-law Also Observed in D=2 Dimensions ?

Some arguments are given, related to the apparent universality with which Bloch's famous T 3/2-law is not only found in d=3-dimensional ferromagnetic systems, but also in lower dimensions. It is argued that • one should not simply apply the usual isotropic dispersion relation ω(k) = D · k 2 known to almost everyone but only valid for circular precession of the spins (i.e. where only the exchange interaction is taken into account), but instead one should consider also the other interactions and use the less-known relation ω(k) = ω a (k) · ω b (k) for elliptical precession, • one might consider the apparent universality of Bloch's T 3/2-law as some kind of 'quantum universality' in a certain finite-temperature crossover region of a quantum phase transition at T=0, • i.e. one should use certain simple crossover-scaling arguments for better understanding of the phenomena, instead of the usual, more complicated derivations by direct integration.