## Seminars and Colloquia Schedule

### Taut foliations and Dehn surgery along positive braid knots

Series
Geometry Topology Seminar
Time
Monday, November 30, 2020 - 14:00 for 1 hour (actually 50 minutes)
Location
online
Speaker
Siddhi KrishnaGeorgia Tech

The L-space conjecture has been in the news a lot lately. It predicts a surprising relationship between the algebraic, geometric, and Floer-homological properties of a 3--manifold Y. In particular, it predicts exactly which 3-manifolds admit a taut foliation". In this talk, I'll discuss some of my past and forthcoming work investigating these connections. In particular, I'll discuss a strategy for building taut foliations manifolds obtained by Dehn surgery along knots realized as closures of positive braids". As an application, I will show how taut foliations can be used to obstruct positivity for cable knots. All are welcome; no background in foliation or Floer homology theories will be assumed.

https://bccte.zoom.us/j/91883463721

Meeting ID: 918 8346 3721

### Embedding spanning structures into vertex-ordered graphs

Series
Graph Theory Seminar
Time
Tuesday, December 1, 2020 - 15:45 for 1 hour (actually 50 minutes)
Location
Speaker
Andrew TreglownUniversity of Birmingham

Over recent years there has been much interest in both Turán and Ramsey properties of vertex ordered graphs (i.e., graphs equipped with an ordering of their vertex set). In a recent paper, József Balogh, Lina Li and I initiated the study of embedding spanning structures into vertex ordered graphs. In particular, we introduced a general framework for approaching the problem of determining the minimum degree threshold for forcing a perfect $H$-tiling in an ordered graph. In this talk I will discuss this work, in particular emphasizing how we adapt the regularity and absorbing methods to be applicable in the ordered setting.

### The Akbulut-Kirby conjecture and the slice-ribbon conjecture

Series
Geometry Topology Student Seminar
Time
Wednesday, December 2, 2020 - 14:00 for 1 hour (actually 50 minutes)
Location
online
Speaker
Weizhe Shen

A knot in the 3-sphere is slice if it bounds a smooth disc in the 4-ball. A knot is ribbon if it bounds a self-intersecting disc with only singularities that are closed arcs consisting of intersection points of the disc with itself. Every ribbon knot is a slice knot; the converse is a famous unsolved conjecture of Fox. This talk will show some recent interesting progress around the slice-ribbon conjecture.

### Variations of canonical measures: Riemann surfaces, graphs and hybrid curves

Series
Algebra Seminar
Time
Wednesday, December 2, 2020 - 15:30 for 1 hour (actually 50 minutes)
Location
ONLINE
Speaker
Noema Nicolussi

In the last years, connections between graphs and Riemann surfaces have been
discovered on several different levels. In particular, graphs are closely related
to singular Riemann surfaces and the boundary in the Deligne–Mumford com-
pactification of moduli spaces. Moreover, in both settings there is a notion of a
canonical measure (the Arakelov–Bergman and Zhang measures) which reflects
crucial geometric information.
In this talk, we focus on the following question: what is the limit of the canon-
ical measures along a family of Riemann surfaces? Combining the canonical
measures on Riemann surfaces and metric graphs, we obtain a full description
and a new compactification of the moduli space of Riemann surfaces in terms
of hybrid curves.

Based on joint work with Omid Amini (École polytechnique).

### A Lévy-driven process with matrix scaling exponent

Series
Stochastics Seminar
Time
Thursday, December 3, 2020 - 15:30 for 1 hour (actually 50 minutes)
Location
https://bluejeans.com/504188361
Speaker
B. Cooper BonieceWashington University in St. Louis

In the past several decades, scale invariant stochastic processes have been used in a wide range of applications including internet traffic modeling and hydrology.  However, by comparison to univariate scale invariance, far less attention has been paid to characteristically multivariate models that display aspects of scaling behavior the limit theory arguably suggests is most natural.

In this talk, I will introduce a new scale invariance model called operator fractional Lévy motion and discuss some of its interesting features, as well as some aspects of wavelet-based estimation of its scaling exponents. This is related to joint work with Gustavo Didier (Tulane University), Herwig Wendt (CNRS, IRIT Univ. of Toulouse) and Patrice Abry (CNRS, ENS-Lyon).

### Nielsen realization problems

Series
School of Mathematics Colloquium
Time
Friday, December 4, 2020 - 15:00 for 1 hour (actually 50 minutes)
Location
ONLINE
Speaker
Bena TshishikuBrown University

This is the opening talk of the 2020 Tech Topology Conference http://ttc.gatech.edu

For a manifold M, the (generalized) Nielsen realization problem asks if the surjection Diff(M) → π_0 Diff(M) is split, where Diff(M) is the diffeomorphism group. When M is a surface, this question was posed by Thurston in Kirby's problem list and was addressed by Morita. I will discuss some more recent work on Nielsen realization problems with connections to flat fiber bundles, K3 surfaces, and smooth structures on hyperbolic manifolds.

### Universality of Random Permutations

Series
Combinatorics Seminar
Time
Friday, December 4, 2020 - 15:00 for 1 hour (actually 50 minutes)
Location