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Fundamental properties of warm dense matter are described by the dielectric function, which gives access to the frequency-dependent electrical conductivity, absorption, emission and scattering of radiation, charged particles stopping and further macroscopic properties. Different approaches to the dielectric function and the related dynamical collision frequency are compared in a wide frequency range. The high-frequency limit describing inverse bremsstrahlung and the low-frequency limit of the dc conductivity are considered. Sum rules and Kramers-Kronig relation are checked for the generalized linear response theory and the standard approach following kinetic theory. The results are discussed in application to aluminum, xenon and argon plasmas.

The theory and simulations of short intense laser pulses propagating in capillary tubes, whose properties are changed in time and space under the action of the laser field, are presented. A hybrid approach has been used in which the dynamics of fields inside the capillary tube is described analytically, whereas the ionization, heating, and expansion of the plasma created at the inner wall of the tube under the action of the transverse energy flux are calculated by numerical simulation. This hybrid method has allowed to determine the behavior of high laser fluxes guided over large distances. The threshold value for the incident intensity at which plasma creation plays a significant role has been estimated analytically and confirmed by numerical results. For intensities above the threshold, the transmission becomes highly sensitive to the energy of the laser pulse, being minimum at the intensity level for which the electron temperature of the capillary wall slightly exceeds the Fermi level and the electron collision frequency has a maximum.