# Bloch spectrum

The Bloch spectrum is a concept in quantum mechanics in the field of theoretical physics; this concept addresses certain energy spectra considerations. Let H be the one-dimensional Schrödinger equation operator

${\displaystyle H=-{\frac {d^{2}}{dx^{2}}}+U_{\alpha },}$

where Uα is a periodic function of period α. The Bloch spectrum[1] of H is defined as the set of values E for which all the solutions of (H − E)φ = 0 are bounded on the whole real axis. The Bloch spectrum consists of the half-line E0 < E from which certain closed intervals [E2j−1E2j] (j = 1, 2, ...) are omitted. These are forbidden bands (or gaps) so the (E2j−2E2j−1) are allowed bands.

## References

1. ^ "An upper bound on the allowed bands of the Bloch spectrum of one-dimensional Schrödinger operators with periodic potentials", N. N. Meiman, Journal of Mathematical Physics, March, 1983, volume 24, issue 3, pp. 539–540