Élise Delphine Le Mélédo, University of Zurich, A conservative correction procedure for Level Set methods in evolving interfaces, Friday, January 29, 2021, time 17:30, online
Abstract:Abstract:
Evolving interfaces is a key feature of many practical applications as e.g. pattern dynamics, multi-phase flows, material design, and their approximation raise tremendous interesting numerical issues. In particular, incompressible two-phase flows require an accurate description of the interface in order to select the proper phase properties and dynamic to consider on each subdomain. Indeed, while the volume of each phase remains constant in time, the interface may develop heavy distortion and change topology across time. There, a small error in the interface location may have dreadful repercussions on the state dynamic (e.g. when vortices are encountered). Therefore, the designed numerical scheme has to pay a particular attention to the representation of the interface(s) and the description of its motion. Using an implicit representation of the interface, the Level Set method is a popular technique that allows a complex interface shape and is suited to topology changes in time. However, it is not natively conservative, that is the quantity of each fluid is not preserved as the interface is evolved. In this talk, we propose a correction technique to the Level Set method that enforces mass conservation while preserving the continuity of each connected component of the interface. Flexible, it can be used in combination with any meshed scheme updating the non-corrected Level Set field.

Davide Macera, Università degli Studi Roma Tre, Full spectrum Anderson localization for a general model of a disordered quantum wire, Friday, January 29, 2021, time 18:15, online
Abstract:Abstract:
Mathematicians have long been interted in rigorously understanding the conductivity properties of disordered materials at the quantum level, in particular after the work of the Nobel Prize winning American physicist Philip W. Anderson (1923-2020) In 1990, Klein, Lacroix and Speis analyzed a well studied random operator model for an electron moving on a portion of lattice of the form Z × [0, W], W ? N and subject to a random potential, called Anderson model on the strip. They showed, in particular, that such a model boasts spectral localization on all of its energy spectrum, a well defined mathematical property that is a very powerful signature of the electron getting trapped in a region by the potential. In thie present work, we focus on a more general model of a quantum particle with internal degrees of freedom moving in a quasi 1D random medium (disordered quantum wire), that we call "generalized Wegner Orbital Model". In particular, we prove spectral and dynamical localization at all energies for such a model suggesting that the disordered materials belonging to the wide class described by this model are all perfect insulators. In this talk, I will start by introducing basic concepts related to Anderson Localization in general, then move to the specific model considered in this work, and outline our proof of its spectral localization. The proof combines techniques from probability theory, spectral theory of selfadjoint operator and ergodic theory, with an unexpected algebraic twist...

Benedetta Noris, Politecnico di Milano, Symmetric solutions to supercritical elliptic problems, Tuesday, January 26, 2021, time 11:15, https://polimi-it.zoom.us/j/82733828774?pwd=UFJWWTBkMmpnR0VOZndTcE54Vjcrdz09
Abstract:Abstract:
When searching for solutions to Sobolev-supercritical elliptic problems, a major difficulty is the lack of Sobolev embeddings, that entrains a lack of compactness. In this talk, I will discuss how symmetry and monotonicity properties can help to overcome this obstacle. In particular, I will present a recent result concerning the existence of axially symmetric solutions to a semilinear equation, in collaboration with A. Boscaggin, F. Colasuonno and T. Weth.

Giulia Cavagnari, Politecnico di Milano, Evolution equations driven by dissipative operators in Wasserstein spaces, Wednesday, January 20, 2021, time 11:15, Link: https://polimi-it.zoom.us/j/88549174352?pwd=dmxXbjdnWlZiK1k1Zk4rR0FDWUN0Zz09
Abstract:Abstract:
In this talk we present new results framing into the recent theory of Measure Differential Equations introduced by B. Piccoli (Rutgers University-Camden). The state space where these evolution equations are set is the Wasserstein space of probability measures, hence tools of Optimal Transport are essential. The key point here is that the vector field itself maps into the space of probability measures lying on the tangent bundle, in a way compatible with the projection on the state space. We give a stronger definition of solution which indeed “selects” only one of the (not unique) solutions in the sense of Piccoli. In addition to uniqueness, we are also able to prove stability results. To do so, we borrow ideas from the theory of evolution equations driven by dissipative operators on Hilbert spaces, giving a notion of solution in terms of a so called Evolution Variational Inequality. This is a joint work with G. Savaré (Bocconi University) and G. E. Sodini (TUM-IAS).

Maurizio Garrione, Politecnico di Milano, Some recent stability results for beams with intermediate piers, Tuesday, January 12, 2021, time 11:15, Link Zoom: https://polimi-it.zoom.us/j/84708758746?pwd=aFpGY09hSzZnNDg3alk4bnhTNDN6UT09
Abstract:Abstract:
We deal with nonlinear fourth-order evolution equations describing the dynamics of beams with one or more intermediate piers. We study the role of the geometry of the structure (that is, of the position of the piers), as well as the effect of a nonhomogeneous density, in the (linear) stability of bi-modal solutions. The analysis gives some evidence that both the asymmetry and the nonhomogeneity reinforce the structure

Vincenzo Vespri, Università di Firenze, Cryptocurrencies: the future of the money?, Thursday, December 17, 2020, time 14:00, aula virtuale
Abstract:Abstract:
In this talk I will speak about bitcoins and cryptocurrencies, how they work and their perspectives. I will consider the possible applications in business and IOT.