If, instead, the symmetry is not exact, i . e . if it is " explicitly broken as well as spontaneously broken ", then the Nambu Goldstone bosons are not massless, though they typically remain relatively light; they are then called "'pseudo-Goldstone bosons "'or "'pseudo-Nambu Goldstone bosons "'( abbreviated "'PNGBs "').
42.
If, instead, the symmetry is not exact, i . e . if it is " explicitly broken as well as spontaneously broken ", then the Nambu Goldstone bosons are not massless, though they typically remain relatively light; they are then called "'pseudo-Goldstone bosons "'or "'pseudo-Nambu Goldstone bosons "'( abbreviated "'PNGBs "').
43.
If, instead, the symmetry is not exact, i . e . if it is " explicitly broken as well as spontaneously broken ", then the Nambu Goldstone bosons are not massless, though they typically remain relatively light; they are then called "'pseudo-Goldstone bosons "'or "'pseudo-Nambu Goldstone bosons "'( abbreviated "'PNGBs "').
