Sanakirja.org

Määritelmät

Substantiivi

1. A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.
2. Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc.
3. (psychology, education, usually with the) The autism spectrum.
4. (chemistry) The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).
5. (mathematics, linear algebra) The set of eigenvalues of a matrix.
6. (mathematics, functional analysis) Of a bounded linear operator A, the set of scalar values λ such that the operator A—λI, where I denotes the identity operator, does not have a bounded inverse; intended as a generalisation of the linear algebra sense.
7. (commutative algebra, algebraic geometry) An abstract object in mathematics created from a commutative ring ${\displaystyle R}$ and denoted ${\displaystyle \operatorname {Spec} (R)}$ or ${\displaystyle \operatorname {Spec} R}$ and said to be the spectrum of ${\displaystyle R}$; useful in the study of such rings for providing a geometric object which encodes many of the properties ${\displaystyle R}$, and in modern geometry for generalizing the notion of an algebraic variety to that of an affine scheme. Formally, the set of all prime ideals ${\displaystyle R}$ equipped with the Zariski topology and augmented with a sheaf of rings called the structure sheaf, generated by the B-sheaf on the distinguished open sets ${\displaystyle D_{f}}$ which assigns the localization of ${\displaystyle R}$ at ${\displaystyle f}$ to each set ${\displaystyle D_{f}}$, regarded as a ring of functions on ${\displaystyle D_{f}}$. See
8. (obsolete) Specter, apparition.
9. The image of something seen that persists after the eyes are closed.