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Seminare - Winter Semester 2019 / 2020

Seminar über "spezielle Probleme in der Theorie der Kolloide"

Ort: HHU Düsseldorf, Seminarraum 25.32.O2.51
Programm:
DatumSprecher/inThemaZeit
Mi 06.11.2019   A. Zampetaki  Buckling in complex plasma crystals  14:30 s.t.
Fr 08.11.2019   S. Goh  Density functional theory for 3D ferrogels  14:30 s.t.
Mi 20.11.2019   R. Wittmann  Optimal topological states of smectic rods in extreme annular confinement  14:30 s.t.
Fr 22.11.2019   S. Mandal  Active hard-sphere glasses  14:30 s.t.
Mi 08.01.2020   J. Kolker  Simulations of microgels under interfacial confinement  14:30 s.t.
Fr 10.01.2020   L. Fischer  Spherical systems of magnetic elastomers - induced deformational effects  14:30 s.t.
Mi 15.01.2020   J. Grauer  t.b.a.  14:30 s.t.
Fr 17.01.2020   A. Sprenger  Active Brownian motion with orientation-dependent motility  14:30 s.t.
Mi 22.01.2020   A. Ider  A circle swimmer in a nematic liquid crystal  14:30 s.t.
Mi 29.01.2020   P. Monderkamp  t.b.a.  14:30 s.t.
gez.: Prof. Dr. H. Löwen

oben

Seminar über "Spezielle Probleme der Computersimulation weicher Materie"

Ort: HHU Düsseldorf, Seminarraum 25.32.O2.51
Programm:
DatumSprecher/inThemaZeit
Mi 30.10.2019   M. Golkia  The effect of deformation and micro-alloying on the Boson peak in metallic glasses  14:30 s.t.
Mi 20.11.2019   R. Wittmann  Optimal topological states of smectic rods in extreme annular confinement  14:30 s.t.
Fr 22.11.2019   S. Mandal  Active hard-sphere glasses  14:30 s.t.
Mi 08.01.2020   J. Kolker  Simulations of microgels under interfacial confinement  14:30 s.t.
Fr 10.01.2020   L. Fischer  Spherical systems of magnetic elastomers - induced deformational effects  14:30 s.t.
Mi 22.01.2020   A. Ider  A circle swimmer in a nematic liquid crystal  14:30 s.t.
Fr 24.01.2020   N. Küchler  Kinetic pathways for the transformation of a glass-forming fluid to a crystal  14:30 s.t.
Mi 29.01.2020   P. Monderkamp  t.b.a.  14:30 s.t.
gez.: Prof. Dr. J. Horbach

oben

Seminar “Soft Matter”

Ort: HHU Düsseldorf, Seminarraum 25.32.O2.51
Programm:
DatumSprecher/inInstitutZeit
Mo 04.11.2019   Daniel de las Heras  Universität Bayreuth  16:30 s.t.
Superadiabatic forces in non-equilibrium systems
Di 15.10.2019   Charlotte Petersen  Institut für Theoretische Physik, Universität Innsbruck, Austria  10:30 s.t.
Charlotte Petersen: „Simple fluids in complex environments: Obstacles, applied fields and periodic boundaries”
Institut für Theoretische Physik, Universität Innsbruck, Austria - Seminar@HHUD: 15.10.2019 10:30 s.t., Seminarroom 25.23 02.62

I will discuss simple fluids in three different environments. The first is a tracer particle moving through an array of fixed obstacles, which we study to understand the emergence of anomalous transport in crowded media. Transport in heterogeneous crowded environments occurs in many situations, including inside of cells, in catalysts, and in porous rock during oil recovery. Both experimentally, and in simple models, the transport in complex crowded media can be subdiffusive. The origin of this anomalous diffusion has been explained theoretically for the paradigmatic Lorentz model. We extend the Lorentz model towards realistic systems by relaxing the hard-exclusion interaction assumption, and find that the system exhibits a percolation transition dependent on the energy of the probe particle, and the dynamics remain anomalous at the percolation point.

The second environment is a liquid confined with periodic boundary conditions, which allows us to disentangle the effects of layering and local packing observed in liquids confined by walls. We observe that the particle correlations in this quasi-confined fluid exhibit a similar non-monotonic behavior to a liquid confined between two walls, even though the density is homogeneous. This indicates that the correlations in real confined liquids may not be intrinsically related to their oscillating density profile.

Finally, I will discuss a liquid under an applied field, which results in a modulated density. In this system we can seek to understand the effects of particle layering independently of confinement. We find that the correlations in this system have a complicated dependence on the period of the applied field, and this is reflected in both components of the pressure, which oscillate out of phase with one another.

Simple fluids in complex environments: Obstacles, applied fields and periodic boundaries
Mi 09.10.2019   Zhi-Feng Huang  Wayne State University, Detroit, Michigan, United States of Amerika  16:30 s.t.
Modeling Structures and Dynamics of Two-Dimensional Solid and Soft-Matter Systems
Mo 08.07.2019   Jasper Immink  Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden  14:30 s.t.
Jasper Immink: „Fluids, Gels and Crystals: Phase behavior of binary thermoresponsive microgel mixtures”
Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden - Seminar@HHUD: 8.7.19 14:30 s.t., Seminarroom 25.32 O2.51

Thermoresponsive colloidal microgels have frequently been studied in order to probe their tunable interaction potentials and their easily manipulatable phase behaviour. The thermoresponsivity of these microgels allows for facile manipulation of their size and for switching between attractive and soft repulsive interaction potentials. This leads to an interesting phase behaviour comprising crystals, glasses, gels and fluids. Here we now extend the study to binary mixtures, using particles with different sizes and transition temperature, and investigate the effects of the size ratio, volume fraction, and specific interaction potential on the phase behaviour and the resulting structural and flow properties. We profit from the fact that these parameters can all be precisely tuned through temperature as an external control parameter, which allows us to probe novel glass dynamics, binary crystal formation, and gel mechanics, and their relevant phase transitions.

Fluids, Gels and Crystals: Phase behavior of binary thermoresponsive microgel mixtures
Do 27.06.2019   Anand Yethiraj  Memorial University of Newfoundland, Canada  14:30 s.t.
NMR studies of crowding
Di 04.06.2019   Bill van Megen  RMIT Melbourne, Australia  14:30 s.t.
Bill van Megen: „Dynamics of solification: A new perspective from colloidal hard spheres”
RMIT Melbourne, Australia - Seminar@HHUD: 4.6.2019 14:30 s.t., Seminarroom 25.32 O3.51

When a liquid is cooled below its freezing point quickly enough to bypass crystallisation its structural relaxation time and resistance to flow increase sharply and can do so to such an extent that, with sufficient (super) cooling, the liquid vitrifies; there is a glass transition (GT). The physics of this phenomenon continues to be one of the more intriguing and studied subjects of classical condensed matter. Growing length scale, caging and dynamic heterogeneity are aspects that feature commonly in discussion of the GT. While there’s no doubt these have bearing on the sluggish structural relaxation dynamics and flow of supercooled fluids, any quantitative connection remains to be established. It’s far from clear how the extent/degree of caging, for example, underpins the degree of solidity. Where the rigidity of crystalline solid is a direct consequence of its structure (lattice modes). So too, the dynamics of the amorphous solid must derive from its structure. It’s most puzzling therefore that structural arrest, formation of the amorphous solid occurs with merely very subtle changes in structure.

The above questions are re-considered with support of data from dynamic light scattering experiments on suspensions of particles whose interactions are like those of hard spheres. This is a well-studied "model" system that shows both first order freezing/melting and glass transitions. The time correlation function of the longitudinal particle current is the central property considered; it, rather than the more usually considered intermediate scattering function, is particularly sensitive to exposing the change in collective dynamics – overdamped to undamped phonons – that characterises "solidification".

Dynamics of solification: A new perspective from colloidal hard spheres
Do 11.04.2019   Ties van der Laar  Wageningen University, The Netherlands  14:30 s.t.
Ties van der Laar: „Sticky, squishy and stuck. A soft matter approach to membrane failure”
Wageningen University, The Netherlands - Seminar@HHUD: 11.4.19 14:30 s.t., Seminarroom 25.32 O2.51

In this talk I will highlight various ways we have used soft matter science to solve problems in membrane technology. We have developed microfluidic tools to study clogging, used colloidal particles to study cake formation and developed sensors to measure very small forces that might play a role in these processes. My focus will be on the colloidal scale and I will highlight two specific examples, one related to clogging and the other related to the colloidal glass transition.

Sticky, squishy and stuck. A soft matter approach to membrane failure
Mi 03.04.2019   Lei Zhu  Case Western Reserve University, Cleveland, Ohio, United States of America  13:00 s.t.
Lei Zhu: „High Energy Density and Low Loss Dielectric Polymers for Electrical Applications”
Case Western Reserve University, Cleveland, Ohio, United States of America - Seminar@HHUD: 3.4.19 13:00 s.t., Seminarroom 25.32 O2.51

High dielectric constant polymers find numerous advanced electrical and power applications such as pulsed power, power conditioning, gate dielectrics for field-effect transistors, electrocaloric cooling, and electromechanical actuation. Unfortunately, it is generally observed that polymers do not have high dielectric constants (only 2-5) and high polarization tends to cause a significantly dielectric loss. Therefore, it is highly desirable that the fundamental science of all types of polarization and loss mechanisms be thoroughly understood for dielectric polymers. In this presentation, we intend to explore advantages and disadvantages for different types of polarization. Among a number of approaches, orientational polarization is promising for high dielectric constant and low loss polymer dielectrics, if the dipolar relaxation peak can be pushed to towards the gigahertz range. In particular, dipolar glass, paraelectric, and relaxor ferroelectric polymers will be discussed for the orientational polarization approach.

High Energy Density and Low Loss Dielectric Polymers for Electrical Applications
gez.: Prof. Dr. Egelhaaf, Prof. Dr. Horbach, Prof. Dr. Löwen

oben

Kolloquien

Ort: HHU Düsseldorf, Hörsaal 5J (Gebäude 25.31 Ebene 00)
Programm:
DatumSprecher/inInstitutZeit
Mo 07.10.2019   Prof. Dr. Matthias Karg  Heinrich-Heine-Universität Düsseldorf  17:00 s.t.
Current research at the institute for colloids and nanooptics
Di 01.10.2019   Prof. Dr. Hari Srikanth  University of South Florida, USA  16:30 s.t.
Prof. Dr. Hari Srikanth: „Tuning magnetic anisotropy in nanostructures for biomedical applications”
University of South Florida, USA - Seminar@HHUD: 1.10.2019 16:30 s.t., Lecture hall 6A

Magnetic nanoparticles have been building blocks in applications ranging from high density recording to spintronics and nanomedicine. Magnetic anisotropies in nanoparticles arising from surfaces, shapes and interfaces in hybrid structures are important in determining the functional response in various applications.

In this talk I will first introduce the basic aspects of anisotropy, how to tune it in nanostructures and ways to measure it. I will discuss resonant RF transverse susceptibility, that we have used extensively, as a powerful method to probe the effective anisotropy in magnetic materials. Tuning anisotropy has a direct impact on the performance of functional magnetic nanoparticles in biomedical applications such as contrast enhancement in MRI and magnetic hyperthermia cancer therapy. There is a need to improve the specific absorption rate (SAR) or heating efficiency of nanoparticles for hyperthermia and I will focus on the role of tuning surface and interfacial anisotropy with a goal to enhance SAR.

Strategies going beyond simple spherical structures such as exchange coupled core-shell nanoparticles, nanowire, nanotube geometries can be exploited to increase saturation magnetization, effective anisotropy and heating efficiency in magnetic hyperthermia. This lecture will combine insights into fundamental physics of magnetic nanostructures along with recent research advances in their application in nanomedicine.

Tuning magnetic anisotropy in nanostructures for biomedical applications
Mo 16.09.2019   Prof. Dr. Niels Madsen  Swansea University, United Kingdom  14:30 s.t.
Prof. Dr. Niels Madsen: „Antihydrogen spectroscopy and beyond”
Swansea University, United Kingdom - Seminar@HHUD: 16.09.2019 14:30 s.t., Lecture hall 25.31 O0.5J

The Standard Model of particle physics has been riding a wave of success for the last decade, latest with the discovery of the Higgs boson at CERN in 2012. However, it still falls short of explaining a number of phenomena, one of which is the apparent lack of significant antimatter in the Universe. Antihydrogen, the bound state of an antiproton and a positron, is currently the only bound system of only antiparticles and is therefore an exciting test-ground for the most fundamental symmetries in nature such as CPT symmetry and the weak equivalence principle, and perhaps elucidate the problem with the missing antimatter.

For almost a decade the ALPHA collaboration has been trapping antihydrogen with the aim of bringing the best atomic physics tools available for investigating matter/antimatter symmetries. Initially only a few could be trapped, allowing the first atomic transitions to be observed, but in the last few years, the techniques have matured to an extent that we envisage experiments on 1000´s of anti-atoms. This development has already borne fruit with the first observation of the1S-2S transition in antihydrogen, and the measurement of the transition to a precision of a few parts in 1012, the most accurate and precise measurement on antimatter to date.

In this talk I´ll discuss how we have achieved these feats, show examples of our measurements and discuss where we plan to go from here. Additionally I´ll discuss our latest upgrade that should allow the first direct measurement of the gravitational to inertial mass of antihydrogen when CERN restarts antiproton delivery in 2021.

Antihydrogen spectroscopy and beyond
Do 27.06.2019   Prof. Dr. Achim Rosch  Universität zu Köln  16:30 s.t.
Prof. Dr. Achim Rosch: „Whirls in magnets: from skyrmions to magnetic monopoles”
Universität zu Köln - Seminar@HHUD: 27.6.19 16:30 s.t., Lecture hall 25.31 O0.5J

In magnets lacking inversion symmetry, topologically quantized magnetic whirls, so-called skyrmions, form due to spin-orbit interactions. Skyrmions are tiny, stable, couple extremely efficiently to electric currents and can be manipulated by small forces. They are therefore promising candidates for, e.g., future magnetic memories. The coupling of skyrmions to electrons arises from Berry phases, which can efficiently be described by an artifical electromagnetic field. We investigate how the topology of skyrmion phase can be changed by singular magnetic defects which can be identified as emergent magnetic monopoles.

Whirls in magnets: from skyrmions to magnetic monopoles
Do 13.06.2019   Prof. Dr. Gérard Mourou  École Polytechnique, Palaiseau, France  17:00 s.t.
Prof. Dr. Gérard Mourou: „Verleihung der Ehrendoktorwürde: Passion extreme light”
École Polytechnique, Palaiseau, France - Seminar@HHUD: 13.6.19 17:00 s.t., Lecture hall 3A 23.01 O0.3A

Extreme-light laser is a universal source providing a vast range of high energy radiations and particles along with the highest field, highest pressure, temperature and acceleration. It offers the possibility to shed light on some of the remaining unanswered questions in fundamental physics like the genesis of cosmic rays with energies in excess of 1020 eV or the loss of information in black-holes. Using wake-field acceleration some of these fundamental questions could be studied in the laboratory. In addition extreme-light makes possible the study of the structure of vacuum and particle production in "empty" space which is one of the field’s ultimate goal, reaching into the fundamental QED and possibly QCD regimes.

Looking beyond today’s intensity horizon, we will introduce a new concept that could make possible the generation of attosecond-zeptosecond high energy coherent pulse, de facto in x-ray domain, opening at the Schwinger level, the zettawatt, and PeV regime; the next chapter of laser-matter interaction.

Verleihung der Ehrendoktorwürde: Passion extreme light
Do 13.06.2019   Prof. Dr. Gérard Mourou  École Polytechnique, Palaiseau, France  10:30 s.t.
Prof. Dr. Gérard Mourou: „Fragestunde mit Nobelpreisträger Prof. Dr. Mourou”
École Polytechnique, Palaiseau, France - Seminar@HHUD: 13.6.19 10:30 s.t., Seminarroom 25.33 O0.61

Within the awarding of the honorary doctorate of the mathematical-scientific faculty to the Nobel prizewinner in physics 2018
Prof. Dr. Gerard Mourou
for the method of
GENERATING HIGH-INTENSITY, ULTRA-SHORT OPTICAL PULSES
the student council in physics and medical physics organizes a time for questions for bachelor, master and PhD students.

organized by Fachschaft Physik/Medizinische Physik

Fragestunde mit Nobelpreisträger Prof. Dr. Mourou
Do 06.06.2019   WE Physik  Heinrich-Heine-Universität Düsseldorf  16:30 s.t.
Gedenkkolloquium für Prof. Dr. Andreas Otto
Do 23.05.2019   Prof. Dr. Thomas Udem  Max-Planck-Institut für Quantenoptik, Garching  16:30 s.t.
Prof. Dr. Thomas Udem: „Challenging QED with atomic Hydrogen”
Max-Planck-Institut für Quantenoptik, Garching - Seminar@HHUD: 23.5.19 16:30 s.t., Lecture hall 25.31 O0.5J

Precise determination of transition frequencies of simple atomic systems are required for a number of fundamental applications such as tests of quantum electrodynamics (QED), the determination of fundamental constants and nuclear charge radii. The sharpest transition in atomic hydrogen occurs between the metastable 2S state and the 1S ground state with a natural line width of only 1.3 Hz. Its transition frequency has been measured with almost 15 digits accuracy using an optical frequency comb and a cesium atomic clock as a reference [1]. A measurement of the Lamb shift in muonic hydrogen is in significant contradiction to the hydrogen data if QED calculations are assumed to be correct [2]. In order to shed light on this discrepancy the transition frequency of one of the broader lines in atomic hydrogen has to be measured with very good accuracy [3].

References

  1. C. G. Parthey et al., Phys. Rev. Lett. 107, 203001 (2011).
  2. A. Antognini et al., Science 339, 417, (2013).
  3. A. Beyer et al., Science 358, 79 (2017).
Challenging QED with atomic Hydrogen
Do 16.05.2019   Prof. Dr. Piet Brouwer  Freie Universität Berlin  16:30 s.t.
Prof. Dr. Piet Brouwer: „Higher-order topological insulators and superconductors”
Freie Universität Berlin - Seminar@HHUD: 16.5.19 16:30 s.t., Lecture hall 25.31 O0.5J

Topological insulators combine an insulating bulk with gapless states at their boundaries. This talk introduces "higher-order topological insulators", which are crystalline insulators with a gapped bulk and gapped crystalline boundaries, but topologically protected gapless states at the intersection of two or more boundaries. I´ll show that reflection symmetry and other spatial symmetries can be employed to systematically generate examples of higher-order topological insulators and superconductors, although the topologically protected states at corners or at crystal edges continue to exist if the crystalline symmetry is broken.

Higher-order topological insulators and superconductors
Do 09.05.2019   Prof. Dr. Stephan Herminghaus  Max-Planck-Institut für Dynamik und Selbstorganisation Göttingen  16:30 s.t.
Prof. Dr. Stephan Herminghaus: „Active Matter and Sustainability: from Plankton to Traffic Flow”
Max-Planck-Institut für Dynamik und Selbstorganisation Göttingen - Seminar@HHUD: 9.5.19 16:30 s.t., Lecture hall 25.31 O0.5J

The most important question of our time is whether, and how, we will be able to run our planet sustainably. Answering this question requires a deep understanding of the earth system, a vast non-equilibrium system which abounds with different active-matter subsystems. Two of them are within the focus of the talk: the plankton, which represents the bottleneck of solar energy entering the marine biosphere, and traffic flow, which is among the strongest sources of greenhouse emissions. Despite the complexity and disparity of the two systems, basic statistical physics methodology may pave the way towards understanding their overall behaviour.

Active Matter and Sustainability: from Plankton to Traffic Flow
Do 11.04.2019   Prof. Dr. Roberto Piazza  Politecnico di Milano, Italy  16:30 s.t.
Prof. Dr. Roberto Piazza: „The magic of soft matter”
Politecnico di Milano, Italy - Seminar@HHUD: 11.04.2019 16:30 s.t., Lecture hall 25.31 O0.5J

What could ever share milk and fine dust, ice cream and shaving foam, rice and sand, tires and ricotta cheese, crude oil and suntan cream, cells and soap bubbles? Nothing, apparently. Yet, the opposite is true. In the air we breathe like in the food we eat, in the clothes we wear like in the detergents used to wash them, in paints in color screens are intimately hidden some little characters, invisible to our eyes but great in creativity and ingenuity.

Besides being at the roots of cutting-edge industrial processes of today and tomorrow, these busy sprites, which are the basic constituents of what scientists call "soft matter", prompt us to explore the deep secrets of matter and to follow step by step self-organizing phenomena ranging from the formation of soap bubbles to the making of biological machines. For life itself is nothing but the "happy hour" of this fantastic Middle-earth between molecules and man.

In this talk, I shall try and guide you along a brief introductory journey to the world of nanoparticles, polymers, surfactants, and biological fluids, with the main aim of fostering a reflection on our intimate bounds with many simple things that surround us.

The magic of soft matter
Für die Dozenten der Physik

oben

Seminar über Examensarbeiten aus dem Institut für Theoretische Physik, Lehrstuhl II

oben

Link: Physikalisches Kolloquium
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