The structure and its role in uncovering the physics of warm dense matter

Warm dense matter states in the transition region from high pressure solids to high temperature plasmas are found in terrestrial planets, giant planets, and exoplanets. Such states are created in the laboratory during interaction of lasers or shock waves with matter. The intention is usually to obtain direct experimental access to equilibrium or nonequilibrium warm dense matter states or it might be an intermediate state on the way to fusion plasmas states or laser-plasma acceleration experiments.
Studying warm dense matter, one faces several challenges. The first is the determination of a full set of basic parameter like density, charge state, temperature, or the momentum distribution function that fixes the state of matter in the phase space. Only then is it meaningful to investigate important quantities like the equation of state, phase transitions, structure, collective excitations, relaxation processes, or the stopping power.
Here, we present recent developments and results in warm dense matter physics. The close interplay between theory and experiment via x-ray scattering and first principle simulations is highlighted. The dynamic structure factor containing a wealth of information serves as the connection between measurements and calculations. Results are given for a number of elements like aluminium, carbon, or iron, and materials like plastic.