Mdtop November 2020

mdtop@mathdept.okstate.edu

2 participants
4 discussions

Today in topology
by Hoffman, Neil 18 Nov '20

18 Nov '20

Hello everyone, Today we are really happy to have Maria Trnkova dropping by (virtually) to give a talk. Maria last spoke here at Redbud, so it's always nice to see a familiar face. Her title and abstract are below: Speaker: Maria Trnkova, UC Davis Date: Nov 18, 2020 Time: 3:45 PM Room: https://meet.google.com/frv-bgow-byi Abstract: A computer program ”SnapPea” and its descendant “SnapPy” compute many invariants of a hyperbolic 3-manifold M. Some of their results can be rigorous but some not. In this talk we will discuss computation of geodesics length and will mention a number of applications when it is crucial to know the precise length spectrum up to some cut off. C.Hodgson and J.Weeks introduced a practical length spectrum algorithm implemented in SnapPea. The algorithm uses a tiling of the universal cover by translations of a Dirichlet domain of M by elements of a fundamental group. In theory the algorithm is rigorous but in practice its output does not guarantee the correct result. It requires to use the exact data for the Dirichlet domain which is available only in some special cases. We show that under some assumptions on M an approximate Dirichlet domain can work equally well as the exact Dirichlet domain. Our result explains the empirical fact that the program ”SnapPea” works surprisingly well despite it not using exact data. ______________________ Neil R. Hoffman Assistant Professor Department of Mathematics 523 Math Science Building Oklahoma State University Stillwater, OK 74078-1058 405-744-7791 http://math.okstate.edu/people/nhoffman

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Topology seminar, Wednesday 3:45pm
by Henry Segerman 10 Nov '20

10 Nov '20

Hi all, This week's speaker is Anna Parlak from the University of Warwick. Title: The taut polynomial and the Alexander polynomial Speaker: Anna Parlak, University of Warwick Time: Wednesday, November 11, 2020 - 3:45pm to 4:45pm Room: Virtual meeting https://meet.google.com/yyt-utuu-imr (note that this is a new link) Abstract: Landry, Minsky and Taylor recently introduced two polynomial invariants of veering triangulations – the taut polynomial and the veering polynomial. I will give the definition of the taut polynomial of a veering triangulation and explain its relationship with the Alexander polynomial of the underlying 3-manifold. I will also discuss how to interpret these results in the case when a veering triangulation carries a fibration over the circle. Thanks, Henry

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Redbud today at 9am
by Hoffman, Neil 08 Nov '20

08 Nov '20

Hello everyone, Just a reminder that the virtual Redbud topology conference is happening today. https://redbud.math.ou.edu/fall-2020/schedule.html https://oklahoma.zoom.us/j/91847314850?pwd=NlhOYXBwWEEzTVBWOWZBckhjUVZFQT09 Meeting ID: 918 4731 4850 Passcode: C7DMd7VL The conference webpage has a gather town link to facilitate the kinds of conversations which could occur if we were in person. Here is the schedule: 9:00 − 9:45 Neil Hoffman Conjectures related to knot complement commensurability<https://redbud.math.ou.edu/fall-2020/schedule.html#Hoffman> 10:00 − 10:45 Nick Castro Isotopy classes of relatively trisected 4-manifolds with boundary<https://redbud.math.ou.edu/fall-2020/schedule.html#Castro> 11:00 − 11:45 Derrick Wigglesworth The Farrell-Jones Conjecture for (most) hyperbolic-by-cyclic groups<https://redbud.math.ou.edu/fall-2020/schedule.html#Wigglesworth> lunch break 1:30 − 2:15 Hitesh Gakhar Künneth formulae in persistent homology<https://redbud.math.ou.edu/fall-2020/schedule.html#Gakhar> 2:30 − 3:15 Wenwen Li Multi-persistent homology of restricted configuration spaces of metric graphs<https://redbud.math.ou.edu/fall-2020/schedule.html#Li> 3:30 − 4:15 Henry Segerman Raytracing and raymarching simulations of non-euclidean geometries<https://redbud.math.ou.edu/fall-2020/schedule.html#Segerman> Best, Neil ______________________ Neil R. Hoffman Assistant Professor Department of Mathematics 523 Math Science Building Oklahoma State University Stillwater, OK 74078-1058 405-744-7791 http://math.okstate.edu/people/nhoffman

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Tomorrow in Topology Seminar
by Hoffman, Neil 03 Nov '20

03 Nov '20

Hello everyone, Tomorrow we have Sam Ballas speaking in topology seminar. His title and abstract are below. Title: Gluing equations in low dimensional geometry Speaker: Sam Ballas, Florida State University Date: Nov 4, 2020 Time: 3:45 PM Central (4:45 PM Eastern) Room: google meet link: https://meet.google.com/frv-bgow-byi Abstract: Geometric structures are ubiquitous objects in low dimensional topology. Roughly speaking, such structures allow one to transport geometry from some nice model space onto a manifold by using charts with appropriate transition functions. Common examples include familiar objects such as Euclidean and hyperbolic structures as well as more exotic structures like affine and Anti-de Sitter structures. Despite their importance, in practice it can be hard to construct examples because the space of all possible charts is very large. In this context, the goal of this talk is to explain the philosophy that gluing equations can be viewed as a growing class of tools designed to “discretize” the problem of constructing geometric structures by using the combinatorial data of a triangulation to shrink the set of possible charts to a more manageable space (i.e. finite dimensional). This philosophy will be motivated by examples including Thurston’s original gluing equations for hyperbolic structures and more recent gluing equations of myself and Casella for projective structures. This work is joint with Alex Casella. ______________________ Neil R. Hoffman Assistant Professor Department of Mathematics 523 Math Science Building Oklahoma State University Stillwater, OK 74078-1058 405-744-7791 http://math.okstate.edu/people/nhoffman

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Mdtop November 2020