...)

Interestingly, the same 3:2 ratio seems to be present in the case of neutron stars sources, indicating the same origin of the observed quasiperiodic oscillations (Abramowicz et al. 2003; see however, Belloni et al. 2004).

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...$a\in (-1,~1)$

Here and henceforth values of a > 0 correspond to corotating orbits, while a < 0 give counterrotating orbits.

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... derivatives

After introducing $^\prime$ as ${\rm d}/{\rm d}r$.

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... maxima

We distinguish which is the global one in Sect. 4.

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... with

Here and henceforth in relation to the wave propagation in the field of black holes $\omega_{{\rm max}}$ denotes the maximum of $\omega _{\rm r}$ at $\mathcal{R}_{\rm r}(a)$ (Fig. 2) in the black-hole range of the rotational parameter.

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... with

In the relation to the wave propagation in discs around Kerr naked singularities, $\omega_{~{\rm MAX}}$ denotes the global maximum of $\omega _{\rm r}$, while $\omega_{{\rm max}}$ denotes a local (lower) one, see Fig. 8.

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... 

Intuitively clear attribution is well founded in the last Sect. 4.4.

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... when

We note that the same condition holds for internal resonance, which describes systems with conserved energy (Horák et al. 2004).

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... disc

Such a claim is motivated by experience from known situations related to the parametric or forced resonance in complex non-linear systems observed in Earth physics (Landau & Lifshitz 1976). Examples of mathematically possible resonances causing damaging bridges, wings, etc. with no specific physical coupling mechanism known are discussed in Nayfeh & Mook (1979).

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