Due to the cosine function's properties, the pattern is periodic on α α with period 1 (it repeats for each quantum flux per unit cell). The graph in the region of α α between 0 and 1 has reflection symmetry in the lines α α = 1 2 and ϵ ϵ = 0 . Note that ϵ ϵ is necessarily bounded between -4 and 4.