Colloquium: Hydrodynamics and holography of charge density wave phases

Hydrodynamics is an old example of an effective description of complex matter, which describes the system's behavior at large length and timescales and lumps microscopic details into transport coefficients. A combination of hydrodynamics and the gauge-gravity duality, which was first explored in the context of string theory, has proven promising for a description of strongly correlated electron fluids. This Colloquium explains how to apply these techniques to strongly correlated materials where the electron fluid crystallizes, and in particular to the strange metal phase of high-temperature superconductors.