Inst. Theoretische Physik

228 Items

Recent Submissions
Non-equilibrium dynamics of confined colloidal suspensions in shear-flow

Gerloff, Sascha (2020)

Shear-driven colloidal suspensions in strong spatial confinement display complex non-equilibrium many-body dynamics. These stem from the intricate interplay between the confinement-induced structures and shear-induced dynamics, yielding phenomena such as shear-thinning, thickening, and banding, as well as shear-induced melting, crystallization, buckling, and laning. The resulting non-linear res...

Covariant Relativistic Non-Equilibrium Thermodynamics of Multi-Component Systems

Muschik, Wolfgang (2019-10-24)

Non-equilibrium and equilibrium thermodynamics of an interacting component in a relativistic multi-component system is discussed covariantly by exploiting an entropy identity. The special case of the corresponding free component is considered. Equilibrium conditions and especially the multi-component Killing relation of the 4-temperature are discussed. Two axioms characterize the mixture: addit...

Theory of Coulomb induced signatures in two dimensional spectroscopy of colloidal quantum dots

Ginter, Anke (2019)

In this thesis, the interplay between the Brownian motion of colloidal quantum dots (QDs) and the position-dependent Coulomb coupling is investigated. The Coulomb interaction plays an important role since it changes the optical and electrical properties of nanostructures such as colloidal QDs, even in the case of non-overlapping electron wave functions. Due to the Coulomb coupling, the individ...

Driven open quantum systems

Restrepo, Sebastian (2019)

Time-periodic quantum systems are present all over science and technology. They have been successfully studied using Floquet theory, and a broad diversity of interesting phenomena such as coherent destruction of tunnelling, dynamical localization and creation of new phases of matter have been discovered. Furthermore, periodic driving has also been introduced as a tool for engineering novel qua...

Lamellipodial dynamics in mesenchymal cell motility

Dolati, Setareh (2019)

Biological processes that require cell migration include a variety of complex and critical processes such as embryonic development, the immune response, and cancer metastasis. Attempts to understand and control the underlying mechanisms of cell movement, especially in cancer research, have recently increased. Although most of the biochemical processes in cell movement are known, some biomechani...

Active poroelastic two-phase model for the motion of physarum microplasmodia

Kulawiak, Dirk Alexander ; Löber, Jakob ; Bär, Markus ; Engel, Harald (2019-08-09)

The onset of self-organized motion is studied in a poroelastic two-phase model with free boundaries for Physarum microplasmodia (MP). In the model, an active gel phase is assumed to be interpenetrated by a passive fluid phase on small length scales. A feedback loop between calcium kinetics, mechanical deformations, and induced fluid flow gives rise to pattern formation and the establishment of ...

Traveling concentration pulses of bacteria in a generalized Keller–Segel model

Seyrich, Maximilian ; Palugniok, Andrzej ; Stark, Holger (2019-10-01)

We formulate a Markovian response theory for the tumble rate of a bacterium moving in a chemical field and use it in the Smoluchowski equation. Based on a multipole expansion for the one-particle distribution function and a reaction-diffusion equation for the chemoattractant field, we derive a polarization extended model, which also includes the recently discovered angle bias. In the adiabatic ...

An Epidemiological and Economic Simulation Model to Evaluate Strategies for the Control of Bovine Virus Diarrhea in Germany

Gethmann, Jörn ; Probst, Carolina ; Bassett, Jason ; Blunk, Pascal ; Hövel, Philipp ; Conraths, Franz J. (2019-11-19)

Models can be used to plan, evaluate, and improve programs for animal disease control. In Germany, a nationwide compulsory program to eradicate Bovine viral diarrhea (BVD) is in force since January 2011. As it is associated with substantial expenditures, the program is currently under revision. To provide the basis for a science-based decision on the future course of BVD control in Germany, we ...

Interplay of different environments in open quantum systems: Breakdown of the additive approximation

Giusteri, Giulio G. ; Recrosi, Filippo ; Schaller, Gernot ; Celardo, G. Luca (2017)

We analyze an open quantum system under the influence of more than one environment: a dephasing bath and a probability-absorbing bath that represents a decay channel, as encountered in many models of quantum networks. In our case, dephasing is modeled by random fluctuations of the site energies, while the absorbing bath is modeled with an external lead attached to the system. We analyze under w...

Synchronization Patterns in Modular Neuronal Networks: A Case Study of C. elegans

Pournaki, Armin ; Merfort, Leon ; Ruiz, Jorge ; Kouvaris, Nikos E. ; Hövel, Philipp ; Hizanidis, Johanne (2019-10-24)

We investigate synchronization patterns and chimera-like states in the modular multilayer topology of the connectome of Caenorhabditis elegans. In the special case of a designed network with two layers, one with electrical intra-community links and one with chemical inter-community links, chimera-like states are known to exist. Aiming at a more biological approach based on the actual connectivi...

Risk of Coinfection Outbreaks in Temporal Networks: A Case Study of a Hospital Contact Network

Rodríguez, Jorge P. ; Ghanbarnejad, Fakhteh ; Eguíluz, Víctor M. (2017-10-06)

We study the spreading of cooperative infections in an empirical temporal network of contacts between people, including health care workers and patients, in a hospital. The system exhibits a phase transition leading to one or several endemic branches, depending on the connectivity pattern and the temporal correlations. There are two endemic branches in the original setting and the non-cooperati...

Modelling epidemics on networks with static and time-varying topologies

Koher, Andreas (2019)

We aim to develop epidemiological models that describe and predict the evolution of infectious diseases. To this end, we integrate mobility data, represented by networks with static and time-varying topologies. As a central result of this work, we present three disease models that facilitate an efficient analysis of complex epidemiological problems. First, in the context of global epidemics, w...

Filtering Suppresses Amplitude Chimeras

Banerjee, Tanmoy ; Bandyopadhyay, Biswabibek ; Zakharova, Anna ; Schöll, Eckehard (2019-02-11)

Amplitude chimera (AC) is an interesting chimera pattern that has been discovered recently and is distinct from other chimera patterns, like phase chimeras and amplitude mediated phase chimeras. Unlike other chimeras, in the AC pattern all the oscillators have the same phase velocity, however, the oscillators in the incoherent domain show periodic oscillations with randomly shifted origin. In t...

Characterizing Complex Networks Using Entropy-Degree Diagrams: Unveiling Changes in Functional Brain Connectivity Induced by Ayahuasca

Viol, Aline ; Palhano-Fontes, Fernanda ; Onias, Heloisa ; de Araujo, Draulio B. ; Hövel, Philipp ; Viswanathan, Gandhi M. (2019-01-30)

With the aim of further advancing the understanding of the human brain’s functional connectivity, we propose a network metric which we term the geodesic entropy. This metric quantifies the Shannon entropy of the distance distribution to a specific node from all other nodes. It allows to characterize the influence exerted on a specific node considering statistics of the overall network structure...

Macroscopic Internal Variables and Mesoscopic Theory: A Comparison Considering Liquid Crystals

Papenfuss, Christina ; Muschik, Wolfgang (2018-01-22)

Internal and mesoscopic variables differ fundamentally from each other: both are state space variables, but mesoscopic variables are additionally equipped with a distribution function introducing a statistical item into consideration which is missing in connection with internal variables. Thus, the alignment tensor of the liquid crystal theory can be introduced as an internal variable or as one...

Collective dynamics in a monolayer of squirmers confined to a boundary by gravity

Kuhr, Jan-Timm ; Rühle, Felix ; Stark, Holger (2019-06-21)

We present a hydrodynamic study of a monolayer of squirmer model microswimmers confined to a boundary by strong gravity using the simulation method of multi-particle collision dynamics. The squirmers interact with each other via their self-generated hydrodynamic flow fields and thereby form a variety of fascinating dynamic states when density and squirmer type are varied. Weak pushers, neutral ...

Second Law and Non-Equilibrium Entropy of Schottky Systems—Doubts and Verification−

Muschik, Wolfgang (2018-09-28)

Meixner’s historical remark in 1969 “... it can be shown that the concept of entropy in the absence of equilibrium is in fact not only questionable but that it cannot even be defined....” is investigated from today’s insight. Several statements—such as the three laws of phenomenological thermodynamics, the embedding theorem and the adiabatical uniqueness—are used to get rid of non-equilibrium e...

Mode locking in systems of globally-coupled phase oscillators

Eydam, Richard Sebastian (2019)

In systems of globally coupled phase oscillators with sufficiently structured natural frequencies, a new type of collective behavior is discovered that exists below the synchronization threshold. The solution type is distinguished by the appearance of sharp pulses in the mean field amplitude which imply a temporary high coherence among the phases. This is similar to a process known in lase...

Synchronization and learning in networks of chemical oscillators

Fengler, Enrico (2019)

In this thesis, the collective behavior of chemical oscillators in adaptive networks with time-dependent coupling weights is studied theoretically and experimentally. About 100-150 micro meter in size catalytic beads based on the Belousov-Zhabotinsky (BZ) oscillatory chemical reaction are fixed in an array of conical slots covered by a gel layer, and are placed into contact with BZ solution in ...

Shaping of membranes by arc-like particles

Bonazzi, Francesco (2019)

This dissertation analyzes the interaction of biomembranes with arc-like particles, which gives rise to complex morphologies of organelles inside cells. The shaping of membranes is investigated with coarse-grained modeling and Monte Carlo simulations. In the coarse-grained model, the membrane is described as a discretized elastic surface, and the particles as segmented arcs. Concave arc-like p...