# BCN seminars

## 2016 - 2017

- Seminar: "The degree of commutativity/nilpotency of an infinite group" (Enric Ventura, UPC) Mar 07, 2017 from 03:15 PM to 04:15 PM — FME, room S03,
- Seminar: "The irrational-slope Thompson groups" (Pep Burillo, UPC) Feb 28, 2017 from 03:00 PM to 04:00 PM — FME (Barcelona),

## 2015 - 2016

- Seminar: "Virtual Limit Groups" (Daniel Wise, McGill University) Jul 29, 2016 from 10:00 AM to 11:00 AM
- Seminar: "A graph coloring problem and its algebraic and topological consequences" (Daniel Wise, McGill University) Jul 28, 2016 from 10:00 AM to 11:00 AM — FME-UPC,
- Seminar: "Labelled graphs and intersection of subgroups in fundamental groups of graphs of groups" (Alexander Zakharov, Universitat del Pais Basc) May 24, 2016 from 01:00 PM to 02:00 PM — FME-UPC room 101,
- Seminar: "Systems of equations in free groups IV" (Albert Garreta, Stevens Institute of Technology) May 03, 2016 from 03:00 PM to 04:00 PM — FME-UPC room 101,
- Seminar: "Systems of equations in free groups III" (Albert Garreta, Stevens Institute of Technology) Apr 19, 2016 from 10:00 AM to 11:00 AM — FME (UPC),
- Seminar: "Systems of equations in free groups II" (Albert Garreta, Stevens Institute of Technology) Apr 12, 2016 from 03:00 PM to 04:00 PM — FME-UPC room 101,
- Seminar: "Systems of equations in free groups I" (Albert Garreta, Stevens Institute of Technology) Apr 05, 2016 from 03:00 PM to 04:00 PM — FME-UPC room 101,
- Seminar: "Normal subgroups of groups of piecewise projective homeomorphisms of R" (Pep Burillo, UPC) Mar 08, 2016 from 03:00 PM to 04:00 PM — FME-UPC room 101,
- Seminar: "Automata Equations" (Albert Garreta, Stevens Institute) Mar 01, 2016 from 01:45 PM to 02:45 PM — FME-UPC room 101,
- Seminar: "Intersecting subgroups in fundamental groups of graphs of groups" (Alexander Zakharov, Universitat del Pais Basc) Feb 01, 2016 from 12:00 PM to 01:00 PM — FME-UPC room 101,
- Seminar: "On the dimension of classifying spaces for families of virtually free abelian subgroups” (Víctor González, University of London) Sep 07, 2015 from 05:00 PM to 06:00 PM
- Seminar: "Quasi-automorphisms of the infinite rooted 2-coloured binary tree” (Brita Nucinkis, University of London) Sep 07, 2015 from 04:00 PM to 05:00 PM — FME (room next to Sala de Professors),

## 2014 - 2015

- Seminar: "Systems of equations in nilpotent groups" (Albert Garreta, Stevens Institute) Jul 14, 2015 from 05:30 PM to 06:30 PM — FME (room next to Sala de Professors),
- Seminar: "Generalizations of Grigorchuk's first group" (Pep Burillo, UPC) Jul 14, 2015 from 04:30 PM to 05:30 PM — FME (room next to Sala de Professors),
- Seminar: "Grigorchuk's first group" (Aitor Perez, UPC) Jun 29, 2015 from 11:00 AM to 12:00 PM — FME (room next to Sala de Professors),
- Seminar: "Conjugacy Problem in Polycyclic Groups: Algorithms and Complexity" (D. Kahrobaei, CUNY) May 26, 2015 12:00 PM
- Seminar: "An introduction to BNS-invariant (VI)" (E. Ventura, UPC) May 19, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "An introduction to BNS-invariant (V)" (E. Ventura, UPC) May 12, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "An introduction to BNS-invariant (IV)" (E. Ventura, UPC) May 05, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "An introduction to BNS-invariant (III)" (E. Ventura, UPC) Apr 28, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "An introduction to BNS-invariant (II)" (E. Ventura, UPC) Apr 21, 2015 from 11:00 AM to 12:00 PM — FME, Barcelona,
- Seminar: "An introduction to BNS-invariant (I)" (E. Ventura, UPC) Apr 14, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "Non-amenability of product replacement graphs" (E. Ventura, UPC) Mar 24, 2015 from 01:00 PM to 02:00 PM — FME, Barcelona,
- Seminar: "Is every distortion function equivalent to a superadditive function?" (E. López, UPC) Mar 17, 2015 from 01:00 PM to 02:00 PM
- Seminar: "The Lodha-Moore group (VI)" (Pep Burillo, UPC) Feb 24, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "Fixed subgroups" (Jianchun Wu, Soochow University and UPC) Feb 17, 2015 from 01:20 PM to 02:20 PM — CRM, room A1,
- Seminar: "The Lodha-Moore group (V)" (Pep Burillo, UPC) Feb 10, 2015 from 01:00 PM to 02:00 PM
- Seminar: "The Lodha-Moore group (IV)" (Pep Burillo, UPC) Feb 03, 2015 from 05:00 PM to 06:00 PM
- Seminar: "The Lodha-Moore group (III)" (Pep Burillo, UPC) Jan 27, 2015 from 01:00 PM to 02:00 PM — CRM, room A1,
- Seminar: "The Lodha-Moore group (II)" (Pep Burillo, UPC) Jan 20, 2015 from 12:30 PM to 01:30 PM
- Seminar: "The Lodha-Moore group (I)" (Pep Burillo, UPC) Jan 09, 2015 from 01:00 PM to 02:00 PM
- Seminar: "Limit groups as limits of free groups (VIII)" (E. Ventura, UPC) Dec 19, 2014 from 01:00 PM to 02:00 PM — CRM, room C1/028,
- Seminar: "Limit groups as limits of free groups (VII)" (E. Ventura, UPC) Dec 12, 2014 from 01:00 PM to 02:00 PM
- Seminar: "Limit groups as limits of free groups (VI)" (E. Ventura, UPC) Dec 05, 2014 from 01:00 PM to 02:00 PM — CRM, room C1/028,
- Seminar: "Calculating the cohomology of Bianchi groups" (E. Berkove, Lafayette College) Nov 28, 2014 from 03:00 PM to 04:00 PM — CRM Bellaterra, room C1/028,
- Seminar: "The rank of subgroups of free groups under generator transformations" (A. Rosenmann, Austrian Institute of Technology) Nov 25, 2014 from 01:00 PM to 02:00 PM — CRM Bellaterra, room C1/028,
- Seminar: "Limit groups as limits of free groups (V)" (E. Ventura, UPC) Nov 21, 2014 from 01:00 PM to 02:00 PM
- Seminar: "Limit groups as limits of free groups (IV)" (E. Ventura, UPC) Nov 14, 2014 from 01:00 PM to 02:00 PM — CRM Bellaterra, room C1/028,
- Seminar: "Limit groups as limits of free groups (III)" (W. Pitsch, UAB). Oct 31, 2014 from 01:00 PM to 02:00 PM — CRM, room C1/028,
- Seminar: "Limit groups as limits of free groups (II)" (E. Ventura, UPC) Oct 17, 2014 from 01:00 PM to 02:00 PM — CRM, room C1/028,
- Seminar: "Limit groups as limits of free groups (I)" (E. Ventura, UPC) Oct 10, 2014 from 01:00 PM to 02:00 PM — CRM, room C1/028,

## 2013 - 2014

- Seminar: "Commuting degree" (Enric Ventura, UPC) May 22, 2014 from 04:00 PM to 05:00 PM — CRM, room C1/028,
- Seminar: "Fusion systems of finite simple groups of Lie type" (Carles Broto, UAB) May 08, 2014 from 04:00 PM to 05:00 PM — CRM-Bellaterra,
- Seminar: "About some strange actions of the free group recently found by A. Ol'shanskii (II)" (Enric Ventura, UPC) Apr 24, 2014 from 04:00 PM to 05:00 PM — CRM-Bellaterra,
- Seminar: "About some strange actions of the free group recently found by A. Ol'shanskii" (Enric Ventura, UPC) Apr 10, 2014 from 04:00 PM to 05:00 PM — CRM-Bellaterra,
- Seminar: "An estimation of the metric for the wreath product of two groups" (Eric López, UPC) Mar 27, 2014 from 04:00 PM to 05:00 PM — CRM-Barcelona,
- Seminar: "Inverting automorphisms of the free group" (E. Ventura, UPC) Mar 06, 2014 from 04:00 PM to 05:00 PM — CRM-Bellaterra,
- Seminar: "Algebraic Constructions for Wireless Channels and Geodesic Flow on Lie Groups" (Dave Karpuk, Aalto University) Feb 19, 2014 from 11:00 AM to 12:00 PM — CRM-Barcelona,
- Seminar: "Haagerup property for graph products" (Yago Antolín, Vanderbilt Univ.) Dec 16, 2013 from 12:45 PM to 01:45 PM
- Seminar: "Is F amenable?" (P. Burillo, UPC) Dec 04, 2013 from 01:10 PM to 02:10 PM — CRM-Barcelona,
- Seminar: "TCP no implica DTCP, II" (E. Ventura, UPC) Nov 13, 2013 from 01:10 PM to 02:10 PM
- Seminar: "TCP no implica DTCP" (E. Ventura, UPC) Nov 06, 2013 from 01:10 PM to 02:10 PM
- Seminar: "El espacio de subgrupos de un grupo abeliano" (W. Pitsch, UAB) Oct 30, 2013 from 01:10 PM to 02:10 PM
- Seminar: El problema de la intersecció a Zm x Fn (Jordi Delgado, UPC) Oct 16, 2013 from 01:00 PM to 02:00 PM — CRM-Barcelona,
- Seminar: A finitely presented solution for the von Newmann-Day problem (Eric López, UPC) Oct 09, 2013 from 01:00 PM to 02:00 PM — CRM-Barcelona,

## 2012 - 2013

- Seminar: Generic-case Complexity and Decision Problems (Ha Lam, CUNY) Jun 28, 2013 12:00 AM
- Seminar: Secret Sharing Using Non-commutative Groups and the Shortlex Order (Bren Cavallo, CUNY) Jun 21, 2013 from 12:00 PM to 01:00 PM
- Seminar: Counting primitive elements, the exact asymptotic amount (E. Ventura, UPC) Jun 14, 2013 from 01:00 PM to 02:00 PM — CRM - Barcelona,
- Seminar: Group-based cryptography (Delaram Kahrobaei, CUNY) Jun 07, 2013 from 12:00 PM to 01:00 PM — CRM - Barcelona,
- Seminar: Conjugacy in Houghton's groups (Pep Burillo, UPC) May 17, 2013 from 12:00 PM to 01:00 PM — CRM, room A2,
- Seminar: Verbally closed subgroups of free groups II (E. Ventura, UPC) Apr 19, 2013 from 12:00 PM to 01:00 PM
- Seminar: Verbally closed subgroups of free groups (E. Ventura, UPC) Apr 12, 2013 from 12:00 PM to 01:00 PM
- Seminar: Metric properties and growth of Baumslag-Solitar groups (J. Burillo, UPC) Mar 22, 2013 from 12:00 PM to 01:00 PM

## Seminar: "Limit groups as limits of free groups (IV)" (E. Ventura, UPC)

Seminari Teoria de Grups 2014/2015, session 4

Date: Friday November 14th, 13-14.

Place: CRM, room C1/028

Títle: "Limit groups-IV".

Speaker: Enric Ventura (UPC).

## Seminar: "An introduction to BNS-invariant (VI)" (E. Ventura, UPC)

Seminari Teoria de Grups 2014/2015, session 25

Date: Tuesday May 19th, 13 - 14.

Place: CRM, room A1

Title: "An introduction to BNS-invariant, VI"

Speaker: Enric Ventura (UPC).

## Seminar: "Automata Equations" (Albert Garreta, Stevens Institute)

-----------------------------------------

Date: Tuesday March 1st, 2016, 13:45

Place: FME-UPC room 101

Title: "Automata Equations"

Speaker: Albert Garreta (Stevens Institute)

Abstract: We will discuss the following problem: Suppose we have two directed graphs, G_1 and G_2, with labels in a set of constants A and a set of variables X. Each G_i has an initial vertex and a set of accepting vertices. We want to find a map f from X to A* so that G_1 and G_2 accept the same language once we substitute each x in X by f(x).

## Seminar: "The irrational-slope Thompson groups" (Pep Burillo, UPC)

Seminari Teoria de Grups 2016/2017, session 1

Date: Tuesday February 28th, 2017, 15:00 - 16:00 h.

Place: FME-UPC room S03

Speaker: Pep Burillo (Universitat Politecnica Catalunya)

Title: "The irrational-slope Thompson groups"

Abstract: In this talk we will introduce the irrational-slope Thompson groups. First described by Cleary in a 1995 paper, the groups use subdivisions of [0,1] in different lengths, using equations such as 1=x+x^2. Subdivision intervals have lengths x^n, and hence the slopes are also powers of x. The elements of the group admit interpretations as pairs of binary trees in pure Thompson style, with the only particularity of distinguishing the intervals given by each edge. We will take advantage of the tree interpretation to find expressions for the metric in the Cayley graph of the group, and also distortions of interesting subgroups.