### Seminari

### Prossimi Seminari

**“The Quantization approach for estimating Exposures in Counterparty risk. Review with numerical Applications”**

MICHELE BONOLLO, NUMERIX

martedì 20 marzo 2018 alle ore 12:15, Aula Seminari Sesto Piano**Isogeometric-analysis-based Multi-Index Stochastic Collocation for Elliptic PDEs with random data**

Lorenzo Tamellini, Istituto “E. Magenes”, Consiglio Nazionale delle Ricerche, Pavia

martedì 20 marzo 2018 alle ore 11:00, Aula Seminari ‘Saleri’ VI Piano MOX-Dipartimento di Matematica, Politecnico di Milano – Edificio 14**Crescita, Instabilità e Asimmetrie nei Sistemi Economici**

Fabio Pammolli, Politecnico di Milano

mercoledì 21 marzo 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**A representation formula for the Laplacian of the distance function**

Andrea Mondino, University of Warwick

mercoledì 21 marzo 2018 alle ore 15:15, Sala del Consiglio 7° piano**Collisions and chaos in the Boltzmann-Grad limit**

Sergio Simonella, ENS Lione

mercoledì 21 marzo 2018 alle ore 14:45 precise, Aula seminari MOX, VI piano**The Spatial Organisation of Early Southeast Asian Landscapes: New Perspectives from Lidar**

Damian Evans, École française d’Extrême-Orient

mercoledì 28 marzo 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**Cosa possono insegnarci i Bitcoin?**

Matteo Bedini, Numerix

mercoledì 11 aprile 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**Nonlinear Schrödinger equations on branched structures: the role of topology in the existence of ground states**

Enrico Serra, Politecnico di Torino

mercoledì 11 aprile 2018 alle ore 11:15, Aula seminari 3° piano**Mixed finite elements and adaptive schemes for eigenvalue problems**

Daniele Boffi, Dipartimento di Matematica “F. Casorati”, Università di Pavia

giovedì 12 aprile 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**Non-canonical embeddings and a canonical torsion-free covering for Mori Dream Spaces**

Michele Rossi, Università di Torino

giovedì 12 aprile 2018 alle ore 14:30 precise, Aula seminari del terzo piano**Ricostruire l’invisibile…fantasmi permettendo**

Paolo Dulio, Politecnico di Milano

mercoledì 18 aprile 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**Computing disconnected bifurcation diagrams of partial differential equations**

Patrick Farrell, Mathematical Institute, Oxford

giovedì 26 aprile 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**Computer, simulazioni ed esperimenti: all’alba di un nuovo metodo sperimentale?**

Viola Schiaffonati, Politecnico di Milano

mercoledì 9 maggio 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**Modellazione paziente specifica in emodialisi**

Maria Laura Costantino, Politecnico di Milano

mercoledì 16 maggio 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**La Scoperta del Secolo – Perché le Onde Gravitazionali valgono un Nobel**

Luca Perri, L’Officina del Planetario

mercoledì 23 maggio 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**TBA**

Valeria Simoncini, Dipartimento di Matematica, Università di Bologna

giovedì 24 maggio 2018 alle ore 14:00, Aula Consiglio VII piano**La geometria delle piramidi egizie**

Corinna Rossi, Politecnico di Milano

mercoledì 30 maggio 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**Missione Planck, l’immagine dell’universo neonato**

Marco Bersanelli, Università degli Studi di Milano

mercoledì 6 giugno 2018 alle ore 12:15, Politecnico di Milano Campus Bonardi Edificio14 aula B21**TBA. This is part I of a couple of joint seminars, second part at 14.00.**

Philippe Moireau, M3DISIM, INRIA, Paris, France

giovedì 7 giugno 2018 alle ore 10:30, Aula Consiglio VII piano**TBA. This is part II of a couple of joint seminars, first part at 10.30.**

Dominique Chapelle, M3DISIM, INRIA, Paris, France

giovedì 7 giugno 2018 alle ore 14:00, Aula Consiglio VII piano**Joint and Individual Variation Explained**

Steve Marron, Department of Statistics and O.R., University of North Carolina

lunedì 18 giugno 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**TBA**

Raymond Ogden, School of Mathematics and Statistics, University of Glasgow

giovedì 28 giugno 2018 alle ore 14:00, Aula Consiglio VII piano

### Seminari Passati

**One-Slice Preserving Functions of a Quaternionic Variable**

Chiara de Fabritiis, Università Politecnica delle Marche

giovedì 15 marzo 2018 alle ore 14:00 precise, Aula seminari del terzo pianoABSTRACTRegular functions on the skew-field of quaternions were introduced by

Gentili and Struppa some 10 years ago in order to give an analogue of

holomorphic functions in a non commutative setting. After a (short)

introduction, I will give a formula which allows us to simplify the

understanding of the *-product, which corresponds to the pointwise

product of holomorphic functions. The peculiar structure of quaternions,

foliated in copies of complex plane, drives naturally to consider the

classes of functions which preserve either one or all complex slices.

The main part of the talk will be devoted to characterize the functions

whose sum, *-product or conjugate preserve a slice. At the end, time permitting, I will address to the case of *-powers which shows an unexpected connection with a problem of algebraic geometry studied by Causa and Re. (Joint work with A. Altavilla)**The constant scalar curvature equation in some singular spaces**

Gilles Carron, Laboratoire de Mathématiques Jean Leray (UMR 6629), Université de Nantes, CNRS

mercoledì 14 marzo 2018 alle ore 16:30, Sala Consiglio, 7 piano, Edificio La Nave, Via Bonardi 9ABSTRACTI will survey the recent results about the Yamabe problem on stratified spaces. I will first introduce the scalar curvature and the Yamabe equation for the constant scalar curvature equation and its variational formulation and the results of Obata, Trudinger, Aubin and Schoen for smooth compact manifold. Then I will describe the geometry of stratified space with some 2D and 3D examples. Eventually I will formulate the Yamabe problem for stratified space and explained some of the recent results and will explain some perspectives.**Spectral distribution of sequences of structured matrices: GLT theory and applications**

Debora Sesana, University of Insubria – Como –

martedì 13 marzo 2018 alle ore 15:00, Aula Seminari ‘Saleri’ VI Piano MOX-Dipartimento di Matematica, Politecnico di Milano – Edificio 14ABSTRACTAny discretization of a given differential problem for some sequence of stepsizes h tending to zero leads to a sequence of systems of linear equations {Am xm = bm}, where the dimension of {Am} depends on h and tends to infinity for h going to 0. To properly face the solution of such linear systems, it is important to deeply understand the spectral properties of the matrices {Am} in order to construct efficient preconditioners and to study the convergence of applied iterative methods. The spectral distribution of a sequence of matrices is a fundamental concept. Roughly speak- ing, saying that the sequence of matrices {Am} is distributed as the function f means that the eigenvalues of Am behave as a sampling of f over an equispaced grid of the domain of f, at least if f is smooth enough. The function f is called the symbol of the sequence. Many distribution results are known for particular sequences of structured matrices: diagonal matrices, Toeplitz matrices, etc. and an approximation theory for sequences of matrices has been developed to deduce spectral distributions of “complicated” matrix sequences from the spectral distribution of “simpler” matrix sequences. In this respect, recently, has played a fundamental role the theory of Generalized Locally Toeplitz (GLT) sequences (introduced by Tilli (1998) and Serra-Capizzano (2002, 2006)), which allows to deduce the spectral properties of matrix sequences obtained as a combination (linear combinations, products, inversion) of Toeplitz matrices and diagonal matrices; to this category belong many stiffness matrices arising from the discretization, using various methods, of PDEs. We present the main concepts of this theory with some applications.

This is a joint work with Stefano Serra-Capizzano and Carlo Garoni.

References

[1] C. Garoni, C. Manni, S. Serra-Capizzano, D. Sesana, H. Speleers. Spectral analysis and spectral symbol of matrices in isogeometric Galerkin methods. Mathematics of Computation 85 (2016), pp. 1639–1680.

[2] C. Garoni, C. Manni, S. Serra-Capizzano, D. Sesana, H. Speleers. Lusin theorem, GLT sequences and matrix computations: an application to the spectral analysis of PDE discretization matrices. Journal of Mathematical Analysis and Applications, 446 (2017), pp. 365–382.

[3] C. Garoni, S. Serra-Capizzano. Generalized Locally Toeplitz Sequences: Theory and Applications. Springer 2017.

[4] C. Garoni, S. Serra-Capizzano, D. Sesana. Block Locally Toeplitz Sequences: Construction and Properties. Springer INdAM Series: proceeding volume of the Cortona 2017 meeting, submitted.

[5] C. Garoni, S. Serra-Capizzano, D. Sesana. Block Generalized Locally Toeplitz Sequences:

Topological Construction, Spectral Distribution Results, and Star-Algebra Structure.

Springer INdAM Series: proceeding volume of the Cortona 2017 meeting, submitted.

Contact: franca.calio@polimi.it

**Post-Quantum Group-based Cryptography**

Delaram Kahrobaei, New York City College of Technology

giovedì 8 marzo 2018 alle ore 14:30 precise, Aula seminari, III piano, Dipartimento di matematicaABSTRACTThe National Security Agency (NSA) in August 2015 announced plans to transition to post-quantum algorithms “Currently, Suite B cryptographic algorithms are specified by the National Institute of Standards and Technology (NIST) and are used by NSA’s Information Assurance Directorate in solutions approved for protecting classified and unclassified National Security Systems (NSS). Below, we announce preliminary plans for transitioning to quantum resistant algorithms.”

Shortly after the National Institute of Standardization and Technology (NIST) announced a call to select standards for post-quantum public-key cryptosystems.

The academic and industrial communities have suggested as the quantum-resistant primitives: Lattice-based, Multivariate, Code-based, Hash-based, Isogeny-based and group-based primitives.

In this talk I will focus on some ideas of (semi)group-based primitives. The one which was proposed to NIST is by SecureRF company based in Connecticut, among its founders there is a number theorist (Goldfeld) and two group theorists (Anshel and Anshel). They proposed a digital signature using a hard algorithmic problem in Braid groups, namely conjugacy problem.

I will then give a survey of some other suggested group-based cryptosystems that could be claimed as post-quantum cryptosystems.**HARK the SHARK: Realized Volatility Modelling with Measurement Errors and Nonlinear Dependencies**

Giuseppe Buccheri, Scuola Normale Superiore Pisa

martedì 6 marzo 2018 alle ore 12:15, Aula seminari terzo piano**Graphene from Molecular Mechanics**

Ulisse Stefanelli, Faculty of Mathematics, University of Vienna, and CNR Pavia

giovedì 1 marzo 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANOABSTRACTI will review recent results on the analysis of graphene via variational methods. The setting is that of Molecular Mechanics: carbon atoms are identified with their nuclear positions and their bonds are described via classical two- and three-body interactions. I will discuss the crystallization problem in both two and three dimensions, the mechanics of the (planar) crystal under tension, the rolling-up of free graphene patches, and the emergence of ripples in suspended samples.

Contact: francesco.bonaldi@polimi.it

**How to eliminate\control flutter arising in flow structure interactions**

Irena Lasiecka, University of Memphis

mercoledì 28 febbraio 2018 alle ore 16:30, Sala Consiglio, 7 piano, Edificio La Nave, Via Bonardi 9**Sobolev and BV functions in infinite dimension**

Alessandra Lunardi, Università di Parma

venerdì 23 febbraio 2018 alle ore 10:30 precise, Sala Consiglio, 7 piano, Edificio La Nave, Via Bonardi 9ABSTRACTIn Hilbert or Banach spaces $X$ endowed with a good probability measure $\mu$ there are a few “natural” definitions of Sobolev spaces and of spaces of bounded variation functions. The available theory deals mainly with Gaussian measures and Sobolev and BV functions defined in the whole $X$, while the study and Sobolev and BV spaces in domains, and/or with respect to non Gaussian measures, is largely to be developed.

As in finite dimension, Sobolev and BV functions are tools for the study of different problems, in particular for PDEs with infinitely many variables, arising in mathematical physics in the modeling of systems with an

infinite number of degrees of freedom, and in stochastic PDEs through Kolmogorov equations.

In this talk I will describe some of the main features and open problems concerning such function spaces.