- NumPI - Mailing list — Dipartimento di Matematica, UniPI

Online Seminar: Peter Taylor, "The Role of Physical Understanding in Matrix-Analytic Methods"
by Federico Poloni 14 Jan '25

14 Jan '25

In case someone is interested, let me share this online event. A flyer is attached. Speaker: Professor Peter Taylor, The University of Melbourne Date: Thursday, February 6 2025 Time: 22:00 Italian time (!!) Title: The Role of Physical Understanding in Matrix-Analytic Methods Abstract: Since Marcel Neuts first showed that Markov chains of GI/M/1 type have a matrix-geometric stationary distribution in the 1970s and 1980s, the interplay between analytic properties and physical interpretation has played a major part in the development of matrix-analytic methods for stochastic models. Most performance measures of interest in such models can be expressed in terms of the solutions of equations involving matrix power series, which have to be solved numerically. Over the years, various iterative algorithms have been proposed for doing this. In order to establish convergence, and gain information about the speed of convergence, it is often helpful to think about the physical interpretation of the iterates. I shall discuss the physical interpretation of matrix-analytic algorithms that have been proposed for analysing block-structured Markov additive models. -- --Federico Poloni Dipartimento di Informatica, Università di Pisa https://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Lauri Nyman, "Riemann-Oracle: A framework for matrix nearness problems" 10/12/2024, 16:00
by Federico Poloni 10 Dec '24

10 Dec '24

The following seminar will take place next week; Lauri Nyman and Vanni Noferini from Aalto University are visiting the department of computer science in that week. Title: Riemann-Oracle: A framework for matrix nearness problems Speaker: Lauri Nyman, Aalto University, Espoo, Finland Where: Sala Seminari Est, Dipartimento di Informatica When: Tuesday December 10, 2024; 16:00 Abstract: In this talk, we propose a versatile approach for addressing a large family of matrix nearness problems. In these problems, the task is to find a matrix nearest to a given one that satisfies a desired constraint. The method is based on splitting a matrix nearness problem into two nested optimization problems, of which the inner one can be solved cheaply and exactly, while the outer one can be recast as an unconstrained optimization task over a smooth real Riemannian manifold. We also show that the objective function to be minimized on the Riemannian manifold can be discontinuous, thus requiring regularization techniques, and we give conditions for this to happen. Finally, we demonstrate the practical applicability of our method by implementing it for a number of matrix nearness problems that are relevant for applications, including nearest singular matrix with a given sparsity structure, nearest singular matrix polynomial, approximate GCD and nearest unstable matrix. -- --Federico Poloni Dipartimento di Informatica, Università di Pisa https://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Short-term Research Associate position @ University of Pisa -- dealii-X project
by Luca Heltai 09 Dec '24

09 Dec '24

Dear all, please share the following information with possible candidates, and to colleagues that may know of possible candidates. Thanks! Luca. Numerical Analysis Group @ University of Pisa Start Date: March 1st Application Deadline: January 24th Application Portal: <https://bandi.unipi.it/public/Bandi/Detail/150eaadb-8fec-4fc5-acb6-593dc7a2…> The University of Pisa invites applications for a short-term Research Associate position within the dealii-X project. This role, based in the Department of Mathematics, will concentrate on Numerical Analysis and the creation of advanced numerical tools for high-performance simulations using the deal.II library. The dealii-X project aims to create an Exascale Framework for Digital Twins of the Human Body. This initiative seeks to enhance personalized medicine through sophisticated computational models, enabling scalable and detailed simulations of human organs. We are looking for dynamic individuals with a strong scientific CV relevant to numerical analysis and simulations (a Master degree in a scientific subject is mandatory, a PhD is a plus). The successful candidate will work on the development and optimization of numerical tools for high-performance simulations in the deal.II library, focusing on meshing techniques, advanced coupling methods, non-matching techniques, reduced order methods, and large scale preconditioning techniques. The role will involve a tight collaboration with other international teams and team members, contributing to the development of the deal.II library. Key information: - Research Focus: Development and optimization of numerical tools for high-performance simulations in the deal.II library - Department of Mathematics, University of Pisa - Numerical Analysis and High Performance Scientific Computing - Contract Duration: 24 months - Gross Annual Salary: €32,427.96 - Application Deadline: 24th January 2025 - Starting Date: 1st March 2025 or as soon as possible thereafter

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Due Giorni di Algebra Lineare Numerica e Applicazioni @ UNIPI 20/21 January 2025 (Reminder)
by Fabio Durastante 25 Nov '24

25 Nov '24

A friendly reminder that registration for the /20th Due Giorni di Algebra Lineare Numerica e Applicazioni/ (January 20-21, 2025, at the University of Pisa) will close on *November 30, 2024*. This is the 20th workshop in a series dedicated to Numerical Linear Algebra and Applications. It aims at gathering the Italian Numerical Linear Algebra scientific community to discuss recent advances in this area and to promote the exchange of novel ideas and collaboration among researchers. We strongly encourage contributions by junior scholars on theoretical and computational topics, as well as on applications. Contributions covering other areas requiring tools from Numerical Linear Algebra are very welcome. Topics of interest include (but are not limited to): iterative methods for large-scale linear systems, preconditioning, eigen and singular values, numerical optimization, numerical dynamical systems, mathematics of machine learning, structured matrices, tensors, matrix functions, Krylov methods, randomized linear algebra algorithms, and high-performance computing for matrix computations. Applications include optimization and control, image processing and inverse problems, networks and graphs, machine learning and artificial neural networks, uncertainty quantification, finance, material sciences, life sciences, and industrial processes. Steering committee: M. Benzi, M. Donatelli, N. Guglielmi, B. Meini, V. Simoncini Important dates: - Registration is open with Deadline 30 Nov 2024 - Call for Abstracts is open with Deadline 30 Nov 2024 Location: - Area Bruno Pontecorvo of the University of Pisa The conference is without registration fee, but registration is mandatory. There is a limited amount of support for PhD students who want to attend the event, application can be done through the registration form. Full information are available at the web-page: https://events.dm.unipi.it/event/280/ The organizing committee, P. Boito, G.M. Del Corso, F. Durastante, S. Gazzola, L. Heltai, S. Massei, C. Pagliantini, F. Poloni, L. Robol.

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"Matematici a Lavoro" Seminar: From the America's Cup to the quantum realm: a math journey - N. Giuliani (Applied Materials)
by Fabio Durastante 06 Nov '24

06 Nov '24

Hi everybody, This is a seminar for the series /Matematici a Lavoro/ ("Mathematicians at Work") organized by the Department of Mathematics and whose speakers are scientists who work outside of the university world and who discuss how mathematics intersects with their work. They are mainly aimed at master's and doctoral students, but given the topic, it may be of wider interest. -- Fabio* * *Title:* From the America's Cup to the quantum realm: a math journey *Speaker: *Nicola Giuliani (Applied Materials) *Date and Time:* Tuesday, Nov 12, 2024 18:00 — 19:00 Aula Magna (Department of Mathematics) *Abstract: *In this seminar I will talk about my work experience. I will explain what inspired me to become an aeronautical engineer and a numerical analyst. Quite interestingly my work has always evolved to study increasingly smaller things. My academic research started with the study of ships (meters) and then It focused on the study of microswimmers (micrometers). In the last five years I worked at Applied Materials developing a software to predict the performance of nanoelectronics devices (some nanometers) where quantum effects can play an important role. *Info:* https://www.dm.unipi.it/en/seminar/?id=672b7f157a42a9b2643d0ca3

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[Indico] Prof. Andreas Frommer, Structure-aware Krylov approximations to generalized Cayley transforms, 25/10/2024, 11:00 Europe/Rome
by fabio.durastante＠unipi.it 24 Oct '24

24 Oct '24

Title: Structure-aware Krylov approximations to generalized Cayley transforms, Speaker(s): Prof. Andreas Frommer, University of Wuppertal, Date and time: 25 Oct 2024, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Scuola Normale Superiore (Aula Mancini). You can access the full event here: https://events.dm.unipi.it/e/296 Abstract -------- Generalized Cayley transforms arise in implicit numerical integration schemes for ordinary differential equations and differential-algebraic equations. We consider Arnoldi-type methods to approximate the action of such a Cayley transform on a vector and investigate how energy conservation or dissipation can be enforced at the level of each Arnoldi iterate, not just at the level of the exact solution. We also investigate generalizations to higher order collocation methods. Note ---- Reminder of tomorrow's seminar -- Indico :: Email Notifier https://events.dm.unipi.it/e/296

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Difesa dottorato - PhD defense
by Igor SIMUNEC 18 Oct '24

18 Oct '24

Cari tutti, Venerdì 25 ottobre alle 14.30 difenderò la mia tesi di dottorato, intitolata "Advances in polynomial and rational Krylov methods for matrix functions with applications", in Aula Bianchi Lettere (Scuola Normale Superiore). Dopo la difesa ci sarà un piccolo brindisi e rinfresco nel chiostro del Palazzo della Carovana. Chiunque volesse partecipare, o anche soltanto passare per un saluto, è benvenuto! A presto, Igor --- Dear all, On October 25th at 14.30 I will defend my PhD thesis, titled "Advances in polynomial and rational Krylov methods for matrix functions with applications", in Aula Bianchi Lettere (Scuola Normale Superiore). After the defense there will be some refreshments in the internal courtyard of the Palazzo della Carovana. You are all welcome to participate! Best, Igor

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[Indico] Prof. Andreas Frommer, Structure-aware Krylov approximations to generalized Cayley transforms, 10/25/24, 11:00 AM Europe/Rome
by fabio.durastante＠unipi.it 17 Oct '24

17 Oct '24

Title: Structure-aware Krylov approximations to generalized Cayley transforms, Speaker(s): Prof. Andreas Frommer, University of Wuppertal, Date and time: Oct 25, 2024, 11:00 AM (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Scuola Normale Superiore (Aula Mancini). You can access the full event here: https://events.dm.unipi.it/e/296 Abstract -------- Generalized Cayley transforms arise in implicit numerical integration schemes for ordinary differential equations and differential-algebraic equations. We consider Arnoldi-type methods to approximate the action of such a Cayley transform on a vector and investigate how energy conservation or dissipation can be enforced at the level of each Arnoldi iterate, not just at the level of the exact solution. We also investigate generalizations to higher order collocation methods. -- Indico :: Email Notifier https://events.dm.unipi.it/e/296

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Seminar announcement: A finite element approximation of a simplified model for smart fluids: an error analysis 9/10
by Fabio Durastante 08 Oct '24

08 Oct '24

Good morning, Colleagues in the Analysis section have organized this seminar by Alex Kaltenbach that may be of interest to some of us. The detailed information follows. Best, Fabio Speaker: Alex Kaltenbach, Technische Universität Berlin Seminar: A finite element approximation of a simplified model for smart fluids: an error analysis Date: October 9th at 5:00 pm, Aula Riunioni (Maths Department) Abstract: In this talk, a finite element approximation of the steady $p(\cdot)$-Navier--Stokes equations ($p(\cdot)$ is variable dependent) is examined for orders of convergence by assuming natural fractional regularity assumptions on the velocity vector field and the kinematic pressure. Numerical experiments confirm the quasi-optimality of the \textit{a priori} error estimates (for the velocity). The steady $p(\cdot)$-Navier--Stokes equations are a prototypical example of a non-linear system with variable growth conditions. They appear naturally in physical models for so-called \textit{smart fluids}, \textit{e.g.}, electro-rheological fluids, micro-polar electro-rheological fluids, magneto-rheological fluids, chemically reacting fluids, and thermo-rheological fluids, and have the potential for an application in numerous areas, \textit{e.g.}, in electronic, automobile, heavy machinery, military, and biomedical industry.

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[Indico] Mehdi Najafi Kalyani, A two-dimensional minimum residual technique for accelerating two-step iterative solvers, 04/10/2024, 11:00 Europe/Rome
by leonardo.robol＠unipi.it 02 Oct '24

02 Oct '24

Title: A two-dimensional minimum residual technique for accelerating two-step iterative solvers, Speaker(s): Mehdi Najafi Kalyani, University of Pisa, Date and time: 4 Oct 2024, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Aula Seminari). You can access the full event here: https://events.dm.unipi.it/e/289 Abstract -------- In this talk, we present a technique to speed up the convergence of a class of two-step iterative methods for solving linear systems of equations. To implement the acceleration technique, the residual norm associated with computed approximations for each sub-iterate is minimized over a certain two-dimensional subspace. Convergence properties of the resulting method will be discussed in detail. It will be further shown that the approach can be developed to solve (regularized) normal equations arising from the discretization of ill-posed problems. Numerical experiments will be disclosed to illustrate the performance of exact and inexact variants of the method for some test problems. -- Indico :: Email Notifier https://events.dm.unipi.it/e/289

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