# field, vector space

• Oct 2nd 2009, 10:59 PM
alexandrabel90
field, vector space
hi!
what is the link between field, set and vector space?

ie

let V be a non empty set and K be a field and E be a subfield.

why isit that V is a vector space over K when a set is smaller than a field.

and when it comes to subfields and fields, K will be a vector space over E..

by saying that sth is a vector space over sth, does it just mean taht the 8 axioms of vector spaces are satisfied?

then what is the difference between vector space and field?

thanks!
• Nov 16th 2012, 03:27 AM
dave0147
Re: field, vector space
A field is an algebraic category in which the elements are an abelian (commutative) group under addition and F/{0} is also an abelian group (this time) under multiplication. The most common field in most people's experience is the set of rational numbers. What this generally boils down to is that every non-zero element has a multiplicative inverse (i.e. division by zero is not allowed.)
A vector space has two operative sets, the vectors and the scalars (the field) where there is a "multiplication" defined between the vectors and the scalars) by a*v = av, a "new" vector. This is called scalar multiplication. There is also an "addition" operation between vectors called vector addition which also yields a "new vector". The scalars (the field) maintains all the addition and multiplication properties of a field.

The easiest example is probably ordered pairs (x,y) (the vectors) and the real numbers, (the field of scalars) which incorporate all the operations in entities called linear combinations, such as 4*(1,-3) + 3*(5,1) = (4,-12) + (15,3) = (19, -9). I could go on forever, but I think you can go on from here and talk about dimension (here it is 2) and bases (here, for example, {(1 , 0), (0,1)}.