Geometria_Pisa

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Seminario geometria domani
by Bruno Martelli 19 Jun '24

19 Jun '24

Buondì, Con colpevole ritardo vi annuncio il seminario di geometria e topologia di domani. A presto, Bruno Orario: Giovedì 20 giugno, ore 14.30, aula seminari. Speaker: Sam Fisher (Oxford) Title: Maps to the circle, the integers, and L2-Betti numbers Abstract: Determining conditions implying that a manifold fibers over the circle is an old and interesting problem. One of the most celebrated results in this direction is Agol's theorem, which states that every hyperbolic 3-manifold has a finite cover that fibers over the circle. In higher dimensions, much less is known. Recently, Italiano--Martelli--Migliorini gave the first example of a (cusped) hyperbolic 5-manifold fibering over the circle, answering open questions in topology and geometric group theory. Hyperbolic 3-manifolds and the IMM example are examples of hyperbolic manifolds whose fundamental groups act geometrically on CAT(0) cube complexes and consequentially have RFRS fundamental group. In this talk, we will discuss an algebraic version of the fibering problem: a group algebraically fibers if it maps onto the integers with finitely generated kernel. In the class of RFRS groups, we will see that finiteness properties of the kernel are controlled by vanishing of L2-invariants. We will also discuss applications of these results to high-dimensional hyperbolic manifolds

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Conferenza Nantes in topologia in bassa dimensione
by Bruno Martelli 10 Jun '24

10 Jun '24

Buondì, Inoltro annuncio di conferenza, attenzione perché le iscrizioni scadono in questi giorni. Bruno ----- Chers collègues, Vous êtes cordialement invité(e)s aux prochaines journées de topologie de basse dimension du Réseau Thématique RTop "Topologie algébrique et géométrique" qui auront lieu à Nantes du 26 au 30 aout prochain. https://www.math.sciences.univ-nantes.fr/~golla/docs/conferences/nantes-tre… Nous aurons le plaisir d'y écouter deux mini-cours : Marco MARENGON (Alfreìd Reìnyi Institute of Mathematics), Laura STARKSON (UC Davis), ainsi que des exposés pléniers de : Cristina ANGHEL-PALMER (University of Leeds), Roger CASALS (UC Davis), Filip MISEV (Universität Regensburg), Hoel QUEFFELEC (Université de Montpellier), Les inscriptions sont ouvertes ici : https://www.math.sciences.univ-nantes.fr/journees-de-basse-dimension/ N'hésitez pas à faire des propositions d'exposés pour enrichir le programme de la semaine et n'hésitez pas à nous contacter si besoin est. Le nombre de places étant limité, nous confirmerons les inscriptions ultérieurement. En espérant vous y voir nombreux ! Les organisateurs (M. Golla, E. Wagner) (English version) Dear colleagues, We are pleased to announce that the next Low-dimensional meeting of the Réseau Thématique RTop "Topologie algébrique et géométrique" will take place in Nantes on August 26th-30th (2024). We will have the pleasure to listen to two mini-courses by: Marco MARENGON (Alfreìd Reìnyi Institute of Mathematics), Laura STARKSON (UC Davis), as well as to plenary talks by: Cristina ANGHEL-PALMER (University of Leeds), Roger CASALS (UC Davis), Filip MISEV (Universität Regensburg), Hoel QUEFFELEC (Université de Montpellier), Registration is open here: https://www.math.sciences.univ-nantes.fr/journees-de-basse-dimension/ Due to the limited number of places, registration will be confirmed later on. Do not hesitate to suggest contributed talks to enrich the program and do not hesitate to contact us if you have any questions. Looking forward to seeing you in Nantes, The organizers (M. Golla, E. Wagner)

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seminario Romeo Segnan Dalmasso
by Diego Conti 21 May '24

21 May '24

Buongiorno, segnalo che giovedì 23 maggio alle 14.30 in aula seminari Romeo Segnan Dalmasso (Università di Milano Bicocca) terrà un seminario dal titolo *Harmful structures and Killing spinors* di cui riporto l'abstract: The existence of Killing spinors on a given manifold imposes strict conditions on its geometry. In the Riemannian setting in particular, this implies, for example, that the metric is Einstein. In the pseudo-Riemannian setting, the situation is less studied, nor as strict, for instance the metric need not be Einstein. In this talk, after an introduction to the language of spinors and some history concerning their study, I will present a new result concerning the existence of a Killing spinor on a pseudo-Riemannian manifold (Z, h). I will show that the existence on (Z, h) implies the existence of a pair of spinors (\psi, \phi) in the spinor bundle of an embedded (non-degenerate) hypersurface (M, g) satisfying a coupled PDE system involving the Weingarten operator of the embedding A, which will be called real or imaginary weakly /harmful structure/, depending on the signature of the normal vector-field to (M, g). The embedding process will require an additional technical condition, namely d tr A+\delta A = 0, and the assumption that the metric and the Weingarten operator are real analytic tensors. Some comments will be given on the special case of Lorentzian signature. Finally, I will present some work in progress regarding a (partial) classification in low dimension of harmful structures on homogeneous manifolds and the resulting cohomogeneity-one embeddings. This talk is based on a joint work with D. Conti and F.A. Rossi. A presto Diego

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Pranzo con lo speaker
by Carlo Collari 15 May '24

15 May '24

Buon pomeriggio, Lo speaker potrebbe non fare in tempo ad arrivare per pranzo. Per cui, con gli interessati ci vedremo direttamente al seminario. A presto, Carlo

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Seminario di Geometria del 16/05
by Carlo Collari 15 May '24

15 May '24

Buongiorno, Vi scrivo per ricordarvi che domani 16 Maggio, in Aula Seminari alle 14:30, Domenico Fiorenza (Sapienza Università di Roma) terrà il seminario dal titolo: * Projective 2-representations of linear Lagrangian correspondences* di cui riporto l'abstract: As recently illustrated by Ludewig and Roos, second quantization of fermions, i.e., the algebraic construction associating with a quadratic vector space its Clifford algebra and to a Lagrangian relation its exterior algebra (the Fock module) is an anomalous functor with values in the 2-category of algebras, bimodules and bimodule morphisms, with anomaly given by determinant lines. This can be equivalently seen as a projective 2-representation of the category of Lagrangian relations. By analogy to what happens with projective representations of groups, this suggests that suitable 2-central extensions of the category of Lagrangian relations should lift this projective 2-representation to an actual, i.e., non-anomalous, 2-representation. This makes the generalized Lagrangian relations considered by Stolz and Teichner naturally appear. Based on joint work in progress with Chetan Vuppulury. Per chi fosse interessato ad andare a pranzo con lo speaker ci troveremo per l'una e mezza in atrio. A presto, Carlo

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I: Postdoc at Lancaster
by Paolo Lisca 08 May '24

08 May '24

Inoltro annuncio di posizione post-doc. Paolo Lisca ________________________________ Da: Evans, Jonny <j.d.evans(a)lancaster.ac.uk> Inviato: mercoledì 8 maggio 2024 11:44 A: Evans, Jonny Oggetto: Postdoc at Lancaster Dear all, We are advertising a 20-month postdoc position in geometry at Lancaster University (UK). This is associated with the EPSRC grant "Frontiers in Symplectic Topology" which is led jointly by me (Jonny Evans, at Lancaster) and YankI Lekili (at Imperial). The grant is about exploring connections between symplectic geometry, algebraic geometry and low-dimensional topology, but eclecticism is welcomed, and people working in other flavours of geometry and topology are also encouraged to apply. The application deadline is 12th June. The position will be available as early as July, but with the possibility of starting later (e.g. September/October) if that's more convenient. If you know anybody who might be interested in applying, they can do so here: https://hr-jobs.lancs.ac.uk/Vacancy.aspx?ref=0593-24 Regards, Jonny Evans

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Seminario di geometria 9 maggio
by Filippo Bianchi 07 May '24

07 May '24

Carə tuttə, Il seminario di geometria di questa settimana si terrà Giovedì 9 Maggio alle 16.00 in Aula Seminari. Peter Smillie (Universität Heidelberg) parlerà di "Big minimal surfaces in symmetric spaces". Di seguito l'abstract. A well-known collection of problems in differential geometry reduce to the study of minimal surfaces in Riemannian symmetric spaces of non-compact type. In general, the derivative of the inclusion of a minimal surface is a holomorphic section of a certain vector bundle — what is special about symmetric spaces is that one can often recreate the minimal surface from this holomorphic data, through what is called the non-Abelian Hodge correspondence. This often lets you describe the moduli space of all minimal surfaces in an interesting way. However, this process of recreating the minimal surface still involves solving an elliptic PDE, and so precise questions require elliptic estimates. In this talk, I will try to describe the idea behind the basic interior estimate of Mochizuki and Simpson and some of its applications, and also tell you about a new version of this estimate with weaker hypotheses and weaker conclusions. This is work in progress with Nathanial Sagman. Ci troveremo alle 13 in atrio per andare a pranzo con lo speaker. Vi segnalo anche il seminario di Combinatoria, Teoria di Lie e Topologia di giovedì 9 maggio, potenzialmente interessante per alcuni membri del gruppo: alle 14.45 in Aula Magna Andrei Neguţ (MIT) parlerà di "Braids and coherent sheaves". Di seguito l'abstract: We will present a conjecture relating the affine Hecke category (an algebraic incarnation of annular braids) to coherent sheaves on the commuting variety. Joint work with Eugene Gorsky. This is an affine version of the conjecture (now a theorem) we proposed with Jacob Rasmussen that relates Khovanov homology to coherent sheaves on Hilbert schemes. Le informazioni sui prossimi seminari si trovano sul sito<https://www.dm.unipi.it/en/seminars/?category=653b522f8f0af760bdc42729>. Vi aspettiamo! Buona serata, Filippo, Giovanni e Giuseppe

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Fwd: Postdoc position at Università di Firenze
by Bruno Martelli 24 Apr '24

24 Apr '24

---------- Forwarded message --------- Da: Daniele Angella <daniele.angella(a)unifi.it> Date: Mer 24 Apr 2024, 08:10 Subject: Postdoc position at Università di Firenze To: geometriaglobale-group(a)unifi.it <geometriaglobale-group(a)unifi.it>, dimai-geometria-group(a)unifi.it <dimai-geometria-group(a)unifi.it>, GEOMETRY(a)listserv.utk.edu <GEOMETRY(a)listserv.utk.edu>, EAGER-GEN(a)listserv.dfn.de <EAGER-GEN(a)listserv.dfn.de> Dear all, We are looking for candidates for a Postdoc position at Università di Firenze, Italy, starting from September 2024. The position is funded by the PRIN2022 Project "Real and Complex Manifolds: Geometry and holomorphic dynamics". The call is open until the deadline June 20th, 2024: https://titulus.unifi.it/albo/viewer?view=files%2F005484724-UNFICLE-93897a4… Please forward the announcement to potential candidates! All the best, daniele

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I: Seminario baby geometri
by Giovanni Framba 22 Apr '24

22 Apr '24

Dato che il seminario di geometria è stato annullato, condivido l'invito al seminario dei BabyGs. Vi aspettiamo, Giovanni ________________________________ Da: Giovanni Framba via Dottorandi <dottorandi(a)lists.dm.unipi.it> Inviato: lunedì 22 aprile 2024 21:32 A: Studenti <studenti(a)dm.unipi.it>; dottorandi(a)dm.unipi.it <dottorandi(a)dm.unipi.it>; babygs-users(a)googlegroups.com <babygs-users(a)googlegroups.com> Oggetto: [dottorato] Seminario baby geometri Carə tuttə, Il seminario dei baby geometri di questa settimana si terrà domani Martedì 23 Aprile alle 14.30 in Aula Riunioni. Manousos Manouras (Université de Pau / Universidad de Zaragoza) parlerà di "Alexander type invariants of line arrangements". Di seguito l'abstract. There have been various definitions of the Alexander invariants of a knot. Following some of these definitions one can generalise them so as to have coefficients twisted by a linear representation. The Alexander type invariants are known to detect non-trivial topological information(genus, hyperbolic volume of a knot etc). The twisted Alexander polynomial was introduced by Wada for knots and has been studied thereafter for more general manifolds as the complement of algebraic curves or line arrangements. We will discuss the relation of the twisted Alexander polynomial of the exterior manifold of a line arrangement and the twisted Alexander polynomial of its boundary manifold. We will present how using twisted Alexander polynomials induced by reducible representations, we can retract nontrivial topological information. We will also deal with the characteristic varieties of line arrangements, studied by various authors such as Zariski, Libgober, Artal. The main problem is to understand if the characteristic varieties are combinatorially determined in general. This is known to be true for their ”homogeneous part”, which corresponds to the resonance variety, as well as for the translated components having dimension at least one, as they are determined by orbifold pencils. This does not work in the same way for the 0-dimensional translated components. Here we present examples such that the characteristic variety has some translated 0-dimensional global component. Ci troveremo alle 13 in atrio per andare a pranzo con lo speaker. Le informazioni sui prossimi seminari si trovano sul sito dei Baby Geometri! Vi aspettiamo! Buona serata, Filippo, Giovanni e Giuseppe

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Seminario di geometria 23/04
by Filippo Bianchi 22 Apr '24

22 Apr '24

Carə tuttə, Il seminario di geometria di questa settimana si terrà domani Martedì 23 Aprile alle 14.30 in Aula Riunioni. Isaac Sundberg (MPIM Bonn) parlerà di "Khovanov homology and surfaces in the 4-ball". Di seguito l'abstract. It is difficult to detect differences between topological and smooth phenomena, so it was surprising when Rasmussen used a purely combinatorial theory, known as Khovanov homology, to obstruct the smooth sliceness of topologically slice knots. In this talk, we discuss another application of this homology theory: obstructing smooth isotopy of topologically isotopic surfaces in the 4-ball. We highlight recent results and give an idea of the construction for this obstruction. Ci troveremo alle 13 in atrio per andare a pranzo con lə speaker. Le informazioni sui prossimi seminari si trovano sul sito<https://www.dm.unipi.it/en/seminars/?category=653b522f8f0af760bdc42729>. Vi aspettiamo! Buona serata, Filippo, Giovanni e Giuseppe

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Geometria_Pisa