In a complex Banach space, it is the set of numbers for a given transformation such that the difference of the transformation and a scalar multiple of the identity is not invertible.
If the set of sizes for possible models of a sentence, called this, is closed under complements, the NP class is also closed under complements. The Zariski topology can be defined on the set of all prime ideals of a ring, which is given this name. In a complex Banach space, it is the set of numbers for a given transformation such that the difference of the transformation and a scalar multiple of the identity is not invertible. A self-adjoint operator in a finite-dimensional, real inner product space can be decomposed into a direct sum called  this type of resolution. For 10 points, name this term which refers to the set of eigenvalues for a transformation and which names theorems which state every symmetric matrix has an orthonormal eigenbasis with real eigenvalues.
If the set of sizes for possible models of a sentence, called this, is closed under complements, the NP class is also closed under complements.
spectrum [or word forms like spectra or spectral]