June 1998 - Categories - categories.org.au

preprint available
by JONATHON FUNK 22 Jul '98

22 Jul '98

Dear Colleagues, A preprint, whose abstract follows, is available in compressed .dvi form (for DOS and for UNIX) from: http://www.emu.edu.tr/academic/facartsc/mathsdep/staffpic/jfunk.htm or if you are browsing the web, click on academics, teaching staff, Mathematics, Jonathon Funk, additional information, after you have reached the EMU homepage http://www.emu.edu.tr If you would like a copy, but are unable to retrieve the preprint, please don't hestitate to contact me, as I would be happy to send you the .dvi file personally. funk(a)mozart.emu.edu.tr ---------------------------------------------------------------- ``On branched covers in topos theory'' Abstract: We present some new findings conerning branched covers in topos theory. Our discussion involves a particular subtopos of a given topos that can be described as the smallest subtopos closed under small coproducts in the including topos. We also have some new results concerning the general theory of KZ-doctrines, such as the the closure under composition of discrete fibrations for a KZ- doctrine (in the sense of Bunge/Funk, ``On a bicomma object condition for KZ-doctrines''). Regards, Jonathon Funk Jonathon Funk Department of Mathematics Eastern Mediterranean University Gazimagusa Turkish Republic of North Cyprus via Mersin 10, Turkey tel: (90) 392 366 6588, Ext: 1227, 1228, 1138 fax: (90) 392 366 1604

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Lectureship in Theoretical Computer Science
by Matthew Hennessy 29 Jun '98

29 Jun '98

Apologies for multiple copies -------------------------------------------------------------------- SCHOOL OF COGNITIVE AND COMPUTING SCIENCES Lectureship in Computer Science Applications are invited for a lectureship in Theoretical Computer Science within the Subject Group of Computer Science and Artificial Intelligence. The expected start date is October 1998 or as soon thereafter as possible. Candidates should be able to show evidence of significant research achievement in any aspect of the Foundations of Computation. They should also be willing to teach in areas other than their research speciality. The appointment is planned on the Lecturer Grade A scale 16,655-21,815 per annum (under review). For exceptional candidates, an appointment on the Lecturer Grade B scale, 22,726-29,048 per annum (under review), may be considered. The posts can be discussed informally with Prof. Matthew Hennessy on (01273) 678101, email: matthewh(a)cogs.susx.ac.uk. Details of the School are available at http://www.cogs.susx.ac.uk. Application forms and further particulars are available from and should be returned to Sarah Marshall, Staffing Services, University of Sussex, Falmer, Brighton, East Sussex, BN1 9RH, UK. Tel: (01273) 606755, ext 8202. Email: S.A.Marshall(a)sussex.ac.uk. Closing date: 24 July 1998. --------------------------------------------------------------------

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WoLLIC'98 - Programme and CfP
by Ruy de Queiroz 26 Jun '98

26 Jun '98

[Please post] 5th Workshop on Logic, Language, Information and Computation (WoLLIC'98) July 28-31, 1998 (Tutorial Day: July 28th) IME-USP, Sao Paulo, Brazil Scientific Sponsorship: IGPL, FoLLI, ASL, SBC, SBL Financial Support: CAPES, CNPq, FAPESP FINAL PROGRAMME and Call for Participation For details (including Registration Form and Accommodation) see: http://www.ime.usp.br/~wollic *********************** Wednesday July 28th, 1998 (Tutorial Day) *********************** TUTORIAL LECTURES: 08:15-10:15 (with a 10min break) Descriptive Complexity by Heinz Dieter Ebbinghaus (15min break) 10:30-12:30 (with a 10min break) Modal Model Theory by Maarten de Rijke 12:30-14:00 (Lunch Break) 14:00-16:00 (with a 10min break) (title to be announced) by Edmund Clarke (15min break) 16:15-18:15 (with a 10min break) Provability Operators by Sergei Artemov (15min break) 18:30-20:30 (with a 10min break) An Introduction to "Basic Logic" by Giovanni Sambin (Sam Buss' tutorial lecture will be given on Wednesday 29th, at 11:25am) ----- *********************** Wednesday July 29th, 1998 *********************** 08:15: Opening Morning: Logic and Language 08:30-09:45 (Invited talk) Chair: Heinz Dieter Ebbinghaus (title to be announced) by Hans Kamp 09:45-09:55 Coffee/Tea break 09:55-11:15 4 contributed papers (20 min each) Chair: Ruy de Queiroz 09:55-10:15 An Extension of DRT with Questions to Analyze Topic Implicatures by Peter Krause 10:15-10:35 A Dynamic Logic of Events and States for the Interaction between Plural Quantification and Verb Aspect in Natural Language by Ralf Naumann 10:35-10:55 Occurrence Graph Grammars by Leila R. Korff 10:55-11:15 Towards a General Model for the Representation of Negated Nuanced Properties in a Fuzzy Context by Daniel Pacholczyk and Bernard Levrat 11:15-11:25 Coffee/Tea break 11:25-13:25 (with a 15min break) (Tutorial) (title to be announced) by Sam Buss 13:25-14:30 Lunch break Afternoon: Modal and Temporal Logics 14:30-15:45 (Invited talk) Chair: Giovanni Sambin Managing Fragments by Maarten de Rijke 15:45-15:55 Coffee/Tea break 15:55-17:15 4 contributed papers (20 min each) Chair: Ana Cristina V. de Melo 15:55-16:15 Interpolation and Bisimulation in Temporal Logic by Carlos Areces and Maarten de Rijke 16:15-16:35 Temporal Logic of Causal Knowledge by Wojciech Penczek 16:35-16:55 Characterising Timing Analyses in Intuitionistic Modal Logic by Michael Mendler 16:55-17:15 The Algebraic Mu-Calculus and MTBDDs by Christel Baier and Edmund Clarke 17:15-17:25 Coffee/Tea break 17:25-18:40 (Invited talk) Chair: Sergei Artemov Symbolic Model Checking by Edmund Clarke 20:30 Welcome Reception/Cocktail ********************** Thursday July 30th, 1998 ********************** Morning: Proof Theory 08:30-09:45 (Invited talk) Chair: Edmund Clarke The Complexity of the Disjunction and Existential Properties by Sam Buss 09:45-09:55 Coffee/Tea break 09:55-11:15 4 contributed papers (20 min each) Chair: Marcelo Finger 09:55-10:15 A System of Analytic Quasi-Classical Logic by Carlos A. Oller 10:15-10:35 Mixed Intuitionistic Linear Logic by Akim Demaille 10:35-10:55 Distributive Linear Logic by Jean Leneutre 10:55-11:15 Formulae-as-Resources Management for an Intuitionistic Theorem Prover by Didier Galmiche and D. Larchey-Wendling 11:15-11:25 Coffee/Tea break 11:25-12:40 (Invited talk) Chair: Maarten de Rijke Logic of Proofs by Sergei Artemov 12:40-14:30 Lunch break Afternoon: Categorical Logic 14:30-15:45 (Invited talk) Chair: Hans Kamp xSLAM: The eXplicit Substitutions Linear Abstract Machine or Implementing Linear Logic by Valeria de Paiva 15:45-15:55 Coffee/Tea break 15:55-17:15 4 contributed papers (20 min each) Chair: E. Hermann Haeusler 15:55-16:15 The Logic of a Tos by Ryan Shelswell and Michael Johnson 16:15-16:35 Selective Lambek Syntactic Calculus by Marcelo da Silva Correa and Edward Hermann Haeusler 16:35-16:55 A New Model Construction for Higher Type Systems by Dieter Spreen 16:55-17:15 Generalization in $\lambda 2$ by Jianguo Lu, Masateru Harao, and Masami Hagiya ********************** Friday July 31st, 1998 ********************** Morning: Logic and Complexity Theory 08:30-09:45 (Invited talk) Chair: Sam Buss Is there a logic for polynomial time? by Heinz Dieter Ebbinghaus 09:45-09:55 Coffee/Tea break 09:55-11:15 4 contributed papers (20 min each) Chair: Ruy de Queiroz 09:55-10:15 Generating hard tautologies using predicate logic and the symmetric group by Soren Riis and Meera Sitharam 10:15-10:35 Function Inversion by Nachum Dershowitz and Subrata Mitra 10:35-10:55 Very Efficient Pattern-Matching for Overlapping Patterns by Nadia Nedjah and Luiza de Macedo Mourelle 10:55-11:15 POM Semantics for 1-Safe Petri Nets by Edelweis H.A. Garcez, Francisco A.M. Nascimento and Wolfgang Rosenstiel 11:15-11:25 Coffee/Tea break 11:25-12:40 (Invited talk) Chair: Valeria de Paiva On the Boundedness Problem for Fragments of First-Order Logic by Phokion Kolaitis 12:40-14:30 Lunch break Afternoon: Constructive Logics and Semantics of Computation 14:30-15:45 (Invited talk) Chair: Phokion Kolaitis Formal Topology via the Basic Picture by Giovanni Sambin 15:45-15:55 Coffee/Tea break 15:55-17:15 4 contributed papers (20 min each) Chair: Flavio Correa da Silva 15:55-16:15 Models of Logic Programs w.r.t. Intuitionistic and Minimal Logics by Evgeny Makarov 16:15-16:35 Extensions of the WFS Semantics for Logic Programming by Mauricio Osorio and Jose Arrazola 16:35-16:55 Semantics for Disjunctive Programs by D. Guller 16:55-17:15 Revising Concepts by Renata Wassermann 17:15 Closing

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``cofinite sieves''
by Steve Lack 26 Jun '98

26 Jun '98

Have any topos-theorists or others come across the following notion? Let C be a small category, and c an object of C. If X is an arbitrary set of arrows with codomain c, then R_X = { f:b-->c | there is no g:a-->b with fg in X} clearly gives a sieve on c. Of course if X itself were a sieve then R_X would be its complement, but I'm not assuming X is a sieve. Say that a sieve R is _cofinite_ if it is of the form R_X for a finite set X. Cofinite sieves are closed under finite intersection and universal quantification along an arbitrary arrow. Best wishes, Steve Lack.

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change of e-mail address
by Rudger Kieboom 24 Jun '98

24 Jun '98

Dear All, My new e-mail address is a simplification of the old one. It now reads: rkieboom(a)vub.ac.be Rudger Kieboom Department of Mathematics Vrije Universiteit Brussel Pleinlaan 2, F10 B-1050 Brussels Belgium

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Marta Bunge's summer phone number
by Michael Barr 23 Jun '98

23 Jun '98

Marta has asked me to announce that during the summer her phone and fax number on Corfu is +30-663-41584 (I think the + means use your long distance access, like 011 in North America, plus that.)

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Units in lax and oplax monoidal functors
by David Yetter 22 Jun '98

22 Jun '98

I seem to recall that there was some difficulty for the coherence of lax and oplax monoidal functors (properly so called, meaning with unit maps in addition to the natural transformation). Epstein's 1966 paper handles what I would call symmetric semigroupal functors (symmetry, but no units), and his proof goes through without the symmetry. I have also once as an exercise prove the coherence theorem for strong monoidal functors. This query arises tangentially in regard to a paper I am writing on the deformation theory of monoidal categories and functors. An answer is not strictly needed, but I'd be greatful for a reference to the difficulty, or a corrective to a mis-recollection on my part. (It would be nice to include in the paper.) Best Thoughts to all, David Yetter

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Chu(Ab,circle) is abelian
by Michael Barr 21 Jun '98

21 Jun '98

The category of topological abelian groups is not abelian. The reason is not hard to explain. In topological spaces, points are primordial and a monomorphism of points need not be a monomorphism of the attached frames (that is a surjection of the open set lattices). When it is, then ignoring the usual separation axiom, it is a subspace and thereby a kernel. In frames, the reverse is true. Now the open sets are all and you ignore the points. In Chu(Ab,circle), the points and open sets are treated with equal respect. Now a monomorphism must be injective on the points and surjective on the opens and is obviously a kernel. The dual is also true. At another conceptual level, abelianess is defined by certain exactness condition, which concerns canonical arrows, usually between limits and colimits. A category is pointed if the canonical map 0 --> 1 is an isomorphism and there is then a canonical arrow A + B --> A x B and when that is an isomorphism, it is additive. There is a map from the domain of any monomoprhism to the kernel of its cokernel.... The conditions are self dual and a limit is computed in a Chu category as the limit of its first component and colimit of its second and all the required isomoprhisms remain isomorphisms. Of course, this is just as true of Chu(A,_|_) whenever A is abelian (and, of course, closed monoidal). The contrast with the case of topological and that of localic abelian groups is striking. I realized all this as a result of listening to Peter Freyd's lecture in Saint John, NB last week. He was trying to discover the initial abelian category with one object. It is self dual, but not this one since this contains no non-zero bijective (that is objects that are simultaneously injective and projective) while Freyd's category has enough of them. Still it might be interesting. And to anticipate Vaughan's question, no chu(Ab,circle) is not abelian, roughly for the same reasons as topological and localic abelian groups.

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projective diagrams
by gaucher＠irma.u-strasbg.fr 17 Jun '98

17 Jun '98

Dear categoricist, Let I be the following small category : a a a --------> --------> --------> .. n n-1 n-2 ...... 0 --------> --------> --------> b b b with the relations a o a = a o b and b o a = b o b. Consider the category C of functors from I to the category of K-modules. How could we characterize the projective objects of C ? Any idea, any reference, is welcome. pg.

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WD4: Extended Deadline
by 4th Workshop on Domains 15 Jun '98

15 Jun '98

======================================================================= E X T E N D E D D E A D L I N E ======================================================================= Workshop on Domains IV Rolandseck, Germany Oktober 2--4, 1998 ======================================================================= The Workshop on Domains is aimed at computer scientist and mathematicians alike who share an active interest in the mathematical foundation of computer science. It will focuse on domains, their application and closely related topics, e.g.~axiomatic and synthetic domain theory. In particular, contributions establishing connections to type theory, recursion theory and topology are welcome. In previous years the workshop was held in Darmstadt (1994 and 1995), Braunschweig (1996) and Munich (1997). This year it will take place in Haus Humboldtstein, Remagen-Rolandseck (Germany), a nice last century villa overlooking the beautiful Rhine valley. There will be a number of guest speakers including *** Thomas Ehrhard (IML, Marseille) *** *** Dag Normann (Oslo Univ. ) *** *** Giovanni Sambin (Padova Univ.) *** If you are interested in signing up for a talk, please send a title and an abstract of your intended presentation to mailto:wd4@informatik.uni-siegen.de by JULY 31, 1998. Each request will be answered by SEPTEMBER 1, 1998. You may also use ordinary mail. The address is: Prof. Dr. Dieter Spreen Workshop on Domains IV Theoretische Informatik Fachbereich Mathematik Universitaet Siegen Hoelderlinstr.3 D-57072 Siegen GERMANY The workshop will start on Friday, October 2, in the afternoon. In order to make a reservation for a room in Haus Humboldtstein, it is necessary to register till JULY 31, 1998. Moreover, the hotel fee has to be paid till this date either by transfering it to the following bank account: no. 146448-500 (Prof. Dieter Spreen) BLZ 370 100 50 bank: Postbank NL Koeln or by sending a cheque to the above address. The cheque should be made payable to Prof. Spreen. The hotel rate is DM 128,- (single room) DM 118,- (double room) per night and person. It includes three meals and two snacks. Please indicate below whether you need any special diet. In addition there will be a small workshop fee. More information about the workshop and Haus Humboldstein can be found on the workshop web page http://www.informatik.uni-siegen.de/~wd4 -------------------------------------------------------------------------- REGISTRATION FORM ================= Name: ----- Postal address: --------------- Electronic mail: ---------------- Phone number: ------------- Fax number: ----------- Hotel reservation: single room:__ double room:__ ------------------ In case of double room: I would like to share the room with: ____________________________________________________________ Special needs for the meal (vegetarian, diet, etc): ____________________________________________________________ Do you want to give a talk? ____ If "YES" Length: ______________(25 or 40 minutes) Authors: Title: Abstract: (preferably in LaTeX) ----------------------------------------------------------------------------- Workshop on Domains IV University of Siegen Department of Mathematics Hoelderlinstr. 3 D-57068 Siegen Phone +49 271 740 3165 Fax +49 271 740 2532 mailto:wd4@informatik.uni-siegen.de http://www.informatik.uni-siegen.de/~wd4 ------------------------------------------------------------------------------.

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