Hydrodynamics describes a great variety of phenomena around and inside us, including, e.g., the flow of water in rivers, seas, and oceans, the atmospheric phenomena, the motion of aircrafts, the flow of petroleum in pipelines, or the blood flow through human vessels. It has been realized a long ago that a current of electrons in a conductor should, under certain circumstances, also obey laws of hydrodynamics and that electrons can show a Poiseuille-type flow analogous to that of liquids in pipes.  Recently several experiments made significant progress to demonstrate the corresponding power-law increase of conductivity with the transverse cross-section of a sample.

 In this talk we will discuss the hydrodynamic behavior that is unique to Dirac systems. First, we will discuss graphene as example and focus on the distinction between information scrambling and thermalization on the one hand and hydrodynamics on the other hand. In addition, we will discuss anisotropic Dirac systems. Here we find a strong violation of the bound, conjectured for the ratio of the viscosity and entropy ratio. We demonstrate that such systems give rise to anisotropic thermal Poiseuille flow and offer a generalization of the above bund for anisotropic systems.

Please note: The Colloquium Ehrenfestii takes place on Wednesday evenings starting at 19:30 hours in the main auditorium of the Oort building. Before the Colloquium, there is a common dinner in the canteen located on the ground floor of the  Oort building. The dinner starts at 18:00 hours sharp and is free of charge, under the condition that one attends the colloquium and that one has made a reservation before noon on the Tuesday preceding the colloquium. The registration form is only accessible from within the University (to block spammers); if you would like to register for the dinner from outside the University, please send an email to fran@lorentz.leidenuniv.nl

The revolving doors to the Oort building  are accessible until 9 pm after that they are locked and one should instead use the sliding doors directly adjacent to the Huygens building: these can be opened with an electronic key (seek help from locals).