Barba, J. CFinkel Morgenstern, FedericoGonzález López, ArtemioRodríguez González, Miguel Ángel2023-06-202023-06-2020091539-375510.1103/PhysRevE.80.047201https://hdl.handle.net/20.500.14352/44691©2009 The American Physical Society. This work was supported in part by the MICINN Grant No. FIS2008-00209 and the UCM–Banco Santander Grant No. GR58/08-910556. J.C.B. acknowledges the financial support of the MICINN.In this paper, we show that there is a family of well-known integrable systems whose spectral fluctuations decay as 1/ f^ 4, and thus do not follow the 1/ f ^2 law recently conjectured for integrable systems. We present a simple theoretical justification of this fact, and propose an alternative characterization of quantum chaos versus integrability formulated directly in terms of the power spectrum of the spacings of the unfolded spectrum.engjournal articlehttp://dx.doi.org/10.1103/PhysRevE.80.047201http://journals.aps.org/open access51-73f noiseChaosFluctuationsQuantum theoryHaldane-Shastry TypeSpin chainBCN TypeStatisticsSpectrumFísica-Modelos matemáticosFísica matemática