- NumPI - Mailing list — Dipartimento di Matematica, UniPI

Seminario a Settembre
by Luca SALUZZI 03 Aug '24

03 Aug '24

Cari tutti, vi mando questa email perche' a Settembre, la settimana del 9-13, verra' in visita Maria Strazzullo dal Politecnico di Torino e vorrei organizzare un suo seminario. Si pensava di farlo o Lunedì 9 o Martedi' 10. Voi avete preferenze su data e orario? Così da permettere di massimizzare il numero di partecipanti. Intanto buone vacanze e ci si vede a Settembre!! Ciao, Luca

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23/07/2024 — R. Van Beeumen — Seminari CN1-SPOKE 10 (Quantum Computing)
by Gianna M. Del Corso 23 Jul '24

23 Jul '24

Dear all, This is a reminder for today’s seminar on quantum computing. Title: Hybrid Quantum-Classical Krylov Methods for Eigenvalue Computation Speaker: Roel Van Beeumen (Lawrence Berkeley National Laboratory) Venue: Sala Gerace, Dipartimento di Informatica Time: Tuesday, 23/07/2024, 14:30 Below the link for the online attendance. https://teams.microsoft.com/l/meetup-join/19%3ameeting_MjliOWRmMDAtMjA4ZC00… Everyone is welcome to attend! Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

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Seminar on Quantum Computing: Roel Van Beeumen Tuesday 23/7, 14:30
by Gianna M. Del Corso 16 Jul '24

16 Jul '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are pleased to announce the last seminar before the summer break. Title: Hybrid Quantum-Classical Krylov Methods for Eigenvalue Computation Speaker: Roel Van Beeumen (Lawrence Berkeley National Laboratory) Venue: Sala Gerace, Dipartimento di Informatica Time: Tuesday, 23/07/2024, 14:30 Abstract: Classical algorithms based on Krylov subspaces are among the most successful tools in the field of numerical linear algebra. More recently, the emergence of quantum subspace methods has resulted in a promising class of hybrid quantum-classical algorithms for eigenvalue approximation, e.g., in the fields of condensed matter physics and electronic structure theory. These quantum Krylov methods harness quantum computers to generate the subspace basis states and retrieve the projected problem through quantum measurement. However, the classical computation of the Ritz values often poses challenges due to the ill-conditioning of the associated generalized eigenvalue problem. In this talk, we present an overview of quantum subspace algorithms from a numerical linear algebra perspective. We discuss strategies to avoid solving an ill-conditioned eigenvalue problem, explain their implementation on quantum computers, and provide numerical and theoretical evidence of their convergence. Furthermore, we present strategies to improve the robustness, especially in the presence of noise. Everyone is welcome to attend! Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@

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[Indico] Dr Jie Meng, Theoretical and computational properties of quasi-Toeplitz M-matrices, 15/07/2024, 15:00 Europe/Rome
by fabio.durastante＠unipi.it 14 Jul '24

14 Jul '24

Title: Theoretical and computational properties of quasi-Toeplitz M-matrices, Speaker(s): Dr Jie Meng, Ocean University of China, Date and time: 15 Jul 2024, 15:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/287 Abstract -------- A quasi-Toeplitz matrix is a semi-infinite matrix of the form $A=T(a)+E$, where $T(a)$ is a Toeplitz matrix with entries $(T(a))_{i,j}=a_{j-i}$, for $a_{j-i}\in\mathbb C$, $i,j\ge 1$ and $E$ is a compact correction. Quasi-Toeplitz $M$-matrices are encountered in the study of quadratic matrix equations arising in the analysis of a 2-dimensional Quasi-Birth-Death (QBD) stochastic process. We investigate the properties of such matrices and provide conditions under which a quasi-Toeplitz matrix is an $M$-matrix. We show that under a mild and easy-to-check condition, an invertible quasi-Toeplitz $M$-matrix has a unique square root that is an $M$-matrix possessing quasi-Toeplitz structure. Some issues concerning the computation of the square root of quasi-Toeplitz $M$-matrices are discussed and numerical experiments are performed -- Indico :: Email Notifier https://events.dm.unipi.it/e/287

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Difesa dottorato
by Angelo Alberto CASULLI 12 Jul '24

12 Jul '24

Cari tutti, Lunedì 22 luglio alle 14.30 discuterò la mia tesi di dottorato dal titolo "Block rational Krylov methods for matrix equations and matrix functions" presso la Scuola Normale. Chiunque abbia piacere di partecipare è il benvenuto! Seguirà un piccolo rinfresco nel chiostro della Scuola. A presto, Angelo Casulli

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[Indico] Dr Jie Meng, Theoretical and computational properties of quasi-Toeplitz M-matrices, 7/15/24, 3:00 PM Europe/Rome
by fabio.durastante＠unipi.it 04 Jul '24

04 Jul '24

Title: Theoretical and computational properties of quasi-Toeplitz M-matrices, Speaker(s): Dr Jie Meng, Ocean University of China, Date and time: Jul 15, 2024, 3:00 PM (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/287 Abstract -------- A quasi-Toeplitz matrix is a semi-infinite matrix of the form $A=T(a)+E$, where $T(a)$ is a Toeplitz matrix with entries $(T(a))_{i,j}=a_{j-i}$, for $a_{j-i}\in\mathbb C$, $i,j\ge 1$ and $E$ is a compact correction. Quasi-Toeplitz $M$-matrices are encountered in the study of quadratic matrix equations arising in the analysis of a 2-dimensional Quasi-Birth-Death (QBD) stochastic process. We investigate the properties of such matrices and provide conditions under which a quasi-Toeplitz matrix is an $M$-matrix. We show that under a mild and easy-to-check condition, an invertible quasi-Toeplitz $M$-matrix has a unique square root that is an $M$-matrix possessing quasi-Toeplitz structure. Some issues concerning the computation of the square root of quasi-Toeplitz $M$-matrices are discussed and numerical experiments are performed -- Indico :: Email Notifier https://events.dm.unipi.it/e/287

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[Indico] Taejun Park, A low-rank approximation of parameter-dependent matrices via CUR decomposition, 13/06/2024, 11:00 Europe/Rome
by leonardo.robol＠unipi.it 11 Jun '24

11 Jun '24

Title: A low-rank approximation of parameter-dependent matrices via CUR decomposition, Speaker(s): Taejun Park, University of Oxford, Date and time: 13 Jun 2024, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/285 Abstract -------- Finding a low-rank approximation for parameter-dependent matrices $A(t)$ is an important task appearing in dynamical systems and image series compression. In this talk, we present an efficient randomized algorithm that computes a low-rank approximation of $A(t)$ at finite specified parameter values using the CUR decomposition. The key idea lies in reusing the same or a similar set of column and row indices for the CUR decomposition at nearby parameter values. The resulting algorithm is rank-adaptive, certifiable and has complexity that compares favorably to existing methods. This is joint work with Yuji Nakatsukasa. -- Indico :: Email Notifier https://events.dm.unipi.it/e/285

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Fwd: seminario Pearson: 6 giugno alle 14:30
by Fabio Durastante 31 May '24

31 May '24

Buonasera, Inoltro il seguente annuncio di seminario. Saluti, Fabio -------- Messaggio Inoltrato -------- Oggetto: seminario Pearson: 6 giugno alle 14:30 Data: Wed, 29 May 2024 12:12:19 +0200 Mittente: Mariarosa Mazza <mariarosa.mazza(a)uniroma2.it> A: mariarosa.mazza(a)uniroma2.it Car* tutt*, giovedi 6 giugno alle 14.30 in aula Dal Passo, Dipartimento di Matematica, Roma Tor Vergata, il Prof. John Pearson (University of Edinburgh) terrà un seminario dal titolo: "Recent Developments in the Numerical Solution of PDE-Constrained Optimization Problems". Il seminario può essere seguito online usando il link: https://teams.microsoft.com/l/meetup-join/19%3ad48916dee7364e0bbb08216ea621… Vi prego di diffondere l'annuncio fra i possibili interessati. Grazie, Mariarosa ----------------------------------------------- ABSTRACT: 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). -- ------------------------------------- Dr. Mariarosa Mazza University of Rome Tor Vergata Via della Ricerca Scientifica, 1 00133, Rome, Italy Email:mariarosa.mazza@uniroma2.it Tel: 0039 06-7259-4636 Url:https://sites.google.com/site/mariarosamazza1/ ---------------------------------

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Due Giorni di Algebra Lineare Numerica e Applicazioni @ UNIPI 20/21 January 2025
by Fabio Durastante 31 May '24

31 May '24

We are pleased to announce the next edition of the Due Giorni di Algebra Lineare Numerica e Applicazioni @ UNIPI 20/21 January 2025 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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[Indico] Taejun Park, A low-rank approximation of parameter-dependent matrices via CUR decomposition, 13/06/2024, 11:00 Europe/Rome
by leonardo.robol＠unipi.it 31 May '24

31 May '24

Title: A low-rank approximation of parameter-dependent matrices via CUR decomposition, Speaker(s): Taejun Park, University of Oxford, Date and time: 13 Jun 2024, 11:00 (Europe/Rome), Lecture series: Seminar on Numerical Analysis, Venue: Dipartimento di Matematica (Sala Riunioni). You can access the full event here: https://events.dm.unipi.it/e/285 Abstract -------- Finding a low-rank approximation for parameter-dependent matrices $A(t)$ is an important task appearing in dynamical systems and image series compression. In this talk, we present an efficient randomized algorithm that computes a low-rank approximation of $A(t)$ at finite specified parameter values using the CUR decomposition. The key idea lies in reusing the same or a similar set of column and row indices for the CUR decomposition at nearby parameter values. The resulting algorithm is rank-adaptive, certifiable and has complexity that compares favorably to existing methods. This is joint work with Yuji Nakatsukasa. -- Indico :: Email Notifier https://events.dm.unipi.it/e/285

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