“…These Laplacians, as well as their generalizations, have been studied extensively in connection with fractal geometry, such as existence of an orthonormal basis of eigenfunctions, spectral dimension and spectral asymptotics, eigenvalues and eigenfunctions, eigenvalue estimates, differential equations, nodal inverse problems, wave equations and wave speed, heat equation and heat kernel estimates, etc. (see [4,7,12,16,[20][21][22][23][24][25]32,35,36,50,51,[53][54][55][56][57]62,63,69] and references therein). We remark that Freiberg and her coauthors defined a class of Laplacians that are more general in that Lebesgue measure is replaced by a more general measure (see, e.g., [21,23]).…”