Notiziario Scientifico
a cura del Dipartimento di Matematica G. Castelnuovo, Sapienza Università di Roma
Settimana dal 15-03-2021 al 21-03-2021
Lunedì 15 marzo 2021
Ore 14:30, aula Picone -- https://meet.google.com/nie-attq-ged , Dipartimento di Matematica, Sapienza Università di Roma
seminario di Analisi Matematica
Luca Rossi (dpt Matematica Spienza U. di Roma)
Are solutions of reaction-diffusion equations asymptotically 1D ?
The symmetry of solutions of elliptic equations is a classical and challenging problem in PDE, connected with stability. In this talk we are concerned with parabolic equations and we ask whether the 1-dimensional symmetry eventually emerges in the long time, for solutions which are initially non-symmetric. We will present a satisfactory answer in the case of the Fisher-KPP equation, together with some counter-examples and open questions. This topic is the object of a joint work with F. Hamel.
Lunedì 15 marzo 2021
Ore 15:45, Aula Picone. In presenza ma anche online via Google Meet all'URL https://meet.google.com/cus-yrdr-tnf, Dipartimento di Matematica, Sapienza Università di Roma
Corso di Dottorato.
Thomas Schick (Universität Göttingen)
The topology of positive scalar curvature
Seconda lezione del corso. Orario definitivo: Lunedi' 15.45- 17.30. Mercoledi 15.30- 17.15. Fino al 31 Marzo incluso.
Per informazioni, rivolgersi a: piazza@mat.uniroma1.it
Lunedì 15 marzo 2021 *** ANNULLATO ***
Ore 16:00, Seminario telematico via Google Meet all'URL https://meet.google.com/cgd-wwjj-xih, Dipartimento di Matematica, Sapienza Università di Roma
Fernando Damiani (Sapienza Università di Roma)
The Wadge hierarchy on the Baire space endowed with the co-compact topology
The talk deals with the Wadge hierarchy on the set \( \mathbb N^\mathbb N\) endowed with the co-compact topology generated from the standard topology of the Baire space. We fully unveil this quasi-order on the \(\Sigma^0_2\) subsets of the Baire space, pointing out how it differs from the well-known Wadge hierarchy of the Baire space. Neverthless, in aiming to build this quasi-order, we higlight a link between the latter and the Wadge hierarchy on the Cantor space \(2^\mathbb N\): the second embedds into the first when it is restricted to its Wadge degrees that contain a dense subset of the Cantor space. This argument lets us study only the hierarchy on the so called "very small" sets and for the other cases we proceed manually. At the end, we will be able to show that the clopen sets occur at a very high level of this hierarchy and below them there are \( \omega_1 \) antichains of length 4 and no infinite decreasing \( \Sigma^0_2 \)-chains.
Per informazioni, rivolgersi a: damiani@mat.uniroma1.it
Mercoledì 17 marzo 2021
Ore 14:00, Seminario telematico via Google Meet all'URL http://meet.google.com/jjt-toji-skw, Dipartimento di Matematica, Sapienza Università di Roma
seminario di Algebra e Geometria
Anne Lonjou (Université Paris-Saclay)
Actions of Cremona groups on CAT(0) cube complexes
A key tool to study the plane Cremona group is its action on a hyperbolic space. Sadly, in higher rank such an action is not available. Recently, in geometric group theory, actions on CAT(0) cube complexes turned out to be a powerful tool to study a large class of groups. In this talk, based on a common work with Christian Urech, we will construct such complexes on which Cremona groups of rank n act. Then, we will see which kind of results on these groups we can obtain.
Per informazioni, rivolgersi a: diverio@mat.uniroma1.it
Mercoledì 17 marzo 2021
Ore 14:30, https://meet.google.com/pip-kvzt-fkz, Dipartimento di Fisica, Università di Roma La Sapienza
Seminario delle Meccaniche
Giovanni Felder (ETH, Zurigo)
The integrable Boltzmann system
Ludwig Boltzmann, in his search for an example of a chaotic dynamical system, studied the planar motion of a particle subject to a central force bouncing elastically at a line. As recently noticed by Gallavotti and Jauslin, the system is actually integrable if the force has an inverse-square law. I will review the construction of the second integral of motion and present the results: the orbits of the Poincaré map are periodic or quasi-periodic and anisochronous, so that KAM perturbation theory (Moser's theorem) applies, implying that for small perturbations of the inverse-square law the system is still not chaotic. The proof relies on mapping the Poincaré map to a translation by an element of an elliptic curve. A corollary is the Poncelet property: if an orbit is periodic for given generic values of the integrals of motions then all orbits for these values are periodic.
Mercoledì 17 marzo 2021
Ore 16:30, https://meet.google.com/gjj-uqoy-euw, Dipartimento di Matematica, Sapienza Università di Roma
Seminario di Fisica Matematica
Biagio Cassano (Università di Bari)
General δ-shell interactions for the two-dimensional Dirac operator
n this talk we will consider the two-dimensional Dirac operator with general local singular interactions supported on a closed curve. A systematic study of the interaction is performed by decomposing it into a linear combination of four elementary interactions: electrostatic, Lorentz scalar, magnetic, and a fourth one which can be absorbed by using unitary transformations. We address the self-adjointness and the spectral description of the underlying Dirac operator, and moreover we describe its approximation by Dirac operators with regular potentials. This is a joint work with V. Lotoreichik, A. Mas and M.Tušek.
Giovedì 18 marzo 2021
Ore 14:00, Seminario online su questo link. , Dipartimento di Matematica, Università di Roma "Tor Vergata"
Seminario di Analisi Matematica
Mario Santilli (University of Augsburg)
Regularity of distance functions from arbitrary closed sets
Let \( \phi \) be a non-Euclidean uniformly convex norm. We show that the gradient of an anisotropic \(\phi\)-distance function \(\delta^\phi_K \) from an arbitrary closed subset \(K\) of \(R^n\) satisfies a local Lipschitz property on the complement of the \(\phi\)-cut-locus of \(K\); namely on \(R^n \setminus (K \cup Cut^\phi(K))\). Then we study the geometric properties of the set points where the distance function is second-order pointwise differentiable. The available known results allow only to conclude that the gradient of \( \delta^\phi_K \) is locally Lipschitz on the interior of \(R^n \setminus (K \cup Cut^\phi(K))\), which might be empty even if \(K\) is a \(C^{1,\alpha}\) hypersurface or \(K\) is the complementary of a convex body with \(C^1\) boundary. NB:This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV CUP E83C18000100006
Per informazioni, rivolgersi a: molle@mat.uniroma2.it
Giovedì 18 marzo 2021
Ore 14:30, Canale Youtube di Cnr-IAC https://www.youtube.com/watch?v=3eo8EVATOJI, Istituto per le Applicazioni del Calcolo, Consiglio Nazionale delle Ricerche
Seminari generali IAC 2021
Stefano Guarino (Istituto per le Applicazioni del Calcolo, Consiglio Nazionale delle Ricerche)
Evaluating non-pharmaceutical interventions at the microscopical scale: the case of Florence's Parco delle Cascine
The recent global pandemic outbreak drew significant attention towards the definition of non-pharmaceutical interventions (NPIs) to mitigate the diffusion of the contagion in the population. In this talk, I will present a new data-driven simulator that leverages on public geographic information systems (GIS) to extract a detailed representation of social interactions occurring within a location of interest. The simulator allows to formulate hypotheses and provides multi-level control of policy options, thus permitting to define probabilistic scenarios and to evaluate them in terms of diffusion of the contagion in the population and in the surrounding territory. I will present experimental results focused on the greatest park of the City of Florence, to show the viability of a data-driven simulation-based approach to the evaluation of possible NPIs.
Per informazioni, rivolgersi a: roberto.natalini@cnr.it
Giovedì 18 marzo 2021
Ore 14:30, Sala di Consiglio - https://meet.google.com/ads-dekx-bgm, Dipartimento di Matematica, Sapienza Università di Roma
Seminario P(n)
Susanna Risa (Università di Napoli)
Spherical rigidity for contractive and expansive ancient flows
Ancient solutions are flows which are defined for all negative times. They model the asymptotic shape of hypersurfaces contracting by extrinsic curvature as tangent flows at singularities, provided the second fundamental form blows up at a spherical scale. We will discuss conditions which ensure that a closed ancient extrinsic flow of hypersurfaces in Euclidean space is a sphere evolving by homotheties for various nonlinear speeds, such as mean curvature, Gaussian curvature and inverse mean curvature. In particular, we will show how a uniform pinching condition on the second fundamental form is sufficient to establish sphericity for contractive flows. On the other hand, expansive flows exhibit stronger rigidity: it suffices to require that the hypersurface "comes out of a point" and apply a modified Alexandrov reflection principle. Joint work with Carlo Sinestrari.
Per informazioni, rivolgersi a: galise@mat.uniroma1.it
Giovedì 18 marzo 2021
Ore 14:30, Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre
Seminario di Geometria
Mirko Mauri (MPIM Bonn)
Intersection cohomology of character varieties of rank two
Character varieties parametrise representations of the fundamental
group of a compact Riemann surface, and in general they are singular
affine varieties. They are prototypes of singular hyperkahler
varieties and provide examples of SYZ mirror pairs. In this seminar,
we will present the computation of the intersection cohomology of rank
two character varieties. We will derive several results concerning the
P=W conjecture and the Hausel-Thaddeus topological mirror symmetry
conjecture for singular character varieties.
Per partecipare al Seminario cliccare sul seguente Link
Giovedì 18 marzo 2021
Ore 15:00, Il seminario sarà tenuto in modalità telematica, Link per partecipare: https://uniroma1.zoom.us/j/85943796292?pwd=dDliSTJBTFVmazRNYXZGV0lBVUJCZz09
Seminari di Ricerca in Didattica e Storia della Matematica
Annalisa Cusi (Sapienza Università di Roma) e Agnese Ilaria Telloni (Università Politecnica delle Marche)
Processi di individualizzazione in matematica a livello universitario: il ruolo delle tecnologie digitali
Venerdì 19 marzo 2021
Ore 15:00, Seminario Telematico, Link
Online Representation Theory Seminar
Daniele Valeri (University of Glasgow)
Lax type operator for W-algebras
In 1985 Zamolodchikov constructed a "non-linear" extension of the Virasoro algebra known as W_3 algebra. This is one of the first appearances of a rich class of algebraic structures, known as W-algebras, which are intimately related to physical theories with symmetries and revealed many applications in mathematics. In the talk I will review some basic facts about the general theory of W-algebras and provide a description using Lax operators. This approach shows the deep connection of the theory of W-algebras with Yangians and integrable Hamiltonian hierarchies of Lax type equations. This is a joint work with A. De Sole and V.G. Kac.
Venerdì 19 marzo 2021
Ore 16:00, Il seminario sarà tenuto in modalità telematica, Link per partecipare: https://uniroma1.zoom.us/meeting/register/tZwtcOGqqzkpE9yen93NMtuUttv031ZmB9lt
Seminari per insegnanti (PLS)
Emiliano Ippoliti (Sapienza Università di Roma)
Matematica e mercati finanziari
Le comunicazioni relative a seminari da includere in questo notiziario devono pervenire esclusivamente
mediante apposita form da compilare online, entro le ore 24 del giovedì precedente la settimana
interessata. Le comunicazioni pervenute in ritardo saranno ignorate.
Per informazioni, rivolgersi all'indirizzo di posta elettronica
seminari@mat.uniroma1.it.
Coloro che desiderano ricevere questo notiziario via e-mail sono pregati
di comunicare il proprio indirizzo di posta elettronica a
seminari@mat.uniroma1.it.