Archivio 2026 110 seminari

In this course, I will present recent research exploring several innovative directions in neural network design, grounded in mathematical modeling and algorithmic insights. First, we introduce a general framework for constructing neural networks via operator splitting schemes. Starting from a suitable control problem, we discretize it using a carefully designed splitting method. Unrolling this scheme naturally yields new network architectures. We demonstrate this approach with two examples: a simplified UNet and the recently proposed PottsMGNet, both of which emerge naturally from the discretization process. Second, we offer a new mathematical explanation of the widely used UNet architecture. While UNet has been immensely successful in image segmentation tasks, its underlying structure has lacked rigorous theoretical interpretation. We show that UNet can be viewed as a one-step operator-splitting method for a control problem. Each component of the architecture corresponds to an element in the control formulation, and multigrid techniques are used to decompose the control variables. This perspective not only explains the effectiveness of UNet but also connects it with numerical PDE methods. Third, we delve into shape representation and segmentation using neural networks, particularly through the lens of the PottsMGNet framework. Encoder-decoder architectures are prevalent in image processing, yet their mathematical foundations remain incomplete. We reinterpret these architectures using the two-phase Potts model, formulating the segmentation problem as a control problem in the continuous setting. The problem is then discretized—temporally via operator splitting (yielding PottsMGNet) and spatially via multigrid methods. This leads to a network structure that is provably equivalent to encoder-decoder architectures. PottsMGNet, with a soft-thresholding regularizer, demonstrates robustness to network width, depth, and high noise levels, outperforming or matching state-of-the-art networks in accuracy and Dice score. We further extend this framework to handle convex shape representation using level set methods. We derive necessary and sufficient conditions for level set functions to represent convex shapes and apply this to variational models for image segmentation. Efficient numerical algorithms are developed and validated through experiments. To improve segmentation in complex images, we incorporate landmark constraints—either enforcing that the boundary passes through specific points or that certain regions belong to foreground or background. These techniques are broadly applicable to convex shape optimization and can be adapted for other applications.
The course sessions will introduce linear time-invariant (LTI) systems and the related concepts and techniques of convolution, the z-transform, transfer functions, pole-zero diagrams, difference equations, frequency responses, the discrete-time Fourier transform, and frequency spectra. The discrete Fourier transform and Fast Fourier transform will be described and utilized. We will discuss the design and use of digital filters including notch filters for the elimination of tonal noise from signals, with examples and exercises in Matlab. The short-time Fourier transform (STFT) will be introduced. To extend these methods (e.g., to signals with missing data or non-uniformly sampled data), we will explain the use of least-squares (in a deterministic setting) to a variety of signal processing problems through their formulation as inverse problems. Standard LTI filters will be viewed and implemented in matrix form, and matrix-free solvers will be noted. The optimization-based inverse problem formulation framework will be extended from least-squares to nonlinear filters based on sparse signal models. The concept of sparse signal models will be introduced, along with transform-domain sparsity. The STFT, discrete wavelet transform, and total variation will be introduced as examples of transform-domain sparsity. For solving the corresponding optimization problems, the majorization-minimization (MM) framework will be illustrated, leading to iterative reweighted least squares and iterative soft-thresholding algorithms.
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Federico Serena
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Anceschi Francesca
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Yevgenieva Yevgeniia
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Bellini Eugenio
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Vianello Giacomo
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Verzellesi Simone
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Liontou Vasiliki
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Piccinini Mirco
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Bolelli Maria Virginia
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Giugno
dal giorno
04/06/2026
al giorno
05/06/2026
Rossi Tommaso
Relazione all'interno del convegno: NonPUB26 - Nonlocal and Nonlinear PDEs at the University of Bologna 4th edition
analisi matematica
TBA
Ludovico Battista
Can you hear the shape of a Hyperbolic Marimba? Concerto di Superfici Iperboliche
algebra e geometria
analisi matematica
didattica della matematica
interdisciplinare
sistemi dinamici
Aprile
dal giorno
08/04/2026
al giorno
10/04/2026
Shaked Bader
Relazione all'interno del convegno: Manifolds and groups in Bologna, IV
algebra e geometria
Aprile
dal giorno
08/04/2026
al giorno
10/04/2026
Giovanni Framba
Relazione all'interno del convegno: Manifolds and groups in Bologna, IV
algebra e geometria
Aprile
dal giorno
08/04/2026
al giorno
10/04/2026
Ervin Hadžiosmanović
Relazione all'interno del convegno: Manifolds and groups in Bologna, IV
algebra e geometria
Aprile
dal giorno
08/04/2026
al giorno
10/04/2026
Ana Isaković
Relazione all'interno del convegno: Manifolds and groups in Bologna, IV
algebra e geometria
Aprile
dal giorno
08/04/2026
al giorno
10/04/2026
Laura Lankers
Relazione all'interno del convegno: Manifolds and groups in Bologna, IV
algebra e geometria
Aprile
dal giorno
08/04/2026
al giorno
10/04/2026
Timothé Lemistre
Relazione all'interno del convegno: Manifolds and groups in Bologna, IV
algebra e geometria
Gennaio
dal giorno
26/01/2026
al giorno
28/01/2026
Sebastian Jaimungal
Equilibrium Liquidity and Risk Offsetting in Decentralised Markets.
finanza matematica
Gennaio
dal giorno
26/01/2026
al giorno
28/01/2026
Andrea Canidio
Becoming Immutable: How Ethereum is Made
finanza matematica
Gennaio
dal giorno
26/01/2026
al giorno
28/01/2026
Fayçal Drissi
The macroeconomics of liquid staking
finanza matematica
Gennaio
dal giorno
26/01/2026
al giorno
28/01/2026
Christof Ferreira Torres
To Spam or Not to Spam: The Rise of Speculative MEV Bots
finanza matematica
Gennaio
dal giorno
26/01/2026
al giorno
28/01/2026
Antonio Russo
DeFi and Crypto-Assets under the MiCA Framework: New Frontiers and Challenges for Financial Supervision
finanza matematica
Gennaio
dal giorno
26/01/2026
al giorno
28/01/2026
Michele Treccani
Token issuance in PoS Networks: where Security meets Economic Sustainability
finanza matematica
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Mirko Mauri
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Brendan Hassett
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Sho Tanimoto
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Ariyan Javan Peykar
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Junliang Shen
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Alessio Sammartano
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Boaz Moerman
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Annalisa Grossi
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
Given an involution on a complex variety, the Smith-Thom inequality says that the total \mathbb{F}_2-Betti number of the fixed locus is no greater than the total \mathbb{F}_2-Betti number of the ambient variety. The involution is called maximal when the equality is achieved. On a Hyper-Kähler manifold X a holomorphic or a anti-holomorphic involution is referred to as a brane involution. While examples of non-compact hyper-Kähler manifolds admitting maximal branes are known, the compact case is more intriguing. In particular, although there exist some K3 surfaces admitting maximal brane involutions, the main result that I will show you is the non-existence of maximal branes on Hyper-Kähler manifolds deformation equivalent to the Hilbert scheme of points on a K3 surface. This talk is based on a joint work with S. Billi, L. Fu and V. Kharlamov.
Gennaio
dal giorno
11/01/2026
al giorno
17/01/2026
Claudio Onorati
Relazione all'interno del convegno: Geometry, arithmetic & cohomology of higher dimensional varieties
algebra e geometria
I will report about my recent joint work with Angel Rios Ortiz on the SYZ conjecture for a special class of singular symplectic varieties. The SYZ conjecture predicts that nef and isotropic line bundles are associated to lagrangian fibrations. After having recalled some generalities about symplectic varieties and the SYZ conjecture, I will state the main result and explain the main ideas behind its proof.