A.Y. 2021/2022

First-level Courses

First year students are required to choose at least one of the following courses

Discrete potential theory and some applications to analysis in the continuum

20 h

Nicola Arcozzi

Program

After introducing two special,classical cases, The course will start with the axiomatic potential theory as it is presented in the monograph od Adams
and Hedberg. Then we will develop in some depth discerete potential theory and some of its applications. Several open problems will be discussed.

Period

November 4 - December 3, 2021

Fundamentals of smooth optimization and an introduction to optimization on manifolds

20 h

Germana Landi,   Margherita Porcelli

Program

Part 1: 10 hours (Landi)

The mathematical properties of the solutions of optimization problems constitute the basis of most optimization algorithms. The goal of this part of the course is to study such properties from a theoretical perspective and provide an overview of corresponding algorithmic schemes.

  •     Optimality conditions for unconstrained problems
  •     First- and second-order optimization algorithms
  •     Optimality conditions for constrained problems
  •     Duality theory
  •     Langrangian-based algorithms

Part 2: 10 hours (Porcelli)

The second part of the course is devoted to an introduction of the definitions and tools of differential geometry in a need-based order for optimization. In particular, theoretical properties of some numerical methods analyzed in the first part of the course will be extended to the general manifold case.

  • Examples of problems modeled as optimization on manifolds
  • Embedded submanifolds of linear spaces
  • Embedded submanifolds: first-order geometry
  • Embedded submanifolds: first-order optimization algorithm
  • Insights about general manifolds.

Period

February 2022

Schedule

Topology of manifolds, varieties, and singular spaces

30 h

Julius Shaneson

University of Pennsylvania

Program

Classification theory of smooth manifolds, for example manifolds homotopy equivalent to projective spaces or tori, with applications to various geometric problems. Invariants of singular spaces: intersection homology and characteristic classes, extending those that appear in the manifold case. Embedding and immersions for singular spaces, especially in codimension two. Applications to varieties, for example L-classes and Todd classes of toric varieties, counting lattice points, Euler-MacLaurin formulae. Discussion of open problems as time and interest permit.

Period

February 23 - April 13, 2022

Schedule

Geometrical Methods for Data Analysis and Machine Learning

20 h

Rita Fioresi,   Patrizio Frosini

Program

Part 1 (10 hours, Fioresi):

Preliminaries of linear algebra: SVD, PCA, circulant matrices. Deep Learning and Geometric Deep Learning. Geometry differential on graphs.

Part 2 (10 hours, Frosini)

Elements of persistent homology. Group Equivariants Non Expansive operators and their application in machine learning.

Period

March 31 - May 6, 2022.

Schedule

Advanced Courses

Misure aleatorie e caos moltiplicativo

30 h

Alexander Bufetov

CNRS Aix-Marseille Université, Institut de Mathématiques

Program

Una misura aleatoria è per definizione una distribuzione di probabilità sullo spazio delle misure . Un processo di punto ne è un esempio chiave. Il caos gaussiano molteplicativo è un altro esempio importante di una misura aleatoria che ha un ruolo prominente nello studio dei modelli gerarchici. Il corso, accessibile a chiunque abbia seguito un corso di algebra lineare e di analisi reale, approfondirà questi argomenti agli sviluppi recenti significativi.

Period

November 16, 2021 - January 18, 2022

Non-smooth large-scale optimization with applications: image restoration and inpainting

15 h

Alessandro Lanza

Program

Non-smooth large scale optimization problems arise naturally in many imaging applications. In particular, when variational approaches are used to solve imaging inverse problems (such as, for instance, image restoration and inpainting or computed tomography reconstruction), the solution is obtained as the (unconstrained or constrained) global minimizer of a cost function which is typically non-differentiable and dependent on hundreds of thousands of variables. The goal of this course is to describe theoretically some state-of-the-art iterative numerical methods with guaranteed convergence for the efficient solution of this kind of challenging optimization problems. The methods will then be experimentally tested and analyzed (using existing Matlab codes) on some realistic imaging problems.

Period

February - March 2022

Schedule

Random matrices: theory and practice

20 h

Pierpaolo Vivo

King's College

Program

  • Simple classification of random matrix models. Gaussian and Wishart ensembles. Warmup calculations: semicircle and Marčenko-Pastur laws.
  • Level spacing statistics: Poisson vs Wigner-Dyson.
  • Coulomb gas method.
  • Orthogonal polynomial technique and numerical checks.
  • Largest eigenvalue of a random matrix. Comparison with Extreme Value Statistics for i.i.d. random variables. Tracy-Widom distribution and third-order phase transitions.
  • The Replica method. Edwards-Jones formalism and the Bay-Rodgers integral equation. Applications to full and sparse matrices (random graphs).
  • Free probability. Sum of free random matrices. Blue's function.
  • The cavity method for sparse graphs (spectral density and largest eigenpair). Comparison with replicas.

Period

March 2022

Schedule

Symmetry problems in geometric analysis

24 h

Vittorio Martino,   Giulio Tralli

UNIBO, UNIPD

Program

The course will focus on some rigidity results for closed hypersurfaces with prescribed curvatures, starting from the connections with symmetry properties for solutions of partial differential equations of elliptic type. In particular two classical approaches will be discussed: the moving planes technique and an integral method based on sharp inequalities.

- Classical inequalities: convex functions, matrices, and perimeters.

- Interior and boundary maximum principles for elliptic operators.

- Serrin’s overdetermined problem (part I): moving planes.

- Serrin’s overdetermined problem (part II): Weinberger’s P-function.

- Hypersurfaces: the Second Fundamental Form and the Mean Curvature.

- Minkowski formulas and Jellett’s theorem.

- Aleksandrov’s theorem (part I): moving planes.

- Aleksandrov’s theorem (part II): Reilly’s integral approach.

Period

March 2022

Schedule

Introduction to singular SPDEs via paracontrolled distributions

8 h

Freie Universitat Berlin

Program

1) Some examples of singular and non-singular SPDEs. Distributions and function spaces

2) Paraproducts and Schauder estimates

3) Regularity of the stochastic heat equation and its monomials, solution of the Phi-4-2 equation

4) Beyond d=2: Paracontrolled distributions and the Phi 4-3 equation

Period

March 28, April 1 2022

Schedule

Stratified spaces and degenerations

6h

Allen Knutson

Cornell University

Program

This mini-course will tie together several topics, in approximately the following order. Very little background will be assumed, essentially basic commutative algebra, though exposure to Gröbner bases would probably be a bonus.

1. Schubert varieties, matrix Schubert varieties, and pipe dreams

2. Frobenius splitting, Kazhdan-Lusztig varieties, and quiver cycles

3. Positroid varieties, Bruhat atlases, and wonderful compactifications of groups.

Period

April 6 - 8 2022

Schedule

Randomness in number Theory: dynamical and probabilistic methods

20 h

Francesco Cellarosi

Queen's University, Canada

Program

The course will focus on recent advances concerning the study of random behaviour of number-theoretical sequences. We will mainly focus on the distribution of square-free integers and their generalisations (e.g. k-free, B-free). We will discuss Sarnak's conjecture on the disjointness of the Mobius function mu(n) from sequences generated by zero-entropy dynamical systems. We will prove that mu^2(n) (the indicator of square-free integers) is completely deterministic and study the statistics of its patterns in long intervals. We will also discuss some very recent progress on the distribution of square-free integers in small intervals. Here are some references:

  • The distribution of squarefree numbers. R.R. Hall. J. Reine Angew. Math., 394:107-117, 1989.
  • Mobius randomness and dynamics. P. Sarnak. Not. S. Afr. Math. Soc. 43, 89-97, 2012.
  • Ergodic properties of square-free numbers. F. Cellarosi, Ya.G. Sinai. J. Eur. Math. Soc. (JEMS), 15(4):1343-1374, 2013.
  • Ergodic and statistical properties of B-free numbers. M. Avdeeva, F. Cellarosi, Ya.G. Sinai. Teor. Veroyatn. Primen., 61(4):805-829, 2016.
  • The Chowla and the Sarnak conjectures from ergodic theory point of view. E.H. El Abdalaoui, J. Kulaga-Przymus, M. Lemanczyk, T. de la Rue. Discrete Contin. Dyn. Syst., 37(6):2899-2944, 2017.
  • On the variance of squarefree integers in short intervals and arithmetic progressions. O. Gorodetsky, K. Matomaki, M. Radziwill, B. Rodgers. Geom. Funct. Anal. 31, 111-149, 2021.

Time permitting, we may discuss the limiting distribution of quadratic Weyl sums and their generalisations (e.g. classical Jacobi theta functions). Quadratic Weyl sums are a special kind of exponential sums that appear naturally in number theory, mathematical physics, and representation theory. They can be interpreted as deterministic walks (with a random `seed') in the complex plane. Generalising Sarnak's equidistribution of horocycles under the action of the geodesic ow, we can study the limiting distribution of such Weyl sums. A stochastic process of number-theoretical origin can be defined using such sums. Understanding the behaviour of trajectories of the geodesic ow in a homogeneous space, we can study this process, that shares only some of its properties with those of the Brownian motion. Here are some references:

  • Asymptotic behavior of periodic orbits of the horocycle ow and Eisenstein series. P. Sarnak. Comm. Pure Appl. Math. 34, 719-739, 1981.
  • Limit theorems for theta sums. J. Marklof. Duke Math. J. 97(1): 127-153, 1999.
  • Quadratic Weyl sums, automorphic functions and invariance principles. F. Cellarosi, J. Marklof. Proc. Lond. Math. Soc. (3), 113(6):775-828, 2016.

The level of the course can be adjusted based on the background of the audience. Basic knowledge of probability and analysis will be assumed, as well as minimal knowledge of number theory. The course's goal is to foster an interactive learning environment around some exciting recent interdisciplinary advances in pure mathematics.

Period

April 11 - May 12, 2022

Schedule - MS Teams virtual room

Harmonic analysis on Hamming cube beyond Enflo's problem

8 h

Alexander Volberg

Michigan State University

Program

Banach space valued Poincaré inequality, extension of Pisier’s inequality, and dimension free estimates of singular integrals on discrete cube are the topics of these lectures.
For Banach space valued functions Poincaré inequality is usually replaced by Pisier’s inequality. It is interesting to understand precisely for which Banach spaces X Pisier inequality on Hamming cube is dimension free. This has been done by Ivanisvili-Van Handel-Volberg (IVHV). This, in particular, gave a solution to Enflo’s conjecture. There is a whole scale of related inequalities filling the gap between Pisier’s inequality and singular integral inequalities on Hamming cube. For those inequalities the description of class of Banach spaces X that allows the dimension free estimates is not known, the reason is related to the following fact: we are used to the “fact” that singular integrals on X-valued functions have to be bounded in Lp(X) if X is UMD. But on Hamming cube this is not true anymore. However, we will show a wide class of spaces for which those inequalities hold. The proofs are the mixture of the formula of IVHV and quantum random variables technique à la Francoise Lust-Piquard.

Lecture 1. What is Enflo's problem? Ribe program. Bourgain's discretization theorem.

Lecture 2. The solution of Enflo's problem. Semi-group approach and special formula.

Lecture 3. Poincaré estimates and beyond Enflo's problem on Hamming cube.

Lecture 4. Francoise Lust-Piquard non-commutative approach to singular integrals estimate on Hamming cube.

Period

April 23, May 21 2022

Stability conditions on stacks

Michael Thaddeus

Columbia University

Program

Many geometric structures on algebraic varieties (such as vector bundles or coherent sheaves) are best studied by considering the collection of all such structures, modulo some natural equivalence, and giving it a geometric structure itself. Depending on the moduli problem considered, this may lead to a moduli scheme, a moduli space, or a moduli stack. Focusing on examples related to vector bundles on smooth curves, we will discuss the geometry of the corresponding moduli spaces and stacks, explaining how the notion of stability throws a bridge from stacks to spaces. This will be preceded by some relevant background (though very informal and example-driven) on stacks and on geometric invariant theory.

Period

May 19, h. 11-12, Seminario II (Topics in Mathematics)
May 20, h. 14-16, Seminario II
May 23, h. 11-13, Aula VIII piano
May 24, h. 11-12, Seminario II

Schedule

Mathematical Modelling of Nonlinear Waves

8 h

Angela Slavova

Institute of Mathematics, Bulgarian Academy of Sciences

Program

The study of water waves involves various disciplines such as mathematics, physics and engineering and within this there are many specific areas of direct or associated interest such as pure mathematics, applied mathematics, modelling, numerical simulation, laboratory experiments, data collection in the field, the design and construction of ships, harbours, the prediction of natural disasters, climate studies and so on. In this course we shall study travelling wave solutions of shallow water waves. Camassa-Holm considered a third order nonlinear PDE of two
variables modelling the propagation of unidirectional irrotational shallow water waves over a flat bed, as well as water waves moving over an underlying shear flow. In the special case of the motion of a shallow water over a flat bottom the corresponding system was simplified by Green and Naghdi and related to an appropriate two component first order Camassa-Holm system. Another interesting system of nonlinear PDE is the viscoelastic generalization of Burger's equation. In the above mentioned systems we are looking for travelling wave solutions and we are studying their profiles. To do this we use several results from the classical Analysis of ODE that enable us to give the geometrical picture and in several cases to express the solutions by the inverse of Legendre's elliptic functions. Moreover, we shall apply microlocal approach in studying the propagation of nonlinear waves. As an application we shall present propagation of tsunami waves from their small disturbance at the sea level to the size they reach approaching the coast. Even with the aid of the most advanced computers it is not possible to find the exact solutions to the nonlinear governing equations for water waves. For this purpose we introduce Cellular Nonlinear Network (CNN) approach.

Main topics:

1. Existence and profiles of traveling waves
2. Traveling wave solutions of special type to third order nonlinear PDE
3. Method of characteristics applied to the Hunter-Saxton equation
4. Integrable multicomponent Generalizations of Camassa-Holm equation
5. Microlocal approach in studying the propagation of non-linear waves
6. Application to tsunami waves

Period

Schedule

Compactified Jacobians and cubic fourfolds

Giulia Saccà

Columbia University

Program

TBD

Period

September 26 - 30, 2022

Regularity Theory for Elliptic equations

Daniela De Silva

Columbia University
Summary: Holder regularity of weak solutions to divergence and non-divergence elliptic equations.
Lesson 1, 27/07 14:00 - 15:15 : Introduction and Preliminaries
Lesson 2: 27/07 15:45 - 17:00: De Giorgi- Nash-Moser Theorem
Lesson 3 28/07 9:00 - 10:30: Harnack Inequality
Lesson 4 28/07 14:00 - 15:30: ABP Estimates
Lesson 5 29/07 9:00 - 10,30: Weak Harnack Inequality
Lesson 6 29/07 14:00 - 15,30: Conclusive remarks and if time and students' preparation allows it, the Dirichlet problem for the minimal surface equation.
Background: Familiarity with basic PDE theory (for example Harmonic functions, max principle...) and basic facts about Sobolev Spaces.

Schools, seminars and other courses

Topics in Mathematics

seminars

September 2021 - May 2022

Advanced methods for math image analysis

21 h

Winter PhD School

UMI-MIVA Group - Serena Morigi

Period

January - February 2022

Geometria della teoria delle stringhe

min 6 - max 24 h

Antonella Grassi

Program

Calabi Yau: mini-corso di dottorato sulla geometria della teoria delle stringe, fruibile anche a distanza, con tempi, dettagli e modalità da definire.

Period

TBD