Quintessence (Q) is a scalar field with an equation of state where wq, the ratio of pressure pq and density {\displaystyle \rho }q, is given by the potential energy {\displaystyle V(Q)} and a kinetic term:

https://en.m.wikipedia.org/wiki/Quintessence_(physics)

https://en.m.wikipedia.org/wiki/Quintom_scenario

https://en.m.wikipedia.org/wiki/Phantom_energy

https://en.m.wikipedia.org/wiki/Photon

https://en.m.wikipedia.org/wiki/Quasiparticle

https://en.m.wikipedia.org/wiki/Polariton