SSMI2026
44. Prof. dr. Florin Bobaru,Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, USA.
Data: 28 iulie 2026, la ora 11:00, în sala PI9, Corpul P
Titlul prezentarii: Modele peridinamice pentru rupere/fractură, deteriorare și coroziune
ABSTRACT: Unele fenomene fizice comune, precum spargerea unui geam sau cedarea unui cablu afectat de coroziune, sunt foarte dificil de prezis. Fracturarea, deteriorarea și coroziunea au pus probleme societăților timp de milenii, însă abia recent am început să facem predicții cantitative pentru aceste fenomene. În această prezentare, voi explica mai întâi de ce fractura fragilă dinamică și deteriorarea prin coroziune sunt greu de anticipat. Modelele peridinamice (PD) oferă modalități noi de a simula astfel de probleme complexe, prin eliminarea ipotezelor restrictive, inerente modelelor clasice. Bifurcarea dinamică a fisurilor în materiale fragile este un exemplu elocvent al neconcordanței dintre predicțiile modelelor clasice și dovezile experimentale. Modelele PD pot contribui în prezent la înțelegerea fracturii fragile dinamice și a evoluției deteriorării prin coroziune, inclusiv fragmentarea prin impact a unei plăci de sticlă și fractura la o interfață intre materiale. Simularea coroziunii, a coroziunii intergranulare și a fisurării induse, coroziunea sub tensiune beneficiază, de asemenea, în mod semnificativ de modelarea peridinamică. Totuși, modelele PD sunt costisitoare din punct de vedere computațional. Pentru a le extinde aplicabilitatea, voi prezenta rezultate recente obținute cu o nouă abordare numerică (Fast Convolution‑Based Method, FCBM), destinată simulărilor PD eficiente. Voi prezenta și unele soluții analitice ale acestor modele nelocale. Modelele PD pot fi utilizate pentru studierea unei varietăți de probleme importante, dar până de curând dificil de abordat, inclusiv cedarea materialelor utilizate în microelectronică, ruperea rocilor stratificate în timpul cutremurelor, eroziunea geomaterialelor, fisurarea și topirea calotelor de gheață arctică sau glaciare, impactul asteroizilor etc.
Scurtă biografie
Dr. Florin Bobaru este profesor universitar în cadrul Departamentului de Inginerie Mecanică și a Materialelor la University of Nebraska–Lincoln. A obținut titlul de Master în Matematică și Mecanica Solidelor la Universitatea din București, România, în anul 1997, și titlul de doctor în Mecanică Teoretică și Aplicată la Cornell University, Ithaca, NY, SUA, în 2001.
43. Prof. Dr. Marius Tărnăuceanu, Faculty of Mathematics, “Al. I. Cuza" University, Iași, Romania
Data: 17 iulie 2026, la ora 11:00, sala PI9, corpul P
Titlul prezentării: The Chermak-Delgado lattice of a finite group
Prof. Marius Tărnăuceanu este specialist in algebra (teoria grupurilor).
42. Prof. Rodica Curtu, Department of Mathematical Sciences Michigan Technological University ("Michigan Tech"), USA
Data: 9 iunie 2026, 14:00, în sala PI9, Corpul P
Titlul prezentarii: Discovering spatiotemporal patterns of activity from single-trial intracranial neural recordings
ABSTRACT: Discovering dynamical patterns from high fidelity time series is typically a challenging task. In this work we studied neural signals recorded from several cortical areas of human subjects who listened to sequences of repeated triplets of tones and reported their perception by pressing a button. Subjects reported spontaneous alternations between two auditory perceptual states: a galloping-like rhythm (1-stream) and a Morse-code like rhythm (2-streams). First, we performed statistical analysis over averaged auditory evoked potentials (AEP) associated with 1-stream and 2-stream percepts. We identified significant differences between them in primary and nonprimary auditory cortex, surrounding auditory-related temporoparietal cortex, and frontal areas. Next, we developed classifiers to identify spatial maps of percept-related differences in the AEP, corroborating findings from statistical analysis. Finally, we built an algorithm that identified neural features in the brain recordings that correlated with subject-reported perception. Our algorithm leveraged recent mathematical methods in time-delayed coordinates, diffusion maps, and dynamic mode decomposition. It revealed a set of latent variables that exhibited alternating dynamics along a low-dimensional manifold, like trajectories of attractor-based models.
41. Prof. Jesús Llorente, Universidad Complutense de Madrid, Spania
Data: 2 iunie 2026, 14:00, în sala PI9, Corpul P
Titlul prezentarii: Dynamics of the Takagi function
ABSTRACT (link)
40. Dr. Zoltan Papp, Department of Mathematics (Institute of Information Technology), University of Dunaújváros, Ungaria
Data: 14 mai 2026, 14:00, în sala PI9, Corpul P
Titlul prezentarii: Projection-Based Conjugate Gradient Methods for Large-Scale Monotone Nonlinear Systems
ABSTRACT: Nonlinear systems of equations arise naturally in many areas of applied mathematics, optimization, variational inequalities, and signal processing. In this talk, we focus on a special but important class of problems, namely monotone nonlinear systems, for which classical merit-function-based methods may suffer from both theoretical and practical limitations.
The lecture presents a class of projection-based conjugate gradient methods that combine hyperplane projection techniques with derivative-free conjugate gradients earch directions. The projection step fully exploits the monotonicity of the underlying operator and provides a simple and effective globalization strategy without the use of merit functions. Conjugate gradient directions, including Fletcher–Reeves, Polak–Ribière–Polyak, and hybrid Hu–Storey-type updates, ensure low memory requirements and make the methods suitable for large-scale problems.
We discuss the geometric interpretation of the projection approach, the role of derivative-free line searches, and the main convergence results guarantee in global convergence of the entire iterative sequence under mild assumptions. Finally, numerical experiments and applications, such as sparse signal recovery, are briefly presented to illustrate the robustness and efficiency of the proposed methods.
39. Dr. Catalina Curceanu, INFN–LNF, Frascati (Italy)
Data: 8 mai 2026, 14:00, în sala PI2, Corpul P
Titlul prezentarii: Probing Quantum Mechanics and Quantum Gravity Underground: Pauli Exclusion Principle Violations and Collapse Models
ABSTRACT: Quantum mechanics is one of the most successful theories in science, yet its conceptual foundations, particularly the measurement problem and the origin of quantum statistics, remain open. In this seminar, I will introduce key elements of quantum mechanics, with emphasis on superposition, indistinguishability, and the Pauli Exclusion Principle.
The experimental program carried out by my group at the Gran Sasso National Laboratory exploits underground conditions to achieve unprecedented sensitivity. I will discuss recent experimental constraints on quantum foundations, focusing on tests of the Pauli Exclusion Principle and of collapse models, and outline future directions, including possible connections with gravity-induced collapse scenarios.
A central part of the seminar will be devoted to the VIP experiment, which tests the Pauli Exclusion Principle for electrons by searching for forbidden atomic transitions. I will highlight how such high-precision measurements probe the symmetrization postulate of quantum mechanics and discuss their possible interpretation within approaches to quantum gravity.
I will then briefly introduce a class of phenomenological modifications of quantum mechanics known as collapse models, focusing on the Continuous Spontaneous Localization (CSL) framework, in which stochastic and nonlinear terms modify the Schrödinger dynamics. These models lead to experimentally testable signatures, such as spontaneous radiation emission, which can be investigated in ultra-low background environments.
The seminar aims to build bridges between experimental searches and foundational questions, illustrating how precision measurements can guide possible extensions of quantum theory, and to foster collaboration with the group in Brașov.
38. Prof. Filip STROBIN, University of Gdansk, POLAND
Data: 21 aprilie 2026, 14:00, în sala PI9, Corpul P
Titlul prezentarii: An introduction to Fractal Theory with applications in real-world modeling
ABSTRACT: During the talk, I will present the basics of fractal theory, focusing in particular on the part related to iterated function systems (IFSs). A classical result due to Hutchinson states that a contractive IFS on a complete metric space admits a unique attractor, and many well-known fractals arise in this way.
I will formulate this result in detail and illustrate it with several examples, including objects from the real world that can be modeled as attractors of simple IFSs. I will also show that small perturbations of the underlying IFS lead to small changes in the attractor, highlighting the flexibility of this approach in the context of modeling.
Finally, I will present two classical algorithms for generating IFS attractors, including the well-known chaos game.
37. Prof. Elif Tan, Ankara University, Turcia
Data: 22 ianuarie 2026, la ora 11.00, în sala PI9, Corpul P
Titlul prezentarii: Fibonacci Cubes and Beyond: Structural and Combinatorial Properties
ABSTRACT: Fibonacci cubes were originally introduced as models for interconnection networks and have since attracted considerable attention due to both their practical relevance and rich combinatorial structure. An n-dimensional Fibonacci cube Γn can be viewed as an induced subgraph of the n-dimensional hypercube, obtained by restricting to binary strings that avoid consecutive 1s. A remarkable feature of these graphs is that the number of their vertices is given by Fibonacci numbers. This close connection between graph structure and classical integer sequences naturally motivates the study of Fibonacci-like cubes. In this talk, we will explore Fibonacci-like cubes and present their combinatorial and graph-theoretical properties.
