Geometria_Pisa

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Seminario di Geometria Giovedì 6 Marzo - Ilaria Castellano
by Filippo Sarti 03 Mar '25

03 Mar '25

Buongiorno, Vi ricordo che il prossimo seminario di Geometria e Topologia sarà tenuto da Ilaria Castellano e si terrà Giovedì 6 Marzo alle ore 14:30 presso l'aula Riunioni. Per gli interessati ad andare a pranzo con la speaker, l'appuntamento è in atrio alle 12:45. Allego titolo e abstract Titolo: Totally disconnected locally compact groups, accessibility and Euler-Poincaré characteristic Abstract: In the first part of the talk I will illustrate how the classical notion of accessibility for finitely generated groups carries over to the realm of compactly generated totally disconnected locally compact (= t.d.l.c.) groups. Then, by means of a new notion of Euler-Poincaré characteristic, I will discuss an accessibility result in the t.d.l.c. framework, under the assumption of rational discrete cohomological dimension = 1. A presto, Carlo e Filippo

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Seminari di Geometria Mercoledì 26 e Giovedì 27 Febbraio
by Carlo Collari 25 Feb '25

25 Feb '25

Buongiorno, Vi ricordo che questa settimana ci sarà un doppio appuntamento del seminario di Geometria e Topologia. Oltre al seminario di Giovedì 27 Febbraio, che sarà tenuto da Daniele Angella alle ore 14:30 presso l'aula Riunioni, avremo un ulteriore appuntamento Domani Mercoledì 26 Febbraio, questo seminario sarà tenuto da Fabrizio Bianchi alle ore 16:00 presso l'aula Seminari. Per gli interessati ad andare a pranzo con la speaker, l'appuntamento è in atrio alle 13:00. Allego titoli e abstract A presto, Carlo e Filippo Seminario del 26 Febbraio Relatore: Fabrizio Bianchi Titolo: On entropy of holomorphic maps Abstract: A celebrated theorem by Gromov (70s, published in Enseign. Math. 2003) states that the topological entropy of a holomorphic self-map of a Kahler manifold is bounded above by the logarithm of the maximum of the dynamical degrees. The proof relies on a geometric interpretation of the entropy and on a volume estimate for complex analytic sets. I will provide some context for this result and present the main ideas of this proof in the case of rational maps of the Riemann Sphere (where the upper bound reduces to the logarithm of the degree). Seminario del 27 Febbraio Relatore: Daniele Angella Titolo: The Hermitian geometry of Chern connections Abstract: We consider some analytic problems concerning the geometry of the Chern connection of Hermitian manifolds, e.g. the existence of metrics with constant Chern-scalar curvature; the generalizations of the Kähler-Einstein condition to the non-Kähler setting; the convergence of the normalized Chern-Ricci flow on compact complex surfaces. The talk is based on joint collaborations with Simone Calamai, Mauricio Correa, Francesco Pediconi, Cristiano Spotti, Valentino Tosatti and others.

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Corso 4-varietà + Teorema di Gromov
by Bruno Martelli 25 Feb '25

25 Feb '25

Cari, Segnalo un paio di eventi che ci saranno fra pochi giorni in dipartimento che secondo me sono particolarmente utili per chi fa geometria e topologia. Mercoledì alle 16 in Aula seminari Fabrizio Bianchi ci illustrerà un teorema di Gromov sull'entropia di mappe olomorfe. Si tratta di un argomento molto bello e fortemente collegato alle mappe pseudo-Anosov su superfici e al seminario di Elia che c'è stato qualche settimana fa (l'idea di chiedere a Fabrizio di illustrarci il teorema è venuta dopo il seminario di Elia). Lunedì prossimo alle 16 su google meet ci sarà la riunione preliminare del corso di dottorato "4- manifolds", tenuto da Marco Marengon. Il link è https://meet.google.com/pvo-musz-gfz A presto, Bruno

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Conference “Leaning towards higher rank”, April 28- May 2, Pisa
by Andrea Tamburelli 20 Feb '25

20 Feb '25

Dear colleague, Francesco Bonsante, Christian El Emam and I are organizing a small conference in Pisa from April 28th to May 2nd, on the general theme of hyperbolic geometry and classical and higher Teichmüller theory. We would appreciate if you could advertise it to people in your group that may be interested. More information is available in the conference webpage (https://pagine.dm.unipi.it/~a019210/Conference25.html) With kind regards, Andrea

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Seminario di Geometria Giovedì 20 Febbraio - Nicoletta Tardini
by Carlo Collari 17 Feb '25

17 Feb '25

Buongiorno, Vi ricordo che il prossimo seminario di Geometria e Topologia sarà tenuto da Nicoletta Tardini e si terrà Giovedì 20 Febbraio alle ore 14:30 presso l'aula Riunioni. Per gli interessati ad andare a pranzo con la speaker, l'appuntamento è in atrio alle 13:00. Allego titolo e abstract Titolo: Special Hermitian metrics on complex manifolds Abstract: Kähler geometry lies at the intersection of complex geometry, Riemannian geometry and symplectic geometry. From the complex geometric point of view it is therefore natural to consider special non-Kähler Hermitian metrics on complex manifolds. Among them, pluriclosed metrics deserve particular attention. These metrics always exist on compact complex surfaces but the situation in higher dimension is very different. We will discuss several properties concerning these metrics also in relation with the Bismut connection having Kähler-like curvature. This is joint work with G. Barbaro and F. Pediconi A presto, Carlo e Filippo

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Workshop "Manifolds and Groups in Bologna, III", announcement
by Filippo Sarti 06 Feb '25

06 Feb '25

Dear all, we are pleased to announce the workshop Manifolds and Groups in Bologna, III ----------------------------------------- Date: Monday, Apr 14, 2025 -- Wednesday , Apr 16, 2025 Place: University of Bologna The aim of this workshop is to bring together young researchers working in low-dimensional topology and geometric group theory in a broad sense. The event consists of main lectures and shorter talks in order to give the opportunity to young researchers to present their own research. Main speakers: Naomi Andrew (Oxford), Macarena Arenas (Cambridge), Carlo Collari (Pisa), James Farre (MPI MIS Leipzig), Mitul Islam (MPI MIS Leipzig), Stavroula Makri (Toulouse), Lorenzo Ruffoni (Binghamton), Matthias Uschold (Regensburg). Junior speakers: Sofia Amontova (Geneva), Valentina Bais (SISSA), Filippo Bianchi (Pisa), Elena Bogliolo (Pisa), Alberto Casali (Pisa), Bruno Dular (Luxembourg), Franziska Hofmann (Regensburg). https://math.unibo.it/en/events/manifolds-and-groups-in-bologna-2025 Looking forward to seeing you in Bologna, Giuseppe Bargagnati, Marco Moraschini, Stefano Riolo (University di Bologna) and Filippo Sarti (University of Pisa)

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seminario di lettura
by Paolo Lisca 05 Feb '25

05 Feb '25

Ciao a tutti, vorrei organizzare un seminario di lettura su questo articolo<https://arxiv.org/abs/2402.10452>, che fornisce la prima dimostrazione dell'esistenza di 4-varietà esotiche compatte orientabili senza l'uso di analisi. Ci sarà un incontro preliminare martedì 11 febbraio alle 14:30 nella saletta seminari. Chi non può (ma vorrebbe) venire martedì mi avverta! A presto, Paolo

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Seminario di Geometria Giovedì 6 Febbraio - Michelle Bucher
by Carlo Collari 03 Feb '25

03 Feb '25

Buongiorno, Vi ricordo che il prossimo seminario di Geometria e Topologia sarà tenuto da Michelle Bucher e si terrà Giovedì 6 Febbraio alle ore 14:30 presso l'aula Riunioni. Per gli interessati ad andare a pranzo con la speaker, l'appuntamento è in atrio alle 13:00. Allego titolo e abstract Titolo: Continuous cocycles on the Furstenberg boundary and applications to bounded cohomology Abstract: Group cohomology comes in many variations. The standard Eilenberg-MacLane group cohomology is the cohomology of the cocomplex {f:Gq+1→R∣f is G−invariant}{f:Gq+1→R∣f is G−invariant} endowed with its natural homogeneous coboundary operator. Now whenever a property P of such cochains is preserved under the coboundary one can obtain the corresponding P-group cohomology. P could be: continuous, measurable, L0L0, bounded, alternating, etc. Sometimes these various cohomology groups are known to differ (eg P=empty and P=continuous for most topological groups), in other cases they are isomorphic (eg P=empty and P=alternating (easy), P=continuous and P=L0L0 (a highly nontrivial result by Austin and Moore valid for locally compact second countable groups)). In 2006, Monod conjectured that for semisimple connected, finite center, Lie groups of noncompact type, the natural forgetful functor induces an isomorphism between continuous bounded cohomology and continuous cohomology (which is typically very wrong for discrete groups). I will focus here on the injectivity and show its validity in several new cases including isometry groups of hyperbolic nn-spaces in degree 4, known previously only for n=2n=2 by a tour de force due to Hartnick and Ott. Monod recently proved that all such continuous (bounded) cohomology classes can be represented by measurable (bounded) cocycles on the Furstenberg boundary. Our main result is that these cocycles can be chosen to be continuous on a subset of full measure. In the real hyperbolic case, this subset of full measure is the set of distinct tuples of points, easily leading to the injectivity in degree 4. This is joint work with Alessio Savini. A presto, Carlo e Filippo

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Seminario di Geometria 30 Gennaio - Elia Fioravanti
by Carlo Collari 27 Jan '25

27 Jan '25

Buongiorno, Vi ricordo che il prossimo seminario di Geometria e Topologia sarà tenuto da Elia Fioravanti e si terrà Giovedì 30 Gennaio alle ore 14:30 presso l'aula Riunioni. Per gli interessati ad andare a pranzo con lo speaker, l'appuntamento è in atrio alle 13:00. Allego titolo e abstract Titolo: Growth of automorphisms of special groups Abstract: Given a (nice) group G, we are interested in how fast the length of a group element can grow when we apply powers of a given outer automorphism of G. If the group G is free or the fundamental group of a closed surface, classical train-track techniques give a complete and precise picture. This can be extended to automorphisms of all negatively curved (a.k.a. Gromov hyperbolic) groups G, using Rips-Sela theory and the canonical JSJ decomposition. Very little seems to be known beyond this setting. We study this problem for a broad class of non-positively curved groups: "virtually special" groups in the Haglund-Wise sense. In this setting, we prove that: (1) the stretch factor of any automorphism is an algebraic integer; (2) if the automorphism is untwisted, then it admits only finitely many growth rates, each of these is polynomial-times-exponential, and there is a Nielsen-Thurston decomposition. A presto, Carlo e Filippo

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Seminario di Geometria 23 Gennaio - Macarena Arenas
by Carlo Collari 20 Jan '25

20 Jan '25

Buongiorno, Vi ricordo che il prossimo seminario di Geometria e Topologia sarà tenuto da Macarena Arenas e si terrà Giovedì 23 Gennaio alle ore 14:30 presso l'aula Riunioni. Per gli interessati ad andare a pranzo con la speaker, l'appuntamento è in atrio alle 13:00. Allego titolo e abstract Titolo: Taut smoothings and shortest geodesics Abstract: In this talk we will discuss the connection between combinatorial properties of minimally self-intersecting curves on a surface S and the geometric behaviour of geodesics on S when S is endowed with a Riemannian metric. In particular, we will explain the interplay between a smoothing, which is a type of surgery on a curve that resolves a self-intersection, and k-systoles, which are shortest geodesics having at least k self-intersections, and we will present some results that partially elucidate this interplay. A presto, Carlo e Filippo

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Geometria_Pisa