SEMINARI DI GEOMETRIA

The amenability conjecture for Gromov-hyperbolic groups

Tipo Seminario: 
Relatore: 
Andrea Sambusetti

We will present a classical conjecture on amenability for groups related
to growth. The original result, which is due to Cohen and,
independently, Grigorchuk, dates back to the 80's: a group Q finitely
presented as F/N, where F is a free group, is amenable if and only if
the exponential growth rates  (or _entropies)_ \omega(N) and \omega(F)
of N and F coincide.

Data Seminario: 
Thursday, December 6, 2018
Aula: 
Sala Seminari (Dip. Matematica)
Ora Fine: 
Saturday, January 1, 0000 - 17:00
Affiliazione: 
Università di Roma
Ora Inizio: 
Saturday, January 1, 0000 - 16:00

Transverse invariants from the deformations of Khovanov sl_3 homology

Tipo Seminario: 
Relatore: 
Carlo Collari

In this talk I will describe some invariants for transverse links in  
S^3 (endowed with the symmetric contact structure) arising from the  
deformations of Khovanov sl_3 homology.

I will start with a brief introduction to the theory of transverse  
links in S^3. Afterward, I will recall some known results concerning  
transverse invariants in link homologies. In particular, I will focus  
on the invariants coming from Khovanov-Rozansky homologies, and those   
coming from the deformations of Khovanov homology.

Data Seminario: 
Thursday, October 4, 2018
Aula: 
Sala Seminari (Dip. Matematica)
Ora Fine: 
Saturday, January 1, 0000 - 17:00
Affiliazione: 
Durham University
Ora Inizio: 
Saturday, January 1, 0000 - 16:00

The AJ conjecture for SU(2) and SL(2,C)

Tipo Seminario: 
Relatore: 
Alessandro Malusà

Given a knot K in S^3, one can consider as invariants the A-polynomial and the coloured Jones polynomial. After illustrating the original AJ conjecture, as formulated by Garoufalidis, I will specify its motivation from quantum SU(2)-Chern-Simons theory, and attempt to make sense of the statement that the two invariants mentioned above are classical and quantum in nature, respectively. This opens the question as of whether one can formulate an analogous conjecture for different Lie groups.

Data Seminario: 
Thursday, June 21, 2018
Aula: 
Sala Seminari (Dip. Matematica)
Ora Fine: 
Saturday, January 1, 0000 - 16:00
Affiliazione: 
Aarhus University
Ora Inizio: 
Saturday, January 1, 0000 - 15:00

Pretzel links, mutation, and the slice-ribbon conjecture

Tipo Seminario: 
Relatore: 
Paolo Aceto

We show that the mutant 2-component pretzel links P(p,q,-q,-p) and P(p,q,-p,-q) are not concordant for any distinct odd integers p and q greater than 1. As a corollary, we obtain a proof of the  slice-ribbon conjecture for 4-stranded 2-component pretzel links. In order to distinguish mutant links up to concordance we consider 3-fold branched covers and use an obstruction based on Donaldson's diagonalization theorem. This is joint work with Min Hoon Kim, JungHwan Park and Arunima Ray.

Data Seminario: 
Wednesday, May 16, 2018
Aula: 
Sala Seminari (Dip. Matematica)
Ora Fine: 
Saturday, January 1, 0000 - 16:30
Affiliazione: 
Rényi Institute (Budapest)
Ora Inizio: 
Saturday, January 1, 0000 - 15:30

Entropia e finitezza per gruppi con scomposizioni acilindriche

Tipo Seminario: 
Relatore: 
Filippo Cerocchi

Si consideri la famiglia dei gruppi finitamente generati che ammettono
una scomposizione k-acilindrica, non-elementare (l'acilindricità è da
intendersi nel senso di Sela). Mostreremo l'esistenza di una funzione
(esplicita) f( - ;k):N--->N, dipendente esclusivamente da k e divergente
all'infinito tale che per ogni gruppo G ed ogni sistema finito di
generatori S di G l'entropia Ent(G,S) di G rispetto ad S sia maggiore o
uguale a f(#(S);k). Spiegheremo come tale disuguaglianza sia la chiave

Data Seminario: 
Wednesday, April 18, 2018
Aula: 
Sala Seminari (Dip. Matematica)
Ora Fine: 
Saturday, January 1, 0000 - 16:30
Affiliazione: 
Università di Roma
Ora Inizio: 
Saturday, January 1, 0000 - 15:30

Geometry of alternating links on surfaces

Tipo Seminario: 
Relatore: 
Joshua Howie

We study links in 3-manifolds which have alternating diagrams onto orientable surfaces of positive genus. When the diagram is sufficiently complicated, we are able to obtain topological and geometrical information about the link exterior. In particular, we can tell if the link is hyperbolic and obtain bounds on volume, know whether the checkerboard surfaces are essential or quasi-fuchsian, and rule out exceptional Dehn fillings. Joint work with Jessica Purcell.

Data Seminario: 
Wednesday, March 21, 2018
Aula: 
Sala Seminari (Dip. Matematica)
Ora Fine: 
Saturday, January 1, 0000 - 16:00
Affiliazione: 
Monash University
Ora Inizio: 
Saturday, January 1, 0000 - 15:00

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