Geometria_Pisa

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I: [rtop] BTW: Program and registration
by Paolo Lisca 21 Nov '24

21 Nov '24

Inoltro annuncio di scuola invernale. Paolo Lisca -------- Forwarded Message -------- Subject: [rtop] BTW: Program and registration Date: Wed, 20 Nov 2024 17:55:47 +0100 From: wagner(a)imj-prg.fr<mailto:wagner@imj-prg.fr> Dear fellow topologists, As previsously annouced, the 5th instance of Topology Between The Waves (aka BTW5) will occur from the 9th to the 14th of March 2025. Like last year we'll be in the Station Biologique of Besse, birth place of Nicolas Bourbaki (not too far from Clermont-Ferrand). This year's topic is a theorem by Giroux called the "Giroux correspondence". It relates open-book decompostions of 3-manifolds (topological structures) and contact structures (geometrical structures). We'll follow the proof strategy of Licata--Vertesi (on the tight case). This winter school is aimed at PhD students and young postdocs (as well as our favorite senior researchers!). The idea is to try to go through this proof together, after have learned about the necessary background. Participants are therefore encourage to give a talk (or to help preparing one). At the moment there are 15.5 talks planned see the program available here: https://lrobert.perso.math.cnrs.fr/BTW5/BTW5Program.pdf This program might changed marginally (especially if you have comment complaints or suggestions). We can have up to 35 people in Besse. Housing cost and food is covered by the conference (and we have a plan to be better on the food side, than last year). A bus shuttle from Clermont Ferrand to Besse on Sunday evening and from Besse to Clermont-Ferrand on friday afternoon will be arranged. Besides this, we do not plan to cover transport, but let us know if you have difficulties. If you want to participate, please answer to this email (with all the organizers in CC) and tell us which talk(s) suit(s) you in preference order. As usual, the final repartition will be decided as soon as possible on a first arrived first served basis with priority given to young PhD students. There is a webpage: https://lrobert.perso.math.cnrs.fr/BTW5/btw5.html Which will soon be updated. Logistical details will be provided to the participants in due time, but bare in mind that due to its relative remoteness, it is difficult to participate to only part of the week. Please circulate this announcement among your colleagues and using your usual math mailing list. Would you have any question, do not hesitate to ask the organizers. Best, Marco De Renzi Quentin Faes Jules Martel Delphine Moussard Louis-Hadrien Robert

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Seminario Baby Geometri 26/11
by Giovanni Framba 21 Nov '24

21 Nov '24

Carə tuttə, Vi invitiamo al seminario dei Baby Geometri della prossima settimana: Martedì 26 Novembre 2024, alle ore 11:30 Presso l’Aula Bianchi Lettere del Palazzo della Carovana Sofia Amontoia (Université de Genève) terrà un seminario dal titolo: Cohomologically flavoured invariants for representations di cui riporto l'abstract: Consider the set of representations of Hom(π1(M),G) for M some manifold and G an interesting Lie group. How can their nature be understood? An approach for a classification of these was kickstarted by Goldman in the 80s leading to the emergence of Higher Teichmueller theory, nowadays an actively growing field. In the talk we shall outline the essence of this approach where the so-called Toledo invariant takes a central role. Then, realizing that the Toledo invariant is actually a cohomological invariant, is the point of view that allows to generalize aspects of Goldman's classification. If time permits, we shall briefly discuss how bounded cohomology comes into play and proves to be a powerful tool. Vi ricordiamo che potrete trovare informazioni sui prossimi seminari sul nostro sito https://sites.google.com/view/babygeometri. Tutte le persone interessate sono invitate a partecipare. A presto, Elena, Pietro, Alessio, Giovanni, Ervin

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I: Topological workshop at Matemale 2025, first announcement
by Paolo Lisca 18 Nov '24

18 Nov '24

Inoltro annuncio di scuola per la prossima primavera. Paolo Lisca -------- Forwarded Message -------- Subject: Topological workshop at Matemale 2025, first announcement Date: Sat, 16 Nov 2024 22:10:36 +0100 From: thomas fiedler <thomas.fiedler(a)math.univ-toulouse.fr><mailto:thomas.fiedler@math.univ-toulouse.fr> Dear friends and colleagues, the next topological spring-summer school in Matemale (formerly Llagonne) will take place from 19/05/2025 to 23/05/2025 about Khovanov homology and exotic phenomena and is organized by Jean-François Barraud, Vincent Florens, Hoel Queffelec, Delphine Moussard and myself. You are very welcome to participate. Khovanov homology is an invariant of knots and links introduced by Khovanov in the 90s and widely studied since then. In particular, a variant of this homology due to Lee allowed Rasmussen to define a numerical invariant called the s-invariant. It appears, thanks to the work of several authors in the last years, that this s-invariant helps to detect exotic phenomena. Please forward the information to everybody who could be interested in it, especially to your students and your colleagues outside of low dimensional topology. Thanks to Delphine and Hoel we have a beautiful program which you can find on the web page https://sites.google.com/view/matemale-maths-school There will be 16 talks. Please feel free to choose a talk if you like to give one. We will be accomodated as usually in the Centre de vacances "La Capcinoise", more precisely in their gites ruraux. They have a web page https://www.lacapcinoise.fr/ . This is just for information, you don't need to make a reservation by yourself. As usual we will completely cover your stay. Please send us a mail if you are interested to participate, if you would like to give a talk and which one, and whether or not you need financial support. We hope to see you all in May! Best regards in the name of the organizers, Thomas

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Seminario Baby Geometri 19/11
by Giovanni Framba 14 Nov '24

14 Nov '24

Carə tuttə, Vi invitiamo al seminario dei Baby Geometri della prossima settimana: Martedì 19 Novembre 2024, alle ore 11:30 Presso l’Aula Seminari del Dipartimento di Matematica Julian Wyckowski (Università di Cambridge) terrà un seminario dal titolo: Three notions of accessibility for profinite groups acting on profinite trees di cui riporto l'abstract: The theory of groups acting on trees—attributed to Bass and Serre—provides a rich framework for the understanding of structural and homological properties of discrete groups. In this talk, I will introduce the profinite analogue of this theory, developed by Melnikov, Zalesskii and Ribes. I will outline some of the difficulties encountered when passing from the discrete to the profinite world, as well as some solutions. I will also introduce three notions of accessibility in the context of profinite/pro-p groups acting on profinite/pro-p trees and discuss a result of mine as well as two open questions regarding accessibility. Time permitting, I will outline some applications to other topics in profinite rigidity. Vi ricordiamo che potrete trovare informazioni sui prossimi seminari sul nostro sito https://sites.google.com/view/babygeometri. Tutte le persone interessate sono invitate a partecipare. A presto, Elena, Pietro, Alessio, Giovanni, Ervin

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Pranzo con lo speaker
by Carlo Collari 12 Nov '24

12 Nov '24

Buongiorno, Per tutti gli interessati ad andare a pranzo con lo speaker del seminario di Geometria di oggi, l'appuntamento è alle 13 in atrio. A presto, Carlo

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Seminario di Geometria del 29 Ottobre - Nikolay Abrosimov
by Carlo Collari 10 Nov '24

10 Nov '24

Buongiorno, Ricordo a tutti gli interessati che il prossimo seminario di geometria sarà tenuto da Nikolay Abrosimov e si terrà Martedì 12 Novembre alle ore 14:30 presso l’Aula Magna. Allego titolo e abstract: Titolo: Euclidean volume of a cone manifold over any hyperbolic knot is an algebraic number Abstract: The talk is based on our joint work [1] with Alexander Kolpakov (Université de Neuchâtel, Switzerland) and Alexander Mednykh (Sobolev Institute of Mathematics, Novosibirsk). A hyperbolic structure on a three-dimensional cone manifold with a knot as a singular set can usually be deformed into a limit Euclidean structure. In our paper [1] we show that the corresponding normalized Euclidean volume of the manifold is always an algebraic number i.e. a root of some polynomial with integer coefficients. This result is a generalization (for cone manifolds) of the well-known Sabitov theorem on the volumes of Euclidean polyhedra which gave an answer to the bellows problem. The fact we established stands out against the background of hyperbolic volumes the number-theoretic nature of which is usually quite complex. In addition to this theorem we propose an algorithm that allows one to explicitly calculate the minimal polynomial for a normalized Euclidean volume. References: [1] N. Abrosimov A. Kolpakov A. Mednykh Euclidean volumes of hyperbolic knots // Proc. Amer. Math. Soc. 152 (2024) 869-881. DOI: 10.1090/proc/16353 A presto, Filippo

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Baby Geometri 12/11
by Giovanni Framba 09 Nov '24

09 Nov '24

Carə tuttə, Vi invitiamo al seminario dei Baby Geometri della prossima settimana: Martedì 12 Novembre 2024, alle ore 11:30 Presso l’Aula Seminari del Dipartimento di Matematica Sirio Resteghini (Università di Pisa) terrà un seminario dal titolo: Topological aspects and dual structures of Artin groups di cui riportiamo l'abstract: The K(π,1) conjecture for Artin groups goes back to the work of Arnol’d, Brieskorn, Pham, and Thom in the '60s. Recently, the dual approach has been instrumental in proving that conjecture in the affine and rank 3 cases. In this talk, we will introduce Coxeter groups and Artin groups, providing some basic examples and stating the K(π,1) conjecture. We will then introduce the standard and dual structures for Artin groups, highlighting the results in the spherical, affine and rank 3 cases. Finally, we will give a few results about the isomorphism between the standard and dual Artin groups. Vi ricordiamo che potrete trovare informazioni sui prossimi seminari sul nostro sito https://sites.google.com/view/babygeometri. Tutte le persone interessate sono invitate a partecipare. A presto, Gli organizzatori

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Seminario Baby Geometri 29/10
by Giovanni Framba 24 Oct '24

24 Oct '24

Carə tuttə, Vi invitiamo al seminario dei Baby Geometri della prossima settimana: Martedì 29 Ottobre 2024, alle ore 11:30 Presso l’Aula Seminari del Dipartimento di Matematica Matteo Verni (Sorbonne Université) terrà un seminario dal titolo: L'omologia d'intersezione e la topologia algebrica di varietà singolari di cui riportiamo l'abstract: Uno degli aspetti che rendono la (co)omologia singolare interessante è il fatto che per spazi topologici particolarmente buoni, presenta simmetrie non banali: per esempio la dualità di Poincaré per varietà topologiche orientabili, e molte altre simmetrie sorprendenti (il cosiddetto Kahler package) per varietà complesse compatte con una buona metrica. Purtroppo, queste simmetrie coomologiche falliscono in presenza di singolarità. In questo talk, introdurremo l'omologia d'intersezione, che coincide con l'omologia singolare classica per varietà topologiche ma ha il vantaggio di produrre gruppi di omologia che rispettano ancora le simmetrie che trovavamo per spazi lisci. Vi ricordiamo che potrete trovare informazioni sui prossimi seminari sul nostro sito https://sites.google.com/view/babygeometri. Tutte le persone interessate sono invitate a partecipare. A presto, Elena Bogliolo Pietro Capovilla Alessio Di Prisa Giovanni Framba Ervin Hadžiosmanović

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Fw: Seminario di Geometria del 29 Ottobre 24 - Andrea Seppi
by Carlo Collari 24 Oct '24

24 Oct '24

________________________________ From: Filippo Sarti via Assegnisti <assegnisti(a)lists.dm.unipi.it> Sent: Thursday, October 24, 2024 10:18:15 AM To: assegnisti(a)lists.dm.unipi.it; dottorandi(a)lists.dm.unipi.it; geometria_pisa(a)lists.dm.unipi.it Subject: [Assegnisti] Seminario di Geometria del 29 Ottobre 24 - Andrea Seppi Buongiorno, Ricordo a tutti gli interessati che il prossimo seminario di geometria sarà tenuto da Andrea Seppi e si terrà Martedì 29 Ottobre alle ore 14:30 presso l'aula Riunioni. Allego titolo e abstract: Titolo: Topology of convex projective four-manifolds Abstract: I will discuss topological obstructions for a closed four-manifold that admits a (real) properly convex projective structure. I will present a vanishing result on the Pontryagin classes, that in dimension four provides information on the geography problem for properly convex projective manifolds, and implies the solution to a question of Yves Benoist on the (in)compatibility of real convex projective structures and complex hyperbolic structures. Time permitting, I will also discuss the construction of examples that realize all possible positive values of the Euler characteristic. Based on joint work with Stefano Riolo and Leone Slavich. A presto, Filippo _______________________________________________ Assegnisti mailing list -- assegnisti(a)lists.dm.unipi.it To unsubscribe send an email to assegnisti-leave(a)lists.dm.unipi.it

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Seminario di Geometria Domani - Miguel Orbegozo Rodriguez
by Carlo Collari 21 Oct '24

21 Oct '24

Buongiorno, Ricordo a tutti gli interessati che il prossimo seminario di geometria sarà tenuto da Miguel Orbegozo Rodriguez e si terrà domani Martedì 22 Ottobre alle ore 14:30 presso l'aula Riunioni. Per gli interessati ad andare a pranzo con lo speaker, l'appuntamento è in atrio alle 12:30. Allego titolo e abstract: Titolo: Murasugi sums and primeness of links Abstact: In this talk I will present some results on how primeness of fibered links behaves under an operation called the Murasugi sum, which generalises the connected sum. As an application, this allows us to resolve a 30 year old conjecture of Cromwell in the case of braid closures. Cromwell showed that, if a link diagram represented as a positive braid features no circles that decompose it as a connected sum (in other words, it is not "obviously" composite), then the link is indeed prime. In his words, "positive braids are visually prime". He further conjectured that the same would hold for link diagrams that yield minimal genus Seifert surfaces when Seifert's algorithm is applied. If the diagram is required to be a braid closure, then Cromwell's condition is equivalent to the braid being homogeneous. Thus, we show that homogeneous braids are visually prime. This is joint work with Peter Feller and Lukas Lewark. A presto, Carlo

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