If a theory is spontaneously broken, you usually make calculations by expanding the field about the ground-state expectation value [itex]\nu [/itex], so that you define a new field [itex]\rho [/itex] such that [itex]\phi=\nu+\rho [/itex] such that [itex]\langle \rho \rangle =0 [/itex].
What if you just calculate perturbation theory with [itex]\phi [/itex] instead of the new field [itex]\rho[/itex]?
It seems that massless [itex]\phi^4[/itex] is spontaneously broken at the 1-loop level. So do you have to do perturbation theory with the field [itex]\rho[/itex] instead of [itex]\phi [/itex]?
What if you just calculate perturbation theory with [itex]\phi [/itex] instead of the new field [itex]\rho[/itex]?
It seems that massless [itex]\phi^4[/itex] is spontaneously broken at the 1-loop level. So do you have to do perturbation theory with the field [itex]\rho[/itex] instead of [itex]\phi [/itex]?
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