Relaño Pérez, ArmandoGómez Gómez, José MaríaRetamosa Granado, JoaquínFaleiro, E.Salasnich, L.Vranicar, M.Robnik, M.2023-06-202023-06-2020050031-900710.1103/PhysRevLett.94.084101https://hdl.handle.net/20.500.14352/51285©2005 The American Physical Society. This work is supported in part by Spanish Government Grant Nos. BFM2003-04147-C02 and FTN2003-08337-C04-04. This work is also supported by the Ministry of Education, Science and Sports of the Republic of Slovenia.The power law 1/ƒ^(α) in the power spectrum characterizes the fluctuating observables of many complex natural systems. Considering the energy levels of a quantum system as a discrete time series where the energy plays the role of time, the level fluctuations can be characterized by the power spectrum. Using a family of quantum billiards, we analyze the order-to-chaos transition in terms of this power spectrum. A power law 1/ƒ^(α) is found at all the transition stages, and it is shown that the exponent alpha is related to the chaotic component of the classical phase space of the quantum system.engjournal articlehttp://dx.doi.org/10.1103/PhysRevLett.94.084101http://journals.aps.org/open access536Energy-Level StatisticsAnalytic BoundariesClassical DynamicsTransition RegionPhase-SpaceBilliardsIntegrabilityFamilyChaosTermodinámica2213 Termodinámica