Symmetric power
# Symmetric power

In mathematics, the n-th symmetric power of an object X is the quotient of the n-fold product $X^{n}:=X\times \cdots \times X$ by the permutation action of the symmetric group ${\mathfrak {S}}_{n}$.

More precisely, the notion exists at least in the following three areas:

* In linear algebra, the n-th symmetric power of a vector space V is the vector subspace of the symmetric algebra of V consisting of degree-n elements (here the product is a tensor product).
* In algebraic topology, the n-th symmetric power of a topological space X is the quotient space $X^{n}/{\mathfrak {S}}_{n}$, as in the beginning of this article.
* In algebraic geometry, a symmetric power is defined in a way similar to that in algebraic topology. For example, if $X=\operatorname {Spec} (A)$ is an affine variety, then the GIT quotient $\operatorname {Spec} ((A\otimes _{k}\dots \otimes _{k}A)^{{\mathfrak {S}}_{n}})$ is the n-th symmetric power of X.
