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Seminars - Summer term 2017

Seminar “Special problems in colloidal physics”

Location: HHU Düsseldorf, Seminarroom 25.32.O2.51
Program:
DateSpeakerTopicTime
Wed 03.05.2017   G. Pessot  Self-induced polar order for pushers and pullers  13:30 s.t.
Mon 08.05.2017   C. Hoell  Dynamical density functional theory for circle swimmers  14:30 s.t.
Wed 10.05.2017   C. Sitta  Tetratic phases of rectangles using DFT  14:30 s.t.
Wed 31.05.2017   C. Scholz  There's something hidden in the basement - active matter driven by vibrations!  14:30 s.t.
Thu 01.06.2017   E. Allahyarov  A review of new developments in responsive nanocomposites  14:30 s.t.
Mon 12.06.2017   S. Babel  DDFT of charged particles in an electric field  14:30 s.t.
Wed 14.06.2017   S. Jahanshahi  The Brazil nut and reverse Brazil nut effects  14:30 s.t.
Wed 28.06.2017   M. Puljiz  Two magnetically interacting rigid inclusions in a soft gel  13:30 s.t.
Wed 28.06.2017   U. Zimmermann  Dynamical Density Functional Theory in 2D Microchannels  14:30 s.t.
Fri 30.06.2017   A. Gabriëlse  Crystallization of nanoparticles with square-shoulder interactions  14:30 s.t.
Prof. Dr. H. Löwen

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Seminar “Special problems in computer simulation of soft matter”

Location: HHU Düsseldorf, Seminarroom 25.32.O2.51
Program:
DateSpeakerTopicTime
Wed 03.05.2017   G. Pessot  Self-induced polar order for pushers and pullers  13:30 s.t.
Mon 29.05.2017   S. Ganguly  Interfacial free energies at solid-solid interfaces  14:30 s.t.
Wed 31.05.2017   C. Scholz  There's something hidden in the basement - active matter driven by vibrations!  14:30 s.t.
Thu 01.06.2017   E. Allahyarov  A review of new developments in responsive nanocomposites  14:30 s.t.
Mon 12.06.2017   S. Babel  DDFT of charged particles in an electric field  14:30 s.t.
Wed 14.06.2017   S. Jahanshahi  The Brazil nut and reverse Brazil nut effects  14:30 s.t.
Fri 16.06.2017   M. Golkia  Residual stresses in glasses  14:30 s.t.
Fri 30.06.2017   A. Gabriëlse  Crystallization of nanoparticles with square-shoulder interactions  14:30 s.t.
Thu 27.07.2017   M. Eshraghi  Calculation of interfacial free energy via Thermodynamic Integration (TI)  14:30 s.t.
Prof. Dr. J. Horbach

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Seminar “Soft Matter”

Location: HHU Düsseldorf, Seminarroom 25.32.O2.51
Program:
DateSpeakerAffiliationTime
Fri 28.07.2017   Suvendu Mandal  Universität Innsbruck, Austria  14:30 s.t.
Suvendu Mandal: „The dynamics of driven and active Brownian particles”
Universität Innsbruck, Austria - Seminar@HHUD: 28.7.17 14:30 s.t., Seminarroom 25.32 O2.51

While the linear response is well-characterized in terms of the fluctuation-dissipation theorem, few exact results are available for strong driving. Here we study the time-dependent velocity of a colloidal particle immersed in a dilute suspension of hard spheres in response to a step force switched on at time zero using Brownian dynamics simulations. Our main quantity of interest is the time-dependent mobility and its approach to the stationary state mobility. A stationary state solution for the mobility exact in first order of the packing fraction has been established earlier in terms of a power-series expansion with respect to the force on the tracer particle [1]. We extend this result to the case of arbitrarily strong driving including the complete time-dependence of the response upon switching on the force. We show that in the stationary state, our analytic solution recovers the anticipated limit for strong driving [1] and captures the response in first order of the packing fraction for any strength of the force.

We also investigate active colloidal hard-sphere glasses using Brownian dynamics simulations. While the properties of passive colloidal glasses are fairly understood over the years, not much is known for active colloidal glasses. In this talk we discuss the decoupling between active speed and rotational diffusion in colloidal glasses. These findings agree with theoretical predictions obtained by the mode-coupling theory of the glass transition.

References

  1. T. M. Squires and J. F. Brady, Physics of Fluids 17, 0731
The dynamics of driven and active Brownian particles
Wed 26.07.2017   Vladimir S. Filinov  Russian Academy of Sciences, Moscow, Russia  14:30 s.t.
t.b.a.
Tue 27.06.2017   William van Megen  RMIT Melbourne, Australia  14:30 s.t.
William van Megen: „Collective modes in hard sphere systems; cage effect”
RMIT Melbourne, Australia - Seminar@HHUD: 27.6.17 14:30 s.t., Seminarroom 25.32 O2.51

It’s axiomatic that the slowing of diffusion, increasing sluggishness of flow and delay of the structural relaxation a fluid when its density is increased are due to the increasing congestion among the particles comprising the fluid. It is also generally accepted that these manifestations of dynamic slowing are due to the ”cage effect“ the microscopic picture in which particles are trapped, at least momentarily, by their respective neighbours. An attempt to examine the role of caging more closely considers the spread of the displacement distributions of Brownian particles. These distributions are necessarily biased by the presence of neighbouring particles. Accommodation of this bias by those neighbours conserves the displacement distribution locally and presents a collective mechanism for exploring configuration space that turns out to be more efficient than the intrinsic Brownian motion. Blocking of the bias effects caging of some particles, however locally in space and time. This incurs, through the impost of global conservation of probability (the average number of caged particles), a delayed, non-local collective process. Both collective mechanisms incur delay or stretching of time correlation functions, in particular the particle number and flux densities. This presentation identifies and distinguishes these mechanisms in existing data from dynamic light scattering experiments and computer simulations on systems of particles with hard sphere interactions.

Collective modes in hard sphere systems; cage effect
Fri 02.06.2017   Gerd Schröder-Turk  Murdoch University, Perth, Australia  14:30 s.t.
Mixtures of Pears and Oranges: From inverse micelles to labyrinth-like bicontinuous phases
Wed 17.05.2017   Rolf Schilling  Johannes-Gutenberg-Universität Mainz  14:30 s.t.
Extremely Confined Fluids: Thermodynamics and Dynamics
Thu 04.05.2017   Christina Kurzthaler  Universität Innsbruck, Austria  14:30 s.t.
Christina Kurzthaler: „From self-propelled particles to semiflexible polymers”
Universität Innsbruck, Austria - Seminar@HHUD: 4.5.17 14:30 s.t., Seminarroom 25.32 O2.51

Self-propelled particles are intrinsically out of equilibrium and exhibit peculiar dynamical behavior. These active agents are subject to strong stochastic fluctuations, that compete with their persistent swimming motion. So far most studies consider the lowest order moments of the displacements only, while more general spatiotemporal information is encoded in the directly measurable intermediate scattering function, i.e. the Fourier transform of the probability density. In this talk, I will discuss analytic solutions of the intermediate scattering function of an active Brownian particle and a Brownian circle swimmer, and show, that our theoretical predictions agree very well with experimental observations of Janus particles. The mathematical analog to the self-propelled particle constitutes the semiflexible polymer. I will also provide an exact solution for the partition sum of a semiflexible polymer under compression and analyze its buckling behavior in terms of the force-extension relation.

From self-propelled particles to semiflexible polymers
Fri 21.04.2017   Céline Ruscher  Institut Charles Sadron, Strasbourg, France  14:30 s.t.
Voronoi glasses: a new model for probing glass transition
Prof. Dr. Egelhaaf, Prof. Dr. Horbach, Prof. Dr. Löwen

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poroSys-Talks

File: poroSys Talkslist

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Colloquia

Location: HHU Düsseldorf, Lecture Hall 5J (Building 25.31 Level 00)
Program:
DateSpeakerAffiliationTime
Thu 29.06.2017   Prof. Dr. Holger Stark  Institut für Theoretische Physik, Technische Universität Berlin  16:30 s.t.
Microswimmers: From design principles to their emergent collective behavior
Thu 26.01.2017   Prof. Karsten Flensberg  Niels Bohr Institute, University of Copenhagen, Denmark  16:30 s.t.
Towards Majorana-based topological qubits?
Thu 19.01.2017   Prof. Michael Eikerling  Simon Fraser University, Vancouver, Canada  16:30 s.t.
The Physics of Electrochemical Energy Conversion
Thu 08.12.2016   PD Dr. Antonio Di Piazza  Max-Planck-Institut für Kernphysik, Heidelberg  16:30 s.t.
Tests of classical and quantum electrodynamics in intense laser beams
Thu 24.11.2016   Prof. Dr. Susana Huelga  Universität Ulm  16:30 s.t.
Vibrations, Quanta and Biology
Thu 27.10.2016   Prof. Joseph Indekeu  Theoretical Physics, KU Leuven, Belgium  16:30 s.t.
Short-range wetting in two dimensions: is it always second-order?
WE Physik, Heinrich-Heine-Universität Düsseldorf

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Seminar about Bachelor, Master and other Theses from the Institut for Theoretical Physics II

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Link: Physics Colloquium
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