['Defining', '(', '1)δn=∫−∞En+1ρ˜(E)dE−n', ',', 'with', 'ρ˜(E', ')', 'the', 'mean', 'level', 'density', 'which', 'allows', 'the', 'mapping', 'to', 'dimensionless', 'levels', 'with', 'unitary', 'average', 'level', 'density', ',', 'and', 'analyzing', 'the', 'energy', 'fluctuations', 'as', 'a', 'discrete', 'time', 'series', ',', 'they', 'found', 'that', 'nuclear', 'power', 'spectra', 'behave', 'like', '1f', 'noise', ',', 'postulating', 'that', 'this', 'might', 'be', 'a', 'characteristic', 'signature', 'of', 'generic', 'quantum', 'chaotic', 'systems', '.']