From dthurston at barnard.edu Mon Jan 21 17:23:40 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Mon, 21 Jan 2008 17:23:40 -0500 Subject: [GT-seminar] Friday: Rick Kenyon at 11AM Message-ID: <20080121222340.GA3492@amaryllis.bostoncoop.net> Hello, and welcome back! This Friday Rick Kenyon will be speaking jointly with the probability and geometry & topology seminar, at 11AM in 520 Math. (NOTE TIME.) The title is "The configuration space of branched polymers", and the abstract is below. In addition, we will also have an organizational meeting at 2:15 PM, after the gauge theory talk at 1. We've already scheduled several speakers for the upcoming semester based on various constraints, but more suggestions are welcome, either at the organizational meeting or before. In particular, we don't yet have a speaker for Feb. 1; several people (including Peter Ozsv?th and myself) will be out of town, but many people will still be here. The web page for the seminar remains at http://math.columbia.edu/~dpt/seminar/schedule.html . To subscribe or unsubscribe from this mailing list, please go to http://www.math.columbia.edu/mailman/listinfo/gt-seminar . Best, Dylan Thurston ------------------------------------------------------------ The configuration space of branched polymers Richard Kenyon, Brown University ------------------------------------------------------------ This is joint work with Peter Winkler. In this talk a "branched polymer" will be a connected collection of unit disks with non-overlapping interiors. Building on and from the work of Brydges and Imbrie, we give an elementary calculation of the volume of the space of branched polymers with n disks in the plane and in 3-space. Our development reveals some more general identities, and allows exact random sampling. In particular we show that a random 3-dimensional branched polymer with n disks has diameter of order sqrt(n). ------------------------------------------------------------ From dthurston at barnard.edu Mon Jan 28 15:31:22 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Mon, 28 Jan 2008 15:31:22 -0500 Subject: [GT-seminar] Korkmaz on Wednesday at 5:30? Message-ID: <20080128203122.GE32485@amaryllis.bostoncoop.net> Hello all, Mustafa Korkmaz will be out of town on Friday, so I'd like to have him speak on Wednesday. Are there any objections to a talk at 5:30 on Wednesday? I don't know the title of his talk yet, but he works on mapping class groups; here's his publication page: http://www.math.metu.edu.tr/~korkmaz/research.html Peace, Dylan From dthurston at barnard.edu Mon Jan 28 21:04:01 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Mon, 28 Jan 2008 21:04:01 -0500 Subject: [GT-seminar] Talk this WEDNESDAY, 5:30 PM In-Reply-To: <20080128203122.GE32485@amaryllis.bostoncoop.net> References: <20080128203122.GE32485@amaryllis.bostoncoop.net> Message-ID: <20080129020401.GA20450@amaryllis.bostoncoop.net> This is just to confirm that Mustafa Korkmaz will be talking on Wednesday, January 30, at 5:30 PM, in Math 507, with title and abstract below. There will be no talk on Friday. --------------------- The curve complex on a nonorientable surface. The study of the mapping class group of an orientable surface via its action on the curve complex was initiated by Nikolai Ivanov, who proved that for most orientable surfaces, the natural map from the mapping class group to the automorphism group of the curve complex is an isomorphism. This remarkable result has been extended in various directions since then. In this talk, I am planning to give an outline of the proof of the nonorientable version of this result, which is a joint work with Ferihe Atalan. From dthurston at barnard.edu Wed Jan 30 12:50:38 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Wed, 30 Jan 2008 12:50:38 -0500 Subject: [GT-seminar] Talk today, 5:30 PM In-Reply-To: <20080129020401.GA20450@amaryllis.bostoncoop.net> References: <20080128203122.GE32485@amaryllis.bostoncoop.net> <20080129020401.GA20450@amaryllis.bostoncoop.net> Message-ID: <20080130175038.GA11727@amaryllis.bostoncoop.net> Just to remind you: there is a talk today, at 5:30. On Mon, Jan 28, 2008 at 09:04:01PM -0500, Dylan Thurston wrote: > This is just to confirm that Mustafa Korkmaz will be talking on > Wednesday, January 30, at 5:30 PM, in Math 507, with title and > abstract below. > > There will be no talk on Friday. > > --------------------- > The curve complex on a nonorientable surface. > > The study of the mapping class group of an orientable surface via its > action on the curve complex was initiated by Nikolai Ivanov, who > proved that for most orientable surfaces, the natural map from the > mapping class group to the automorphism group of the curve complex is > an isomorphism. This remarkable result has been extended in various > directions since then. In this talk, I am planning to give an outline > of the proof of the nonorientable version of this result, which is a > joint work with Ferihe Atalan. > From dthurston at barnard.edu Thu Feb 7 15:31:41 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Thu, 7 Feb 2008 15:31:41 -0500 Subject: [GT-seminar] Tomorrow: Hiroshi Matsuda Message-ID: <20080207203141.GB29978@amaryllis.bostoncoop.net> Hello, Tomorrow, Hiroshi Matsuda will be speaking on "A Calculus on Links via Closed Braids". We will meet for lunch a little before noon as usual. Best, Dylan From dthurston at barnard.edu Wed Feb 13 15:01:33 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Wed, 13 Feb 2008 15:01:33 -0500 Subject: [GT-seminar] Talk on Friday Message-ID: <20080213200133.GA28495@amaryllis.bostoncoop.net> Hello, On Friday, Moira Chas is scheduled to talk, title and abstract below. However, she has warned us that she may not be able to talk; if she isn't able to come, Yi Ni will talk instead. Best, Dylan Thurston Minimal intersection of curves on surfaces Moira Chas Consider the set of directed free homotopy classes of curves on a orientable surface and consider the Z-module generated by this set. Goldman proved that there exists a Lie algebra structure on this module, obtained by combining the geometric intersection of curves with the usual loop product. In this talk, we will first give the definition and properties of the Goldman Lie bracket. Secondly, we will show how to characterize simple closed classes curves in terms of the Lie bracket when the surface has non-empty boundary. Finally we will show that if a and b are two free homotopy classes, and either a or b has a simple representative, then the bracket of a and b encodes the minimal intersection number of a and b. From dthurston at barnard.edu Thu Feb 14 17:52:04 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Thu, 14 Feb 2008 17:52:04 -0500 Subject: [GT-seminar] Tomorrow: Yi Ni In-Reply-To: <20080213200133.GA28495@amaryllis.bostoncoop.net> References: <20080213200133.GA28495@amaryllis.bostoncoop.net> Message-ID: <20080214225204.GA21922@amaryllis.bostoncoop.net> Tomorrow we will be hearing from Yi Ni, title and abstract below. Moira Chas will be rescheduled for later in the semester. ------------------------------------------------------------ Dehn surgeries that reduce the Thurston norm of a fibred manifold ------------------------------------------------------------ I will give a brief introduction to Gabai's sutured manifold theory, then show that how one can use it to get restrictions on Dehn surgeries that reduce the Thurston norm of a fibred manifold. ------------------------------------------------------------ From dthurston at barnard.edu Tue Feb 19 17:39:37 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Tue, 19 Feb 2008 17:39:37 -0500 Subject: [GT-seminar] Friday: Christian Zickert Message-ID: <20080219223937.GA21260@amaryllis.bostoncoop.net> Hello, On Friday we will here from Christian Zickert: ------------------------------------------------------------ The volume and Chern-Simons invariant of a hyperbolic manifold. ------------------------------------------------------------ Let M be a hyperbolic manifold. If M is complete and of finite volume, it follows from Mostow rigidity that the volume is a topological invariant of M. The Chern-Simons invariant is defined by integrating a certain 3-form over a section of the orthonormal frame bundle. It can be regarded as the imaginary part of a complex volume with the real part being the usual volume. In this talk we shall discuss methods of computing the complex volume from purely topological descriptions of M. As a result, we obtain a very efficient algorithm for computing the Chern-Simons invariant. ------------------------------------------------------------ From dthurston at barnard.edu Wed Feb 27 21:43:07 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Wed, 27 Feb 2008 21:43:07 -0500 Subject: [GT-seminar] Friday: Olga Plamenevskaya Message-ID: <20080228024307.GA12983@amaryllis.bostoncoop.net> On Friday, Olga Plamenevskaya will be speaking, title and abstract below. She will be hear in time for lunch (at noon) for anyone interested. Title: Transverse knots and their branched covers Abstract: A transverse knot in a contact manifold is a knot that is everywhere transverse to contact planes. A simple invariant called self-linking number distinguishes different transverse knots that are smoothly isotopic. However, there exist different transverse knots of the same smooth type and self linking number (many examples were given by Birman--Menasco, Etnyre--Honda, and later by Ng--Ozsvath--Thurston). In this talk, we discuss studying transverse knots via their cyclic branched covers, which are contact manifolds naturally associated to transverse knots. We show that in many cases branched covers of two transverse knots are contactomorphic if the knots have the same smooth type and self-linking number. (This is joint work with S.Harvey and K.Kawamuro.) From dthurston at barnard.edu Fri Feb 29 17:28:51 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Fri, 29 Feb 2008 17:28:51 -0500 Subject: [GT-seminar] Seminars now in 312 math Message-ID: <20080229222851.GA2896@amaryllis.bostoncoop.net> Hello, The seminar has been growing recently, and is now too large for 507 Math; for the rest of the semester we will be meeting in 312 Math (at least when we meet from 2:15 to 3:15). It will be quite a while before we outgrow that room! Best, Dylan From dthurston at barnard.edu Mon Mar 3 19:52:31 2008 From: dthurston at barnard.edu (Dylan Paul Thurston) Date: Mon, 3 Mar 2008 19:52:31 -0500 Subject: [GT-seminar] Fwd: joint seminar lunch - RSVP Message-ID: <20080304005231.GB26637@whitehail.bostoncoop.net> Hello all, There's a symplectic geometry meeting on Friday in the afternoon; both talks (Dusa McDuff, Ko Honda) are likely to be relatively geometric, so you may enjoy attending. (In the Geometry-Topology seminar, we have Daryl Cooper speaking in the morning.) In any case, let's join them for a catered lunch in the lounge; please RSVP to Robert Lipshitz if you plan to attend. Best, Dylan ----- Forwarded message from Robert Lipshitz ----- To: Floer at googlegroups.com From: Robert Lipshitz Subject: [Floer group, 116] joint seminar lunch - RSVP Reply-To: Floer at googlegroups.com Hi folks, For the joint seminar on Friday (March 7), instead of dinner we'll have lunch. The plan is to have it catered. So, if you plan to attend the seminar lunch, PLEASE RSVP TO ME so we can order lunch for the right number. To make sure I don't overlook your message, please include "seminar lunch" in the subject. Please reply no later than Wednesday evening. Thanks, Robert --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Floer Homology" group. To post to this group, send email to Floer at googlegroups.com To unsubscribe from this group, send email to Floer-unsubscribe at googlegroups.com For more options, visit this group at http://groups.google.com/group/Floer?hl=en -~----------~----~----~----~------~----~------~--~--- ----- End forwarded message ----- From dthurston at barnard.edu Fri Mar 7 07:52:10 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Fri, 7 Mar 2008 07:52:10 -0500 Subject: [GT-seminar] Talk this morning Message-ID: <20080307125210.GA28195@amaryllis.bostoncoop.net> Hello, I mentioned this earlier this week, but just a reminder: Daryl Cooper is speaking today from 10:45 to 11:45, in 507 Math. Best, Dylan ------------------------------------------------------------ Real Projective Structures and Non-standard analysis Daryl Cooper, UCSB ------------------------------------------------------------ We investigate the analog of the Thurston boundary of Teichmuller space in the context of convex real projective structures on closed manifolds. In particular we give a new interpretation of measured laminations in terms of non-standard hyperbolic structures over the hyper-reals. ------------------------------------------------------------ From dthurston at barnard.edu Tue Mar 11 07:56:11 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Tue, 11 Mar 2008 07:56:11 -0400 Subject: [GT-seminar] Friday: Jeremy Van Horn-Morris Message-ID: <20080311115611.GA11619@amaryllis.bostoncoop.net> On Friday we will hear from Jeremy Van Horn-Morris on "Transverse Fibered Links", abstract below. Robert Lipshitz points out that there's a time conflict with Ravi Vakil's talk, which many people may be interested in going to; are there any objections to having Jeremy's talk at 1:00 this Friday? (There's no gauge theory talk that day.) In any case, the talk will be in 312 Mathematics. Best, Dylan Thurston ------------------------------------------------------------ Transverse Fibered Links Jeremy Van Horn-Morris, UT Austin ------------------------------------------------------------ When does a fibered link realize the Eliashberg-Bennequin bound? We'll answer this question and see how it relates to Giroux's work on open book decompositions and what it might say about the classification of transverse links. This is joint work with John Etnyre. ------------------------------------------------------------ From dthurston at barnard.edu Thu Mar 13 16:56:05 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Thu, 13 Mar 2008 16:56:05 -0400 Subject: [GT-seminar] Talk tomorrow at 1PM Message-ID: <20080313205605.GA19771@amaryllis.bostoncoop.net> Hello, This is just to verify that the talk tomorrow by Jeremy Van Horn-Morris is at 1:00, in room 312. Note both the time and place! We will meet for lunch at 11:45. ------------------------------------------------------------ Transverse Fibered Links Jeremy Van Horn-Morris, UQAM ------------------------------------------------------------ When does a fibered link realize the Eliashberg-Bennequin bound? We'll answer this question and see how it relates to Giroux's work on open book decompositions and what it might say about the classification of transverse links. This is joint work with John Etnyre. ------------------------------------------------------------ From dthurston at barnard.edu Fri Mar 14 00:27:54 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Fri, 14 Mar 2008 00:27:54 -0400 Subject: [GT-seminar] [shmuel@math.uchicago.edu: conference next week] Message-ID: <20080314042753.GA28596@amaryllis.bostoncoop.net> Please see below for a conference at the Courant Institute next week. -------------- next part -------------- An embedded message was scrubbed... From: "Shmuel Weinberger" Subject: conference next week Date: Thu, 13 Mar 2008 20:39:04 -0500 Size: 6426 Url: http://www.math.columbia.edu/pipermail/gt-seminar/attachments/20080314/825d2e4b/attachment.mht From dthurston at barnard.edu Wed Mar 26 16:27:00 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Wed, 26 Mar 2008 16:27:00 -0400 Subject: [GT-seminar] Friday: Tim Cochran in room 520 Message-ID: <20080326202659.GA26614@amaryllis.bostoncoop.net> On Friday, Tim Cochran will speak on "Derivatives of Knots and Second-order signatures", in room 520, at 2:15. We will be meeting in 520 for the remainder of the semester. As usual, we will meet for lunch at 11:45. ------------------------------------------------------------ Derivatives of Knots and Second-order signatures Tim Cochran, Rice University ------------------------------------------------------------ We define a notion of partial derivative and antiderivative for knots and use these to define what we call "second-order signatures", generalizing Casson-Gordon invariants, that are defined for any algebraically slice knot. These obstruct a knots being a slice knot. ------------------------------------------------------------ From dthurston at barnard.edu Thu Apr 3 15:20:49 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Thu, 3 Apr 2008 15:20:49 -0400 Subject: [GT-seminar] Tomorrow: Daniel Allcock Message-ID: <20080403192048.GC10850@amaryllis.bostoncoop.net> Tomorrow we will hear from Daniel Allcock on "The metric completion of a locally CAT(0) space". He will be here for lunch; we will meet as usual shortly before noon by the door to the math building. ------------------------------------------------------------ The metric completion of a locally CAT(0) space If X is an noncomplete nonpositively curved space (formally: it is locally CAT(0)) then its completion may easily fail to be. But in some interesting cases the completion is CAT(0), for example Teichmuller space and the many branched covers of Riemannian manifolds over totally geodesic submanifolds. We have found a simple criterion which forces X to be CAT(0). Its key hypothesis is a statement about X *near* the boundary but not at the boundary. ------------------------------------------------------------ From dthurston at barnard.edu Wed Apr 9 09:22:08 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Wed, 9 Apr 2008 09:22:08 -0400 Subject: [GT-seminar] Friday: Menasco, "Climbing a Legendrian mountain range without Stabilization" Message-ID: <20080409132208.GB22879@amaryllis.bostoncoop.net> On Friday at 2:15, William Menasco will speak on "Climbing a Legendrian mountain range without stabilization". I will unfortunately be out of town, but there will be a group eating lunch at The Mill, meeting at 11:50 in front of the math department. ------------------------------------------------------------ Climbing a Legendrian mountain range without stabilization William Menasco, University at Buffalo ------------------------------------------------------------ Joint work with Doug LaFountain. Etnyre and Honda provide a classification of the Legendrian isotopy classes for a (2,3)-cable of a (2,3)-torus knot as it is embedded in 3-sphere with the standard contact structure. To do this, they use the theory of convex surfaces in a tight contact structure. Their classification takes the visual form of a mountain range formed from points having values of (r,tb), where r is the rotation number and tb is the Thurston-Bennequin number. In this talk we show how the two Legendrian classes at (r,tb)=(2,5) can be realized as rectangular braided diagrams, and are seen to be related by an elementary negative flype. We will talk about how we can obtain for this particular cable knot type a Legendrian Markov Theorem without Stabilization and a transverse Markov Theorem without Stabilization. ------------------------------------------------------------ From dthurston at barnard.edu Thu Apr 17 16:21:42 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Thu, 17 Apr 2008 16:21:42 -0400 Subject: [GT-seminar] Tomorrow: Moira Chas Message-ID: <20080417202142.GC12215@amaryllis.bostoncoop.net> Moira Chas will be speaking tomorrow on "Minimal intersection of curves on surfaces" at 2:15. We will be meeting for lunch at 11:45 in front of the math department. See you then! ------------------------------------------------------------ Minimal intersection of curves on surfaces Moira Chas, SUNY Stony Brook ------------------------------------------------------------ Consider the set of directed free homotopy classes of curves on a orientable surface and consider the Z-module generated by this set. Goldman proved that there exists a Lie algebra structure on this module, obtained by combining the geometric intersection of curves with the usual loop product. In this talk, we will first give the definition and properties of the Goldman Lie bracket. Secondly, we will show how to characterize simple closed classes curves in terms of the Lie bracket when the surface has non-empty boundary. Finally we will show that if a and b are two free homotopy classes, and either a or b has a simple representative, then the bracket of a and b encodes the minimal intersection number of a and b. ------------------------------------------------------------ From dthurston at barnard.edu Mon Apr 21 08:29:02 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Mon, 21 Apr 2008 08:29:02 -0400 Subject: [GT-seminar] Question: Marc Culler, May 7 Message-ID: <20080421122902.GA4677@amaryllis.bostoncoop.net> Hello, Marc Culler will be visiting May 5-7, and we've tentatively scheduled a talk for him on Wednesday, May 7, at 1:15 PM, room to be determined. (That's in the middle of the study days.) If I don't here objections within a few days, I'll go ahead and confirm that. Best, Dylan From dthurston at barnard.edu Fri May 2 10:23:08 2008 From: dthurston at barnard.edu (Dylan Thurston) Date: Fri, 2 May 2008 10:23:08 -0400 Subject: [GT-seminar] Today: Hao Zheng Message-ID: <20080502142308.GA5493@amaryllis.bostoncoop.net> Hello, Today Hao Zheng will be speaking on the "Geometric approach to the categorification of braiding relations". I am unfortunately not available, but I hope that there will still be a lunch beforehand. Next week note that there are GT seminar talks on Tuesday and Wednesday (by Stavros Garoufalidis and Marc Culler) and the Ritt lectures by David Gabai on the same two days. ------------------------------------------------------------ Geometric approach to the categorification of braiding relations Hao Zheng, Zhongshan University ------------------------------------------------------------ The construction of a knot homology usually involves a verification of its invariance under various Reidemeister moves and such work is usually carried out by brute force checking. A similar problem arises in the categorification of Hecke algebras for one has to establish homotopy equivalences mimicing the braiding relations involved there. I will show how the task can be facilitated by certain deep results in algebraic geometry (towards the Weil conjectures). ------------------------------------------------------------ From neumann at math.columbia.edu Thu May 1 16:56:50 2008 From: neumann at math.columbia.edu (Walter Neumann) Date: Thu, 1 May 2008 16:56:50 -0400 (EDT) Subject: [GT-seminar] Topology/Geometry seminar and lunch Message-ID: We will meet for lunch as usual at 11:45am in the stairwell. The Geometry/Topology seminar tomorrow (Friday May 2 2:15pm) is Geometric approach to the categorification of braiding relations Hao Zheng, Zhongshan University Abstract: The construction of a knot homology usually involves a verification of its invariance under various Reidemeister moves and such work is usually carried out by brute force checking. A similar problem arises in the categorification of Hecke algebras for one has to establish homotopy equivalences mimicing the braiding relations involved there. I will show how the task can be facilitated by certain deep results in algebraic geometry (towards the Weil conjectures). --walter neumann p.s. There will be two additional seminars next week: Tuesday May 6 11am Stavros Garoufalidis Gevrey asymptotics of the perturbative U(N)-invariants of closed 3-manifolds Abstarct: The universal perturbative invariant of a closed 3-manifold is a graph-valued series, which becomes a formal power series in two variables when we apply the U(N) weight system. We discuss the convergence/divergence properties of this 2-variable power series, of importance to M-theory. Wednesday May 7 2pm Marc Culler Quantitative connections between hyperbolic volume and topological complexity We will discuss joint work with Ian Agol and Peter Shalen in which we obtain lower bounds on the volume of a hyperbolic manifold that exhibits a certain degree of topological complexity. For example, if a hyperbolic manifold has mod 5 first homology of rank greater than 2 then it must have volume at least 1.22. The methods combine displacement estimates based on Patterson-Sullivan conformal densities, topological embedding theorems proved with towers of coverings, and other recent results such as the Marden Tameness Conjecture, proved by Agol and Calegari-Gabai, and the bounds on volume change under drilling due to Agol, Storm, Thurston and Dunfield. ----------- Also, a reminder of the Ritt lectures each of those days at 4pm, Speaker Dave Gabai. http://www.math.columbia.edu/~lrb/RittLecturesS2008.pdf From neumann at math.columbia.edu Tue Sep 2 17:02:50 2008 From: neumann at math.columbia.edu (Walter Neumann) Date: Tue, 2 Sep 2008 17:02:50 -0400 (EDT) Subject: [GT-seminar] Columbia Geometry/Topology Seminar Message-ID: There will be an organizational meeting of the seminar this Friday at 2:30pm, joint with the Gauge Theory Seminar. The tentative meeting time for the Geometry/Topology seminar this semester will be 10:45 am Fridays. Please come with suggestions of speakers. If you can't come but have suggestions, please email me before the meeting. Walter Neumann