Difference between revisions of "Geometry and Topology Seminar"

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The [[Geometry and Topology]] seminar meets in room 901 of Van Vleck Hall on Fridays from 1:20pm - 2:10pm.
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The [[Geometry and Topology]] seminar meets in room '''901 of Van Vleck Hall''' on '''Fridays''' from '''1:20pm - 2:10pm'''.
<br>
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<br>  
For more information, contact [http://www.math.wisc.edu/~rkent Richard Kent].
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For more information, contact Shaosai Huang.
  
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[[Image:Hawk.jpg|thumb|300px]]
  
== Fall 2012==
 
  
  
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== Fall 2019 ==
  
 
{| cellpadding="8"
 
{| cellpadding="8"
Line 14: Line 16:
 
!align="left" | host(s)
 
!align="left" | host(s)
 
|-
 
|-
|September 21
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|Oct. 4
| [http://www.math.wisc.edu/~josizemore/ Owen Sizemore] (Wisconsin)
+
|Ruobing Zhang (Stony Brook University)
| [[#Owen Sizemore (Wisconsin) |
+
| TBA
''Operator Algebra Techniques in Measureable Group Theory'']]
+
|(Chen)
| local
 
|-
 
|September 28
 
|[https://engineering.purdue.edu/~mboutin/ Mireille Boutin] (Purdue)
 
|[[#Mireille Boutin (Purdue) |
 
''The Pascal Triangle of a discrete Image: <br>
 
definition, properties, and application to object segmentation'']]
 
|[http://www.math.wisc.edu/~maribeff/ Mari Beffa]
 
|-
 
|October 5
 
| [http://www.math.msu.edu/~schmidt/ Ben Schmidt] (Michigan State)
 
| [[#Ben Schmidt (Michigan State)|
 
''Three manifolds of constant vector curvature'']]
 
|[http://www.math.wisc.edu/~dymarz/ Dymarz]
 
 
|-
 
|-
|October 12
 
| [https://www2.bc.edu/ian-p-biringer/ Ian Biringer] (Boston College)
 
| [[#Ian Biringer (Boston College)|
 
''Growth of Betti numbers and a probabilistic take on Gromov Hausdorff convergence'']]
 
|[http://www.math.wisc.edu/~dymarz/ Dymarz]
 
 
|-
 
|-
|October 19
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|Oct. 25
| Peng Gao (Simons Center for Geometry and Physics)
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|Emily Stark (Utah)
| [[#Peng Gao (Simons Center for Geometry and Physics)|
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| TBA
''string theory partition functions and geodesic spectrum'']]
+
|(Dymarz)
|[http://www.math.wisc.edu/~bwang/ Wang]
 
 
|-
 
|-
|October 26
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|Nov. 7
| [http://www.math.wisc.edu/~nelson/ Jo Nelson] (Wisconsin)
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|Max Forester (University of Oklahoma)
| [[#Jo Nelson (Wisconsin) |
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| TBA
''Cylindrical contact homology as a well-defined homology theory? Part I'']]
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|(Dymarz)
| local
 
 
|-
 
|-
|November 2
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|Nov. 22
| [http://www.bowdoin.edu/~jtaback/ Jennifer Taback] (Bowdoin)
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|Yu Li (Stony Brook University)
| [[#Jennifer Taback (Bowdoin)|
+
|On the structure of Ricci shrinkers
''TBA'']]
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|(Huang)
|[http://www.math.wisc.edu/~dymarz/ Dymarz]
 
|-
 
|November 9
 
| [http://math.uchicago.edu/~wilsonj/ Jenny Wilson] (Chicago)
 
| [[#Jenny Wilson (Chicago)|
 
''TBA'']]
 
| [http://www.math.wisc.edu/~ellenber/ Ellenberg]
 
|-
 
|November 16
 
|[http://www.math.uic.edu/people/profile?id=GasJ574 Jonah Gaster] (UIC)
 
|[[#Jonah Gaster (UIC)|
 
''TBA'']]
 
|[http://www.math.wisc.edu/~rkent/ Kent]
 
|-
 
| Thanksgiving Recess
 
|
 
|
 
|
 
|-
 
|November 30
 
| [http://www.its.caltech.edu/~shinpei/ Shinpei Baba] (Caltech)
 
|[[#Shinpei Baba (Caltech)|
 
''TBA'']]
 
|[http://www.math.wisc.edu/~rkent/ Kent]
 
|-
 
|December 7
 
| [http://math.uchicago.edu/~mann/ Kathryn Mann] (Chicago)
 
|[[#Kathryn Mann (Chicago)|
 
''TBA'']]
 
|[http://www.math.wisc.edu/~rkent/ Kent]
 
|-
 
|December 14
 
|
 
|
 
|
 
 
|-
 
|-
 
|}
 
|}
  
== Fall Abstracts ==
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==Fall Abstracts==
 
 
===Owen Sizemore (Wisconsin)===
 
''Operator Algebra Techniques in Measureable Group Theory''
 
 
 
Measurable group theory is the study of groups via their actions on measure spaces. While the classification for amenable groups was essentially complete by the early 1980's,  progress for nonamenable groups has been slow to emerge. The last 15 years has seen a surge in the classification of ergodic actions of nonamenable groups, with methods coming from diverse areas. We will survey these new results, as well as, give an introduction to the operator algebra techniques that have been used.
 
 
 
===Mireille Boutin (Purdue)===
 
''The Pascal Triangle of a discrete Image: definition, properties, and application to object segmentation''
 
 
 
We define the Pascal Triangle of a discrete (gray scale) image as a pyramidal ar-
 
rangement of complex-valued moments and we explore its geometric significance. In
 
particular, we show that the entries of row k of this triangle correspond to the Fourier
 
series coefficients of the moment of order k of the Radon transform of the image. Group
 
actions on the plane can be naturally prolonged onto the entries of the Pascal Triangle. We study the induced action of some common group actions, such as translation,
 
rotations, and reflections, and we propose simple tests for equivalence and self-
 
equivalence for these group actions. The motivating application of this work is the
 
problem of recognizing ”shapes” on images, for example characters, digits or simple
 
graphics. Application to the MERGE project, in which we developed a fast method for segmenting hazardous material signs on a cellular phone, will be also discussed.
 
 
 
This is joint work with my graduate students Shanshan Huang and Andrew Haddad.
 
 
 
===Ben Schmidt (Michigan State)===
 
''Three manifolds of constant vector curvature.''
 
 
 
A Riemannian manifold M is said to have extremal curvature K if all sectional curvatures are bounded above by K or if all sectional curvatures are bounded below by K.  A manifold with extremal curvature K has constant vector curvature K if every tangent vector to M belongs to a tangent plane of curvature K.  For surfaces, having constant vector curvature is equivalent to having constant curvature.  In dimension three, the eight Thurston geometries all have constant vector curvature.  In this talk, I will discuss the classification of closed three manifolds with constant vector curvature.  Based on joint work with Jon Wolfson.
 
  
===Ian Biringer (Boston College)===
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===Ruobing Zhang===
''Growth of Betti numbers and a probabilistic take on Gromov Hausdorff convergence''
 
  
We will describe an asymptotic relationship between the volume and the Betti numbers of certain locally symmetric spaces. The proof uses an exciting new tool: a synthesis of Gromov-Hausdorff convergence of Riemannian manifolds and Benjamini-Schramm convergence from graph theory.
+
"TBA"
  
===Peng Gao (Simons Center for Geometry and Physics)===
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===Emily Stark===
''string theory partition functions and geodesic spectrum''
 
  
String theory partition functions often have nice modular properties, which is well understood within the context of representation theory of (supersymmetric extensions) of Virasoro algebra.
+
"TBA"
However, many questions of physical importance are preferrably addressed when string theory is formulated in terms of non-linear sigma model on a Riemann surface with a Riemannian manifold as target space. Traditionally, physicists have studied such sigma models within the realm of perturbation theory, overlooking a large class of very natural critical points of the path integral, namely, closed geodesics on the target space Riemannian manifold. We propose how to take into account the effect of these critical points on the path integral, and initiate its study on Ricci flat targe spaces, such as the K3 surface.
 
  
 +
===Max Forester===
  
 +
“TBA”
  
===Jo Nelson (Wisconsin)===
+
===Yu Li===
''Cylindrical contact homology as a well-defined homology theory? Part I''
+
We develop a structure theory for non-collapsed Ricci shrinkers without any curvature condition. As an application, we show that any Ricci shrinker whose second eigenvalue of the curvature operator is positive must be a quotient of sphere.
 
 
In this talk I will define all the concepts in the title, starting with what a contact manifold is.  I will also  explain how the heuristic arguments sketched in the literature since 1999 fail to define a homology theory and provide a foundation for a well-defined cylindrical contact homology, while still providing an invariant of the contact structure.  A later talk will provide us with a large class of examples under which one can compute a well-defined version of cylindrical contact homology via a new approach the speaker developed for her thesis that is distinct and completely independent of previous specialized attempts.
 
 
 
===Jennifer Taback (Bowdoin)===
 
''TBA''
 
 
 
===Jenny Wilson (Chicago)===
 
''TBA''
 
 
 
===Jonah Gaster (UIC)===
 
''TBA''
 
 
 
===Shinpei Baba (Caltech)===
 
''TBA''
 
 
 
===Kathryn Mann (Chicago)===
 
''TBA''
 
 
 
== Spring 2013 ==
 
 
 
 
 
{| cellpadding="8"
 
!align="left" | date
 
!align="left" | speaker
 
!align="left" | title
 
!align="left" | host(s)
 
|-
 
|January 25
 
|
 
|
 
|
 
|-
 
|February 1
 
|
 
|
 
|
 
|-
 
|February 8
 
|
 
|
 
|
 
|-
 
|February 15
 
|
 
|
 
|
 
|-
 
|February 22
 
|
 
|
 
|
 
|-
 
|March 1
 
|
 
|
 
|
 
|-
 
|March 8
 
|
 
|
 
|
 
|-
 
|March 15
 
|
 
|
 
|
 
|-
 
|March 22
 
| [http://www-personal.umich.edu/~mishlie/ Michelle Lee] (Michigan)
 
|[[#Michelle Lee (Michigan)|
 
''TBA'']]
 
|[http://www.math.wisc.edu/~rkent/ Kent]
 
|-
 
|Spring Break
 
|
 
|
 
|
 
|-
 
|April 5
 
|
 
|
 
|
 
|-
 
|April 12
 
|
 
|
 
|
 
|-
 
|April 19
 
|
 
|
 
|
 
|-
 
|April 26
 
|
 
|
 
|
 
|-
 
|May 3
 
|
 
|
 
|
 
|-
 
|May 10
 
|
 
|
 
|
 
|-
 
|}
 
 
 
== Spring Abstracts ==
 
 
 
===Michelle Lee (Michigan)===
 
''TBA''
 
  
 
== Archive of past Geometry seminars ==
 
== Archive of past Geometry seminars ==
 
+
2018-2019  [[Geometry_and_Topology_Seminar_2018-2019]]
 +
<br><br>
 +
2017-2018 [[Geometry_and_Topology_Seminar_2017-2018]]
 +
<br><br>
 +
2016-2017  [[Geometry_and_Topology_Seminar_2016-2017]]
 +
<br><br>
 +
2015-2016: [[Geometry_and_Topology_Seminar_2015-2016]]
 +
<br><br>
 +
2014-2015: [[Geometry_and_Topology_Seminar_2014-2015]]
 +
<br><br>
 +
2013-2014: [[Geometry_and_Topology_Seminar_2013-2014]]
 +
<br><br>
 +
2012-2013: [[Geometry_and_Topology_Seminar_2012-2013]]
 +
<br><br>
 
2011-2012: [[Geometry_and_Topology_Seminar_2011-2012]]
 
2011-2012: [[Geometry_and_Topology_Seminar_2011-2012]]
 
<br><br>
 
<br><br>
 
2010: [[Fall-2010-Geometry-Topology]]
 
2010: [[Fall-2010-Geometry-Topology]]

Latest revision as of 13:10, 16 September 2019

The Geometry and Topology seminar meets in room 901 of Van Vleck Hall on Fridays from 1:20pm - 2:10pm.
For more information, contact Shaosai Huang.

Hawk.jpg



Fall 2019

date speaker title host(s)
Oct. 4 Ruobing Zhang (Stony Brook University) TBA (Chen)
Oct. 25 Emily Stark (Utah) TBA (Dymarz)
Nov. 7 Max Forester (University of Oklahoma) TBA (Dymarz)
Nov. 22 Yu Li (Stony Brook University) On the structure of Ricci shrinkers (Huang)

Fall Abstracts

Ruobing Zhang

"TBA"

Emily Stark

"TBA"

Max Forester

“TBA”

Yu Li

We develop a structure theory for non-collapsed Ricci shrinkers without any curvature condition. As an application, we show that any Ricci shrinker whose second eigenvalue of the curvature operator is positive must be a quotient of sphere.

Archive of past Geometry seminars

2018-2019 Geometry_and_Topology_Seminar_2018-2019

2017-2018 Geometry_and_Topology_Seminar_2017-2018

2016-2017 Geometry_and_Topology_Seminar_2016-2017

2015-2016: Geometry_and_Topology_Seminar_2015-2016

2014-2015: Geometry_and_Topology_Seminar_2014-2015

2013-2014: Geometry_and_Topology_Seminar_2013-2014

2012-2013: Geometry_and_Topology_Seminar_2012-2013

2011-2012: Geometry_and_Topology_Seminar_2011-2012

2010: Fall-2010-Geometry-Topology