@article{Xiang2023, 
author = {Yanyu Xiang and Aiping Wang},
title = {On symmetry of the product of two higher-order quasi-differential operators},
year = {2023},
journal = {AIMS Mathematics},
volume = {8},
number = {4},
pages = {9483-9505},
keywords = {product of differential operators, symmetric boundary conditions, singular operators},
url = {https://www.sciopen.com/article/10.3934/math.2023478},
doi = {10.3934/math.2023478},
abstract = {The symmetric realizations of the product of two higher-order quasi-differential expressions in Hilbert space are investigated. By means of the construction theory of symmetric operators, we characterize symmetric domains determined by two-point boundary conditions for product of two symmetric differential expressions with regular or limit-circle singular endpoints. The presented result contains the characterization of self-adjoint domains as a special case. Several examples of singular symmetric product operators are given.}
}