: John Baez and Aaron Lauda, Higher-dimensional algebra V: 2-Groups, Theory and Applications of Categories 12 (2004), 423-491. http://www.tac.mta.ca/tac/volumes/12/14/12-14abs.html One might also seek a "lax" version of the concept of crossed module, where "lax" is taken in the Australian sense of replacing equations by morphisms rather than isomorphisms - "lax" as opposed to "pseudo". If I were forced to do this, I'd try to do it by laxifying the concept of group object in Cat. But, I don't see which way all the 2-arrows should point. Best, jb From rrosebru@mta.ca Mon Sep 26 20:38:45 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 26 Sep 2005 20:38:45 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EK2Ve-0000et-E6 for categories-list@mta.ca; Mon, 26 Sep 2005 20:35:46 -0300 Message-ID: <1127763608.43384e986b4a6@mymail.tcd.ie> Date: Mon, 26 Sep 2005 20:40:08 +0100 From: Shane O'Conchuir To: categories@mta.ca Subject: categories: Computational category theory paper - request for comments MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 User-Agent: Internet Messaging Program (IMP) 3.2.3 X-Originating-IP: 213.94.242.155 Content-Transfer-Encoding: quoted-printable Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 28 Hi all, I've written a paper on computational category theory but have for a while been unable to determine whether or not my methods or results are new. I would greatly appreciate any input from the community on this matter. The paper, "Proper Diagrams for Constructing Presheaf-Valued Limits", is about the construction of limits of diagrams of presheaves. The content is not too deep mathematically and is aimed more at computation. The basic idea is that given a functor D from a small category C into a category of presheaves, I construct a second functor D' of the same type where there is a natural transformation D'->D whose components are monomorphisms. The construction has the property that the limit of D is isomorphic to the limit of D'. The intuition is that we remove parts of the presheaves so that the computation of the limit is easier. I like to think of this approach as orthogonal to the use of initial functors to construct limits. Both methods preserve the limit but initial functors reduce the number of objects in the domain of a diagram whereas our transformation reduces the objects in the codomain of the dia= gram. A concise version of the paper is available at https://www.cs.tcd.ie/Shane.OConchuir/limits/limitspaper.pdf A draft technical report with the missing proofs and some appendices is available at https://www.cs.tcd.ie/Shane.OConchuir/limits/limitstr.pdf The technical report explains how I derived my definition of "spare" element. Any comments, corrections, criticisms, or references are welcome. In particular, I would like to know if any of this seems familiar (apologies in advance!) Also, my choice of terminology ("proper", "inconsistent") probably conflicts with normal use and one of my constructions, 'final proper diagram', may well be called 'initial proper diagram'. Many regards, Shane O'Conchuir Department of Computer Science Trinity College Dublin From rrosebru@mta.ca Mon Sep 26 20:38:45 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 26 Sep 2005 20:38:45 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EK2RV-0000Rk-7t for categories-list@mta.ca; Mon, 26 Sep 2005 20:31:29 -0300 From: "Michael Mislove" To: categories@mta.ca Subject: categories: Announcing www.entcs.org Content-Type: text/plain; charset=iso-8859-1 Message-Id: Date: Sat, 24 Sep 2005 15:37:28 -0600 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 29 Dear Colleagues, One of the minor inconveniences that Hurricane Katrina caused has been the temporary failure of the Tulane email servers, both university-wide and within the math department. The latter hosted the ENTCS Macro Home Page, so progress on publishing ENTCS volumes has been hindered since the hurricane. I am happy to announce that ENTCS now has its own, separate web host, which can be found at www.entcs.org Please point your browser at this page, where you will find detailed instructions on how to prepare proposals for publishing material in ENTCS, as well as instructions about how to prepare files both for preliminary, hard copy versions of proceedings for limited distribution at meetings, as well as how to prepare the final versions of papers for publication online at Science at Direct. While the ENTCS production has been hampered over the past month or so, it has been restarted, and publication of ENTCS issues and volumes is now proceeding as usual, with minimal delays. An important point to note is that the procedure for submitting final versions of files for ENTCS has changed. We now ask that the corresponding author of each paper - including the Preface of each volume - submit an electronic copy of the signed Copyright Transfer Form that can be found at the ENTCS Macro Home Page archives. To do this, authors should download the pdf file containing the form, print it out and complete it, including signing it, and then scan it in and include this scanned copy with the files for the final version of their paper that are sent to the Guest Editors of their proceedings. This will expedite the publishing of ENTCS volumes: we now can have final versions online within four weeks of when the files are sent to me for final processing. As usual, if you have any problems or questions about the ENTCS macros, or about ENTCS in general, please let me know. Best regards, Mike Mislove -- Michael Mislove Managing Editor ENTCS From rrosebru@mta.ca Tue Sep 27 20:21:33 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 27 Sep 2005 20:21:33 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EKOdr-0002BI-4m for categories-list@mta.ca; Tue, 27 Sep 2005 20:13:43 -0300 To: categories@mta.ca Subject: categories: ENTCS Message-Id: From: Paul Taylor Date: Tue, 27 Sep 2005 10:42:34 +0100 Sender: cat-dist@mta.ca Precedence: bulk Status: O X-Status: X-Keywords: X-UID: 30 I am sure that I speak for all of us in the category theory community when I say that I am very (relieved and) pleased to hear from Mike Mislove that he and ENTCS are alive and well following the hurricane. On the other hand, I am alarmed by the keenness of Mike (and the many conference organisers who use the services of ENTCS) to give away their colleagues' intellectual property to a company whose sole contribution nowadays to the process of publication is to run a web server. In point of fact, Elsevier DOES NOT require ENTCS authors to transfer copyright. When they were processing my paper for last year's CTCS, they asked me for a copyright transfer, but I refused. Instead, they promptly offered me a license agreement. Although the first version of this was also unacceptable, I succeeded in negotiating another one, which I signed, and they published my paper. You can obtain a LaTeX version of this agreement from www.cs.man.ac.uk/~pt/drafts/Elsevier-licence.tex I urge all of my colleagues to use this, and not give a commercial publisher the monopoly of research in theoretical computer science. I fully understand that younger researchers in particular feel that they have no alternative but to give in to pressure, being in a polically weak position myself. But I have demonstrated that even individuals can have an effect, simply by saying no. If more of us say no then we will succeed in recovering what is properly ours. Paul Taylor PS there is lots of new stuff on the ASD web page since my last posting to "categories" about it. From rrosebru@mta.ca Tue Sep 27 20:21:33 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 27 Sep 2005 20:21:33 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EKOew-0002Fb-NC for categories-list@mta.ca; Tue, 27 Sep 2005 20:14:50 -0300 Date: Tue, 27 Sep 2005 08:49:45 -0400 (EDT) From: Susan Niefield To: categories@mta.ca Subject: categories: Union College Conference Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 31 UNION COLLEGE MATHEMATICS CONFERENCE Saturday and Sunday Schenectady December 3-4, 2005 New York This is a preliminary announcement of the twelfth Union College Mathematics Conference. This year the conference topics will be algebraic topology, category theory, and commutative algebra. In addition to plenary lectures, of interest to the entire conference audience, there will be shorter contributed talks in parallel sessions. Anyone interested in giving such a talk should contact one of the organizers. The deadline for submission of abstracts is November 11th, and for registration is November 18th. PLENARY SPEAKERS John Baez (University of California, Riverside) David Cox (Amherst College) Jesper Grodal (University of Chicago) The meeting will begin with an evening reception on Friday, December 2, and end on Sunday afternoon. For more information about the conference, including registration, submission of abstracts, housing and transportation, please visit our website at www.math.union.edu/~leshk/05Conference/ Union College is centrally located in New York's capital district about 10 miles from the Albany International Airport, easily accessible by train from NYC, and just 3 to 4 hours by car from NYC, Boston, and Montreal. CONFERENCE ORGANIZERS Category Theory Susan Niefield niefiels@union.edu Algebraic Topology Brenda Johnson johnsonb@union.edu Kathryn Lesh leshk@union.edu Commutative Algebra Pedro Teixeira teixeirp@union.edu David Vella vellad@union.edu We hope to see you in December! From rrosebru@mta.ca Wed Sep 28 11:36:54 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 28 Sep 2005 11:36:54 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EKcvK-0000sy-H6 for categories-list@mta.ca; Wed, 28 Sep 2005 11:28:42 -0300 Message-Id: <200509280621.j8S6LRX04022@math-cl-n03.ucr.edu> Subject: categories: Re: ENTCS To: categories@mta.ca (categories) Date: Tue, 27 Sep 2005 23:21:27 -0700 (PDT) From: "John Baez" X-Mailer: ELM [version 2.5 PL6] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 32 Paul Taylor writes: > In point of fact, Elsevier DOES NOT require ENTCS authors to > transfer copyright. > > When they were processing my paper for last year's CTCS, they > asked me for a copyright transfer, but I refused. Instead, > they promptly offered me a license agreement. Although the > first version of this was also unacceptable, I succeeded in > negotiating another one, which I signed, and they published > my paper. When I was an editor for an Elsevier-edited journal - before I decided they were so nasty I should resign - I discovered how this works. They're scared to death that people will switch to free electronic journals. But, they don't want to openly cave in and institute a universal policy of letting authors keep the copyrights to their work. So, they cut a deal with anyone who pressures them, but don't advertise this. For more on the evils of Reed Elsevier, and what to do about it, see this: http://math.ucr.edu/home/baez/journals.html To see the copyright policies of most publishers, see this: http://www.sherpa.ac.uk/romeo.php Best, jb From rrosebru@mta.ca Fri Sep 30 09:51:59 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Fri, 30 Sep 2005 09:51:59 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1ELK8Q-0002Vs-7O for categories-list@mta.ca; Fri, 30 Sep 2005 09:37:06 -0300 X-Authentication-Warning: triples.math.mcgill.ca: barr owned process doing -bs Date: Thu, 29 Sep 2005 18:15:54 -0400 (EDT) From: Michael Barr X-X-Sender: barr@triples.math.mcgill.ca To: Categories list Subject: categories: Name of concept? Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 33 Is there a name for the following situation: I have a diagram of categories and functors DO(F) DO(A) ------> DO(B) | | | | H | |H | | v F v A ----------> B It does not commute, nor is there even a 2 cell in either direction. What I do have is illustrated below: DO(A) DO(A) /|\ /|\ / | \ / | \ / | \ / | \ H/ | \DO(F) H/ | \DO(F) / P \ / P' \ / | \ / | \ v | v v | v A <== | ==> DO(B) A ==> | <== DO(B) \ | / \ | / \ | / \ | / F\ | /H F\ | /H \ | / \ | / \ | / \ | / vvv vvv B B and, moreover, P -------> HF | | | | | | | | | | v v FH ------> P' commutes. From rrosebru@mta.ca Sun Oct 2 15:59:37 2005 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Sun, 02 Oct 2005 15:59:37 -0300 Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1EM8sH-000416-Fu for categories-list@mta.ca; Sun, 02 Oct 2005 15:47:49 -0300 Date: Fri, 30 Sep 2005 14:37:14 -0400 (EDT) From: Michael Barr To: Categories list Subject: categories: Re: Name of concept? In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 34 Incidentally, did you know that if Z and Z' are defined so that a d a' 0 --> Z ---> C ---> C ---> Z' ---> 0 is exact, then the homology is the image (= coimage) of a'.a: Z --> Z'? This is a triviality, but it gives a symmetric definition of homology. Notice that it defines something even when d.d is not 0. I guess it is Z mod Z meet ker(d). Mike