Math 2.0

Linear and multilinear algebra; matrix theory Definition

Linear map

Builds on Vector space

Definition

Let FF be a field and let VV and WW be vector spaces over FF. A map T ⁣:V→WT \colon V \to W is linear when, for all u,v∈Vu, v \in V and a∈Fa \in F, T(u+v)=T(u)+T(v),T(av)=a T(v).T(u + v) = T(u) + T(v), \qquad T(av) = a\, T(v). A linear map is also called a linear transformation.

Remarks

A linear map sends 00 to 00 and linear combinations to linear combinations: T(∑aivi)=∑aiT(vi)T(\sum a_i v_i) = \sum a_i T(v_i). For an m×nm \times n matrix AA, the map Fn→FmF^n \to F^m, x↦Axx \mapsto Ax, is linear. Rotations of ℝ2\R^2 about the origin are linear; translations by a nonzero vector are not linear. Each linear map between finite-dimensional spaces has a matrix in a choice of bases.

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  1. Vector space definition
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Further reading

  1. Web https://en.wikipedia.org/wiki/Linear_map, Definition and first consequences
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