| 29/04/26 | Colloquium | 16:00 | 17:00 | 1201 Dal Passo | Mikael Rørdam | University of Copenhagen |
Colloquium "Levi-Civita"
The Connes Embedding Problem, Kirchberg’s reformulations, Tsirelson’s conjecture, and MIP*=RE
In his seminal classification paper from 1976, Connes remarked that every separable tracial von Neumann algebra ought to be embeddable into an ultrapower of the hyperfinite type II_1 factor, or, in other words, be approximable by matrices. Over the following decades, the Connes Embedding Problem (CEP) remained unsolved, but many interesting and deep reformulations were discovered. Prominently, Kirchberg proved in his famous 1991 Inventiones paper that CEP is equivalent to several questions concerning C*-algebras and their tensor product, including his QWEP conjecture. He also showed that CEP holds if and only if there is a unique C*-norm of the tensor product of two copies of the full group C*-algebra of the free group. The latter was shown (by several authors) to be equivalent to Tsirelson’s conjecture about quantum correlations. CEP also relates to the open problems in group theory if all infinite discrete groups are sofic. Recently, Ji-Natarajan-Vidick-Wright-Yuen announced a negative solution to Tsirelson’s conjecture, and hence also a negative answer to CEP by proving that two complexity classes are the same |
| 28/04/26 | Seminario | 14:30 | 16:00 | 1101 D'Antoni | Sébastien Boucksom | Institut de Mathématiques de Jussieu | Geometry Seminar
Around the Yau-Tian-Donaldson conjecture
The YTD conjecture predicts that the existence of "canonical" Kähler metrics on a polarized projective manifold is governed by a purely algebro-geometric notion known as K-stability. Recently, solutions to (variants of) this conjecture have been proposed, and the purpose of this talk is to review this recent progress.
Note:
This talk is part of the activity of the MIUR Department of Excellence Project MatMod@TOV (2023-2027) and the PRIN 2022 Moduli Spaces and Birational Geometry and Prin PNRR 2022 Mathematical Primitives for Post Quantum Digital Signatures |
| 28/04/26 | Seminario | 14:30 | 15:30 | 1201 Dal Passo | Judith Vancostenoble | Université de Toulouse | Seminario di Equazioni Differenziali
Recovering insolation functions in Sellers climate models
We are interested in climate models introduced by Sellers in 1969 which takes the form of some nonlinear parabolic equation with a degenerate diffusion coefficient. We investigate here some inverse problem issue that consists in recovering the so-called insolation function. We not only solve the uniqueness question but also provide some strong stability result, more precisely unconditional Lipschitz stability.
NB:
This talk is part of the activity of the MUR Excellence Department Project MATH@TOV CUP E83C23000330006
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| 24/04/26 | Seminario | 16:00 | 17:00 | 1201 Dal Passo | Tobias ROSSMANN | Galway University |
Algebra & Representation Theory Seminar (ARTS)
"Counting orbits"
N.B.: this talk is part of the activity of the MIUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)
This talk revolves around generating functions enumerating linear orbits and conjugacy classes of unipotent groups. We will study these generating functions by means of their linearised siblings ("ask zeta functions") obtained by averaging over sizes of kernels in modules of matrices. The study of the latter functions involves a happy blend of algebra, combinatorics, and geometry.
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<em> <strong><u>N.B.</u>:</strong> this talk is part of the activity of the MIUR Excellence Department Project MatMod@TOV (CUP E83C23000330006) </em>
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| 24/04/26 | Seminario | 14:30 | 15:30 | 1201 Dal Passo | Thomas GOBET | Université Clermont Auvergne |
Algebra & Representation Theory Seminar (ARTS)
"Bruhat orders and Hecke algebra modules attached to Coxeter subgroups"
N.B.: this talk is part of the activity of the MIUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)
Given a Coxeter group and a standard parabolic subgroup, Deodhar constructed a module over the Iwahori-Hecke algebra of the Coxeter group, giving rise to the so-called parabolic Kazhdan-Lusztig polynomials. <br>
There is no general theory of "Coxeter subgroups" of Coxeter groups, but several families of subgroups of Coxeter groups themselves admit a canonical structure of Coxeter group. <br>
We explain how to generalize Deodhar's construction to subgroups obtained as fixed points of an automorphism of order at most two of a standard parabolic subgroup of an arbitrary Coxeter group. This is joint work with P.-E. Chaput and L. Fresse, relying on properties of elements of minimal length in cosets modulo such subgroups obtained in a joint work with N. Chapelier.
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<em> <strong><u>N.B.</u>:</strong> this talk is part of the activity of the MIUR Excellence Department Project MatMod@TOV (CUP E83C23000330006) </em>
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| 22/04/26 | Seminario | 16:00 | 17:00 | 1101 D'Antoni | Klaudiusz Czudek | Gdańsk University of Technology | Seminario di Sistemi Dinamici
On a certain characterization of Birkhoff billiards inside discs
I am going to discuss a certain characterization of Birkhoff Billiards inside discs which is related to the expansion of the formal Lazutkin conjugacy at the boundary. Based on the joint work with Jacopo De Simoi, Andrew Gad and Marco Poon.
Note: This talk is part of the activity of the MIUR Department of Excellence Project MatMod@TOV (2023–2027). |
| 22/04/26 | Seminario | 16:00 | 17:00 | 1201 Dal Passo | Sergey Neshveyev | University of Oslo |
Operator Algebras Seminar
Generalized Cuntz-Pimsner algebras and their quantum symmetries
Note:This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)
Noncommutative function theory and dilation theory for semigroups of completely positive maps have led to an interesting class of algebras generalizing Cuntz and Cuntz-Pimsner algebras. While formally they are defined in a familiar way, using creation operators on Fock-type spaces, what makes them difficult to study is that it is not clear how to obtain mixed commutation relations between the creation and annihilation operators. As a result until recently these algebras have been understood only in a few special cases, and there are still no general methods of obtaining relations in them, analyzing the ideal structure or computing the K-theory. Some of these algebras admit large quantum symmetries, and quantum groups provide then tools to analyze them, which are not accessible from a more classical point of view. The talk will review some results, examples and open problems in this area. |
| 21/04/26 | Seminario | 16:00 | 17:00 | 2001 | Simone Diverio | Sapienza | Geometry Seminar
Varietà kähleriane compatte con rivestimento universale biolomorfo e dimensione di Kodaira
La dimensione di Kodaira è un invariante bimeromorfo discreto fondamentale per le varietà kähleriane compatte. Per il teorema di uniformizzazione, due superfici di Riemann compatte hanno la stessa dimensione di Kodaira se e solo se ammettono rivestimenti universali biolomorfi. Questa equivalenza viene completamente meno in dimensione superiore, ma ciononostante, grazie alla classificazione di Enriques-Kodaira, è possibile dimostrare che due superfici kähleriane compatte aventi rivestimenti universali biolomorfi hanno necessariamente la stessa dimensione di Kodaira.
Inoltre, nel 1996 H. Tsuji ha dimostrato che, in qualsiasi dimensione, ogni quoziente compatto non ramificato del rivestimento universale di una varietà proiettiva di tipo generale (ossia con dimensione di Kodaira massimale) deve essere anch'esso di tipo generale.
In questo seminario presenteremo un lavoro in corso di Anna Choblet, mia studentessa di dottorato (in congiuntamente con B. Claudon), che mira a dimostrare come il risultato di Tsuji resti valido anche in dimensione tre nel caso di dimensione di Kodaira zero. |
| 21/04/26 | Seminario | 14:30 | 15:30 | 1201 Dal Passo | Filippo Quattrocchi | LMO- Orsay | Seminario di Equazioni Differenziali
Acceleration-based optimal transport
Finding smooth interpolations between probability measures is a problem of broad interest, with natural applications, e.g., in biology (trajectory inference) and computer graphics (image interpolation). In this talk, I will discuss a model in which such interpolations are obtained by minimizing an action functional of the acceleration. This minimization defines a discrepancy between measures that -- in analogy with Wasserstein distances from optimal transport theory -- admits an equivalent fluid-dynamical formulation and induces a Riemannian-like geometry on the space of measures. These results suggest possible applications to kinetic PDEs. This talk is based on arXiv:2502.15665, in collaboration with G. Brigati (ISTA) and J. Maas (ISTA), and ongoing work with G. Brigati (ISTA), G. Carlier (CEREMADE, Paris Dauphine-PSL), and J. Dolbeault (CEREMADE, Paris Dauphine University-PSL).
NB:
This talk is part of the activity of the MUR Excellence Department Project MATH@TOV CUP E83C23000330006
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| 21/04/26 | Seminario | 14:30 | 16:00 | 1101 D'Antoni | Paola Frediani | Università di Pavia | Geometry Seminar
A canonical projective structure on $mathbb{R}_g$
I will report on a joint work in progress with I. Biswas, E. Colombo and A. Ghigi in which we describe a canonical projective structure on every etale double cover of a curve $C$ of genus $g>6$. This projective structure is the restriction to the second infinitesimal neighborhood of the diagonal in $C imes C$ of the second fundamental form of the Prym map. It gives a section of the space of projective structures on $mathbb{R}_g$ and the $(0,1)$-component of the differential of this section is proven to be the pullback via the Prym map of the Kaehler form on $A_{g-1}$. This generalises a previous result obtained in collaboration with Biswas, Colombo, and Pirola in the case of $M_g$, showing the existence of a canonical projective structure on every curve of genus $g>3$, obtained by the second fundamental form of the Torelli map.
Note:
This talk is part of the activity of the MIUR Department of Excellence Project MatMod@TOV (2023-2027) and the PRIN 2022 Moduli Spaces and Birational Geometry and Prin PNRR 2022 Mathematical Primitives for Post Quantum Digital Signatures |