Datum | Vortrag |
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04.04.2017 | Sondertermin How to tie a (linear optical) field into a knot Prof. Mark Dennis, School of Physics, University of Bristol It is a challenging question to write down a function from real 3-dimensional space to the complex numbers such that the preimage if zero (say) is a given knot or link. If, in addition, the function appears as a solution of some physically interesting partial differential equation, or minimizes some physically motivated functional, then the knotted field might be realisable in nature. I will discuss our approach and (partial) solution this problem applied to such knotted fields in coherent optical fields (i.e. laser beams), but with applications to other systems such as knotted vorticity lines in fluids. If there is time, I will also describe how random fields (which model modes of chaotic wave systems) naturally contain a tangle of many knotted nodal lines. Einladende: C. Denz |
18.04.2017 |
Mitgliederversammlung |
Thursday 04.05.2017 |
Vortrag im Rahmen des allgemeinen Physikalischen Kolloquiums Pattern formation in active matter – From mechano-chemical waves to mesoscale turbulence
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09.05.2017 |
Nach dem Physikstudium in die KI-Industrie oder: Wie man die schlauen Maschinen endlich zum Arbeiten bringt Dr. Michael Köpf, Cognotekt GmbH, Köln
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Thursday 18.05.2017 |
Vortrag im Rahmen des allgemeinen Physikalischen Kolloquiums Experiments with freely suspended and freely floating liquid films Prof. Ralf Stannarius, Universität Magdeburg, Institut f. Experimentelle Physik |
23.05.2017 |
Nonlinear dynamics of beating cilia and flagella: Swimming, steering, and synchronization Dr. Benjamin M. Friedrich, TU Dresden, Center for Advancing Electronics Dresden (cfaed), Biological Algorithms Group
Einladende: Dr. S. Gurevich |
30.05.2017 |
Timing stability of quantum dot based semiconductor lasers Dr. Stefan Breuer, Technische Universität Darmstadt, Angewandte Halbleiteroptik und Photonik Passively mode-locked semiconductor lasers based on nano-scale quantum dots offer access to sub-picosecond short optical pulses thanks to their broad spectral bandwidth and ultra-fast gain dynamics. Their small footprint, multi-Gigahertz repetition rates, direct modulation capability as well as their monolithic layout makes them promising candidates for optical clock distribution, high bit-rate optical time division multiplexing and compact microwave/millimeter-wave signal generation. Their intrinsic pulse train timing stability and fixed pulse repetition rate however can be limiting factors towards their widespread implementation into time-critical applications. Experimental concepts to improve the timing stability and to enable repetition rate agility are therefore demanded. This talk will start by reviewing timing stability fundamentals of semiconductor lasers. Then, a selection of experimental concepts to improve the timing stability will be described in detail. Next, by means of a reconfigurable laser layout, higher harmonics of the fundamental repetition rate can be generated leading to a substantially improved timing stability. Finally, experimental results will be discussed and explained in the framework of a time-domain description that is able to reproduce the timing stability improvement and repetition rate agility. Einladende: Dr. S. Gurevich |
31.05.2017 |
Sondertermin On-chip generation of complex optical quantum states and their coherent control Dr. Michael Kues, Institut national de la recherche scientifique, Varennes (Québec), Canada Entangled optical quantum states are essential towards solving questions in fundamental physics, and are at the heart of applications in quantum information science [1]. For advancing the research and development of quantum technologies, practical access to the generation and manipulation of complex photon states is required. Recently, integrated (on-chip) photonics has become a leading platform for the compact, cost-efficient, and stable generation and processing of optical quantum states [2]. However, on-chip sources are currently limited to basic two-dimensional (qubit) two-photon states.
Zeit: Mittwoch, 31. Mai 2017, 09:30 Uhr Ort: Seminarraum 005/006 des CeNTechs 1, Heisenbergstraße 11 Einladender: Prof. Dr. C. Fallnich |
06.06.2017 | Pfingstferien - kein Kolloquium |
13.06.2017 |
Structure formation in confinement: photonic balls and active granular rotors Prof. Dr. Michael Engel, Friedrich-Alexander Universität Erlangen-Nürnberg, Institute for Multiscale Simulation Natural and biological systems achieve emergent behavior with elementary building blocks. Research in my group focuses on modeling structure formation processes in soft and hard condensed matter. In this talk, I discuss two joint computational-experimental works that have in common that they concern structure formation of particles in confinement. (1) A binary mixture of 3D-printed macroscopic rotors with opposite sense of rotation is excited on an electromagnetic shaker in circular confinement. Phase-separation reminiscent of spinodal decomposition is observed. Evolution of the domain size is compared to two-dimensional Langevin dynamics simulations. (2) Droplet-based microfluidics creates homogeneous emulsion droplets as sources for defined spherical confinement. We observe a discrete series of multiply twinned colloidal clusters with icosahedral symmetry. To understand and explain the formation of the clusters, we test a geometric model and extract extremal principles. Einladender: U. Thiele |
27.06.2017 |
Network robustness and the impact of transmission line failures Prof. Dr. Dirk Witthaut, Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung, Systemforschung und Technologische Entwicklung (IEK-STE) The robust operation of physical distribution and supply networks is fundamental for economy, industry, and our daily life. For instance, a reliable supply of electric power fundamentally underlies the function of most of our technical infrastructure. In periods of high loads, the breakdown of a single element of the power grid can cause a global cascade of failures implying large-scale outages with potentially catastrophic consequences. Einladender: Dr. O. Kamps |
04.07.2017 |
Spontaneous and Coherent Raman microscopy for biomedical applications Dr. Cees Otto, University of Twente, Faculty of Science and Technology, Medical Cell BioPhysics (MCBP) Raman microscopy is well known as a powerful method for the study of molecular changes and processes. In biomedical applications the chemical information is usually extremely complex. Einladender: Prof. Dr. C. Fallnich |
11.07.2017 |
Theory, structure and experimental justification of the metal/electrolyte interface Dr. Manuel Landstorfer, Weierstrass Institute for Applied Analysis and Stochastics (WIAS), Berlin Various types of modeling approaches are used to investigate the structure of the metal/electrolyte interface and its behaviour due to adsorption, intercalation and other surface effects [1]. While atomistic resolved models address reaction mechanisms, continuum models are the foundation for a comparison to voltage- or current-controlled experiments. References [1] M. Landstorfer and T. Jacob, Chem. Soc. Rev., 2013, 42, pp 3234–3252. Einladender: Prof. A. Heuer |
25.07.2017 | Static and Dynamic Functional Brain Connectivity at Sensor and Source level: Evidences from EEG-MEG Group Analysis
Static and Dynamic Functional Brain Connectivity at Sensor and Source level: Evidences from EEG-MEG Group Analysis Dr. Stavros Dimitriadis, Aristotle University of Thessaloniki The human brain can be modelled as a complex networked structure with brain regions as individual nodes and their anatomical/functional links as edges. Functional brain networks are constructed by first extracting weighted connectivity matrices, and then thresholding them to minimize the noise level. Different methods have been used to estimate the dependency values between the nodes The adaptation of both bivariate (mutual information) and multivariate (Granger causality) connectivity estimators to quantify the synchronization between multichannel recordings yields a fully connected, weighted, (a)symmetric functional connectivity graph (FCG), representing the associations among all brain areas. The aforementioned procedure leads to an extremely dense network of tens up to a few hundreds of weights. Therefore, this FCG must be filtered out so that the “true” connectivity pattern can emerge. For that reason, statistical filtering based on surrogates analysis and also topological filtering based on the maximization of information flow in the network under the constraint of the wiring cost (Dimitriadis et al., 2017) should be adopted to get a subject and condition specific functional connectivity pattern. References: [1] Dimitriadis SI et al., . Topological Filtering of Dynamic Functional Brain Networks Unfolds Informative Chronnectomics: A Novel Data-Driven Thresholding Scheme Based on Orthogonal Minimal Spanning Trees (OMSTs). Front. Neuroinform., 26 April 2017 | https://doi.org/10.3389/fninf.2017.00028 Einladender: Prof. C. Wolters |