A version of Goldstone's theorem also applies to nonrelativistic theories. It essentially states that, for each spontaneously broken symmetry, there corresponds some quasiparticle which is typically a boson and has no energy gap. In condensed matter these goldstone bosons are also called gapless modes (i.e. states where the energy dispersion relation is like E ∝ ∝ p n and is zero for p = 0 ), the nonrelativistic version of the massless particles (i.e. photons where the dispersion relation is also E = p c and zero for p = 0 ). Note that the energy in the non relativistic condensed matter case is H − μN − α → ⋅ P → and not H as it would be in a relativistic case. However, two different spontaneously broken generators may now give rise to the same Nambu–Goldstone boson.