Inst. Theoretische Physik

253 Items

Recent Submissions
Squirmer rods as elongated microswimmers: flow fields and confinement

Zantop, Arne W. ; Stark, Holger (2020-06-25)

Microswimmers or active elements, such as bacteria and active filaments, have an elongated shape, which determines their individual and collective dynamics. There is still a need to identify what role long-range hydrodynamic interactions play in their fascinating dynamic structure formation. We construct rods of different aspect ratios using several spherical squirmer model swimmers. With the h...

Fully coupled Maxwell-Kohn-Sham systems

Jestädt, René (2020)

Light-matter interactions have always been an essential aspect of research. They cover the main properties of light and matter in atomic and molecular systems, in condensed phase, in chemical reactions, and in optics. This thesis presents a feasible implementation to simulate three- imensional, real-time, real-space, self-consistently coupled light-matter systems based on the theoretical backgr...

Effect of topology upon relay synchronization in triplex neuronal networks

Drauschke, Fenja ; Sawicki, Jakub ; Berner, Rico ; Omelchenko, Iryna ; Schöll, Eckehard (2020-05-07)

Relay synchronization in complex networks is characterized by the synchronization of remote parts of the network due to their interaction via a relay. In multilayer networks, distant layers that are not connected directly can synchronize due to signal propagation via relay layers. In this work, we investigate relay synchronization of partial synchronization patterns like chimera states in three...

Two populations of coupled quadratic maps exhibit a plentitude of symmetric and symmetry broken dynamics

Andrzejak, Ralph G. ; Ruzzene, Giulia ; Schöll, Eckehard ; Omelchenko, Iryna (2020-03-17)

We numerically study a network of two identical populations of identical real-valued quadratic maps. Upon variation of the coupling strengths within and across populations, the network exhibits a rich variety of distinct dynamics. The maps in individual populations can be synchronized or desynchronized. Their temporal evolution can be periodic or aperiodic. Furthermore, one can find blends of s...

Stability and control of power grids with diluted network topology

Tumash, Liudmila ; Olmi, Simona ; Schöll, Eckehard (2019-12-09)

We consider sparse random networks of Kuramoto phase oscillators with inertia in order to mimic and investigate the dynamics emerging in high-voltage power grids. The corresponding natural frequencies are assumed to be bimodally Gaussian distributed, thus modeling the distribution of both power generators and consumers, which must be in balance. Our main focus is on the theoretical analysis of ...

Hierarchical frequency clusters in adaptive networks of phase oscillators

Berner, Rico ; Fialkowski, Jan ; Kasatkin, Dmitry ; Nekorkin, Vladimir ; Yanchuk, Serhiy ; Schöll, Eckehard (2019-10-23)

Adaptive dynamical networks appear in various real-word systems. One of the simplest phenomenological models for investigating basic properties of adaptive networks is the system of coupled phase oscillators with adaptive couplings. In this paper, we investigate the dynamics of this system. We extend recent results on the appearance of hierarchical frequency multiclusters by investigating the e...

Synchronization of spiral wave patterns in two-layer 2D lattices of nonlocally coupled discrete oscillators

Bukh, Andrei V. ; Schöll, Eckehard ; Anischenko, Vadim Semenovich (2019-05-07)

The paper describes the effects of mutual and external synchronization of spiral wave structures in two coupled two-dimensional lattices of coupled discrete-time oscillators. Each lattice is given by a 2D N×N network of nonlocally coupled Nekorkin maps which model neuronal activity. We show numerically that spiral wave structures, including spiral wave chimeras, can be synchronized and establis...

Dynamical self-assembly of dipolar active Brownian particles in two dimensions

Liao, Guo-Jun ; Hall, Carol K. ; Klapp, Sabine H. L. (2020-02-24)

Based on Brownian Dynamics (BD) simulations, we study the dynamical self-assembly of active Brownian particles with dipole–dipole interactions, stemming from a permanent point dipole at the particle center. The propulsion direction of each particle is chosen to be parallel to its dipole moment. We explore a wide range of motilities and dipolar coupling strengths and characterize the correspondi...

Stochastic systems with time delay

Loos, Sarah Anna Marie (2020)

In addition to the ever-present random fluctuations due to noise, many systems in biology, physics and technology involve discrete time delay, stemming, e.g., from finite information transmission times. The combination of noise and delay yields non-Markovian dynamics describable by time-nonlocal Langevin equations with a delta-peaked memory kernel. Despite their omnipresence, the understanding ...

Statistical physics of bacterial chemotaxis

Seyrich, Maximilian (2020)

Das Darmbakterium Escherichia coli (E.coli ) ist in den Bereichen der Molekularbiologie, der Zellbiologie und des Forschungsfeldes der Mikroschwimmer eines der am besten erforschten Lebewesen. Die vorliegende Arbeit leistet einen Beitrag zur Grundlagenforschung der Chemotaxis von E.coli (gerichtete Bewegung entlang eines externen chemischen Stimulus). Insbesondere werden neue theoretische Model...

Spectra and dynamics of driven linear quantum rotors

Mirahmadi, Marjansadat (2020)

The development of laser technologies and techniques to cool atoms and molecules has opened new possibilities to manipulate and control quantum matter by tailored external fields. In particular, quantum rotors subject to external fields have enjoyed considerable interest of both the physics and chemistry communities. Furthermore, experimental as well as theoretical investigations of the dynamic...

Two-dimensional spatiotemporal complexity in dual-delayed nonlinear feedback systems: Chimeras and dissipative solitons

Brunner, Daniel ; Penkovsky, Bogdan ; Levchenko, Roman ; Schöll, Eckehard ; Larger, Laurent ; Maistrenko, Yuri (2018-10-09)

We demonstrate for a photonic nonlinear system that two highly asymmetric feedback delays can induce a variety of emergent patterns which are highly robust during the system’s global evolution. Explicitly, two-dimensional chimeras and dissipative solitons become visible upon a space-time transformation. Switching between chimeras and dissipative solitons requires only adjusting two system param...

Qualitative stability and synchronicity analysis of power network models in port-Hamiltonian form

Mehrmann, Volker ; Morandin, Riccardo ; Olmi, Simona ; Schöll, Eckehard (2018-10-18)

In view of highly decentralized and diversified power generation concepts, in particular with renewable energies, the analysis and control of the stability and the synchronization of power networks is an important topic that requires different levels of modeling detail for different tasks. A frequently used qualitative approach relies on simplified nonlinear network models like the Kuramoto mod...

Networks of coupled oscillators: From phase to amplitude chimeras

Banerjee, Tanmoy ; Biswas, Debabrata ; Ghosh, Debarati ; Schöll, Eckehard ; Zakharova, Anna (2018-11-30)

We show that amplitude-mediated phase chimeras and amplitude chimeras can occur in the same network of nonlocally coupled identical oscillators. These are two different partial synchronization patterns, where spatially coherent domains coexist with incoherent domains and coherence/incoherence referring to both amplitude and phase or only the amplitude of the oscillators, respectively. By changi...

Time-delayed feedback control of coherence resonance chimeras

Zakharova, Anna ; Semenova, Nadezhda ; Anishchenko, Vadim ; Schöll, Eckehard (2017-10-26)

Using the model of a FitzHugh-Nagumo system in the excitable regime, we investigate the influence of time-delayed feedback on noise-induced chimera states in a network with nonlocal coupling, i.e., coherence resonance chimeras. It is shown that time-delayed feedback allows for the control of the range of parameter values where these chimera states occur. Moreover, for the feedback delay close t...

Chimera states and the interplay between initial conditions and non-local coupling

Kalle, Peter ; Sawicki, Jakub ; Zakharova, Anna ; Schöll, Eckehard (2017-03-15)

Chimera states are complex spatio-temporal patterns that consist of coexisting domains of coherent and incoherent dynamics. We study chimera states in a network of non-locally coupled Stuart-Landau oscillators. We investigate the impact of initial conditions in combination with non-local coupling. Based on an analytical argument, we show how the coupling phase and the coupling strength are link...

Nonlinearity of local dynamics promotes multi-chimeras

Omelchenko, Iryna ; Zakharova, Anna ; Hövel, Philipp ; Siebert, Julien ; Schöll, Eckehard (2015-08-06)

Chimera states are complex spatio-temporal patterns in which domains of synchronous and asynchronous dynamics coexist in coupled systems of oscillators. We examine how the character of the individual elements influences chimera states by studying networks of nonlocally coupled Van der Pol oscillators. Varying the bifurcation parameter of the Van der Pol system, we can interpolate between regula...

Controlling chimera states via minimal coupling modification

Ruzzene, Giulia ; Omelchenko, Iryna ; Schöll, Eckehard ; Zakharova, Anna ; Andrzejak, Ralph G. (2019-05-07)

We propose a method to control chimera states in a ring-shaped network of nonlocally coupled phase oscillators. This method acts exclusively on the network’s connectivity. Using the idea of a pacemaker oscillator, we investigate which is the minimal action needed to control chimeras. We implement the pacemaker choosing one oscillator and making its links unidirectional. Our results show that a ...

Chimera states in networks of Van der Pol oscillators with hierarchical connectivities

Ulonska, Stefan ; Omelchenko, Iryna ; Zakharova, Anna ; Schöll, Eckehard (2016-09-22)

Chimera states are complex spatio-temporal patterns that consist of coexisting domains of coherent and incoherent dynamics. We analyse chimera states in ring networks of Van der Pol oscillators with hierarchical coupling topology. We investigate the stepwise transition from a nonlocal to a hierarchical topology and propose the network clustering coefficient as a measure to establish a link betw...

Complex partial synchronization patterns in networks of delay-coupled neurons

Nikitin, D. ; Omelchenko, Iryna ; Zakharova, Anna ; Avetyan, M. ; Fradkov, Alexander L. ; Schöll, Eckehard (2019-07-22)

We study the spatio-temporal dynamics of a multiplex network of delay-coupled FitzHugh–Nagumo oscillators with non-local and fractal connectivities. Apart from chimera states, a new regime of coexistence of slow and fast oscillations is found. An analytical explanation for the emergence of such coexisting partial synchronization patterns is given. Furthermore, we propose a control scheme for th...