Hey,
How free are we in chosing our axis when drawing a dispersion relation? For example, in exam 2019 they ask you to draw w(k), but can I also have my y axis as a*w^2, where a is a constant? I do explain what the a is.
You may do so (and we will not subtract points for it), but it is not the best style. This option is particularly relevant for phonons, but plotting \omega(k) shows the linear dispersion of acoustic phonons, which is otherwise harder to see.