Spectrum of a matrix
In mathematics, the spectrum of a matrix is the set of its eigenvalues. (More precisely, it is its multiset of eigenvalues, where each eigenvalue comes with an associated multiplicity, and two spectra are only considered to be equal if each eigenvalue has the same multiplicity in each spectrum.) More generally, if T : V → V {\displaystyle T\colon V\to V} is a linear operator on any finite-dimensional vector space, its spectrum is the set of scalars λ {\displaystyle \lambda } such that T − λ I {\displaystyle T-\lambda I} is not invertible.