Title: Dynamical states of chemotactic particles

Speaker: Federico Fadda (UvA)

Abstract:

Self-propelled active particles, mimicking micro-organisms like bacteria, can move and reorient due to a chemical gradient. This is called chemotaxis. In this work, we explore the dynamics of self-propelled chemotactic particles at various particle densities and self-propulsions by means of Langevin dynamics simulations. The balance of particle density, steric interactions, self-propulsion, and chemical interactions gives rise to different dynamical states. For low self-propulsion speeds, we find particles collapsing onto one single giant cluster. For higher self-propulsion speeds and in the dilute regime, particles form small dynamical clusters. At higher densities and self-propulsion speeds, particles form a cluster surrounded by isolated moving particles quite reminiscent of the clusters forming in the Motility-Induced Phase Separation of active Brownian particles without chemotactic interactions.

Title: How disordered are glasses?

Speaker: Karina Gonzalez Lopez (UvA)

Glasses are essentially arrested liquids, and as such they lack the long-range order that crystalline solids feature. Despite lacking long range order, glasses are true solids, in the sense that they resist (small) shear deformations. While all glasses are disordered, their featured degree of disorder can vary substantially between different glasses, depending both on their formation history and on details of their microscopic interactions. In this talk I will review the results from three computer experiments in which the strength of attractive interactions –stickiness– can be tuned via the pairwise interaction potential of particles constituting the glasses, show how glassy disorder can be quantified in a physically-meaningful way and address the question: “what is the effect that attractive pairwise interactions have on mechanical disorder of glasses?”.

The event will take place in C4.174