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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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Reminder: seminar of the quantum series. Taday at 15:00 G. De Palma
by Gianna M. Del Corso 27 May '24

27 May '24

This is a reminder for today’s seminar: Title: Quantum neural networks are Gaussian processes Speaker: Giacomo De Palma (University of Bologna) Venue: sala Galilei, room 131, Ed. C, Polo Fibonacci Time: Monday, 27/05/2024, 15:00 Here the link for attending online https://teams.microsoft.com/l/meetup-join/19%3ameeting_YWY5ZTRjN2MtOWI5OC00… <https://teams.microsoft.com/l/meetup-join/19:meeting_YWY5ZTRjN2MtOWI5OC00OD…> Gianna @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@ 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] Dierk Schleicher, The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, 24/05/2024, 16:00 Europe/Rome
by leonardo.robol＠unipi.it 23 May '24

23 May '24

Title: The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, Speaker(s): Dierk Schleicher, Aix-Marseille Université, Date and time: 24 May 2024, 16:00 (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/282 Abstract -------- Finding roots of complex polynomials in one variable is a fundamental challenge at the interface of theoretical and applied mathematics, as well as in many applications. Many methods have been proposed; the best known is Newton’s method that tries to find a single root at a time. There are several methods that try to approximate all roots at the same time. The best known are the Weierstrass—Durand—Kerner and Ehrlich—Aberth methods. These are known to work very well in practice, but little is known about their properties as global dynamical systems. We discuss various global dynamical properties, especially the search for attracting periodic orbits (which rule out general convergence) and orbits that diverge to infinity. This reports on joint work, partially still in progress, with Bernhard Reinke, Michael Stoll, and others. -- Indico :: Email Notifier https://events.dm.unipi.it/e/282

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[Indico] Dierk Schleicher, The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, 24/05/2024, 16:00 Europe/Rome
by leonardo.robol＠unipi.it 20 May '24

20 May '24

Title: The Weierstrass and Ehrlich-Aberth root finders as dynamical systems, Speaker(s): Dierk Schleicher, Aix-Marseille Université, Date and time: 24 May 2024, 16:00 (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/282 Abstract -------- Finding roots of complex polynomials in one variable is a fundamental challenge at the interface of theoretical and applied mathematics, as well as in many applications. Many methods have been proposed; the best known is Newton’s method that tries to find a single root at a time. There are several methods that try to approximate all roots at the same time. The best known are the Weierstrass—Durand—Kerner and Ehrlich—Aberth methods. These are known to work very well in practice, but little is known about their properties as global dynamical systems. We discuss various global dynamical properties, especially the search for attracting periodic orbits (which rule out general convergence) and orbits that diverge to infinity. This reports on joint work, partially still in progress, with Bernhard Reinke, Michael Stoll, and others. -- Indico :: Email Notifier https://events.dm.unipi.it/e/282

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Next week's seminar on quantum Computing : Monday 20 at 17:00 Oliver Morsch
by Gianna M. Del Corso 16 May '24

16 May '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. Next week's there will be: Title: Rydberg qubits for simulation and sensing Speaker: Oliver Morsch (CNR-INO and University of Pisa) Venue: Seminar room of Math department (1st floor on the left) Time: Monday, 20/05/2024, 17:00 Abstract: In recent years, Rydberg atoms have been increasingly used in several quantum technologies. In this talk I will give a brief introduction to Rydberg qubits and their applications in quantum simulation and quantum sensing. I will then give some examples of our recent work on these two technologies: the simulation of open quantum systems (phase transitions in driven quantum systems with controlled dissipation) and spatially resolved temperature measurements in a cold atomic gas using Rydberg- Doppler broadening thermometry. Everyone is welcome! 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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Next week's seminars on quantum Computing : Monday 6 and Friday 10
by Gianna M. Del Corso 02 May '24

02 May '24

Dear All, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. This week, exceptionally we will have two seminars: Title: The effect of phase noise in superconducting qubit control Speaker: Agata Barsotti (Università di Pisa) Venue: room 250, first floor Ed. C, Polo Fibonacci (Physics Dept.) Time: Monday, 06/05/2024, 17:00 At the end of the same week there is: Title: Certified randomness from single-particle entanglement Speaker: Sonia Mazzucchi (Università di Trento) Venue: Sala Gerace, Ed. C Polo Fibonacci (Computer Science Dept.) Time: Friday, 10/05/2024, 16:00 The abstracts of both the seminars are attached. Everyone is welcome! Gianna Del Corso @@@@@@@@@@@@@@@@@ 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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Next week's seminar on quantum Computing : Today at 14:00 Lindsay Bassman Oftelie
by Gianna M. Del Corso 22 Apr '24

22 Apr '24

Dear all, this message is a reminder for today's quantum series seminar. Title: Dynamic Cooling of Qubits on Contemporary Quantum Computers Speaker: Lindsay Bassman Oftelie (NEST-CNR) Venue: Sala Polifunzionale, Ed. C, Polo Fibonacci (Dip. Informatica) Time: Monday, 22/04/2024, 14:00 Abstract: Quantum computers require qubits to be initialized in a pure (i.e., cold) state for successful computation. Dynamic cooling offers a route to effectively lower qubit temperatures beyond what is possible with direct, physical cooling techniques. It works by cooling a subset of qubits, at the expense of heating others, by applying certain logic gates to the entire system. While it was initially dismissed as impractical for the high-temperature NMR-based quantum computers available at the time of its inception, we show how dynamic cooling is substantially more effective and efficient on the low-temperature quantum computers available today. In this talk, we will examine how optimal dynamic cooling scales with total system size, in terms of the minimal achievable final temperature, the work cost, and the complexity of the associated quantum circuits. We will observe the effect of hardware noise on cooling and we will propose a sub-optimal dynamic cooling scheme with fixed (low) complexity to improve the feasibility of implementation on noisy quantum hardware. Here the link for the online attendance https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzgwYmY4NDMtZWUwZi00… <https://teams.microsoft.com/l/meetup-join/19:meeting_YzgwYmY4NDMtZWUwZi00Mz…> See you there. Gianna Del Corso @@@@@@@@@@@@@@@@@ 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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Next week's seminar on quantum Computing : Lindasy Bassman Oftelie
by Gianna M. Del Corso 16 Apr '24

16 Apr '24

Dear all, As part of the CN1-SPOKE 10 on Quantum Computing, we are organizing a weekly seminar series. Next week’s seminar is: Title: Dynamic Cooling of Qubits on Contemporary Quantum Computers Speaker: Lindsay Bassman Oftelie (NEST-CNR) Venue: Sala Polifunzionale, Ed. C, Polo Fibonacci (Dip. Informatica) Time: Monday, 22/04/2024, 14:00 Abstract: Quantum computers require qubits to be initialized in a pure (i.e., cold) state for successful computation. Dynamic cooling offers a route to effectively lower qubit temperatures beyond what is possible with direct, physical cooling techniques. It works by cooling a subset of qubits, at the expense of heating others, by applying certain logic gates to the entire system. While it was initially dismissed as impractical for the high-temperature NMR-based quantum computers available at the time of its inception, we show how dynamic cooling is substantially more effective and efficient on the low-temperature quantum computers available today. In this talk, we will examine how optimal dynamic cooling scales with total system size, in terms of the minimal achievable final temperature, the work cost, and the complexity of the associated quantum circuits. We will observe the effect of hardware noise on cooling and we will propose a sub-optimal dynamic cooling scheme with fixed (low) complexity to improve the feasibility of implementation on noisy quantum hardware. Everyone is welcome! Please, note the change of venue and time. ======================================================================= @@@@@@@@@@@@@@@@@ Gianna M. Del Corso, PhD Dipartimento di Informatica, Università di Pisa Largo Pontecorvo, 3 56127 Pisa, Italy ph. +39-050-2213118 @@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@@ 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] Ivan Bioli, Preconditioned Low-Rank Riemannian Optimization for Multiterm Linear Matrix Equations, 11/04/2024, 16:00 Europe/Rome
by fabio.durastante＠unipi.it 10 Apr '24

10 Apr '24

Title: Preconditioned Low-Rank Riemannian Optimization for Multiterm Linear Matrix Equations, Speaker(s): Ivan Bioli, Università degli Studi di Pavia, Date and time: 11 Apr 2024, 16:00 (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/268 Abstract -------- We focus on the development and analysis of Riemannian optimization methods for solving multiterm linear matrix equations, when the associated linear operator is symmetric positive definite. Assuming low-rank approximability of the solution, we employ first- and second-order Riemannian optimization algorithms on low-rank matrix manifolds. To enhance competitiveness with existing solvers on realistic problems, significant efforts are dedicated to developing efficient Riemannian preconditioners, which are interpreted as changing the Riemannian metric. By alternating between fixed-rank Riemannian optimization and rank updates, we devise a rank-adaptive algorithm that does not require fixing the rank a priori. In numerical experiments, we illustrate the effectiveness of the developed Riemannian preconditioners, comparing our approach with established solvers such as Conjugate Gradient with truncation. Results indicate that the Riemannian optimization approach, in both its fixed-rank and rank-adaptive variants, is competitive with other solvers and can avoid excessive growth of ranks in intermediate iterations. References [Bou23] Nicolas Boumal. An Introduction to Optimization on Smooth Manifolds. 1st ed. Cambridge University Press, Mar. 16, 2023. [KSV16] Daniel Kressner, Michael Steinlechner, and Bart Vandereycken. “Preconditioned Low-rank Riemannian Optimization for Linear Systems with Tensor Product Structure”. In: SIAM Journal on Scientific Computing 38.4 (Jan. 2016), A2018–A2044. [VV10] Bart Vandereycken and Stefan Vandewalle. “A Riemannian Optimization Ap proach for Computing Low-Rank Solutions of Lyapunov Equations”. In: SIAM Journal on Matrix Analysis and Applications 31.5 (Jan. 2010), pp. 2553–2579. -- Indico :: Email Notifier https://events.dm.unipi.it/e/268

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