Pagina 38

17/12/20Seminario14:0015:001200 Biblioteca StoricaVitaly MorozSwansea UniversityAsymptotic profiles of groundstates for a class of Choquard equations

We study the asymptotic behaviour of groundstates for a class of singularly perturbed Choquard type equations with a local repulsion term. We identify seven different asymptotic regimes and provide a characterisation of the limit profiles of the groundstates when perturbation parameter is small. We also outline the behaviour of groundstates when perturbation is strong. This is a joint work with Zeng Liu (Suzhou, China). Seminario online su questo link.
14/12/20Seminario16:0017:00Edoardo PersichettiFlorida Atlantic UniversityCode-based Cryptography and Post Quantum Standardization

Code-based cryptography has emerged as one of the strongest candidate to replace current cryptographic standards based on classical number theory problems such as RSA and El Gamal. In this talk, I will give an overview of the area, and describe some of my work towards the design of secure and efficient post-quantum primitives.

This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV. It is also part of the series of seminars "De Cifris Schola Latina" on cryptography.

The talk will be streamed on Teams. This is the link.
14/12/20Seminario13:0014:00Michele SalviUniversità di Roma "Tor Vergata"Scale-free percolation in continuous space

The scale-free percolation random graph features three fundamental properties that are often present in large real-world structures (social networks, communication networks, inter-banking system and so on), but which are never present at once in classical models: (1) Scale-free: the degree of nodes follows a power law; (2) Small-world: two nodes are typically at a very small graph distance; (3) Positive clustering coefficient: two nodes with a common neighbour have a good chance to be linked. We study a continuous version of scale-free percolation and its possible application to the statistical analysis of a dataset provided by the French Ministry of Agriculture. We discuss some stochastic processes (random walks and particle systems) on this kind of structures with the final goal of understanding how an epidemic would spread.
10/12/20Seminario16:0017:00Carlangelo LiveraniUniversità di Roma "Tor Vergata" DinAmicI: Another Internet Seminar (DAI Seminar)
      Locating Ruelle-Pollicott resonances  
     - in  streaming  mode -  
     (see the  instructions in the abstract)  

We study the spectrum of transfer operators associated to various dynamical systems. Our aim is to obtain precise information on discrete spectrum. To this end we propose a unitary approach. We consider various settings where new information can be obtained following different branches along the proposed path. These settings include affine expanding Markov maps, uniformly expanding Markov maps, non-uniformly expanding maps, hyperbolic diffeomorphisms. We believe this to be the germ of a general theory. Joint work with O. Butterley and N. Kiamari.

Note: The zoom link to the seminar will be posted on the DinAmicI website and on Moreover, it will be also streamed live via the youtube DinAmicI channel.
10/12/20Seminario14:0015:00Gabriele BenedettiRuprecht-Karls-Universitat HeidelbergStrong magnetic fields on surfaces: trapped motions and fully periodic systems

It is a central problem in experimental physics to design magnetic fields that trap charged particles in a region of space. In this talk, we show how to use the KAM theorem to trap particles constrained on a surface if the magnetic field is strong and certain non-degenerate conditions on the field or on the curvature of the surface are satisfied. Using similar ideas we show that the motion of a particle in a strong magnetic field is periodic for every initial condition if and only if the field is constant and the surface has constant curvature. This is joint work with Luca Asselle. The talk is part of the activity of the MIUR Department of Excellence Project CUP E83C18000100006.
03/12/20Colloquium16:0017:00Andrei OkounkovColumbia University (NY, USA) Colloquium di Dipartimento
     ”Lie theory without groups”  
     - in  streaming  mode -  
     (see the  link in the abstract)  

Lie theory, which deals with smooth groups of transformations, is one of the cornerstones of mathematics and has great importance for both theory and applications. It is also visibly limited, as the globe of Lie groups has been explored and inhabited. However, in recent years, some new geometric and algebraic structures have been recognized as being as good as Lie groups in every respect, including e.g. their contribution to the supply of special functions. My goal in this talk will be to explain where these new avenues of Lie theory lead.

Note: This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV CUP E83C18000100006

Link for the streaming (via Teams)
26/11/20Seminario17:0018:00Anna Miriam BeniniUniversità di Parma DinAmicI: Another Internet Seminar (DAI Seminar)
      Infinite entropy for transcendental entire functions  
     - in  streaming  mode -  
     (see the  instructions in the abstract)  

Defining entropy on noncompact metric spaces is a tricky business, since there are several natural and nonequivalent generalizations of the usual notions of entropy for continuous maps on compact spaces. By defining entropy for transcendental maps on the complex plane as the sup over the entropy restricted to compact forward invariant subsets, we prove that with this definition the entropy of such functions is infinite. The proof relies on covering results which are distinctive to holomorphic maps.

Note: The zoom link to the seminar will be posted on the DinAmicI website and on Moreover, it will be also streamed live via the youtube DinAmicI channel.
26/11/20Seminario14:0015:00Elsa MarchiniPolitecnico di MilanoMinimal time optimal control for the moon lander problem

We study a variant of the classical safe landing optimal control problem in aerospace, introduced by Miele in the Sixties, where the target was to land a spacecraft on the moon by minimizing the consumption of fuel. Assuming that the spacecraft has a failure and that the thrust (representing the control) can act in both vertical directions, the new target becomes to land safely by minimizing time, no matter of what the consumption is. In dependence of the initial data (height, velocity, and fuel), we prove that the optimal control can be of four different kinds, all being piecewise constant. Our analysis covers all possible situations, including the nonexistence of a safe landing strategy due to the lack of fuel or for heights/velocities for which also a total braking is insufficient to stop the spacecraft.

N.B.: this talk is part of the activity of the MIUR Excellence Department Project CUP E83C18000100006
19/11/20Seminario14:0015:00Sara DaneriGran Sasso Science InstituteSymmetry breaking for local/nonlocal interaction functionals

In this talk I will review some recent results obtained in collaboration with E. Runa and A. Kerschbaum on the one-dimensionality of the minimizers of a family of continuous local/nonlocal interaction functionals in general dimension. Such functionals have a local term, typically the perimeter or its Modica-Mortola approximation, which penalizes interfaces, and a nonlocal term favouring oscillations which are high in frequency and in amplitude. The competition between the two terms is expected by experiments and simulations to give rise to periodic patterns at equilibrium. Functionals of this type are used to model pattern formation, either in material science or in biology. The difficulty in proving the emergence of such structures is due to the fact that the functionals are symmetric with respect to permutation of coordinates, while minimizers are not. We will present new techniques and results showing that for two classes of functionals (used to model generalized anti-ferromagnetic systems, respectively colloidal suspensions), both in sharp interface and in diffuse interface models, minimizers are one-dimensional and periodic, in general dimension. In the discrete setting such results had been previously obtained for a smaller set of functionals with a different approach by Giuliani and Seiringer.
N.B.: this talk is part of the activity of the MIUR Excellence Department Project CUP E83C18000100006
The seminar will be online at the following link
16/11/20Seminario14:0015:00Isaia NisoliUniversidade Federal de Rio de Janeiro (Brasile) DinAmicI: Another Internet Seminar (DAI Seminar)
     A simple system presenting Noise Induced Order  
     - in  streaming  mode -  
     (see the  instructions in the abstract)  

In this talk I will present a family of one dimensional systems with random additive noise such that, as the noise size increases, the Lyapunov exponent of the stationary measure transitions from positive to negative. This phenomena is known in literature as Noise Induced Order, and was first observed in a model of the Belosouv-Zhabotinsky reaction and its existence was proven only recently by Galatolo-Monge-Nisoli. In the talk I will show how this phenomena is strictly connected with non-uniform hyperbolicity and the coexistence of regions of expansion and contraction in phase space; the result is attained through a result on the continuity of the Lyapunov exponent of the stationary measure with respect to the size of the noise.

Note: The zoom link to the seminar will be posted on the DinAmicI website and on Moreover, it will be also streamed live via the youtube DinAmicI channel.

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