Seminari/Colloquia

Pagina 2


DateTypeStartEndRoomSpeakerFromTitle
06/06/24Seminario14:3015:301201 Dal PassoJohn PearsonUniversity of EdinburghRecent Developments in the Numerical Solution of PDE-Constrained Optimization Problems

Optimization problems subject to PDE constraints form a mathematical tool that can be applied to a wide range of scientific processes, including fluid flow control, medical imaging, option pricing, biological and chemical processes, and electromagnetic inverse problems, to name a few. These problems involve minimizing some function arising from a particular physical objective, while at the same time obeying a system of PDEs which describe the process. It is necessary to obtain accurate solutions to such problems within a reasonable CPU time, in particular for time-dependent problems, for which the “all-at-once” solution can lead to extremely large linear systems. In this talk we consider iterative methods, in particular Krylov subspace methods, to solve such systems, accelerated by fast and robust preconditioning strategies. In particular, we will survey several new developments, including block preconditioners for fluid flow control problems, a circulant preconditioning framework for solving certain optimization problems constrained by fractional differential equations, and multiple saddle-point preconditioners for block tridiagonal linear systems. We will illustrate the benefit of using these new approaches through a range of numerical experiments. This talk is based on work with Santolo Leveque (Scuola Normale Superiore, Pisa), Spyros Pougkakiotis (Yale University), Jacek Gondzio (University of Edinburgh), and Andreas Potschka (TU Clausthal). This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006).
06/06/24Seminario14:0015:001101 D'AntoniLei ZhangUniversity of Florida
Seminario di Equazioni Differenziali
(Nota: Cambio di giorno, orario e aula)
      Asymptotic Analysis and Uniqueness of blowup solutions of non-quantized singular mean field equations  

For singular mean field equations defined on a compact Riemann surface, we prove the uniqueness of bubbling solutions when blowup points are either regular points or non-quantized singular sources. In particular the uniqueness result covers the most general case extending or improving all previous works. For example, unlike previous results, we drop the assumption of singular sources being critical points of a suitably defined Kirchoff-Routh type functional. Our argument is based on refined estimates, robust and flexible enough to be applied to a wide range of problems requiring a delicate blowup analysis. In particular we come up with a major simplification of previous uniqueness proofs. This is a joint work with Daniele Bartolucci and Wen Yang.
Note: This talk is part of the activity of the MIUR Department of Excellence Project MatMod@TOV (2023-2027)
04/06/24Colloquium14:3015:301201 Dal Passo
Martin HAIRER
EPFL Lausanne & Imperial College, London
Colloquium Levi Civita (CMTP)
“Supercritical KPZ equations”

  Like many discrete statistical mechanics models, stochastic PDEs can exhibit a “critical dimen-sion” beyond which their large-scale behaviour is expected to be trivial (i.e. governed by Gaussian fluc-tuations). While such sweeping heuristics allow us to formulate rather precise conjectures, there are relatively few cases where these have actually been proven. In this talk, we will mainly focus on the KPZ equation, a standard model of interface fluctuations. There has recently been substantial progress in our mathematical understanding of its large-scale behaviour in the supercritical regime.
29/05/24Seminario17:3018:301201 Dal PassoClaudio Dappiaggi Università di Pavia
Operator Algebras Seminar
On the stochastic Sine-Gordon model: an AQFT perspective

We investigate the massive Sine-Gordon model in the finite ultraviolet regime on the two-dimensional Minkowski spacetime with an additive Gaussian white noise. In particular we construct the expectation value and the correlation functions of a solution of the underlying stochastic partial differential equation (SPDE) as a power series in the coupling constant, proving ultimately uniform convergence. This result is obtained combining an approach to study SPDEs at a perturbative level which a recent analysis of the quantum sine-Gordon model using techniques proper of the perturbative, algebraic approach to quantum field theory (pAQFT). This is a joint work with A. Bonicelli and P. Rinaldi, https://arxiv.org/pdf/2311.01558

Note: This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)

The Operator Algebra Seminar schedule is here: https://sites.google.com/view/oastorvergata/home-page?authuser=0
29/05/24Seminario16:0017:001201 Dal PassoStefaan VaesKU Leuven
Operator Algebras Seminar
Ergodic states on type III_1 factors and ergodic actions

I will report on a joint work with Amine Marrakchi. Since the early days of Tomita-Takesaki theory, it is known that a von Neumann algebra that admits a state with trivial centralizer must be a type III_1 factor, but the converse remained open. I will present a solution of this problem, proving that such ergodic states form a dense G_delta set among all normal states on any III_1 factor with separable predual. Through Connes' Radon-Nikodym cocycle theorem, this problem is related to the existence of ergodic cocycle perturbations for outer group actions, which I will discuss in the second half of the talk.

Note: This talk is part of the activity of the MUR Excellence Department Project MatMod@TOV (CUP E83C23000330006)
28/05/24Seminario14:3016:001101 D'AntoniKarl ChristUT Austin
Geometry Seminar
Irreducibility of Severi varieties on toric surfaces

Severi varieties parametrize integral curves of fixed geometric genus in a given linear system on a surface. In this talk, I will discuss the classical question of whether Severi varieties are irreducible and its relation to the irreducibility of other moduli spaces of curves. I will indicate how tropical methods can be used to answer such irreducibility questions. The new results are from ongoing joint work with Xiang He and Ilya Tyomkin.

Note: This talk is part of the activity of the MIUR Department of Excellence Project MatMod@TOV (2023-2027)
24/05/24Seminario16:0017:001101 D'Antoni
Ulrich KRÄHMER
TU Dresden
Algebra & Representation Theory Seminar (ARTS)
(N.B.: mind the change of room!)
The ring of differential operators on a monomial curve is a Hopf algebroid
N.B.: this talk is part of the activity of the MIUR Excellence Department Project Mat-Mod@TOV (CUP E83C23000330006)

  The ring of differential operators on a cuspidal curve whose coordinate ring is a numerical semigroup algebra is shown to be a cocommutative and cocomplete left Hopf algebroid. If the semigroup is symmetric so that the curve is Gorenstein, it is a full Hopf algebroid (admits an antipode). Based on joint work with Myriam Mahaman.
24/05/24Seminario14:3015:301101 D'Antoni
Giovanni PAOLINI
Università di Bologna
Algebra & Representation Theory Seminar (ARTS)
joint session with
Topology Seminar
(( N.B.: mind the change of room! ))
"Dual Coxeter groups of rank three"
N.B.: this talk is part of the activity of the MIUR Excellence Department Project Mat-Mod@TOV (CUP E83C23000330006)

  In this presentation, I will discuss the combinatorics of the noncrossing partition posets associated with Coxeter groups of rank three. In particular, I will describe the techniques used to prove the lattice property and lexicographic shellability. These properties can then be used to solve several problems on the corresponding Artin groups, such as the K(π,1) conjecture, the word problem, the center problem, and the isomorphism between standard and dual Artin groups.
  This is joint work with Emanuele Delucchi and Mario Salvetti.
24/05/24Seminario12:0013:001201 Dal PassoVitaly MorozSwansea University
Seminario di Dipartimento
Nonlinear elliptic problems with nonlocal interactions

We present a survey of nonlinear elliptic equations with nonlocal interactions. These equations describe the collective behavior of self-interacting many-body systems at different scales, from atoms and molecules to the formation of stars and galaxies. What sets these models apart from classical nonlinear PDEs is the presence of nonlocal terms in the equations, introduced via Coulomb-type interactions or a fractional Laplacian term, or both. We provide an overview of typical problems with repulsive interactions originating from Density Functional Theory; and Choquard type problems with attractive gravitational interactions. We also outline recent results in problems featuring competing attractive/ repulsive terms, which create particularly complex structures.
NB:This talk is part of the activity of the MIUR Excellence Department Project MATH@TOV CUP E83C23000330006
22/05/24Seminario16:0017:001201 Dal PassoAlessio RanalloUniversity of Geneva
Operator Algebras Seminar
Low energy spectrum of the XXZ model coupled to a magnetic field

I will report on recent developments concerning the control of a class of short-range perturbations of the Hamiltonian of an Ising chain. An example covered by our analysis is the celebrated XXZ chain. The talk is based on a joint work with S. Del Vecchio, J. Fröhlich, and A. Pizzo.

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