Integrated Calendar

The dominant interaction that pops into our mind when considering like charges constraint to move in a plane is no doubt the repulsive Coulomb interaction. It produces the celebrated fractional quantum Hall effect that continues to fascinate and whose appearance frequently acts as a Litmus test for the quality of emerging materials. However, every so often the ubiqui-tous Coulomb repulsion has to give way to physics that apparently involves local attractive interactions among our like charges instead. Electron pairing, mediated by electron phonon interactions and leading to superconductivity, would be an obvious example outside of the context of flatland. However, the mechanism mediating or delivering a local attractive interaction is commonly not that obvious. In this presentation instances of such local attraction physics in flatland without phonon involvement will be covered. We will address various techniques beyond simple magneto-transport that help us to unveil these local attractive interactions and its consequences. This physics is very fragile and its study has been the exclusive privilege of the very mature GaAs community so far. We will highlight that this is no longer true.

Regime shifts in ecosystems are typically understood to be abrupt global transitions from one stable state to an alternative stable state, induced by slow environmental changes or global disturbances. This is especially relevant to drylands, where desertification is a major concern. However, spatially extended ecosystems, and dryland vegetation systems in particular, often exhibit patterned states, which allow for more complex dynamics to take place. Periodic patterns can have many different wavelengths, implying different length-scales of patchy vegetation. Further, a bistability of a patterned state and a uniform state can lead to a multitude of stable hybrid states, with small domains of one state embedded in the other state. The response of the system to local disturbances or change in global parameters in these systems can lead to gradual regime shifts, involving the expansion of alternative-state domains by front propagation, rather than a global collapse. Moreover, a regime of periodic perturbations can give rise to step-like gradual shifts with extended pauses at these states. The implications of different forms of patterned states on the dynamics of the system will be discussed, with three points in mind: The question of desertification as a front propagation process, the effect of local disturbances on the system, and a specific case study on the dynamics of fairy circles in Namibia as a concrete example.