The Spectrum of a Nonlocal Difference Operator with Variable Coefficients

The spectrum of a non-symmetric matrix A is studied, which resulting from difference approximation of the differential operators of the second order with nonlocal boundary conditions and variable coefficients. Such matrices can be both simple and double real eigenvalue and a complex conjugate pairs of eigenvalues. The original matrix A is mapped to the so-called associated matrix L – symmetric tridiagonal matrix, little differing from A . It is known that all eigenvalues of the matrix L are real and different. They can be found by the bisection method using a sequence of the Sturm’s polynomials. In the paper on the basis of numerous examples are compared the properties of the spectra of matrices L and A . The method offers of approximate calculating of eigenvalues of the matrix A .