Spectral dimensions of Krein-Feller operators and Lq-spectra

We study the spectral dimensions and spectral asymptotics of Krein-Feller operators for arbitrary finite Borel measures on (0, 1). Connections between the spectral dimension, the L-q-spectrum, the partition entropy and the optimized coarse multifractal dimension are established. In particular, we show that the upper spectral dimension always corresponds to the fixed point of the L-q-spectrum of the corresponding measure. Natural bounds reveal intrinsic connections to the Minkowski dimension of the support of the associated Borel measure. Further, we give a sufficient condition on the L-q-spectrum to guarantee the existence of the spectral dimension. As an application, we confirm the existence of the spectral dimension of self-conformal measures with or without overlap as well as of certain measures of pure point type. We construct a simple example for which the spectral dimension does not exist and determine explicitly its upper and lower spectral dimension. (c) 2022 Elsevier Inc. All rights reserved.