Previous Seminars |
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Academic Year 2022-2023 |
| Dr. Christiana Mavroyiakoumou Courant Institute of Mathematical Sciences Η διάλεξη θα πραγματοποιηθεί την Τετάρτη 28 Ιουνίου 2023 και ώρα 10:00 στην αίθουσα 039-ΘΕΕ01 στη Πανεπιστημιούπολη με θέμα "Membrane flutter in three-dimensional inviscid flows" Abstract: Many previous works have studied fluid-structure interactions induced by thin flexible bodies. In most of these studies the body is nearly inextensible, with a moderate bending modulus. Here we consider softer materials — extensible membranes — that have zero bending modulus, and undergo significant stretching in a fluid flow that can lead to flutter. Examples include rubber, textile fabric, and the skin of swimming and flying animals. We develop a mathematical model and numerical method to study the large-amplitude flutter of rectangular membranes that shed a trailing vortex-sheet wake in a 3D inviscid flow. This extends our previous work on membrane dynamics in a 2D flow, where the membrane is a 1D curvilinear segment that undergoes small and large deflections. Here we consider 12 distinct boundary conditions at the membrane edges and compute the stability thresholds and the subsequent large-amplitude dynamics across the three-parameter space of membrane mass ratio, pretension, and stretching rigidity. We find that 3D dynamics in the 12 cases naturally form four groups based on the conditions at the leading and trailing edges. The conditions at the side edges are generally less important, but may have qualitative effects on the membrane dynamics — e.g. steady versus unsteady, periodic versus chaotic, or the variety of spanwise curvature distributions — depending on the group and the physical parameter values. |
| Ivan C. Christov School of Mechanical Engineering (Purdue University) Τετάρτη 3η Μαϊου 2023 Η ομιλία θα διεξαχθεί στις 11:00πμ στην αίθουσα ΘΕΕ01-039 καi ο τίτλος της είναι "Nonlinear Dynamics of Magnetic Fluid Interfaces". Abstract: I will discuss some recent progress from my research group on the nonlinear dynamics of flow-driven interfaces, specifically the surface-tension-endowed interface between a magnetic fluid and air. Under specific flow conditions that we identify, the interface becomes unstable and undergoes complex, unsteady deformations, which we capture with reduced models. Our work is motivated by the recent interest in the physics of active and responsive fluids. Magnetic fields allow non-invasive manipulation of dynamics for biological applications (microswimmers, drug delivery) due to the safe operation of magnetic fields in the medical setting. By tuning an external field, we demonstrate coherently spinning ferrofluid droplets. Nonlinear periodic interfacial waves drive the motion, emerging from the linearly unstable base state upon saturating nonlinearity and arresting the instability. Nonlinear simulations using a sharp-interface (boundary-element type) numerical method confirm the predictions, allowing us to construct a phase diagram for perturbations that "grow" into stable spinning gears. Further, we derive a new thin-film equation (of generalized Kuramoto--Sivashinsky type) for long waves on a confined ferrofluid interface subject to an "angled" magnetic film. We find nonlinear, periodic traveling wave solutions, which are shown to be a new class of non-localized 'dissipative solitons'. Numerical simulations via a pseudospectral method with exponential-time-differencing (to handle the stiffness of the fourth-order derivative) reveal transitions between nonlinear wave states. These transitions are explained by numerically evaluating the linear stability of periodic solutions to our thin-film equation. |
| Marc Hallin Université libre de Bruxelles Τετάρτη 5η Απριλίου 2023 Η ομιλία θα διεξαχθεί στις 12:30πμ στην αίθουσα ΘΕΕ01-038 καi ο τίτλος της είναι From copulas and depth to measure transportation: the long quest for multivariate quantiles and ranks”. Abstract: The univariate concept of a quantile function---the inverse of a distribution function---plays a fundamental role in most areas of Probability and Statistics, including Econometrics. In dimensions two and higher, however, inverting traditional distribution functions does not lead to any satisfactory notion. In their quest for an adequate concept of multivariate quantiles, statisticians developed two extremely fruitful theoretical pathways: copula transforms, where marginal quantiles are privileged over global ones, and depth functions, where a centeroutward ordering is substituting the more traditional South-West/North-East one. None of these, unfortunately, induces a satisfactory concept of quantile function. We show how a recent center-outward definition, based on measure transportation ideas, of the concept of distribution function, yields notions of multivariate quantiles, ranks, and signs satisfying, in arbitrary dimension d, all the properties that make their univariate versions successful and vital tools of statistical inference. |
| Χρίστος Μαραγκός Πανεπιστήμιο Κύπρου Τετάρτη 1η Φεβρουαρίου 2023 Η ομιλία θα διεξαχθεί στις 11:00πμ στην αίθουσα ΘΕΕ01-037 καi ο τίτλος της είναι Wave interaction with metamaterials. Abstract: The science of metamaterials has developed rapidly over the last two decades. We will use them to manipulate water waves and create phenomena that are difficult to see using natural materials. |
Fall Semester 2022-2023 |
| Christos, Raent, Onti University of Cyprus Subject: TBA December 14 2022 Regular meeting time: Wednesdays 10:00-11:00 (Coffee and tea served at 09:30) Place: ΘEE01 038 * Part of a series of seminars |
| Theodoros Vlachos University of Ioannina Subject: Homology vanishing theorems for pinched submanifolds December 7 2022 Regular meeting time: Wednesdays 10:00-11:00 (Coffee and tea served at 09:30) Place: ΘEE01 038 * Part of a series of seminars |
| Konstantinos Bourazas University of Cyprus Subject: A Bayesian Online Change Point Model for Short Runs November 30 2022 11:00 a.m. Room 110-XOD02, University Campus |
| Ioannis Athanasopoulos University of Crete Μία απουσιάζουσα ιδιότητα μονομερών προβλημάτων και οι συνέπεις της November 23 2022 Regular meeting time: Wednesdays 10:00-11:00 (Coffee and tea served at 09:30) Place: ΘEE01 038 * Part of a series of seminars |
| Y. Yiatrakos Tsinghua University Limitations of the Wasserstein MDE for Univariate data November 16 2022 |
| Georgios Petridis University of Cyprus Cryptography, shift-registers and secure implementations. Σε αυτή την παρουσίαση, αφού κάνουμε πρώτα μια "αφηρημένη" εισαγωγή στην κρυπτογραφία, θα αναφερθώ σε δυο συγκεκριμένους τομείς που με ενδιαφέρουν ερευνητικά. November 16 2022 Regular meeting time: Wednesdays 10:00-11:00 (Coffee and tea served at 09:30) Place: ΘEE01 038 * Part of a series of seminars |
| Alexei Skorobogatov Imperial College London Cohomology of diagonal surfaces. October 26 2022 Regular meeting time: Wednesdays 10:00-11:00 (Coffee and tea served at 09:30) Place: ΘEE01 038 * Part of a series of seminars |
Spring Semester 2021-2022 |
| Grigorios Fournodavlos Princeton University Abstract * 27 April 2022 |
| Colin Adams Williams College Abstract * 16 March 2022 |
| Georgios Sakellaris Aristotle University of Thessaloniki Scale invariant regularity estimates for second order elliptic equations with lower order coefficients in optimal spaces * 09 March 2022 |
| Christopher Hacon University of Utah Geometry of Complex Algebraic Varieties * 02 March 2022 |
| Alexandros Eskenazis University of Cambridge Abstract * 23 February 2022 |
| Dimitrios Ntalampekos Stony Brook University Removability and Rigidity Problems in the Complex Plane * 16 February 2022 |
| Konstantinos Zemas University of Münster Rigidity estimates for isometric and conformal maps on the sphere * 09 February 2022 |
| Panayotis Smyrnelis Basque Center for Applied Mathematics Elliptic systems of phase transition type * 02 February 2022 |
| Efthymios Sofos University of Glasgow Prime values of integer polynomials and random Diophantine equations * 26 January 2022 |
| Christoforos Neofytidis Ohio State University Aspherical manifolds and endomorphisms of their fundamental groups * 19 January 2022 |
| Louis H. Kauffman University of Illinois at Chicago Knots and Physics * 12 January 2022 |
| * The Greek Mathematical Seminar is a joint online seminar of the departments of mathematics of the University of Athens, the University of Crete, the University of Cyprus, the University of Ioannina, the National Technical University of Athens, the University of Patras and the Aristotle University of Thessaloniki. |
2021 |
| Athanasios Chatzikaleas University of Munster Non-linear periodic waves on the Einstein cylinder. 15 December 2021 |
| Georgios Dimitroglou Rizell Uppsala University Symplectic topology of cotangent bundles and exotic differentiable structures on spheres 08 December 2021 |
| Evis Ieronymou University of Cyprus Brauer-Manin obstruction and zero-cycles on certain varieties 01 December 2021 |
| Petros Valettas University of Missouri Gaussian methods in linear Dvoretzky theory. 24 November 2021 |
| Evgenios Kakariadis Newcastle University Rigidity of analytic operator algebras 10 November 2021 |
| Grigoris Paouris Texas AM University Some results on anti-concentration phenomenon. 03 November 2021 |
| Xenia Spilioti University of Aarhus Fried ‘s conjecture and dynamical zeta functions of Selberg and Ruelle on locally symmetric spaces. 27 October 2021 |
| Stefanos Aretakis University of Toronto Asymptotics for the wave equation on black hole spacetimes 20 October 2021 |
| Sotiris Sambanis University of Edinburgh A review of recent advances of Euler’s polygonal approximation 13 October 2021 |
| Georgios Kydonakis University of Heidelberg Surgeries in representation varieties. 06 October 2021 |
| Christos Mantoulidis Rice University A nonlinear spectrum on closed manifolds 29 September 2021 |
| Ivan Cheltsov University of Edinburgh Kahler Einstein smooth Fano threefolds. 22 September 2021 |
| Panagiotis Polymerakis Max Planck Institute for Mathematics, Bonn. Liouville type properties of covering spaces. 15 September 2021 |
| Maria Chlouveraki Université Paris Saclay On the reality of complex reflexive groups 08 September 2021 |
| Theodora Bourni University of Tennessee Polygonal ancient solutions to mean curvature flow 30 June 2021 |
| Ioannis Sakellaridis Johns Hopkins University Αρμονική ανάλυση και L-συναρτήσεις 23 June 2021 |
| Dimitris Koukoulopoulos University of Montreal Irreducibility of random polynomials of large degree. 16 June 2021 |
| Georgios Pappas Michigan State University Symplectic structures in arithmetic geometry. 09 June 2021 |
| Agelos Georgakopoulos University of Warwick Convergence of square tilings to the Riemann map 02 June 2021 |
| Charalambos Tamvakis University of Maryland The roots of mathematical thought 26 May 2021 |
| Andreas Artemiou University of Cardiff SVM-based real time sufficient dimension reduction 19 May 2021 |
| Stavros Papadakis University of Ioannina The face numbers of convex polytopes and simplicial spheres 12 May 2021 |
| Marina Iliopoulou University of Kent A discrete Kakeya-type inequality 05 May 2021 |
| Mihalis Mourgoglou Universidad del Pais Vasco Blow-ups of Caloric measure in time-varying domains and applications to two-phase problems. 21 April 2021 |
| Mihalis Dafermos Princeton University and University of Cambridge Η μη γραμμική ευστάθεια των μελανών οπών Schwarzschild στη γενική σχετικότητα 14 April 2021 |
| Nikos Tziolas University of Cyprus Families of surfaces of general type 07 April 2021 |
| Hamid Ahmadinezhad University of Loughborough Fano Varieties 31 March 2021 |
| Stavros Garoufallidis Southern University of Science and Technology and Max Planck Institute for Mathematics Arithmetic aspects of hyperbolic geometry. 24 March 2021 |
| Wolfgang Arendt University of Ulm Semigroup Properties of the Dirichlet-to-Neumann Operator 17 March 2021 |
| Spyros Alexakis University of Toronto Singularities in black holes interiors 03 March 2021 |
2020 |
| Camille Labourie University of Cyprus Plateau Problems 25 November 2020 |
| Christos, Raent, Onti University of Cyprus On the conjectured extension of Hilbert’s theorem. 7 October 2020 |
| Stefan Schröer University of Düsseldorf The Albanese map 23 September 2020 |
2018 |
| Peter Mathé Weierstrass Institute, Berlin Complexity of statistical ill-posed problems in Hilbert space 07 December 2018 |
| Athanasios Fokas University of Cambridge From Acoustics to the Lindelof Hypothesis 07 December 2018 |
| Demetrios Papageorgiou Imperial College London Mathematical problems arising in some microfluidic applications. 05 December 2018 |
| Efstratios Prasidis University of Aegean Combinatorial methods in problems of topological classification 29 November 2018 |
| Ioannis Athanasopoulos University of Crete A Fractional Heat Obstacle Problem 28 November 2018 |
| Krzysztof Podgórski University of Lund A Slepian model for moving average processes driven by Laplace motion 28 November 2018 |
| Rita Giuliano University of Pisa Renyi α-dimension of random variables with generailzed Cantor distribution and Hausdorff dimension of generalized Cantor sets. 16 November 2018 |
| Carlos Amendola Ceron University of Munich An introduction to Algebraic Statistics. 14 November 2018 |
| Anne van Delft Ruhr Universitat, Bochum A similarity measure for second order properties of non-stationary functional time series with applications to clustering and testing 06 November 2018 |
| Panagiotis Batakides University of Cyprus Poisson geometry for the Classification of 4-manifolds. 31 October 2018 |
| Manolis Georgoulis National Technical University of Athens and University of Leicester hp-version Discontinuous Galerkin methods on polygonal and polyhedral meshes 25 October 2018 |
| Athanasios Georgiadis University of Cyprus Analysis on metric spaces associated with operators. 17 October 2018 |
| Meinolf Geck Stuttgart University News about Lie algebras 10 October 2018 |
| Arman Taghavi-Chabert American University of Beirut Conformal geometry and CR structures 03 October 2018 |
| Andrew Kresch University of Zurich Rationality in families of algebraic varieties 26 September 2018 |
| Christos Athanasiadis University of Athens Gamma-positive polynomials in combinatorics and geometry 19 September 2018 |
| Raj Narayan Dhara Norwegian University of Science and Technology Waves of maximal height for a class nonlocal equations with homogeneous symbol 13 September 2018 |
| Stefanos Aretakis University of Toronto Asymptotics for the wave equation and applications to general relativity 12 September 2018 |
