Entanglement and thermalisation at the butterfly velocity

After a quench the entanglement entropy will saturate to its thermal value within a char- acteristic saturation time which is bounded by $R/v_B$ with $R$ the radius of the largest inscribed sphere and vB the butterfly velocity. In this talk I will introduce the ‘membrane paradigm’, which gives a hydrodynamic description of entanglement growth coming both from tensor networks as well as holography. Interestingly, both spheres and cylinders in neutral holographic plasmas saturate the butterfly bound, whereas stripes or spheres in charged plasmas do not saturate it. In this talk I will present results for a wide variety of shapes, showing that also a generic class ‘between’ spheres and cylinders saturates the bound.