“…6 According to theoretical predictions, in the smectic C * a phase, two modesthe so mode and the Goldstone one, like in the ferroelectric phase, can be observed. However, in many experimental investigations, a single collective mode is observed, [7][8][9][10][11][12] similar to the smectic A* phase. In some studies, opinion is expressed that it has an amplitude character (so mode), 7,11 while in the other ones it is considered as a phasetype Goldstone mode associated with the perturbation of the helical structure.…”