Seminari/Colloquia
Pagina 37
Date  Type  Start  End  Room  Speaker  From  Title 

04/02/21  Seminario  10:00  11:00  Gary Froyland  University of New South Wales (Australia)  The dynamic ocean  in streaming mode  (see the instructions in the abstract)
The circulation of our oceans strongly influences climate, weather and biology. Our ocean currents are dynamic, and fluctuate to varying extents. I will introduce datadriven numerical tools that can tease apart dynamic components of the ocean, with information sourced from ocean drifters, satellite imagery, and ocean models. These components, their lifecycles, and their response to external forcing, help us to build a dynamic picture of our ocean.
Note: The zoom link to the seminar will be posted on the DinAmicI website and on Mathseminars.org. Moreover, it will be also streamed live via the youtube DinAmicI channel.  
03/02/21  Seminario  16:00  17:00  Vincenzo Morinelli  Tor Vergata   in streaming mode  (see the instructions in the abstract)
In Algebraic Quantum Field Theory (AQFT), a canonical algebraic construction of the fundamental free field models was provided by Brunetti Guido and Longo in 2002. The BrunettiGuidoLongo (BGL) construction relies on the identification of spacetime regions called wedges and oneparameter groups of Poincaré symmetries called boosts, the BisognanoWichmann property and the CPTtheorem. The last two properties make geometrically meaningful the TomitaTakesaki theory.
In this talk we recall this fundamental structure and explain how the oneparticle picture can be generalized. The BGLconstruction can start just by considering the Poincaré symmetry group and forgetting about the spacetime. Then it is natural to ask what kind of Lie groups can support a oneparticle net and in general a QFT. Given a Z_2graded Lie group we define a local poset of abstract wedge regions. We provide a classification of the simple Lie algebras supporting abstract wedges in relation with some special wedge configurations. This allows us to exhibit an analog of the HaagKastler axioms for oneparticle nets undergoing the action of such general Lie groups without referring to any specific spacetime. This set of axioms supports a first quantization net obtained by generalizing the BGLconstruction. The construction is possible for a large family of Lie groups and provides several new models.
Based on the joint work with KarlHermann Neeb (FAU ErlangenNürnberg)
"Covariant homogeneous nets of standard subspaces"
https://arxiv.org/abs/2010.07128
Link al seminario: https://teams.microsoft.com/l/meetupjoin/19%3a428ea736adc6424c8ae37f187c91b51b%40thread.tacv2/1611656244968?context=%7b%22Tid%22%3a%2224c5be2ad76440c5997582d08ae47d0e%22%2c%22Oid%22%3a%22e6325df73e744c88ab0b65ff8a758e69%22%7d
 
28/01/21  Seminario  16:00  17:00  Michele Gianfelice  Università della Calabria  Stochastic stability of classical Lorenz flow under impulsive type forcing  in streaming mode  (see the instructions in the abstract)
Inspired by the problem of modeling the so called anthropogenic forcing in climatology, e.g. the effects of the emissions of greenhouse gases in the atmosphere, we introduce a novel type of random perturbation for the classical Lorenz flow and prove its stochastic stability. The perturbation acts on the system in an impulsive way, hence is not of diffusive type. Namely, given a crosssection M for the unperturbed flow, each time the trajectory of the system crosses M the phase velocity field is changed with a new one sampled at random from a suitable neighborhood of the unperturbed one. The resulting random evolution is therefore described by a piecewise deterministic Markov process. The proof of the stochastic stability for the unperturbed flow is then carried on working either in the framework of the Random Dynamical Systems or in that of semiMarkov processes. Joint work with Sandro Vaienti.
Note: The zoom link to the seminar will be posted on the DinAmicI website and on Mathseminars.org. Moreover, it will be also streamed live via the youtube DinAmicI channel.  
21/01/21  Seminario  14:00  15:00  Alessandra Pluda  Università di Pisa  Motion by curvature of networks: analysis of singularities and “restarting” theorems (MS Teams link for the streaming at the end of the abstract)
A regular network is a finite union of sufficiently smooth
curves whose end points meet in
triple junctions. I will present the stateoftheart of the problem of
the motion by curvature of a regular network
in the plane mainly focusing on singularity formation. Then I will
discuss the need of a “restarting”
theorem for networks with multiple junctions of order bigger than three
and I will give an idea of a possible strategy to prove it.
This is a research in collaboration with Jorge Lira (University of
Fortaleza), Rafe Mazzeo (Stanford University) and Mariel Saez (P.
Universidad Catolica de Chile).
MS Teams Link for the streaming Note: This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV CUP E83C18000100006  
14/01/21  Seminario  16:00  17:00  Andrea Venturelli  Université d'Avignon (France)  DinAmicI: Another Internet Seminar (DAI Seminar)  in streaming mode  (see the instructions in the abstract)
We prove for the Nbody problem the existence of hyperbolic motions for any prescribed limit shape and any given initial configuration of the bodies. The energy level h>0 of the motion can also be chosen arbitrarily. Our approach is based on the construction of a global viscosity solutions for the HamiltonJacobi equation H(x,du(x))=h. Our hyperbolic motion is in fact a calibrating curve of the viscosity solution. The presented results can also be viewed as a new application of Marchal’s theorem, whose main use in recent literature has been to prove the existence of periodic orbits. Joint work with Ezequiel Maderna.
Note: The zoom link to the seminar will be posted on the DinAmicI website and on Mathseminars.org. Moreover, it will be also streamed live via the youtube DinAmicI channel.  
14/01/21  Seminario  14:00  15:00  Matteo Muratori  Politecnico di Milano  Nonlinear diffusion equations on noncompact manifolds and relations with stochastic completeness
The talk is based on joint projects with G. Grillo, K. We prove that the mass conservation property for the heat flow on a complete, connected, noncompact Riemannian manifold $M$, namely stochastic completeness, is equivalent to the uniqueness of nonnegative bounded solutions for a certain class of nonlinear evolution equations. Such a connection was well known in the pure linear case only, i.e. for the heat equation itself. Here we consider equations of the type of $u_t=Delta(phi(u))$, where $phi$ is any nonnegative, concave, increasing function, $C^1$ away from the origin and satisfying $ phi(0)=0 $. We provide optimal criteria for uniqueness/nonuniqueness of nonnegative, bounded (distributional) solutions taking general nonnegative, bounded initial data $u_0$. In particular our results apply to the fast diffusion equation $u_t=Delta(u^m)$ (where $m in (0,1)$), and they show that there is a large class of manifolds in which uniqueness actually fails. This is in sharp contrast, for instance, with the Euclidean case, where existence and uniqueness hold for merely $L^1_{loc}$ initial data thanks to the theory developed by M.A. Herrero and M. Pierre in the '80s. We will also address existence/nonexistence of nonnegative, nontrivial, bounded solutions to a strictly related nonlinear elliptic equation and, if time allows, some work in progress devoted to removing the concavity assumption.
The talk is based on joint projects with G. Grillo, K. Ishige and F. Punzo. MS Teams Link for the streaming Note: This talk is part of the activity of the MIUR Excellence Department Project CUP E83C18000100006  
02/01/21  Seminario  15:10  19:12  27  Prova  Prova  Prova
Prova

18/12/20  Seminario  14:30  16:30  Terza Giornata DinAmica  DinAmicI online workshop  (See Abstract below for the schedule)
14:30  Sara Di Ruzza (Università degli studi di Padova, Italy), Italy) Symbolic dynamics in a binary asteroid system. 15:30 Emanuele Haus (Università Roma Tre, Italy) Normal form and existence time for the Kirchhoff equation. Note: The abstracts of the talks and the zoom link for the streaming are posted on http://daiday2020.unisalento.it/.  
17/12/20  Seminario  16:30  17:30  Giuseppe Pucacco  Università di Roma "Tor Vergata"  Normal forms for the Laplace resonance
We describe a comprehensive model for systems locked in the Laplace resonance. The framework is based on the simplest possible dynamical structure provided by the Keplerian problem perturbed by the resonant coupling truncated at first order in the eccentricities. The reduced Hamiltonian, constructed by a transformation to resonant coordinates, is then submitted to a suitable ordering of the terms and to the study of its equilibria. Henceforth, resonant normal forms are computed. The main result is the identification of two different classes of equilibria. In the first class, only one kind of stable equilibrium is present: the paradigmatic case is that of the Galilean system. In the second class, three kinds of stable equilibria are possible and, at least one of them, is characterised by a high value of the forced eccentricity for the 'first planet': here the paradigmatic case is the exoplanetary system GJ876. The normal form obtained by averaging with respect to the free eccentricity oscillations, describes the libration of the Laplace argument for arbitrary amplitudes and allows us to determine the libration width of the resonance.
This activity is made in collaboration with the Departments of Mathematics of the Universities of Milano, Padova, Pisa and Roma Tor Vergata (Excellence Department project MATH@TOV).
 
17/12/20  Seminario  14:30  16:30  Terza Giornata DinAmica  DinAmicI online workshop  (See Abstract below for the schedule)
14:30  Nicola Guglielmi (Gran Sasso Science Institute, Italy) Approximating Lyapunov exponents of switching systems. 15:30 Anna Florio (Sorbonne Universite, France) Spectral rigidity of contact 3D Axiom A flows. Note: The abstracts of the talks and the zoom link for the streaming are posted on http://daiday2020.unisalento.it/. 
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