Hydrogen at high density

The physics of dense hydrogen can be developed starting with separate proton and electron (or deuteron and electron) plasmas and formally introducing the coupling between them. If this coupling is treated beyond linear response in the interacting electron gas the dominant pairing features of low-density hydrogen are captured. Progression of effective proton–proton pair interactions, especially with respect to the domain of repulsive behaviour in relation to cell size, and the overall scale of zero-point energy, indicates the possible onset of a near ground-state fluid above a critical density. This fluid will be metallic and unusually different in its properties when compared to more conventional liquid metals. Further assessment of the quantum aspects of such a state suggests the need for a more general analytical approach to the hydrogen problem and one possible route is via scaling relations.