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Linear Algebra, Theory And Applications, 2012a

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Vector Spaces <strong>And</strong> Fields<br />

8.1 Vector Space Axioms<br />

It is time to consider the idea of a Vector space.<br />

Definition 8.1.1 A vector space is an Abelian group of “vectors” satisfying the axioms of<br />

an Abelian group,<br />

v + w = w + v,<br />

the commutative law of addition,<br />

(v + w)+z = v+(w + z) ,<br />

the associative law for addition,<br />

the existence of an additive identity,<br />

v + 0 = v,<br />

v+(−v) =0,<br />

the existence of an additive inverse, along with a field of “scalars”, F which are allowed to<br />

multiply the vectors according to the following rules. (The Greek letters denote scalars.)<br />

α (v + w) =αv+αw, (8.1)<br />

(α + β) v =αv+βv, (8.2)<br />

α (βv) =αβ (v) , (8.3)<br />

1v = v. (8.4)<br />

The field of scalars is usually R or C and the vector space will be called real or complex<br />

depending on whether the field is R or C. However, other fields are also possible. For<br />

example, one could use the field of rational numbers or even the field of the integers mod p<br />

for p a prime. A vector space is also called a linear space.<br />

For example, R n with the usual conventions is an example of a real vector space and C n<br />

is an example of a complex vector space. Up to now, the discussion has been for R n or C n<br />

and all that is taking place is an increase in generality and abstraction.<br />

There are many examples of vector spaces.<br />

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