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Spring Semester 2020

Date / Time Speaker Title Location
20 February 2020
14:00-15:00 		Sam Shepherd
University of Oxford, UK
Details

Geometry Graduate Colloquium

Title Variants of Leighton's Theorem
Speaker, Affiliation Sam Shepherd, University of Oxford, UK
Date, Time 20 February 2020, 14:00-15:00
Location HG G 19.2
Abstract Leighton's Theorem states that if two finite graphs have a common universal cover then they have a common finite cover. I will explain how this theorem can be generalised to various different kinds of decorated graphs. I will also discuss applications to 3-manifolds and graphs of groups.
Variants of Leighton's Theoremread_more
HG G 19.2
27 February 2020
14:00-15:00 		Bharatram Rangarajan
The Hebrew University of Jerusalem, Israel
Details

Geometry Graduate Colloquium

Title A Cohomological Approach to Ulam Stability of Groups
Speaker, Affiliation Bharatram Rangarajan, The Hebrew University of Jerusalem, Israel
Date, Time 27 February 2020, 14:00-15:00
Location HG G 19.2
Abstract Broadly speaking, group stability is a question about robustness of group homomorphisms, where we ask whether a map that is "almost" a group homomorphism (local condition) is necessarily "close" (globally) to a homomorphism. In this talk, we will explore this question in the context of unitary representations, and see examples (and non-examples) of stable groups. The question of stability in certain settings may be thought of as an extension problem, which leads to connections with vanishing results for group cohomology. If time permits, I shall recast some classical proofs in a cohomological framework and hint at further possibilities.
A Cohomological Approach to Ulam Stability of Groupsread_more
HG G 19.2
5 March 2020
14:00-15:00 		Ivo Slegers
University of Bonn, Germany
Details

Geometry Graduate Colloquium

Title Barycentric maps and the degree theorem
Speaker, Affiliation Ivo Slegers, University of Bonn, Germany
Date, Time 5 March 2020, 14:00-15:00
Location HG G 19.2
Abstract In 1986 Douady and Earle introduced a method for extending homeomorphisms of the circle to homeomorphisms of the unit disk. This idea was later generalized by Besson, Courtois and Gallot to the case of rank one symmetric spaces. These extension maps, also called barycentric maps, allow you to find in each homotopy class of maps between closed locally symmetric spaces a representative with bounded Jacobian. These barycentric maps have recently been applied to obtain several interesting results. One of which is the degree theorem by Connel and Farb which states that the degree of a map between closed locally symmetric spaces can be bounded only in terms of the volume and curvature of these spaces. In this talk I will discuss the degree theorem, some of its corollaries and give an overview of the proof using barycentric maps.
Barycentric maps and the degree theoremread_more (CANCELLED)
HG G 19.2
5 March 2020
14:00-15:00 		Yannick Krifka
ETH Zurich, Switzerland
Details

Geometry Graduate Colloquium

Title On the IRS compactification of moduli space
Speaker, Affiliation Yannick Krifka, ETH Zurich, Switzerland
Date, Time 5 March 2020, 14:00-15:00
Location HG G 19.2
Abstract In this talk we will learn what an invariant random subgroup is and how they show up in the study of lattices in Lie groups. From there we will see how one can embed the moduli space of finite area hyperbolic surfaces into the space of invariant random subgroups of PSL(2,R). By taking the closure of the image one obtains a compactification of moduli space, the so called IRS compactification. We will see how to make sense of the IRS compactification geometrically using nodal surfaces.
On the IRS compactification of moduli spaceread_more
HG G 19.2
12 March 2020
14:00-15:00 		Mareike Pfeil
Ruprecht-Karls-Universität Heidelberg, Germany
Details

Geometry Graduate Colloquium

Title Deformations of Anosov representations: From earthquake maps to cataclysms
Speaker, Affiliation Mareike Pfeil, Ruprecht-Karls-Universität Heidelberg, Germany
Date, Time 12 March 2020, 14:00-15:00
Location HG G 19.2
Abstract TBA
Deformations of Anosov representations: From earthquake maps to cataclysmsread_more (CANCELLED)
HG G 19.2
19 March 2020
14:00-15:00 		Dr. Patricia Dietzsch
ETH Zurich, Switzerland
Details

Geometry Graduate Colloquium

Title Lagrangian Hofer Metric
Speaker, Affiliation Dr. Patricia Dietzsch, ETH Zurich, Switzerland
Date, Time 19 March 2020, 14:00-15:00
Location HG G 19.2
Abstract I'd like to introduce the Lagrangian Hofer metric, focusing on concrete examples like equators in the 2-disc, the cylinder and the 2-sphere. Then we can discuss the question of (un)boundedness of the Lagrangian Hofer metric in these three examples: M. Khanevsky proved in 2009 that it is unbounded for the disc and the cylinder, but the question is still open for the sphere.
Lagrangian Hofer Metricread_more (CANCELLED)
HG G 19.2
26 March 2020
14:00-15:00 		Harry Petyt
University of Bristol, UK
Details

Geometry Graduate Colloquium

Title Mapping class groups in geometric group theory
Speaker, Affiliation Harry Petyt, University of Bristol, UK
Date, Time 26 March 2020, 14:00-15:00
Location HG G 19.2
Abstract TBA
Mapping class groups in geometric group theoryread_more (CANCELLED)
HG G 19.2
2 April 2020
14:00-15:00 		Dr. Konstantin Golubev
ETH Zurich, Switzerland
Details

Geometry Graduate Colloquium

Title High Dimensional Expanders
Speaker, Affiliation Dr. Konstantin Golubev, ETH Zurich, Switzerland
Date, Time 2 April 2020, 14:00-15:00
Location HG G 19.2
Abstract TBA
High Dimensional Expandersread_more (CANCELLED)
HG G 19.2
* 9 April 2020
13:00-14:00 		Mareike Pfeil
Heidelberg University, Germany
Details

Geometry Graduate Colloquium

Title Deforming Anosov representations: From earthquake maps to cataclysms
Speaker, Affiliation Mareike Pfeil, Heidelberg University, Germany
Date, Time 9 April 2020, 13:00-14:00
Location Zoom
Abstract In the 1980's, Thurston introduced earthquake maps as specific deformations of hyperbolic structures. His "Earthquake theorem" states that for any two points in Teichmüller space, there exists an earthquake map sending one to the other. I will explain what these words actually mean, and then introduce cataclysms, which can be seen as a generalization of earthquake maps in the context of Anosov representations. Any knowledge on Anosov representations that is necessary to understand the construction of cataclysms will also be given during the talk. Invitation (The zoom meeting will be available from 12:30, the talk will start at 13:00): Topic: GGC Time: Apr 9, 2020 12:30 PM Zurich Join Zoom Meeting https://ethz.zoom.us/j/152792432?pwd=VXJRZGhVeitZQURIWnJrbUpFN2pCQT09 Meeting ID: 152 792 432 Password: 093358 Join by Skype for Business https://ethz.zoom.us/skype/152792432
Deforming Anosov representations: From earthquake maps to cataclysmsread_more
Zoom
9 April 2020
14:00-15:00 		Livio Ferretti
University of Bern, Switzerland
Details

Geometry Graduate Colloquium

Title Topology and combinatorics in knot theory: the Levine-Tristram signature
Speaker, Affiliation Livio Ferretti, University of Bern, Switzerland
Date, Time 9 April 2020, 14:00-15:00
Location HG G 19.2
Abstract TBA
Topology and combinatorics in knot theory: the Levine-Tristram signatureread_more (CANCELLED)
HG G 19.2
* 16 April 2020
13:00-14:00 		Ivo Slegers
University of Bonn, Germany
Details

Geometry Graduate Colloquium

Title Barycentric maps and the degree theorem
Speaker, Affiliation Ivo Slegers, University of Bonn, Germany
Date, Time 16 April 2020, 13:00-14:00
Location Zoom
Abstract In 1986 Douady and Earle introduced a method for extending homeomorphisms of the circle to homeomorphisms of the unit disk. This idea was later generalized by Besson, Courtois and Gallot to the case of rank one symmetric spaces. These extension maps, also called barycentric maps, allow you to find in each homotopy class of maps between closed locally symmetric spaces a representative with bounded Jacobian. These barycentric maps have recently been applied to obtain several interesting results. One of which is the degree theorem by Connel and Farb which states that the degree of a map between closed locally symmetric spaces can be bounded only in terms of the volume and curvature of these spaces. In this talk I will discuss the degree theorem, some of its corollaries and give an overview of the proof using barycentric maps. Topic: Ivo Slegers (Bonn) -- GGC Time: Apr 16, 2020 12:30 PM Zurich Join Zoom Meeting https://ethz.zoom.us/j/303405482?pwd=c2dDUTRqU3FtcWlLWDBCM0xIZjlJZz09 Meeting ID: 303 405 482 Password: 077437 Join by Skype for Business https://ethz.zoom.us/skype/303405482
Barycentric maps and the degree theoremread_more
Zoom
23 April 2020
14:00-15:00 		Laura Grave de Peralta
University of Neuchâtel, Switzerland
Details

Geometry Graduate Colloquium

Title Combinatorial maps
Speaker, Affiliation Laura Grave de Peralta, University of Neuchâtel, Switzerland
Date, Time 23 April 2020, 14:00-15:00
Location HG G 19.2
Abstract TBA
Combinatorial mapsread_more (CANCELLED)
HG G 19.2
* 30 April 2020
13:00-14:00 		Harry Petyt
University of Bristol, UK
Details

Geometry Graduate Colloquium

Title Mapping class groups in geometric group theory
Speaker, Affiliation Harry Petyt, University of Bristol, UK
Date, Time 30 April 2020, 13:00-14:00
Location Zoom
Abstract The mapping class group of a surface is a group of homeomorphisms of that surface, and these groups have been extensively studied, providing an interface between several branches of mathematics. The aim of this talk is to describe some of the ways that mapping class groups have influenced the area of geometric group theory in recent years. Time: Apr 30, 2020 12:30 PM Zurich Join Zoom Meeting https://ethz.zoom.us/j/98079289955?pwd=c2FWcUNXek9zOElVQVNXZHY0RTRzQT09 Meeting ID: 980 7928 9955 Password: 062335 Join by Skype for Business https://ethz.zoom.us/skype/98079289955
Mapping class groups in geometric group theoryread_more
Zoom
* 7 May 2020
13:00-14:00 		Alexandra Edletzberger
University of Vienna, Austria
Details

Geometry Graduate Colloquium

Title Residually Finite Groups
Speaker, Affiliation Alexandra Edletzberger, University of Vienna, Austria
Date, Time 7 May 2020, 13:00-14:00
Location Zoom
Abstract Residual finiteness is an ambivalent property of groups. The talk aims to illustrate why: One the one hand, resiudal finiteness is a powerful and desirable property, as for example every finitely presented, residually finite group has solvable word problem. But unfortunately, very often it is not an easy task to determine whether a given group is residually finite or not. We will see where we have methods at hand to tackle this question: 1) For free groups and Baumslag Solitar groups. 2) A classical result of Malcev affirms that finitely generated. linear groups are residually finite 3) With the closely related Hopf-property, non-residual finiteness of certain groups can be established. Join Zoom Meeting https://ethz.zoom.us/j/99090148553?pwd=RVVIbmdKTjhweVNtUkIwMml5VDFNQT09 Meeting ID: 990 9014 8553 Password: 022892 Join by Skype for Business https://ethz.zoom.us/skype/99090148553
Residually Finite Groupsread_more
Zoom
* 14 May 2020
13:00-14:00 		Laura Grave de Peralta
University of Neuchâtel, Switzerland
Details

Geometry Graduate Colloquium

Title Combinatorial Maps
Speaker, Affiliation Laura Grave de Peralta, University of Neuchâtel, Switzerland
Date, Time 14 May 2020, 13:00-14:00
Location Zoom
Abstract Given a graph embedded in the plane, one can represent it by just two permutations. Such a representation is usually called a combinatorial map. This definition allows for many generalizations : hypermaps, constellations, n-maps,... Combinatorial maps have proven to be simple but efficient ways of encoding information. After giving the definitions and some examples, I will try and give a few examples of applications of combinatorial maps to some, apparently unrelated, topics. I will try and mention topics from group theory, knot theory and physics. ---------------- Time: May 14, 2020 12:30 PM Zurich Join Zoom Meeting https://ethz.zoom.us/j/97919073412?pwd=ejNWNmVtSlptOW1neWhmL2NhN1hGZz09 Meeting ID: 979 1907 3412 Password: 299017
Combinatorial Mapsread_more
Zoom
* 28 May 2020
13:00-14:00 		Livio Ferretti
University of Bern, Switzerland
Details

Geometry Graduate Colloquium

Title Topology and combinatorics in knot theory: the Levine-Tristram signature
Speaker, Affiliation Livio Ferretti, University of Bern, Switzerland
Date, Time 28 May 2020, 13:00-14:00
Location Zoom
Abstract Knots are very interesting mathematical objects, which have a special position at the intersection of several mathematical domains. They are of course fundamental in low-dimensional topology, but can also be considered as combinatorial objects, and in recent years deep relations with algebra and quantum physics have begun to emerge. In this talk I will introduce some basic notions of Knot Theory and explain how different techniques can be used to obtain interesting invariants. The main example all along the talk will be the Levine-Tristram signature, a classical topological invariant for which a combinatorial interpretation has been recently conjectured. ------------------------ Join Zoom Meeting https://ethz.zoom.us/j/98775765168?pwd=OHhseVh5a3RyejlTV2JOOE5jNE1odz09 Meeting ID: 987 7576 5168 Password: 050556
Topology and combinatorics in knot theory: the Levine-Tristram signatureread_more
Zoom

Notes: events marked with an asterisk (*) indicate that the time and/or location are different from the usual time and/or location.

Organisers: Luca De Rosa, Xenia Lorena Flamm, Yannick Krifka, Davide Spriano

Archive: AS 24 SS 24 AS 23 SS 23 AS 22 SS 22 AS 21 SS 21 AS 20 SS 20 AS 19 AS 18 SS 18

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