Eigenvalues Sought.

We give three typical cases:

``IE''

stands for one or a few isolated eigenvalues at the end of the spectrum. This is the simplest case, a typical example being the computation of a few leading singular values of a data matrix.

``CE''

stands for one or several eigenvalues at the end of the spectrum, possibly clustered, a typical example being the computation of the lowest eigenmodes of a vibrating mechanical system, modeled by the finite element method.

``M,''

finally, means some eigenvalues in the middle of the spectrum, most often in a specified interval, like seeking all eigenmodes of a mechanical or electrical system excited by an external load of a prescribed frequency.