{\sl ab-initio} simulations of the time-resolved optical properties of warm dense gold.

Recent experiments on gold suggest that the electrical and optical properties of metals in the warm dense matter regime can be accessed by performing time-resolved measurements after the illumination of a metallic thin film by a short-pulse laser[1]. The non-equilibrium situation created in this experimental setup poses new challenges to simulation methods as the time evolution of the atomic structure needs to be followed. We used a combination of classical and {\sl ab-initio} molecular dynamics simulations, to calculate the evolution of the atomic structure and the electrical conductivity of warm dense gold during the first pico-seconds after a short-pulse laser illumination. The time-resolved electrical conductivities calculated under these non-equilibrium conditions are compared with recent measurements. [1] K. Widmann, T. Ao, M.E. Foord, D.F. Price, A.D. Ellis, P.T. Springer,and A. Ng, Phys. Rev. Lett. {\bf 92}, 125002 (2004).