The Bloch spectrum is a concept in quantum mechanics in the field of theoretical physics; this concept addresses certain energy spectrum considerations. Let H be the one-dimensional Schrödinger equation operator
where U<sub>ñ</sub> is a periodic function of period ñ. The Bloch spectrum of H is defined as the set of values E for which all the solutions of (H â E)à= 0 are bounded on the whole real axis. The Bloch spectrum consists of the half-line E<sub>0</sub> < E from which certain closed intervals [E<sub>2jâÂÂ1</sub>, E<sub>2j</sub>] (j = 1, 2, ...) are omitted. These are forbidden bands (or gaps) so the (E<sub>2jâÂÂ2</sub>, E<sub>2jâÂÂ1</sub>) are allowed bands.