Optical probing of relativistic plasma singularities

Singularities in multi-stream flows of relativistic plasmas can efficiently produce coherent high-frequency radiation, as exemplified in the concepts of the Relativistic Flying Mirror [Bulanov et al., Phys. Rev. Lett. 91, 085001 (2003)] and Burst Intensification by Singularity Emitting Radiation [Pirozhkov et al., Sci. Rep. 7, 17968 (2017)]. Direct observation of these singularities is challenging due to their extreme sharpness (tens of nanometers), relativistic velocity, and transient non-local nature. We propose to use an ultrafast (a few light cycles) optical probe for identifying relativistic plasma singularities. Our estimations and Particle-in-Cell simulations show that this diagnostic is feasible