Geometria_Pisa

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geometria_pisa@lists.dm.unipi.it

September 2025

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Fwd: [Junk released by Allowed List] [CENTRO DE GIORGI] -- ANNOUNCEMENT -- COLLOQUIO DE GIORGI - PROF. SERGE CANTAT (October 8th, 2025)
by Bruno Martelli 26 Sep '25

26 Sep '25

Buondì, Mi permetto di consigliare a tutti la presenza a questo seminario. Cantat è uno speaker eccellente. Buno ---------- Forwarded message --------- Da: CRM <crm(a)sns.it> Date: gio 25 set 2025 alle ore 12:05 Subject: [Junk released by Allowed List] [CENTRO DE GIORGI] -- ANNOUNCEMENT -- COLLOQUIO DE GIORGI - PROF. SERGE CANTAT (October 8th, 2025) To: <crm(a)sns.it> Cc: <crm(a)sns.it> *Colloquio De Giorgi* *8* *October** 2025 ore 4:00 pm* Aula Dini, Palazzo del Castelletto, via del Castelletto, Pisa <https://www.google.it/maps/place/Palazzo+del+Castelletto/@43.7183335,10.398…> Prof. *SERGE* *CANTAT* Université de Rennes Title: *Degree Growth * Abstract : Consider a polynomial transformation f of a vector space V and iterate f; that is, compose f with itself, and then with f again, etc. Doing so, one gets a sequence of polynomial transformations f^n. Computing the degree of the formulas defining f^n, one obtains a sequence of integers deg(f^n). The problem I will discuss is : what type of sequences do we obtain in this way? For instance, in dimension 2, the degree of f(x,y)=(y,xy) is 2, then the degree of f^2(x,y)=(xy, xy^2) is 3, then f^3(x,y)=(xy^2,x^2y^3) has degree 5, … and the degree of f^n is given by a sequence which is well known in Pisa. The question is related to dynamical systems, basic algebraic geometry, and some number theory. No previous knowledge will be assumed. *Web site: *https://crmdegiorgi.sns.it/evento/colloquio-de-giorgi-2024-2025/ *The event will take place in person.* Those who are unable to be physically present may attend the talk via zoom by following the link: *https://us02web.zoom.us/j/81126340951?pwd=cUQ2SldDK0xKU3hqdENEU3FiUXNkUT09 <https://us02web.zoom.us/j/81126340951?pwd=cUQ2SldDK0xKU3hqdENEU3FiUXNkUT09>* *Luisa Ferrini* *Centro di Ricerca Matematica* Ennio De Giorgi Palazzo Puteano Piazza <https://www.google.com/maps/search/Piazza+dei+Cavalieri+3?entry=gmail&sourc…> <https://www.google.com/maps/search/Piazza+dei+Cavalieri+3?entry=gmail&sourc…> dei <https://www.google.com/maps/search/Piazza+dei+Cavalieri+3?entry=gmail&sourc…> <https://www.google.com/maps/search/Piazza+dei+Cavalieri+3?entry=gmail&sourc…> Cavalieri <https://www.google.com/maps/search/Piazza+dei+Cavalieri+3?entry=gmail&sourc…> 3 <https://www.google.com/maps/search/Piazza+dei+Cavalieri+3?entry=gmail&sourc…> 56126 PISA

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Seminario Martedì 30 Settembre - François Bacher
by Filippo Sarti 25 Sep '25

25 Sep '25

Buongiorno, Vi segnalo che François Bacher (Dijon) terrà il prossimo seminario di Geometria in data Martedì 30 Settembre alle ore 14:30 presso l'aula Seminari. Per gli interessati ad andare a pranzo con lo speaker, potete contattare Fabrizio Bianchi (in copia). L'appuntamento è in atrio alle 12:45. Allego titolo e abstract. Titolo: Hénon maps and Kato surfaces Abstract: Friedland and Milnor showed that among the polynomial automorphisms of the affine complex plane, the only ones dynamically non-trivial are the Hénon maps. Considering their birationnal extension to the projective plane, these maps admit a super-attracting point at infinity. Dloussky and Oeljeklaus noticed that one could compactify the quotient by the dynamics of its basin of attraction into a Kato surface. I will recall the construction of such surfaces, and talk about a recent result, according to which the obtained Kato surface completely characterizes the Hénon automorphism; conversely, one obtains the description of the space of Kato surfaces coming from Hénon maps. A presto, Filippo

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