R\'enyi and Tsallis entropies related to eigenfunctions of quantum graphs

Abstract

For certain families of finite quantum graphs, we study the question of how eigenfunctions are distributed over the graph. To characterize properties of the distribution, generalized entropies of the R\'{e}nyi and Tsallis types are considered. The presented approach is similar to entropic uncertainty relations of the Maassen-Uffink type. Using the Riesz theorem, we derive lower bounds on symmetrized generalized entropies of eigenfunctions. A quality of such estimates will depend on boundary conditions used at vertices of the given graph. R\'{e}nyi and Tsallis entropies of eigenfunctions of star graphs are separately examined. Relations between generalized entropies and variances of eigenfunctions are considered as well. When such relations remain valid on average, they may be used in studies of quantum ergodicity.