Goldstone modes
Goldstone modes (also known as Goldstone bosons) arise from Goldstone's conjecture; that if there is continuous symmetry transformation under which the Lagrangian is invariant, then either the vacuum state is also invariant under the transformation, or there must exist spinless particles of zero mass.
See also
References
- Y. Nambu and G. Jona-Lasinio "Dynamical Model of Elementary Particles Based on an Analogy with Superconductivity. I", Physical Review 122 345-358 (1961)
- Jeffrey Goldstone, Abdus Salam and Steven Weinberg "Broken Symmetries", Physical Review 127 965-970 (1962)
- Sidney Coleman "There are no Goldstone bosons in two dimensions", Communications in Mathematical Physics 31 pp. 259-264 (1973)