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Graded vector space

In mathematics, a graded vector space is a vector space with an extra piece of structure, known as a grading.

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Graded vector spaces

A graded vector space is a vector space V which can be written as a direct sum of the form

V = \bigoplus_{n \in \mathbb{N}} V_n

for each natural number n. The elements of Vi are known as homogeneous elements of degree n.

Graded vector spaces are common. For example the set of all polynomials in one variable form a graded vector space, where the homogeneous elements of degree n are exactly the polynomials of degree n.

I-graded vector spaces

I-graded vector spaces generalize graded vector spaces. Let I be a set. An I-graded vector space V is a vector space that can be written as a direct sum of subspaces indexed by I:

V = \bigoplus_{i \in I} V_i.

A graded vector space, as defined above, is just an N-graded vector space, where N is the set of natural numbers.

The case when I=Z2 is particularly important in physics. A Z2-graded vector space also known as a supervector space.

If I is a semigroup, then the tensor product of two I-graded vector spaces V and W is another I-graded vector space, V \otimes W

(V \otimes W)_i = \bigoplus_{j,k, jk=i} V_j \otimes W_k

See also

Last updated: 08-28-2005 23:10:40
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