Three out of its four components would ordinarily amount to Goldstone bosons, if they were not coupled to gauge fields.
12.
They have found that the resulting Goldstone boson leads to, among other things, a new kind of Cherenkov radiation.
13.
The pion field is a Goldstone boson, and the shift symmetry is the lowest order approximation to moving along the flat directions.
14.
With Abdus Salam and Steven Weinberg, he proved that in such theories zero-mass particles ( Nambu Goldstone bosons ) must exist.
15.
Also, the axial symmetry is broken spontaneously in this model, leading to a massless Goldstone boson unlike QCD, where it is broken anomalously.
16.
In the standard understanding of the strong force interaction as defined by quantum chromodynamics, pions are loosely portrayed as Goldstone bosons of spontaneously broken chiral symmetry.
17.
If there is a compensatory term canceling the QCD anomaly breaking term, the axion becomes an exactly massless Goldstone boson and ? is no longer fixed.
18.
This is because if such a spontaneous symmetry breaking occurred, then the corresponding Goldstone bosons, being massless, would have an infrared divergent correlation function.
19.
But there is no mass gap for all the superselection sectors labeled by zero because there are massless Goldstone bosons describing fluctuations in the direction of the condensate.
20.
The former has difficulties with flavor-changing neutral currents and light pseudo-Goldstone bosons, while the latter predicts superpartner particles that have not been currently observed.
