Mathematical Methods in the Applied Sciences, 2025 (SCI-Expanded)
In this study, we obtain the asymptotic formula for the sum of fourth power of the negative eigenvalues of the operator (Formula presented.), which we created with the differential expression (Formula presented.) and boundary condition (Formula presented.) in the space (Formula presented.). It is known that the operator (Formula presented.) is self-adjoint, semibounded below, and the negative part of its spectrum is discrete. is self-adjoint, semibounded below, and the negative part of its spectrum is discrete. Additionally, there are some asymptotic formulas for the number of negative eigenvalues of the operator. Our result applies to a class of mathematical physics equations.