28/01/22  Seminario  16:00  17:00  1201 Dal Passo  René SCHOOF  Università di Roma 
Algebra & Representation Theory Seminar (ARTS)
"Class numbers of cyclotomic fields"
 in live & streaming mode 
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It is notoriously difficult to compute class numbers of cyclotomic fields.
In this expository lecture we describe an experimental approach to this problem.
N.B.: please click HERE to attend the talk in streaming.

28/01/22  Seminario  14:30  15:30  1201 Dal Passo  Andrea FERRAGUTI  SNS Pisa 
Algebra & Representation Theory Seminar (ARTS)
"Abelian dynamical Galois groups"
 in live & streaming mode 
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Dynamical Galois groups are invariants associated to dynamical systems generated by the iteration of a selfrational map of P^{1}. These are still very mysterious objects, and it is conjectured that abelian groups only appear in very special cases. We will show how the problem is deeply related to a dynamical property of these rational maps (namely that of being postcritically finite) and we will explain how to approach and prove certain nontrivial cases of the conjecture.
This is based on joint works with A. Ostafe, C. Pagano and U. Zannier.

25/01/22  Seminario  16:00  17:00  1201 Dal Passo  Rafael Ruggiero  PUC Rio De Janeiro  Seminario di Equazioni Differenziali
On the graph property for totally irrational Lagrangian invariant tori
(MS Teams link for the streaming at the end of the abstract)
We show that every C2 Lagrangian invariant torus W of a Tonelli Hamiltonian defined in the ntorus
containing an orbit with totally irrational homology class is a graph of the canonical projection. This result extends the graph property obtained by Bangert and BialyPolterovich for Lagrangian minimizing tori without periodic orbits in the unit tangent bundle of a Riemannian metric in the two torus. Motivated by the famous Hedlund's examples of Riemannian metrics in the ntorus with n closed, homology independent, minimizing geodesics having minimizing tunnels, we also show the C1generic nonexistence of Lagrangian invariant tori with "large" homology.
MS Teams Link for the streaming
Note:
This talk is part of the activity of the MIUR Department of Excellence Project MATH@TOV CUP E83C18000100006 
25/01/22  Seminario  14:30  15:30  1201 Dal Passo  Simone Diverio  La Sapienza  Geometry Seminar
Universal Gysin formulae and positivity of some characteristic
In the last years there have been a renewed interest for a conjecture by Griffiths stated in 1969. The conjecture characterises the positive characteristic forms for positive (in the sense of Griffiths) holomorphic Hermitian vector bundles: those should be the exactly the forms belonging to the positive cone spanned by Schur forms. After recalling the various definitions of positivity for holomorphic Hermitian vector bundles and (p,p)forms, we shall explain a recent result, obtained in collaboration with my PhD student F. Fagioli, which partially confirms Griffiths' conjecture. The result is obtained as an application of a pointwise, differentialgeometric version of a Gysin type formula for the pushforward of the curvature of tautological bundles over the flag bundle. 
18/01/22  Seminario  14:30  15:30  1201 Dal Passo  Eleonora di Nezza  Ecole Polytechnique de Paris  Geometry Seminar
Families of KählerEinstein metrics.
In a lot of geometric situations we need to work with families of varieties. In this talk we focus on families of singular KählerEinstein metric. In particular we study the case of a family of Kähler varieties and we develop the first steps of pluripotential theory in family, which will allow us to have a control on the C^0 estimate when the complex structure varies. This type of result will be applied in different geometric contexts. This is a joint work with V. Guedj and H. Guenancia. 
14/01/22  Seminario  14:30  15:30  1201 Dal Passo  Jens EBERHARDT  University of Bonn 
Algebra & Representation Theory Seminar (ARTS)
"Motivic Springer theory"
 in live & streaming mode 
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N.B.: this talk is part of the activity of the MIUR Excellence Department Project CUP E83C18000100006
Algebras and their representations can often be constructed geometrically in terms of convolution of cycles. For example, the Springer correspondence describes how irreducible representations of a Weyl group can be realised in terms of a convolution action on the vector spaces of irreducible components of Springer fibers. Similar situations yield the affine Hecke algebra, quiver Hecke algebra (KLR algebra), quiver Schur algebra or Soergel bimodules.
N.B.: please click HERE to attend the talk in streaming.

16/12/21  Colloquium  16:00  17:30  1201 Dal Passo  Nicola Gigli  SISSA Trieste  Differentiating in a nondifferentiable environment
( MS Teams Link for the streaming )
We all know what the differential of a smooth map from R to R is. By looking at coordinates and then at charts, we also know what it is the differential of a smooth map between differentiable manifolds. With a little bit of work, we can also define a (weak) differential for Sobolev/BV maps in this setting (but the case of manifoldvalued maps presents challenges already at this level). In this talk I will discuss how it is possible to differentiate maps between spaces that have no underlying differentiable structure at all. The concepts of Sobolev/BV maps in this setting will also be discussed.
NB:This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV CUP E83C18000100006 
16/12/21  Seminario  15:15  16:15  21  Enrico Bozzo  Università degli Studi di Udine  Ordinamento attento al tempo e problema del consenso
Si esamina l'integrazione in alcuni noti metodi di ordinamento proposti in ambito sportivo dell'informazione relativa al momento in cui avvengono gli incontri. I metodi ottenuti, definibili attenti al tempo, sono descritti da ricorrenze a coefficienti variabili in cui appaiono delle matrici stocastiche. Nell'ambito della teoria dei sistemi lo studio della convergenza di queste ricorrenze viene definito problema del consenso. Malgrado sul problema del consenso esita una vasta letteratura ci sono meno risultati sulla velocità di convergenza che ha importanti ricadute pratiche.
È una ricerca in collaborazione con Paolo Vidoni e Massimo Franceschet dell'Università di Udine.
Questo seminario è parte dell'attività del Progetto MIUR Dipartimento d'Eccellenza CUP E83C18000100006.
MS Teams link for the streaming

14/12/21  Seminario  14:30  15:30  1201 Dal Passo  Sara Torelli  Lebniz University Hannover  Geometry Seminar
Holomorphic one forms on moduli of curves
In the talk I will prove that the moduli spaces Mg,n of nmarked curves of any genus g > 4 do not admit holomorphic 1forms. The main difficulty is to prove the result for Mg, then one concludes the other cases by an inductive argument. This sheds new light on the question of how far Mg,n is from being projective. The work is joint with F.F. Favale and G.P.Pirola. 
10/12/21  Seminario  16:00  17:00   Riccardo BIAGIOLI  Università di Bologna 
Algebra & Representation Theory Seminar (ARTS)
"TemperleyLieb algebra and fully commutative elements in affine type C"
 in live & streaming mode 
( please click HERE to attend the talk in streaming )
N.B.: this talk is part of the activity of the MIUR Excellence Department Project CUP E83C18000100006
The TemperleyLieb algebra is a well studied finite dimensional associative algebra: it can be realized as a diagram algebra and it has a basis indexed by the fully commutative elements in the Coxeter group of type A. A few years ago, Dana Ernst introduced an elegant generalization of such diagrammatic representation for the generalized TemperleyLieb algebra of affine type C. The proof that such representation is faithful is quite involved and the same author wonders if an easier proof exists.
In this talk, we present a new combinatorial way to describe Ernst's algebra homomorphism, from which injectivity and subjectivity follow more easily. Our results are based on a classification of fully commutative elements of affine type C in terms of heaps of pieces, and on certain operations that we define on such heaps.
This talk is based on a joint work with Giuliana Fatabbi and Gabriele Calussi.
N.B.: please click HERE to attend the talk in streaming
