Notiziario Scientifico

Notiziario dei seminari di carattere matematico
a cura del Dipartimento di Matematica G. Castelnuovo, Sapienza Università di Roma

Settimana dal 25-05-2020 al 31-05-2020

Lunedì 25 maggio 2020
Ore 14:00, teleconferenza, collegarsi al link, https://meet.google.com/pip-kvzt-fkz
Seminari delle Meccaniche
Giovanni Gallavotti (Università di Roma La Sapienza)
Chaos theory for mechanics and fluids: modern views, controversies
New ideas generate misunderstandings and controversies. The theory of chaotic evolution has key implications on topics like nonequilibrium thermodynamics, ergodicity, entropy, turbulence, ensembles: these will be presented to discuss novelties stemming out of Ruelle's and Bowen contributions and from the preceding work of Anosov, Sinai ....


Martedì 26 maggio 2020
Ore 15:00, ZOOM Meeting ID: 962 612 6392 Pwd: mdn265, Dipartimento di Matematica, Sapienza Università di Roma
Seminario di Modellistica Differenziale Numerica On-Line
Andrea Thomann (Dottorato, Università dell'Insubria)
A low Mach relaxation scheme for the Euler equations
Low Mach problems arise in gas dynamics when the local speed is much smaller than the acoustic waves.. In these regimes, a full resolution of all the waves requires very small time steps, while usually one is interested in the slow dynamics of the material wave. In this work, we use a relaxation approach to separate the slow and the fast scales, and integrate the fast scales implicitly. We also prove that we recover the correct asymptotic limit, if the initial data is close to the vanishing Mach limit, which yields the incompressible Euler equations. Joint work with G. Puppo (La Sapienza) and C. Klingenberg (JMU Würzburg).
Per informazioni, rivolgersi a: falcone@mat.uniroma1.it


Martedì 26 maggio 2020
Ore 15:45, ZOOM Meeting ID: 962 612 6392 Pwd: mdn265, Dipartimento di Matematica, Sapienza Università di Roma
Seminario di Modellistica Differenziale Numerica On-Line
Elisa Iacomini (Università di Mannheim)
A time-delayed first order model for traffic flow and its properties
In this talk I will investigate the theoretical and numerical properties of the first-order Lighthill-Whitham-Richards (LWR) traffic flow model with time delay. Since standard results from the literature are not directly applicable to the delayed model, we will mainly focus on the numerical analysis of the proposed finite difference discretization. The numerical tests will also show that the delayed model is able to reproduce Stop & Go waves, a typical feature of congested traffic.
Per informazioni, rivolgersi a: falcone@mat.uniroma1.it


Mercoledì 27 maggio 2020
Ore 14:00, https://meet.google.com/vsz-nxkm-hav, Dipartimento di Matematica, Sapienza Università di Roma
Seminario di Algebra e Geometria
Michele D'Adderio (Université libre de Bruxelles)
Partial and global representations of finite groups
The notions of partial actions and partial representations have been extensively studied in several algebraic contexts in the last 25 years. In this talk we introduce these concepts and give a short overview of the results known for finite groups. We will briefly show how this theory extends naturally the classical global theory, in particular in the important case of the symmetric group. This is joint work with William Hautekiet, Paolo Saracco and Joost Vercruysse.
Per informazioni, rivolgersi a: giovanni.cerulliirelli@uniroma1.it


Mercoledì 27 maggio 2020
Ore 15:00, Link alla videoconferenza, Dipartimento di Matematica, Università di Roma "Tor Vergata"
Colloquium di dipartimento
Marcelo Viana (IMPA - Rio de Janeiro)
Lyapunov exponents
The concept of Lyapunov exponent goes back to Lyapunov's 1892 thesis on the stability of differential equations, and has numerous applications in various branches of mathematics and science. Starting from the 1960s, it found its proper mathematical framework in ergodic theory, where it has had a prominent role ever since. In this colloquium lecture I will review a few recent developments, especially about the way Lyapunov exponents depend on the underlying dynamical system.
N.B.: this talk is part of the activity of the MIUR Excellence Department Project CUP E83C18000100006.
Per informazioni, rivolgersi a: molle@mat.uniroma2.it


Giovedì 28 maggio 2020
Ore 14:00, Il seminario sarà tenuto in modalità telematica, Link per partecipare al seminario: https://meet.google.com/mpv-nitc-sed
Seminari di Ricerca in Didattica della Matematica
Lorenzo Mazza (Sapienza Università di Roma)
Giocare con la matematica


Giovedì 28 maggio 2020
Ore 17:00, On line Seminar , Web site for information: https://www.dinamici.org/dai-seminar/
DinAmicI: Another Internet Seminar (DAI Seminar)
Francesco Cellarosi (Queen's University (Canada))
Rational Horocycle lifts and the tails of Quadratic Weyl sums
Equidistribution of horocycles on hyperbolic surfaces has been used to dynamically answer several probabilistic questions about number-theoretical objects. In this talk we focus on horocycle lifts, i.e. curves on higher-dimensional manifolds whose projection to the hyperbolic surface is a classical horocycle, and their behaviour under the action of the geodesic flow. It is known that when such horocycle lifts are `generic’, then their push forward via the geodesic flow becomes equidistributed in the ambient manifold. We consider certain ‘non-generic’ (i.e. rational) horocycle lifts, in which case the equidistribution takes place on a sub-manifold. We then use this fact to study the tail distribution of quadratic Weyl sums when one of their arguments is random and the other is rational. In this case we obtain random variables with heavy tails, all of which only possess moments of order less than 4. Depending on the rational argument, we establish the exact tail decay, which can be described with the help of the Dedekind \psi-function. Joint work with Tariq Osman. Note: The zoom link to the seminar will be posted on https://www.dinamici.org/dai-seminar/ and on https://mathseminars.org/seminar/DinAmicI. Moreover, it will be streamed live on youtube via the DinAmicI channel: https://www.youtube.com/channel/UCyNNg155G3iLS7l-qZjboyg
Per informazioni, rivolgersi a: sorrentino@mat.uniroma2.it


Venerdì 29 maggio 2020
Ore 10:30, Modalità telematica, Dipartimento di Matematica e Fisica, Università degli Studi RomaTre
Seminario di Logica e Informatica Teorica
Jean-Yves Girard (CNRS, Directeur de recherche émeérite)
La logique déconfinée
Nul besoin de système pour raisonner, il suffit d’utiliser des tests. Jusqu’à une date récente, je pensais que cette approche d’usine achoppait sur des problèmes de finitude. Mais si l’on considère des tests suffisants (pas nécessaires donc), les batteries de tests peuvent rester finies. L’opposition traditionnelle entre Curry et Church se retrouve sous la forme usage/usine. L’usage (BHK) définit les signifiants logiques implicitement : le type comme comportement. L’usine (Herbrand) définit les signifiants logiques explicitement : le type comme critère de correction. Ces deux approches sont reliées par un résultat d’adéquation, élimination des coupures si l’on veut : les tests suffisent à garantir l’usage. La trinité réaliste axiomatique syntaxe/sémantique/méta est ainsi remplacée par une trinité déréaliste usine/usage/adéquation.
Il seminario sarà tenuto in lingua francese. Per partecipare al seminario bisognerà chiedere il link all’indirizzo email vitomichele.abrusci@uniroma3.it o cliccare sul seguente link Teams Meeting: link


Venerdì 29 maggio 2020
Ore 14:30, Videoconference talk - visit the ARTS web page and click on the link that you find there., dipartimento di Matematica - Università di Roma "Tor Vergata"
ARTS - Algebra and Representation Theory Seminar
Mattia COLOMA (Università di Roma "Tor Vergata")
The Hirzebruch-Riemann-Roch theorem in the fancy language of Spectra
The category of spectra indubitably is the best of possible worlds for cohomology theories. For instance in spectra one can start with a few basic morphisms, be confident that every natural diagram built from them will commute, and end up with a proof of the Hirzebruch-Riemann-Roch theorem. As in every good story we'll have a deus ex machina: Atiyah's identifi-cation of the Spanier-Whitehead dual of a manifold with the Thom spectrum of minus its tangent bundle. I will try to gently introduce all of this tools assuming basic notions of topology, geometry and algebra. Based on a joint work with Domenico Fiorenza and Eugenio Landi.
Per informazioni, rivolgersi a: gavarini@mat.uniroma2.it


Venerdì 29 maggio 2020
Ore 15:00, Modalità telematica, Dipartimento di Matematica e Fisica, Università degli Studi RomaTre
Seminario di Logica e Informatica Teorica
Matteo Acclavio (SAMOVAR - Telecom SudParis, INRIA - Saclay)
Logic programming with generalized multiplicative connectives
Logic programming is a paradigm which makes use of mathematical logic to represent programs by means of sets of formal sentences. In this talk we recall Andreoli's logic programming paradigm, which is based on linear logic proof structures. We focus on the so called "multiplicative" fragment, that is, the one which only employs linear and context-free methods. We show how to revise this construction in order to accommodate specific generalized multiplicative connectives. This allows us to implement some non-linear and context-sensitive methods in a pure multiplicative fragment. This talk is based on a joint work with Roberto Maieli
Per partecipare al seminario: chiedere il link all'indirizzo email vitomichele.abrusci@uniroma3.it o cliccare sul seguente link: link


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