Date:Fri, 26 Jul 1996 10:37:25 -0400To:kcollins(at-sign)mail.wesleyan.eduFrom:kcollins(at-sign)wesleyan.edu (Karen L. Collins)Subject:Fall meetings

NSF renewed our grant!! The first two CoNE meetings in 96-97 will be September 28th and October 26th.

Date:Tue, 30 Jul 1996 19:03:52 -0400To:kcollins(at-sign)mail.wesleyan.eduFrom:kcollins(at-sign)wesleyan.edu (Karen L. Collins)Subject:job announcement

>From The Connecticut Post, Sunday, July 28, 1996 ____________________________________________________ MATHEMATICS Western Connecticut State University. One year, full-time non-tenure track position for Academic Year 1996-1997 to teach discrete mathematics for CS students, theory of computation, introductory and remedial mathematics courses. Teaching excellence and master's degree in mathematics required; doctorate preferred. Review of applications begin August 8, 1996. Send letter of application, resume, transcript copies and three letters of recommendation to Dr. E. Sandifer, Mathematics and Computer Science Department, WCSU, 181 White St., Danbury, CT 06810. Western is an Affirmative Action Equal Opportunity Educator/Employer -----------------------------------------------------

Date:Fri, 30 Aug 1996 08:05:52 -0400To:kcollins(at-sign)mail.wesleyan.eduFrom:kcollins(at-sign)wesleyan.edu (Karen L. Collins)Subject:First fall CoNE meeting

Come to the Twenty-first one day conference on Combinatorics and Graph Theory Saturday, September 28, 1996 10 a.m. to 4:30 p.m. at Smith College Northampton MA 01063 Schedule 10:00 Lixin Gao (Smith College) Balancing Computational Load on Rings of Processors 11:10 Sorin Istrail (Sandia National Laboratories and University of New Mexico) Protein Folding: Combinatorial Problems and Algorithms 12:30 Lunch 2:00 Robin Pemantle (University of Wisconsin at Madison) Recursions Coming in from Infinity on a Tree, Applied to Models of Information Propagation 3:10 Clara Chan (Wesleyan University) Counting Faces of Cubical Spheres Modulo 2 Our NSF grant to support these conferences has been renewed! This will allow us to provide a modest transportation allowance to those attendees who are not local. Our Web page site has directions to Smith College, abstracts of speakers, dates of future conferences, and other information. The address is: http://math.smith.edu/~rhaas/coneweb.html Michael Albertson (Smith College), (413) 585-3865, albertson(at-sign)smith.smith.edu Karen Collins (Wesleyan Univ.), (860) 685-2169, kcollins(at-sign)wesleyan.edu Ruth Haas (Smith College), (413) 585-3872, rhaas(at-sign)smith.smith.edu From sara(at-sign)math.mit.edu Thu Sep 19 22:52:07 1996 To: combinatorics(at-sign)math.mit.edu Subject: tomorrow Combinatorics seminar for tomorrow, Friday September 1996: "The Proof of a Conjecture of Zeilberger and Noonan". Miklos Bona Abstract: Recently, attention has been paid to the problem of counting the number of permutations of length $n$ containing a {\em given number $r$} (as opposed to 0) of subsequences of a certain type $q$. The main question is to describe this function for {\em any given $r$}, not just for $r=0$ or 1. Zeilberger and Noonan have conjectured that for {\em any} given subsequence $q$ and for {\em any} given $r$, the number of $n$-permutations containing exactly $r$ subsequences of type $q$ is a $P$-recursive function of $n$. To illustrate how far the solution of this conjecture can be we note that if $q$ is longer than three, then we do not have a proof even for $r=0$. In this paper we solve this conjecture for the subsequence 132. This is the first result we know of when the case of each $r$ is solved for some given $q$. Some interesting consequences and special cases are included. \end{document} Upcoming events: date: Friday, September 27, 1996 speaker: Brian Taylor title: "A quadratic straightening law for row-convex tableaux." date: Friday October 4, 1996 speaker: Christian Lenart title: Necklace Algebras and Witt Vectors Associated with Formal Group Laws. From goemans(at-sign)math.mit.edu Mon Sep 23 10:04:13 1996 X-Sender: goemans(at-sign)severi To: combinatorics(at-sign)math.mit.edu Subject: Paul Erdos MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII ----- Begin Included Message ----- >From Diestel(at-sign)Mathematik.TU-Chemnitz.DE Sat Sep 21 20:30:07 1996 Message from Miklos Simonovits Paul Erdos died Friday afternoon (20 September, 1996), in Warsaw. Early morning he felt some health problems, in a hotel in Warsaw. So he was carried into a hospital, where he died in the afternoon. (He was 83). ===================================== As far as I know, he had a heart attack, rather serious, very early in the morning, in this Warsaw hotel, where he stayed while visiting the Minisemester for Combinatorics, (for two weeks), gave two lectures. Vera Sos and Andras Sarkozy are leaving Budapest for Warsaw right now, Saturday morning, and Paul's original plans were to fly from Warsaw to Vilnius (for the Kubilius Conference) with Vera and Andras together, on Sunday. The doctor informed us that he had two heart attacks and the second one killed him. (Perhaps even the first one was serious enough to prevent him from communicating to his surrounding. This may explain e.g. that he could not reach the mathematicians. We learned about his heart attacks only after his death.) Miki Simonovits. ----- End Included Message ----- From schulte(at-sign)neu.edu Mon Sep 23 11:19:33 1996 X-Sender: schulte(at-sign)nuhub.dac.neu.edu (Unverified) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: combinatorics(at-sign)math.mit.edu Subject: seminar NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ Northeastern's Combinatorics Seminar is back again (after a "sabbatical year")! The seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. September 25: Alex Suciu, Northeastern University Combinatorics and topology of complex line arrangements October 2: Alexander Postnikov, MIT Deformations of Coxeter Arrangements From schulte(at-sign)neu.edu Mon Sep 23 13:22:49 1996 X-Sender: schulte(at-sign)nuhub.dac.neu.edu (Unverified) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: combinatorics(at-sign)math.mit.edu Subject: NU seminar NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ Usually the seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. September 25: Alex Suciu, Northeastern University Combinatorics and topology of complex line arrangements October 2: Alexander Postnikov, MIT Deformations of Coxeter arrangements Extra seminar on Friday October 11 at 1pm in 544 Nightingale Hall: Eric Mendelsohn, University of Toronto Intercalates (and Other Partial Latin Squares in 4 Cells) Everywhere November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves From schulte(at-sign)neu.edu Thu Sep 26 17:36:23 1996 X-Sender: schulte(at-sign)nuhub.dac.neu.edu (Unverified) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: combinatorics(at-sign)math.mit.edu Subject: seminar NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ Usually the seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. October 2: Alexander Postnikov, MIT Deformations of Coxeter arrangements Extra seminar on Friday October 11 at 1pm in 544 Nightingale Hall: Erik Mendelsohn, University of Toronto Intercalates (and Other Partial Latin Squares in 4 Cells) Everywhere October 30: Ludwig Danzer, University of Dortmund SCD, a space-filler of 3-space with some surprising properties November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves From sara(at-sign)math.mit.edu Fri Sep 27 11:12:34 1996 To: combinatorics(at-sign)math.mit.edu Subject: today **** Combinatorics Seminar 4:15pm Today**** Brian Taylor from M.I.T. will speak on "A quadratic straightening law for row-convex tableaux." See the abstract below OR chech out our new Combinatorics Web Page designed by Maurice Rojas at http://www-math.mit.edu/~rojas/Combinatorics/combi.html or you can get to it by just going to "www-math.mit.edu" and clicking on "seminars". A Quadratic Straightening Law for Row-Convex Tableaux Brian Taylor, MIT Just as (semi)standard Young tableaux index a basis for the irreducible representations of $S_n$ (or $GL_n$) associated to the diagram of a partition, one can ask for bases of the representations associated to more general shapes. Considerable progress has been made, notably by Magyar and by Reiner and Shimozono towards finding bases and character formulas for the representations associated to a generalized shape. Most of these results rely on either the Schensted algorithm or on jeu-de-taquin. In the case of row-convex shapes, i.e. shapes like {\obeyspaces\obeylines\global\let =\ \tt xxxxxxxxxxxxx xxxxxxxxxxxxx xxxxxxxxxx xxxxxxxxxxxxxx xxxxxxxx xx xxxxxxx }\par\noindent which have no gaps in any row, it is possible to tell if a tableau indexes a basis element by an easy combinatorial criterion involving only pairs of rows. Further, for any pair of rows not fitting the criterion, there exists a simple ``straightening law'' that replaces the original pair of rows by a linear combination of ``better'' two-rowed tableaux. Repeated applications of this straightening law expand any tableau into a linear combination of basis elements. The row-convex straightening law is characteristic-free and generalizes to supertableaux and to quantum tableaux. The representations used here are constructed, following Deruyts, as subspaces (of a polynomial ring) which are spanned by products of certain minors of a generic matrix. In keeping with the elementary nature of the underlying construction, {\it this talk should be accessible to non-specialists.} Up coming events: October 4: Christian Lenart Necklace Algebras and Witt Vectors Associated with Formal Group Laws October 11: Sara Billey Kostant polynomials; interpolating polynomials for Schubert Polynomials October 18: NO LECTURE (due to Posets Workshop at MSRI) October 25: J. Maurice Rojas Multisymmetric Functions via Toric Resultants October 30 (Wednesday!): Gian-Carlo Rota The Work of K. T. Chen (part I of II) From IARROBIN(at-sign)neu.edu Mon Sep 30 13:34:40 1996 Subject: Combinatorics topic at NU GAS Oct 7 To: combinatorics(at-sign)math.mit.edu X-Envelope-to: combinatorics(at-sign)math.mit.edu X-VMS-To: IN%"combinatorics(at-sign)math.mit.edu" MIME-version: 1.0 Content-transfer-encoding: 7BIT Announcement: Andrei Zelevinsky of Northeastern will speak on "Total positivity in Schubert varieties" in the GAS Seminar, Monday Oct 7 at noon, 509 Lake Hall, Northeastern. A.I.

Date:Tue, 1 Oct 1996 14:26:35 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ Usually the seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. October 2: Alexander Postnikov, MIT Deformations of Coxeter arrangements Extra seminar on Friday October 11 at 1pm in 544 Nightingale Hall: Erik Mendelsohn, University of Toronto Intercalates (and Other Partial Latin Squares in 4 Cells) Everywhere October 23: Igor Pak, Harvard University Partition identities, bijections and Groebner bases October 30: Ludwig Danzer, University of Dortmund SCD, a space-filler of 3-space with some surprising properties November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves November 13: Alan Hoffman, IBM T.J. Watson Research Center Greedy Algorithms in Linear Programming

Date:Tue, 1 Oct 1996 14:53:33 -0400 (EDT)From:Jim Propp <propp(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar archive and web-page

We have been having trouble with automatic archiving of messages sent to combinatorics(at-sign)math.mit.edu; until it's fixed, messages will not automatically be appended to http://www-math.mit.edu/~propp/combinatorics-archive/96b. Sorry for any inconvenience. In the meantime, you can keep up with what's happening through Maurice Rojas' combinatorics seminar web page: http://www-math.mit.edu/~rojas/Combinatorics/combi.html Jim Propp

Date:Wed, 2 Oct 1996 17:29:05 -0400 (EDT)From:Jim Propp <propp(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:Re: seminar archive and web-page

The archive is working once again. You can access it via http://www-math.mit.edu/~propp/combinatorics-archive/96b Jim Propp

Date:Thu, 3 Oct 1996 12:04:12 -0400 (EDT)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar tomorrow

****Combinatorics Seminar Tomorrow **** Necklace Algebras and Witt Vectors Associated with Formal Group Laws Christian Lenart (M.I.T.) Abstract: We define and study a generalization of the {\em necklace algebra} defined by N. Metropolis and G.-C. Rota [{\em Adv. Math}, {\bf 50}, 1983, 95--125]; the generalized necklace algebra is associated with an arbitrary formal group law $F(X,Y)$ over a torsion free ring $A$. The map from the ring of Witt vectors associated with $F(X,Y)$ to the necklace algebra is constructed in terms of certain generalizations of the necklace polynomials. The actions of the {\em Verschiebung} and {\em Frobenius} operators, as well as of the {\em p-typification idempotent}, are described and interpreted combinatorially. A formal group-theoretic generalization of the {\em cyclotomic identity} is also presented. In general, the necklace algebra can only be defined over the rationalization of $A$, that is $A\otimes{\mathbb Q}$. Nevertheless, we show that for an important family of formal group laws over the integers, namely $F(X,Y)=(X+Y-(1+q)XY)/(1-qXY)$ with integer $q$, the corresponding necklace algebra can be defined over the integers. Furthermore, the generalized necklace polynomials turn out to be {\em integral polynomials} in the variables $x$ and $q$, and they can be interpreted combinatorially when $q$ is a prime power. We have thus defined a $q$-deformation of the necklace algebra of Metropolis and Rota. Our results imply the existence of nice ring structures on the group of Witt vectors and the group of curves associated with the formal group law parametrized by $q$. Upcoming events: date: Friday October 11, 1996 speaker: Sara Billey title: Kostant polynomials; interpolating polynomials for Schubert Polynomials date: Friday October 18, 1996 NO COMBINATORICS SEMINAR DUE TO "POSETS" WORKSHOP AT MSRI

Date:Mon, 7 Oct 1996 14:16:14 -0400To:kcollins(at-sign)mail.wesleyan.eduFrom:kcollins(at-sign)wesleyan.edu (Karen L. Collins)Subject:Oct. 26

Come to the Twenty-second one day conference on Combinatorics and Graph Theory Saturday, October 26, 1996 10 a.m. to 4:30 p.m. at Smith College Northampton MA 01063 Schedule 10:00 Bruce Kitchens (IBM) Two Combinatorial Problems from Symbolic Dynamics 11:10 Joan Hutchinson (Macalester College) Some 3- and 4-coloring theorem for the Plane, the Projective Plane, and the Torus or Variations on some themes of Heawood and Hadwiger 12:30 Lunch 2:00 Lenore Cowen (Johns Hopkins University) Favorite Coloring Relaxations 3:10 Herman Servatius (WPI) Doubly Periodic Self-dual Graphs and Tilings Our NSF grant to support these conferences has been renewed! This will allow us to provide a modest transportation allowance to those attendees who are not local. We gratefully acknowledge support from Smith College and Wesleyan University as well. Our Web page site has directions to Smith College, abstracts of speakers, dates of future conferences, and other information. The address is: http://math.smith.edu/~rhaas/coneweb.html Michael Albertson (Smith College), (413) 585-3865, albertson(at-sign)smith.smith.edu Karen Collins (Wesleyan Univ.), (860) 685-2169, kcollins(at-sign)wesleyan.edu Ruth Haas (Smith College), (413) 585-3872, rhaas(at-sign)smith.smith.edu

Date:Wed, 9 Oct 1996 12:15:07 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ Extra seminar on Friday October 11 at 1pm in 544 Nightingale Hall: Erik Mendelsohn, University of Toronto Intercalates (and Other Partial Latin Squares in 4 Cells) Everywhere Usually the seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. October 23: Igor Pak, Harvard University Partition identities, bijections and Groebner bases October 30: Ludwig Danzer, University of Dortmund SCD, a space-filler of 3-space with some surprising properties November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves November 13: Alan Hoffman, IBM T.J. Watson Research Center Greedy Algorithms in Linear Programming

Date:Wed, 9 Oct 1996 12:20:17 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:Mendelsohn

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ Extra seminar on Friday October 11 at 1pm in 544 Nightingale Hall: Eric Mendelsohn, University of Toronto Intercalates (and Other Partial Latin Squares in 4 Cells) Everywhere \documentstyle{article} \title{Intercalates (and Other Partial Latin Squares in 4 Cells) Everywhere} \author{P. Danziger \\ Department of Mathematics \\ Ryerson University$^*$\\ \& \\ E. Mendelsohn \\ Department of Mathematics \\ University of Toronto \thanks{The authors acknowledge the support of NSERC (research grants \#OGP0170220 and \#OGP0077681 )}} \date{} \newtheorem{theorem}{Theorem} \newtheorem{definition}{Definition} \newtheorem{lemma}{Lemma} \newtheorem{conjecture}{Conjecture} \def\bt{\bibitem} \begin{document} \maketitle \begin{center} {\em This paper is dedicated to the memory of Peter Rodney Z{\tt "}L. (1965 -- 1 995)} \end{center} \begin{abstract} The counting of the number of Intercalates, $2\times 2$ subsquares, possible in a latin Square of side $n$ is in general a hard problem. $N_2$--Free latin squares, those for which there are no intercalates, are known to exist for $n \neq 1,2,4$. $N_2$--complete latin Squares, those which have the property that they have the maximum number of $N_2$'s possible, $\frac{n}{2}\cdot {n\choose 2}$, must be isotopic to $Z^k_2$ and thus of side $2^k$. The maximum for $n\neq 2^k$ is in general unknown. We propose an intermediate possibility, that of $N_2$--ubiquitous. A latin Square is $N_2$ ubiquitous if and only if every cell $a_{ij}$ is contained in some $2\times 2$ subsquare. We show these exist for $n\neq 1,3,5,7$. It is also determined for which $n$. $\cal C$--ubiquitous latin Squares exist for every partial latin Square, $\cal C$ with four cells. We also enumerate the number of times each 4-cell configuration can appear in a latin square and show that this number depends only on $n$ and the number of intercalates. \end{abstract} \end{document}

Date:Thu, 10 Oct 1996 12:02:59 -0400 (EDT)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar tomorrow

****Combinatorics Seminar, Friday 4:15pm, 2-338 **** Kostant polynomials; Interpolating Polynomials for Schubert Polynomials Sara Billey (M.I.T.) We will discuss the Kostant polynomials and their relationship to Schubert polynomials and the Schubert calculus for $G/B$. These polynomials are defined by vanishing properties on the orbit of a regular point under the action of the Weyl group. For each element $w$ in the Weyl group the polynomials also have non-zero values on the orbit points corresponding to elements which are larger in the Bruhat order than $w$. Our main theorem is an explicit formula for these values. The matrix of orbit values can then be used to determine the cup product for the cohomology ring for $G/B$, using only linear algebra. The main focus of the discussion will be for the case $W$ is the symmetric group, however the results all hold for the Weyl group of a Kac-Moody algebra. Upcoming events: date: Friday October 18, 1996 NO COMBINATORICS SEMINAR DUE TO "POSETS" WORKSHOP AT MSRI date: October 25, 1996 speaker: J. Maurice Rojas title: Multisymmetric Functions via Toric Resultants

From:ALBERTSON(at-sign)smith.smith.eduDate:Tue, 15 Oct 1996 14:35:23 -0500 (EST)Subject:CoNE 10/26/96 inquiryTo:joellis(at-sign)griffin.emba.uvm.edu, ssauyet(at-sign)claude.math.wesleyan.edu, majors(at-sign)emmy.smith.edu, sheila(at-sign)claude.math.wesleyan.edu, cchan(at-sign)claude.math.wesleyan.edu, dwylie(at-sign)claude.math.wesleyan.edu, dlieb(at-sign)picasso.cslab.wesleyan.edu, gao(at-sign)grendel.csc.smith.edu, goldston(at-sign)bard.edu, colbourn(at-sign)emba.uvm.edu, hurlbert(at-sign)cantor.la.asu.edu, mduchin(at-sign)abel.math.harvard.edu, gsarkozy(at-sign)math.upenn.edu, hoffa(at-sign)watson.ibm.com, wilf(at-sign)central.cis.upenn.edu, wilf(at-sign)math.upenn.edu, calkin(at-sign)math.gatech.edu, loebl(at-sign)kam.ms.mff.cuni.cz, whcunnin(at-sign)math.uwaterloo.ca, laura.hegerle(at-sign)dartmouth.edu, michael.orrison(at-sign)dartmouth.edu, pcassidy(at-sign)smith.smith.edu, lkrompar(at-sign)Oakland.edu, efa0(at-sign)lehigh.edu, rlg(at-sign)research.att.com, pw(at-sign)research.att.com, shor(at-sign)research.att.com, JEGCC%CUNYVM.BITNET(at-sign)eagle.wesleyan.edu, trenk(at-sign)dimacs.rutgers.edu, LLESNIAK(at-sign)drew.edu, etesar(at-sign)drew.edu, klein(at-sign)sci.brooklyn.cuny.edu, zamfi(at-sign)roz.hunter.cuny.edu, lvsnyder(at-sign)amherst.edu, bservat(at-sign)wpi.wpi.edu, David.Mauro(at-sign)mail.cc.trincoll.edu, melanie.stein(at-sign)mail.cc.trincoll.edu, chen(at-sign)math.umass.edu, ramesh(at-sign)oahu.cs.umass.edu, aab(at-sign)christa.unh.edu, elcox(at-sign)conncoll.edu, epetrie(at-sign)emo.merrimack.edu, carducci(at-sign)lafvax.lafayette.edu, pak(at-sign)abel.math.harvard.edu, fomin(at-sign)math.mit.edu, sara(at-sign)math.mit.edu, cathan(at-sign)math.mit.edu, apost(at-sign)math.mit.edu, lpachter(at-sign)math.mit.edu, dfinberg(at-sign)math.mit.edu, bona(at-sign)math.mit.edu, djk(at-sign)math.mit.edu, ariki(at-sign)math.mit.edu, mshimo(at-sign)math.mit.edu, satomi(at-sign)math.mit.edu, beveridg(at-sign)pascal.math.yale.edu, JBONIN(at-sign)gwuvm.gwu.edu, rejam(at-sign)clemson.edu, peterrc(at-sign)wpi.edu, lawsonn(at-sign)cs.rpi.edu, mathman(at-sign)brick.purchase.edu, ftbbb(at-sign)cunyvm.bitnet, spaletaj(at-sign)wpi.wpi.edu, elkies(at-sign)abel.math.harvard.edu, nate(at-sign)research.att.com, moorthy(at-sign)cs.rpi.edu, streinu(at-sign)grendel.csc.smith.edu, chung(at-sign)math.upenn.edu, jalfano(at-sign)eve.assumption.edu, bkitchens(at-sign)MAIL.WESLEYAN.EDU, hochberg(at-sign)math.rutgers.edu, jah(at-sign)christa.unh.edu, romanik(at-sign)dimacs.rutgers.edu, lenhart(at-sign)cs.williams.edu, sheila(at-sign)paris-gw.cs.miami.edu, pavol(at-sign)cs.sfu.ca, wantland(at-sign)mcs1.wcsu.ctstateu.edu, ross(at-sign)cs.amherst.edu, kia(at-sign)oregano.unh.edu, simion%gwuvm.bitnet(at-sign)eagle.wesleyan.edu, innes(at-sign)cs.uri.edu, finizio(at-sign)uriacc.uri.edu, macula%geneseo.bitnet(at-sign)eagle.wesleyan.edu, kcirino(at-sign)lynx.dac.neu.edu, propp(at-sign)math.mit.edu, rstan(at-sign)math.mit.edu, k.p.bogart(at-sign)dartmouth.edu, sdc(at-sign)cs.albany.edu, peterrc(at-sign)wpi.wpi.edu, kcollins(at-sign)WESLEYAN.EDU, rhaas(at-sign)smith.smith.edu, lrose(at-sign)sallie.WELLESLEY.EDU, jjr(at-sign)linus.mitre.org, sandifer(at-sign)wcsub.ctstateu.edu, orourke(at-sign)sophia.smith.edu, senechal(at-sign)minkowski.smith.edu, immerman(at-sign)freya.cs.umass.edu, ccm(at-sign)cs.amherst.edu, diwan(at-sign)freya.cs.umass.edu, grupen(at-sign)freya.cs.umass.edu, herbordt(at-sign)cs.umass.edu, krithi%nirvan(at-sign)cs.umass.edu, lam(at-sign)cs.amherst.edu, liu(at-sign)freya.cs.umass.edu, atrenk(at-sign)sallie.WELLESLEY.EDU, landau(at-sign)freya.cs.umass.edu, malitz%oahu(at-sign)cs.umass.edu, rsnbrg(at-sign)freya.cs.umass.edu, adean(at-sign)skidmore.edu, jzca%marist.bitnet(at-sign)eagle.wesleyan.edu, FRANZBLA(at-sign)dimacs.rutgers.edu, jhs(at-sign)math.cornell.edu, kamck(at-sign)mvax.cc.conncoll.edu, albertson(at-sign)smith.smith.edu, llangley(at-sign)carbon.denver.colorado.edu, Tom.Sundquist(at-sign)dartmouth.edu, dbeers(at-sign)vmsvax.simmons.edu, bennett(at-sign)math.umass.edu, fishel(at-sign)scsud.ctstateu.edu, gptesler(at-sign)euclid.ucsd.edu, streinu(at-sign)sophia.smith.edu, eaton(at-sign)cs.uri.edu, susan(at-sign)max.math.brandeis.edu, archdeac(at-sign)uvm-gen.emba.uvm.edu, kenney(at-sign)siena.edu, hutchinson(at-sign)macalstr.edu, plock%stlawu.bitnet(at-sign)eagle.wesleyan.edu, dvella(at-sign)skidmore.edu, kwong(at-sign)mary.cs.fredonia.edu, lbutler(at-sign)acc.haverford.edu, jsims(at-sign)eagle.wesleyan.edu, ecoven(at-sign)eagle.wesleyan.edu, jlewis(at-sign)uriacc.uri.edu, sanjoy(at-sign)emba.uvm.edu, rjyanco(at-sign)unix.amherst.edu, gara(at-sign)emba.uvm.edu, ravi(at-sign)cs.uri.edu, quintas(at-sign)pacevm.dac.pace.edu, kennedyf(at-sign)pacevm.dac.pace.edu, lfeng(at-sign)eagle.wesleyan.edu, ssilberger(at-sign)eagle.wesleyan.edu, bheiles(at-sign)eagle.wesleyan.edu, Rhoades(at-sign)emmy.smith.edu, hull(at-sign)cs.uri.edu, silbergd%snynewvm.bitnet(at-sign)eagle.wesleyan.edu, discrete-math(at-sign)CS.YALE.EDU, combinatorics(at-sign)math.mit.edu

We have received a request to alter the schedule of talks for the October 26 meeting. The revised schedule would have Servatius at 10, Hutchinson at 11:10, Cowen at 2, and Kitchens at 3:10. (Servatius and Kitchens would trade places). If you are planning to attend this meeting and the proposed changes would have a negative impact upon you, please let me know. Combinatorially, Mike Albertson

From:ALBERTSON(at-sign)smith.smith.eduDate:Fri, 18 Oct 1996 13:20:28 -0500 (EST)Subject:CoNE 10/26/96To:joellis(at-sign)griffin.emba.uvm.edu, ssauyet(at-sign)claude.math.wesleyan.edu, majors(at-sign)emmy.smith.edu, sheila(at-sign)claude.math.wesleyan.edu, cchan(at-sign)claude.math.wesleyan.edu, dwylie(at-sign)claude.math.wesleyan.edu, dlieb(at-sign)picasso.cslab.wesleyan.edu, gao(at-sign)grendel.csc.smith.edu, goldston(at-sign)bard.edu, colbourn(at-sign)emba.uvm.edu, hurlbert(at-sign)cantor.la.asu.edu, mduchin(at-sign)abel.math.harvard.edu, gsarkozy(at-sign)math.upenn.edu, hoffa(at-sign)watson.ibm.com, wilf(at-sign)central.cis.upenn.edu, wilf(at-sign)math.upenn.edu, calkin(at-sign)math.gatech.edu, loebl(at-sign)kam.ms.mff.cuni.cz, whcunnin(at-sign)math.uwaterloo.ca, laura.hegerle(at-sign)dartmouth.edu, michael.orrison(at-sign)dartmouth.edu, pcassidy(at-sign)smith.smith.edu, lkrompar(at-sign)Oakland.edu, efa0(at-sign)lehigh.edu, rlg(at-sign)research.att.com, pw(at-sign)research.att.com, shor(at-sign)research.att.com, JEGCC%CUNYVM.BITNET(at-sign)eagle.wesleyan.edu, trenk(at-sign)dimacs.rutgers.edu, LLESNIAK(at-sign)drew.edu, etesar(at-sign)drew.edu, klein(at-sign)sci.brooklyn.cuny.edu, zamfi(at-sign)roz.hunter.cuny.edu, lvsnyder(at-sign)amherst.edu, bservat(at-sign)wpi.wpi.edu, David.Mauro(at-sign)mail.cc.trincoll.edu, melanie.stein(at-sign)mail.cc.trincoll.edu, chen(at-sign)math.umass.edu, ramesh(at-sign)oahu.cs.umass.edu, aab(at-sign)christa.unh.edu, elcox(at-sign)conncoll.edu, epetrie(at-sign)emo.merrimack.edu, carducci(at-sign)lafvax.lafayette.edu, pak(at-sign)abel.math.harvard.edu, fomin(at-sign)math.mit.edu, sara(at-sign)math.mit.edu, cathan(at-sign)math.mit.edu, apost(at-sign)math.mit.edu, lpachter(at-sign)math.mit.edu, dfinberg(at-sign)math.mit.edu, bona(at-sign)math.mit.edu, djk(at-sign)math.mit.edu, ariki(at-sign)math.mit.edu, mshimo(at-sign)math.mit.edu, satomi(at-sign)math.mit.edu, beveridg(at-sign)pascal.math.yale.edu, JBONIN(at-sign)gwuvm.gwu.edu, rejam(at-sign)clemson.edu, peterrc(at-sign)wpi.edu, lawsonn(at-sign)cs.rpi.edu, mathman(at-sign)brick.purchase.edu, ftbbb(at-sign)cunyvm.bitnet, spaletaj(at-sign)wpi.wpi.edu, elkies(at-sign)abel.math.harvard.edu, nate(at-sign)research.att.com, moorthy(at-sign)cs.rpi.edu, streinu(at-sign)grendel.csc.smith.edu, chung(at-sign)math.upenn.edu, jalfano(at-sign)eve.assumption.edu, bkitchens(at-sign)MAIL.WESLEYAN.EDU, hochberg(at-sign)math.rutgers.edu, jah(at-sign)christa.unh.edu, romanik(at-sign)dimacs.rutgers.edu, lenhart(at-sign)cs.williams.edu, sheila(at-sign)paris-gw.cs.miami.edu, pavol(at-sign)cs.sfu.ca, wantland(at-sign)mcs1.wcsu.ctstateu.edu, ross(at-sign)cs.amherst.edu, kia(at-sign)oregano.unh.edu, simion%gwuvm.bitnet(at-sign)eagle.wesleyan.edu, innes(at-sign)cs.uri.edu, finizio(at-sign)uriacc.uri.edu, macula%geneseo.bitnet(at-sign)eagle.wesleyan.edu, kcirino(at-sign)lynx.dac.neu.edu, propp(at-sign)math.mit.edu, rstan(at-sign)math.mit.edu, k.p.bogart(at-sign)dartmouth.edu, sdc(at-sign)cs.albany.edu, peterrc(at-sign)wpi.wpi.edu, kcollins(at-sign)WESLEYAN.EDU, rhaas(at-sign)smith.smith.edu, lrose(at-sign)sallie.WELLESLEY.EDU, jjr(at-sign)linus.mitre.org, sandifer(at-sign)wcsub.ctstateu.edu, orourke(at-sign)sophia.smith.edu, senechal(at-sign)minkowski.smith.edu, immerman(at-sign)freya.cs.umass.edu, ccm(at-sign)cs.amherst.edu, diwan(at-sign)freya.cs.umass.edu, grupen(at-sign)freya.cs.umass.edu, herbordt(at-sign)cs.umass.edu, krithi%nirvan(at-sign)cs.umass.edu, lam(at-sign)cs.amherst.edu, liu(at-sign)freya.cs.umass.edu, atrenk(at-sign)sallie.WELLESLEY.EDU, landau(at-sign)freya.cs.umass.edu, malitz%oahu(at-sign)cs.umass.edu, rsnbrg(at-sign)freya.cs.umass.edu, adean(at-sign)skidmore.edu, jzca%marist.bitnet(at-sign)eagle.wesleyan.edu, FRANZBLA(at-sign)dimacs.rutgers.edu, jhs(at-sign)math.cornell.edu, kamck(at-sign)mvax.cc.conncoll.edu, albertson(at-sign)smith.smith.edu, llangley(at-sign)carbon.denver.colorado.edu, Tom.Sundquist(at-sign)dartmouth.edu, dbeers(at-sign)vmsvax.simmons.edu, bennett(at-sign)math.umass.edu, fishel(at-sign)scsud.ctstateu.edu, gptesler(at-sign)euclid.ucsd.edu, streinu(at-sign)sophia.smith.edu, eaton(at-sign)cs.uri.edu, susan(at-sign)max.math.brandeis.edu, archdeac(at-sign)uvm-gen.emba.uvm.edu, kenney(at-sign)siena.edu, hutchinson(at-sign)macalstr.edu, plock%stlawu.bitnet(at-sign)eagle.wesleyan.edu, dvella(at-sign)skidmore.edu, kwong(at-sign)mary.cs.fredonia.edu, lbutler(at-sign)acc.haverford.edu, jsims(at-sign)eagle.wesleyan.edu, ecoven(at-sign)eagle.wesleyan.edu, jlewis(at-sign)uriacc.uri.edu, sanjoy(at-sign)emba.uvm.edu, rjyanco(at-sign)unix.amherst.edu, gara(at-sign)emba.uvm.edu, ravi(at-sign)cs.uri.edu, quintas(at-sign)pacevm.dac.pace.edu, kennedyf(at-sign)pacevm.dac.pace.edu, lfeng(at-sign)eagle.wesleyan.edu, ssilberger(at-sign)eagle.wesleyan.edu, bheiles(at-sign)eagle.wesleyan.edu, Rhoades(at-sign)emmy.smith.edu, hull(at-sign)cs.uri.edu, silbergd%snynewvm.bitnet(at-sign)eagle.wesleyan.edu, discrete-math(at-sign)CS.YALE.EDU, combinatorics(at-sign)math.mit.edu

The schedule for the October 26th meeting will be Servatius at 10, Hutchinson at 11:10, Cowen at 2, and Kitchens at 3:10. Refer to our home page or a previous announcement for titles. Mike Albertson

Date:Mon, 21 Oct 1996 14:29:04 -0400To:kcollins(at-sign)mail.wesleyan.eduFrom:kcollins(at-sign)wesleyan.edu (Karen L. Collins)Subject:CoNE meeting

**************Second Announcement************** Come to the Twenty-second one day conference on Combinatorics and Graph Theory Saturday, October 26, 1996 10 a.m. to 4:30 p.m. at Smith College Northampton MA 01063 Schedule 10:00 Herman Servatius (WPI) Doubly Periodic Self-dual Graphs and Tilings 11:10 Joan Hutchinson (Macalester College) Some 3- and 4-coloring theorem for the Plane, the Projective Plane, and the Torus or Variations on some themes of Heawood and Hadwiger 12:30 Lunch 2:00 Lenore Cowen (Johns Hopkins University) Favorite Coloring Relaxations 3:10 Bruce Kitchens (IBM) Two Combinatorial Problems from Symbolic Dynamics Our NSF grant to support these conferences has been renewed! This will allow us to provide a modest transportation allowance to those attendees who are not local. We gratefully acknowledge support from Smith College and Wesleyan University as well. Our Web page site has directions to Smith College, abstracts of speakers, dates of future conferences, and other information. The address is: http://math.smith.edu/~rhaas/coneweb.html Michael Albertson (Smith College), (413) 585-3865, albertson(at-sign)smith.smith.edu Karen Collins (Wesleyan Univ.), (860) 685-2169, kcollins(at-sign)wesleyan.edu Ruth Haas (Smith College), (413) 585-3872, rhaas(at-sign)smith.smith.edu

Date:Tue, 22 Oct 1996 12:25:45 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

Usually the seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. October 23: Igor Pak, Harvard University Partition identities, bijections and Groebner bases October 30: Ludwig Danzer, University of Dortmund (at 3:00pm) SCD, a space-filler of 3-space with some surprising properties November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves November 13: Alan Hoffman, IBM T.J. Watson Research Center Greedy Algorithms in Linear Programming

Date:Tue, 22 Oct 1996 18:47:02 -0400 (EDT)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:pretalks

Starting with this Friday's Combinatorics seminar, we will initiate pretalk discussions. These will take place (unless otherwise noted) in 2-338 from 3:30 to 4:00, and will be of a more casual nature. These are primarily geared towards graduate students and others who want more background before the ``official'' talk. This Week!: October 25: J. Maurice Rojas Multisymmetric Functions via Toric Resultants

Date:Sun, 27 Oct 1996 16:45:46 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:this week

This week we have two talks! Prof. Rota will give a two part lecture starting this Wednesday and continuing one week later. There will be no pretalk on Wednesday but I am trying to schedule one for Friday at 3:00. This will be confirmed in a second message. Upcoming events are also below. date: Wednesday, October 30, 1996 speaker: Gian-Carlo Rota title: "The work of K.T. Chen" date: Friday, November 1, 1996 speaker: Arun Ram title: A proof, a generalization, and an application of a theorem of Roichman abstract: Recently, Y. Roichman gave a beautiful new formula for the irreducible characters of the Iwahori-Hecke algebra (and for the symmetic group and other Weyl groups). In the type A case this formula turns out to be equivalent to the ``Frobenius formula'' and, indeed, looking at it this way yields a very simple proof of Roichman's formula via the Robinson-Schensted-Knuth insertion scheme. Armed with this simpler proof we can generalize Roichman's formula to get new character formulas for Brauer and Birman-Wenzl algebras. Finally, we shall apply this whole setup to compute the bitrace of the regular representation of the Iwahori-Hecke algebra as a weighted sum of matrices with nonnegative integer entries. Upcoming events: date: Wednesday, November 6, 1996 speaker: Gian-Carlo Rota title: An Introduction to Baxter Operators date: Friday, November 8, 1996 speaker: Peter Hamburger title: Venn Said it Couldn't be Done:\\ Planar Graphs, Hamiltonian Cycle, and Special Families of Simple Jordan Curve date: Friday, November 15, 1996 speaker: Huafei Yan title: Generalized Tree Inversions and $k$-Parking Function

Date:Sun, 27 Oct 1996 21:51:57 -0500 (EST)From:G-C Rota <rota(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.edu, sara(at-sign)math.mit.eduSubject:Re: this week

Perhaps I should give an inkling as to what the talk "The work of K.T. Chen" is about. As you know, a word in a free group with n generators can be represented as a path in n-space. This representation has led to a number of conjectures and theorems about words in free groups. Chen's idea is to extend the notion of a free group so as to allow a generalized word to be associated with any directed path in n space. I will describe how this is done, in the hope that someone will get interested in getting "continuous" analogs of several known facts about words. Gian-Carlo Rota.

Date:Mon, 28 Oct 1996 15:55:07 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ All talks are in 509 Lake Hall. The talk on October 30 is at 3:00pm. All other talks are at 1:30pm. October 30: Ludwig Danzer, University of Dortmund (at 3:00pm) SCD, a space-filler of 3-space with some surprising properties November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves November 13: Alan Hoffman, IBM T.J. Watson Research Center Greedy Algorithms in Linear Programming

Date:Fri, 1 Nov 1996 13:05:59 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar today

Today's seminar will be at 4:30pm instead of the usual 4:15 due to the Faculty-Student get-together. The Pretalk will be at 3:00 in 2-338. ****Combinatorics Seminar Today **** A proof, a generalization, and an application of a theorem of Roichman Arun Ram (Princeton University) Recently, Y. Roichman gave a beautiful new formula for the irreducible characters of the Iwahori-Hecke algebra (and for the symmetric group and other Weyl groups). In the type A case this formula turns out to be equivalent to the ``Frobenius formula'' and, indeed, looking at it this way yields a very simple proof of Roichman's formula via the Robinson-Schensted-Knuth insertion scheme. Armed with this simpler proof we can generalize Roichman's formula to get new character formulas for Brauer and Birman-Wenzl algebras. Finally, we shall apply this whole setup to compute the bitrace of the regular representation of the Iwahori-Hecke algebra as a weighted sum of matrices with nonnegative integer entries. Upcoming Events: date: Wednesday, November 6, 1996 speaker: Gian-Carlo Rota title: Continuation of "The work of K.T.Chen" date: Friday, November 8, 1996 speaker: Peter Hamburger title: Venn Said it Couldn't be Done:\\ Planar Graphs, Hamiltonian Cycle, and Special Families of Simple Jordan Curve date: Friday, November 15, 1996 speaker: Huafei Yan title: Generalized Tree Inversions and $k$-Parking Function

Date:Fri, 1 Nov 1996 19:10:57 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ The seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. November 6: Peter Hamburger, Indiana-Purdue University Venn said it couldn't be done -- Planar graphs, Hamiltonian cycles and special families of simple Jordan curves November 13: Alan Hoffman, IBM T.J. Watson Research Center Greedy Algorithms in Linear Programming

Date:Fri, 1 Nov 1996 18:24:11 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:correction

My last message incorrectly stated the title of next week's talk. The correct title is as follows: title: An Introduction to Baxter Operators speaker: Gian-Carlo Rota date: Wednesday, November 6, 1996 The coming talk will be independent from the talk this past Wednesday.

Date:Thu, 7 Nov 1996 12:07:54 -0500 (EST)From:Lauren Rose <rose(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:Combinatorics Lunch - this Friday

We are starting a weekly combinatorics lunch at the MIT faculty lunchroom, on the 2nd floor of Walker Hall (above the cafeteria). We will meet on Fridays from 12:00 - 1:00 pm, starting TOMORROW. All are welcome, but graduate students and non-MIT faculty must be escorted by an MIT faculty member. Please meet at Sara Billey's office (2-334) at 11:50am. and we will walk over together. The cost is only $3.00 and the food is pretty good!

Date:Fri, 8 Nov 1996 12:11:03 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ The seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. November 13: Alan Hoffman, IBM T.J. Watson Research Center Greedy Algorithms in Linear Programming November 20: J. Maurice Rojas, MIT Counting Solutions of Sparse Polynomial Equation via Resultants

Date:Fri, 8 Nov 1996 11:13:29 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:today

****Combinatorics Seminar Today **** 4:15 in room 2-338, refreshments at 3:45 Speaker: Peter Hamburger (Indiana-Purdue University) Title: Venn Said it Couldn't be Done: Planar Graphs, Hamiltonian Cycle, and Special Families of Simple Jordan Curve Abstract: Using topological graph theory we will develop planar graph models to study the properties of special simple families of plane and spherical Jordan curves. Utilizing these procedures we solved some geometrical and topological problems. Among the others we answered some of the problems and conjectures of Professor Grunbaum. In this talk I will present some of our results on convex and strongly convex, simple, irreducible planar and spherical Venn diagrams. One of these results finally and fully corrects the erroneous statements that started with John Venn more than a century ago in 1880 and have been repeated frequently by others since then. We also will solve a conjecture of Grunbaum: Every Venn diagram on n curves can be extended to a Venn diagram of n+1 curves by the addition of a suitable simple closed Jordan curve. This finally solves a problem that goes back a century to John Venn's paper in 1880. We also will discuss a related conjecture of Peter Winkler. I will raise several problems and conjectures that arise from our work. I believe the talk will interest graph theorists and topologists as well as geometers, but it is accessible for any faculty or student with minimal knowledge of graph theory, topology, and geometry. Some of the results are joint results with Kiran B. Chilakamarri and/or Raymond E. Pippert (IPFW). } Upcoming events: date: Friday, November 15, 1996 speaker: Huafei Yan title: Generalized Tree Inversions and $k$-Parking Function date: Friday, November 22, 1996 speaker: Miller Maley title: "Hall Polynomials for Classical Groups"

Date:Wed, 13 Nov 1996 18:31:35 -0500To:combinatorics(at-sign)math.mit.eduFrom:schulte(at-sign)neu.edu (SCHULTE)Subject:seminar

NORTHEASTERN COMBINATORICS SEMINAR -- Fall 1996 _________________________________________________ The seminar meets Wednesdays at 1:30 - 2:30 pm in 509 Lake Hall. November 20: J. Maurice Rojas, MIT Counting Solutions of Sparse Polynomial Equations via Resultants

Date:Wed, 13 Nov 1996 19:23:56 -0500 (EST)From:Lauren Rose <rose(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:Combinatorics Lunch - this Friday

Come to the MIT faculty lunchroom on FRIDAY from 12-1 for the weekly combinatorics lunch. Get to know your colleagues! Last week we had a great turnout, including the speaker for that day. The lunchroom is on the 2nd floor of Walker Hall, and it's $3.00 for a buffet lunch.

Date:Thu, 14 Nov 1996 13:34:39 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar

****Combinatorics Seminar Tomorrow **** Generalized Tree Inversions and $k$-Parking Function Catherine Yan (M.I.T.) Abstract: Kreweras studied a polynomial $P_n(q)$ which enumerates (labeled) rooted forests by number of inversions, as well as complements of parking functions by the sum of their terms. Moreover, $P_n(1+q)$ enumerates labeled connected graphs by their number of excess edges. For any positive integer $k$, there are known notions of $k$-parking functions and of (labeled) rooted $k$-forests, generating the case $k=1$ studied by Kreweras. We show that the enumerator $\overline{P}_n^{(k)}(q)$ for complements of $k$-parking functions by the sum of their terms is identical to the enumerator of $I_n^{(k)}(q)$ of rooted $k$-forests by the number of their inversions. In doing so we find recurrence relations satisfied by $\overline{P}_n^{(k)}(q)$ and $I_n^{(k)}(q)$, and we introduce the concept of a {\em multirooted $k$-graph} whose excess edges and roots are enumerated by a polynomial denoted $C_n^{(k)}(q)$. We show that $C_n^{(k)}(q)$ satisfies the same recurrence relations as both $\overline{P}_n^{(k)}(1+q)$ and $I_n^{(k)}(1+q)$, proving that $\overline{P}_n^{(k)}(q) =I_n^{(k)}(q)$. Upcoming Events: date: Friday, November 22, 1996 speaker: Miller Maley title: "Hall Polynomials for Classical Groups" pretalk at 3:30pm for graduate students and non-experts in Hall polynomials. date: Friday, November 29, 1996 NO SEMINAR. Happy Thanksgiving.

Date:Sat, 16 Nov 1996 09:14:42 -0500To:kcollins(at-sign)mail.wesleyan.eduFrom:kcollins(at-sign)wesleyan.edu (Karen L. Collins)Subject:December 7

Come to the Twenty-third one day conference on Combinatorics and Graph Theory Saturday, December 7, 1996 10 a.m. to 4:30 p.m. at Smith College Northampton MA 01063 Schedule 10:00 Gary Gordon (Lafayette College) Tutte Polynomials for Everyone 11:10 Noga Alon (Institute of Advanced Study, Tel Aviv Univ.) Randomness and Pseudo-Randomness in Discrete Mathematics 12:30 Lunch 2:00 Norm Finizio (Univ. of Rhode Island) Some Amazing Whist Tournament Designs 3:10 David Mauro (Trinity College) Vertex Labelings with a Condition at Distance Two Our NSF grant to support these conferences has been renewed! This will allow us to provide a modest transportation allowance to those attendees who are not local. We gratefully acknowledge support from Smith College and Wesleyan University as well. Our Web page site has directions to Smith College, abstracts of speakers, dates of future conferences, and other information. The address is: http://math.smith.edu/~rhaas/coneweb.html Michael Albertson (Smith College), (413) 585-3865, albertson(at-sign)smith.smith.edu Karen Collins (Wesleyan University), (860) 685-2169, kcollins(at-sign)wesleyan.edu Ruth Haas (Smith College), (413) 585-3872, rhaas(at-sign)smith.smith.edu

Date:Fri, 22 Nov 1996 11:09:47 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:today

Miller Maley will be speaking today in the combinatorics seminar starting at 4:15pm in 2-338 as usual. The title of his talk will be "Hall Polynomials for Classical Groups". There will be a pretalk starting at 3:30 in the same room for those who would like a more elementary introduction. Abstract: Hall polynomials, which count invariant subspaces for a nilpotent linear transformation acting on a vector space over a finite field, are a key ingredient in the character theory of the group GL(n,q). We discuss the natural generalization of these polynomials to symplectic, orthogonal, and unitary groups over the q-element field. The speaker has developed an efficient algorithm for computing these "Hall functions", which makes it possible to discover and establish some of their properties. In particular, the algorithm shows that Hall functions are polynomials in q with rational coefficients, and that certain signed sums of these polynomials have integer coefficients. Upcoming events: date: Wednesday, December 4, 1996 (tentative) speaker: Nantel Bergeron title: Multiplication of Schubert Polynomials and Partial order date: Friday, December 6, 1996 speaker: Sheila Sundaram title: The Whitehouse module in the homology of posets of partitions

Date:Fri, 22 Nov 1996 13:52:11 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:correction

Correction to my last message. Bergeron's talk is definite. date: Wednesday, December 4, 1996 speaker: Nantel Bergeron title: Multiplication of Schubert Polynomials and Partial order Also, there won't be a talk on Nov. 29. Happy Thanksgiving.

Date:Fri, 22 Nov 1996 17:21:55 -0500 (EST)From:Jim Propp <propp(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:Combinatorial Commutative Algebra

First Announcement Conference on ``Combinatorial Commutative Algebra'' June 27. - 29. 1997 Universit\"at GH-Essen Germany General Topics & Program : The conference is intended to promote the interaction between Commutative Algebra and Combinatorics. Our plan is to gather researchers that will provide expositions of classical and recent developments on the borderline between Commutative Algebra & Combinatorics. Together with a second announcement, that will be posted in December, we will mail out registration forms. In case there are any questions, please contact us under the following address: Emanuela De Negri Fachbereich 6, Mathematik Universit\"at GH-Essen 45117 Essen Germany mat306(at-sign)uni-essen.de List of speakers (preliminary, status November 22. 1996) : Annetta Aramova (Bulgarian Academy of Sciences, Bulgaria) J\"orgen Backelin (Stockholm Universitet, Sweden) Takayuki Hibi (Osaka University, Japan) Aldo Conca (Genova, Italy) Ralf Fr\"oberg (Stockholm Universitet, Sweden) Josef Gubelaze (A. Razmadze Mathematical Institute, Georgia) Gil Kalai (Hebrew University, Jerusalem, Israel) Clas L\"ofwall (Stockholm Universitet, Sweden) Vic Reiner (University of Minnesota, USA) Dorin Popescu (Bukarest, Rumania) Emil Sk\"oldberg (Stockholm Universitet, Sweden) Bernd Sturmfels (NOT CONFIRMED) (University of California, Berkeley, USA) Program committee : Winfried Bruns (Osnabr"uck) J\"urgen Herzog (Essen) Volkmar Welker (Essen) G\"unter M. Ziegler (Berlin) Participant support : The conference is sponsored by the German Research Council DFG through the Graduiertenkolleg ``Theoretische und experimentelle Methoden in der reinen Mathematik'' and the Forschergruppe ``Arithmetik und Geometrie.'' We can offer limited funds for supporting some participants. Participants that would like to request funds should contact us as soon as possible. Local Arrangements : The conference will take place on the main campus of the University of Essen located centrally in the city of Essen. Talks will start in morning on Friday June 27 and the last talk will be given in the late afternoon of June 29. We have made arrangements with several hotels in Essen, so that we can offer reduced rates for conference participants. A list of hotels will be provided together with the second announcement. Organizing committee : Emanuela De Negri (Essen) J\"urgen Herzog (Essen) Volkmar Welker (Essen)

Date:Wed, 27 Nov 1996 13:25:16 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.edu, combinatorics(at-sign)euclid.ucsd.eduSubject:Combinatorics position (fwd)

Date:Wed, 27 Nov 1996 12:15:07 -0500 (EST)From:KE Smith <kesmith(at-sign)math.lsa.umich.edu>

Date:Wed, 27 Nov 1996 05:50:32 -0500 (EST)From:Alexandre Barvinok <barvinok(at-sign)math.lsa.umich.edu>

Below is the message I got from Victor Klee concerning possible openings in combinatorics. - -Sasha - - - - - - - For employment starting in September 1997, the University of Washington Mathematics Department will have some open positions --- two tenure-track assistant professorships and one non-tenure- track acting assistant professorship. (Appointments at higher levels are not excluded, but would be significantly more difficult to arrange.) In connection with these appointments, the department has several areas of priority, and Combinatorics is one of them. Since the number of priority areas exceeds the number of available positions, there is no guarantee that an appointment in combinatorics will be made, but there is certainly some reason to be hopeful in this connection. Thus I am writing to say that, if you know of some especially promising young combinatorialists who might be interested in moving to Seattle, I would appreciate your informing them of this opportunity. Applications should be sent to the following address: Appointments Committee Chair, Department of Mathematics, Box 354350, University of Washington, Seattle, WA 98195--4350. A copy of the full announcement is appended below. Within the Department of Mathematics, there are strong groups in Discrete Geometry, in Optimization, and in parts of Graph Theory, so candidates whose interests overlap with one or more of these fields might be especially welcome. The same is true of those with algorithmic interests, and there is a possibility of interaction with the UW's strong Computer Science Department. However, overall mathematical (and combinatorial) strength is of greater importance than is any specific orientation within combinatorics. Some breadth of research interests is also desirable, as that would facilitate interaction with colleagues. - - - - - - - Here is the official announcement. Applications are invited for several positions starting in September, 1997. There is one three-year non-tenure track acting assistant professorship available. There are also two positions initially budgeted as tenure-track assistant professorships, but sufficiently outstanding candidates may be considered at the associate professor or professor level. Applicants must have the Ph.D. degree in hand by the starting date. Duties include undergraduate and graduate teaching and independent research. Applications should include a curriculum vitae, statement of research and teaching interests, three letters of recommendation, and a Mathematics Subject Classification (as found in the December index volumes of Mathematical Reviews) of their primary research interest. Applications should be sent to: Appointments Committee Chair, Department of Mathematics, Box 354350, University of Washington, Seattle, WA 98195--4350. Priority will be given to applications received by December 15, 1996. The University of Washington is building a culturally diverse faculty and strongly encourages applications from female and minority candidates. The University is an Equal Opportunity/Affirmative Action employer. Availability of positions is subject to budgetary approval. ------- End of forwarded message -------

Date:Mon, 2 Dec 1996 14:47:42 -0500 (EST)From:Lauren Rose <rose(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:Lecture: Monday Dec 2nd, 8pm

There is an interesting lecture tonight about polyhedra sponsored by the Philomorph Society. The meetings are open to the general public. ***************************************************** Dear Philomorphs, Please join us for our next meeting: "Virtual Reality Polyhedra" George W. Hart Dept. of Computer Science Hofstra University Monday, December 2nd, 1996 at 8:00 p.m. Harvard University Carpenter Center for the Visual Arts, Room 401 24 Quincy Street Cambridge, Massachusetts "Three-dimensional shapes can be described in standardized computer file formats which may be seamlessly integrated with the internet and world-wide web pages. Author/artists can create three-dimensional objects which are instantaneously viewable by interested readers around the world. The viewer can spin the objects on their screen (as real-time computer animations) or move closer or further away, to gain different perspectives, just as one does with a sculpture or physical three-dimensional model. These virtual reality models also have certain advantages over physical models: one can travel inside them; they can be physically disconnected; they can incorporate motion and transformation. I have been building a large collection of 3D polyhedron models of this sort, many of which have never been constructed in paper. I will show examples and discuss some possibilities of these techniques. A preview is available at http://www.li.net/~george/virtual-polyhedra/vp.html" The Philomorphs meet on the first Monday of each month during the Spring and Fall semesters unless otherwise noted. All meetings are free and open to the public. Interested friends and colleagues are welcome to attend. Suggestions for future speakers or meeting topics, and notes on other items of interest are encouraged. Those wishing to receive future notices via email may send a note to kthidemann(at-sign)aol.com. All who receive this announcement by mail are asked to make a modest donation to defray the reproduction and postage costs. Many thanks to all who have donated. The 2-digit number next to your name on the address label is the year through which you will remain on the active mailing list (i.e., '96 means you'll receive mailings at least through Dec. '96). If no number appears, you're on the list until further notice. If you wish to be dropped from the list at any time, please let us know that as well. (Note: The mailing list is continually in the process of being updated. If you have sent a renewal notice recently, the date listed next to your name on the address label may not yet reflect this.) Contributions and address changes may be sent to the following address. Please make checks payable to "Philomorphs." Philomorphs Carpenter Center for the Visual Arts Harvard University Cambridge, MA 02138

Date:Tue, 3 Dec 1996 13:58:32 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar tomorrow

****Combinatorics Seminar Tomorrow **** 4:15pm in 2-334 Multiplication of Schubert Polynomials and Partial order Nantel Bergeron (York University) Abstract: We introduce a partial order of the symmetric group related to the multiplication of an arbitrary Schubert polynomial with a Schur polynomial. Analogously to the weak Bruhat order and the nil-Coxeter monoid, this order has an associated monoid M. Finding a well behaved Knuth-cell decomposition of M would solve the multiplication problem describe above. The conjecture proposed by Winkel was promising, but our study discovered a counter-example to it. Upcoming events: date: Friday, December 6, 1996 speaker: Sheila Sundaram title: The Whitehouse module in the homology of posets of partitions abstract: ***************** We present a class of subposets of the partition lattice $\Pi_n$ with the following property: The order complex is homotopy equivalent to the order complex of $\Pi_{n-1},$ and the $S_n$-module structure of the homology coincides with a recently discovered lifting of the $S_{n-1}$-action on the homology of $\Pi_{n-1}.$ This is the Whitehouse representation on Robinson's space of fully-grown trees, and has since appeared in work of Mathieu, and Hanlon and Stanley. One example is the subposet $P_n^{n-1}$ of the lattice of set partitions $\Pi_n,$ obtained by removing all elements with a unique nontrivial block. More generally, for $2\leq k\leq n-1,$ let $Q_n^k$ denote the subposet of the partition lattice $\Pi_n$ obtained by removing all elements with a unique nontrivial block of size equal to $k,$ and let $P_n^k=\cap_{i=2}^k Q_n^i.$ We show that $P_n^k$ is Cohen-Macaulay with free integral homology, and that $P_n^k$ and $Q_n^k$ are homotopy equivalent, with Betti number $n!/k-(n-1)!.$ The posets $Q_n^k$ are neither shellable nor Cohen-Macaulay. We give a simple formula for the homology as an $S_n$-module, in terms of the homology modules of the partition lattices $\Pi_k$ and $\Pi_n.$ *************** date: Wednesday, December 11, 1996 speaker: Vladimir V. Kisil Odessa University (Ukraine) and Ghent University (Belgium) title: Interaction between Combinatorics and Harmonic Analysis We try to systematically employ observations that different combinatorial notions (polynomial sequence of binomial type, incidence coefficients, etc.) are generalization of group characters. This allows to develop a new sort of harmonic analysis rooted in combinatorics. Re-export of abstractly elaborated tools to combinatorics widens their scope of applications.

Date:Tue, 3 Dec 1996 17:29:01 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:pretalk

There will be a pretalk tomorrow at 3:30pm before Nantel Bergeron's talk. Anyone interested in learning some background is welcome to attend.

Date:Fri, 6 Dec 1996 14:51:41 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:seminar today

****Combinatorics Seminar Today **** The Whitehouse module in the homology of posets of partitions Sheila Sundaram (Wesleyan University) There is no pretalk today. abstract: ***************** We present a class of subposets of the partition lattice $\Pi_n$ with the following property: The order complex is homotopy equivalent to the order complex of $\Pi_{n-1},$ and the $S_n$-module structure of the homology coincides with a recently discovered lifting of the $S_{n-1}$-action on the homology of $\Pi_{n-1}.$ This is the Whitehouse representation on Robinson's space of fully-grown trees, and has since appeared in work of Mathieu, and Hanlon and Stanley. One example is the subposet $P_n^{n-1}$ of the lattice of set partitions $\Pi_n,$ obtained by removing all elements with a unique nontrivial block. More generally, for $2\leq k\leq n-1,$ let $Q_n^k$ denote the subposet of the partition lattice $\Pi_n$ obtained by removing all elements with a unique nontrivial block of size equal to $k,$ and let $P_n^k=\cap_{i=2}^k Q_n^i.$ We show that $P_n^k$ is Cohen-Macaulay with free integral homology, and that $P_n^k$ and $Q_n^k$ are homotopy equivalent, with Betti number $n!/k-(n-1)!.$ The posets $Q_n^k$ are neither shellable nor Cohen-Macaulay. We give a simple formula for the homology as an $S_n$-module, in terms of the homology modules of the partition lattices $\Pi_k$ and $\Pi_n.$ *************** date: Wednesday, December 11, 1996 speaker: Vladimir V. Kisil Odessa University (Ukraine) and Ghent University (Belgium) title: Interaction between Combinatorics and Harmonic Analysis We try to systematically employ observations that different combinatorial notions (polynomial sequence of binomial type, incidence coefficients, etc.) are generalization of group characters. This allows to develop a new sort of harmonic analysis rooted in combinatorics. Re-export of abstractly elaborated tools to combinatorics widens their scope of applications.

Date:Wed, 11 Dec 1996 13:06:48 -0500 (EST)From:Sara Billey <sara(at-sign)math.mit.edu>To:combinatorics(at-sign)math.mit.eduSubject:today

This will be the last seminar for 1996. Have a nice vacation. See you in February. ****Combinatorics Seminar Today **** 4:15pm in 2-338 speaker: Vladimir V. Kisil title: Interaction between Combinatorics and Harmonic Analysis institution: Odessa University (Ukraine) and Ghent University (Belgium) abstract: We try to systematically employ observations that different combinatorial notions (polynomial sequence of binomial type, incidence coefficients, etc.) are generalization of group characters. This allows to develop a new sort of harmonic analysis rooted in combinatorics. Re-export of abstractly elaborated tools to combinatorics widens their scope of applications.