Physik - Open Access LMU - Teil 01/02

Localized wave fronts are a fundamental feature of biological systems from cell biology to ecology. Here, we study a broad class of bistable models subject to self-activation, degradation, and spatially inhomogeneous activating agents. We determine the conditions under which wave-front localization is possible and analyze the stability thereof with respect to extrinsic perturbations and internal noise. It is found that stability is enhanced upon regulating a positional signal and, surprisingly, also for a low degree of binding cooperativity. We further show a contrasting impact of self-activation to the stability of these two sources of destabilization. DOI: 10.1103/PhysRevLett.110.038102

Actively propelled particles undergoing dissipative collisions are known to develop a state of spatially distributed coherently moving clusters. For densities larger than a characteristic value, clusters grow in time and form a stationary well-ordered state of coherent macroscopic motion. In this work we address two questions. (i) What is the role of the particles’ aspect ratio in the context of cluster formation, and does the particle shape affect the system’s behavior on hydrodynamic scales? (ii) To what extent does particle conservation influence pattern formation? To answer these questions we suggest a simple kinetic model permitting us to depict some of the interaction properties between freely moving particles and particles integrated in clusters. To this end, we introduce two particle species: single and cluster particles. Specifically, we account for coalescence of clusters from single particles, assembly of single particles on existing clusters, collisions between clusters and cluster disassembly. Coarse graining our kinetic model, (i) we demonstrate that particle shape (i.e. aspect ratio) shifts the scale of the transition density, but does not impact the instabilities at the ordering threshold and (ii) we show that the validity of particle conservation determines the existence of a longitudinal instability, which tends to amplify density heterogeneities locally, and in turn triggers a wave pattern with wave vectors parallel to the axis of macroscopic order. If the system is in contact with a particle reservoir, this instability vanishes due to a compensation of density heterogeneities.

Eine naturphilosophische Leitwährung für die Beschreibung der Wirlichkeit ist bereits bei Aristoteles die Form. Sie informiert die Materie und vermittelt dadurch das Sein. Der Informationsbegriff jedoch ist multivalent: man kann zwischen potentieller Information (QuBits), basaler einfacher Information (Bits) und komplexer Information (Systemordner-Information) unterscheiden. Die komplexe Information wird im Bit kodiert, indem es das QuBit disponiert. Die Kodierung erfolgt holografisch und somit analog. Letztlich inkarnieren sich Systeme in der physikalischen Wirklichkeit, indem sie sie komplex informieren (ordnen, ermöglichen, steuern, formieren). Das Universum würde dann der Materialisierung und Dekodierung von autopoetischen Systemen dienen.