Warm dense matter
Warm dense matter, abbreviated WDM, can refer to either equilibrium or non-equilibrium states of matter in a (loosely defined) regime of temperature and density between solid and plasma. It can be defined as the state that is too dense to be described by weakly coupled plasma physics yet too hot to be described by condensed matter physics. In this state, the potential energy of the interaction between electrons and nuclei and the kinetic energy of electrons are of roughly the same magnitude. WDM has a density of the same order of magnitude as a solid (typically somewhere between 0.01 and 100 grams per cc) and a temperature on the order of a few tens of thousands of kelvins (typically somewhere between 1 and 100 electronvolts/Boltzmann constant, in the units favored by practitioners).
WDM is expected in the cores of some large planets, in the Inertial confinement fusion context during the solid to plasma phase transition driven by laser pulses, and other systems that start as solids and are heated to become plasmas. The latter two categories imply that WDM physics are also relevant to nuclear explosions. Warm Dense Matter is also created during intense laser-target interactions and particle beam-target interactions.