Matter whose energy density corresponds to pressures above about 1 million atmospheres behaves differently from the more familiar solid, liquid, gaseous, and plasma states. Instead, its properties and behavior overlap with systems known from astronomy and astrophysics—planetary interiors, stars, and the early universe.
To understand the interiors of planets, one must create and measure the behavior of matter at planetary pressures. To understand the structure of stars, one must create and measure the interactions between stellar matter and x-ray photons. To understand astrophysical explosions such as supernovae, one must create and measure the relevant dynamical processes. To understand strongly relativistic systems such as existed in the early universe, one must create and measure strongly relativistic interactions of matter and photons. In none of those areas is theory or simulation straightforward; validation of theoretical and numerical results requires benchmark measurements that offer the potential for novel discoveries. All the systems mentioned...
