Séminaire GT3
organisé par l'équipe Géométrie
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Fernando Camacho Cadena
Hamiltonian flows and subsurface deformations
3 février 2025 - 14:00Salle de séminaires IRMA
Given a closed compact surface S and a reductive Lie group G, Goldman introduced a symplectic structure on the character variety Hom(pi_1(S),G)//G (the space of representations modulo conjugation). For Teichmüller space, the form coincides with the Weil-Petersson form. The symplectic structure gives rise to Hamiltonian flows associated to functions on character varieties, and therefore gives ways of deforming representations. I will talk about joint work with Anna Wienhard and James Farre, where we focus on a particular type of function on the character variety, whose input includes families of curves on S. The result I will present states that the Hamiltonian flows of such functions are what we call subsurface deformations, which roughly means that the flow is concentrated on a subsurface of S that depends on the curves defining the function. If time permits, I will discuss some applications to Hamiltonian flows of length functions associated to some self intersecting curves. -
Ken'ichi Ohshika
TBA
10 mars 2025 - 14:00Salle de séminaires IRMA
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Ingrid Irmer
The Thurston spine and critical points of the systole function on Teichm\"uller space
14 avril 2025 - 14:00Salle de séminaires IRMA
Abstract - Thurston defined a mapping class group-equivariant spine for Teichm\"uller space; the ``Thurston spine''. This spine is a CW complex, consisting of the points in Teichm\"uller space at which the set of shortest geodesics - the systoles - cut the surface into polygons. The systole function is a map from Teichm\"uller space to $\mathbb{R}_{+}$ whose value at any point is given by the length of the systoles. It is known that the systole function is a topological Morse function on Teichm\"uller space, whose critical points are contained in the Thurston spine. This talk surveys what the systole function tells us about the Thurston spine.