Are Vector Spaces over non-commutative fields ever studied? Are Vector Spaces over non-commutative fields ever studied?
If not, why?
If they are, I'd like to learn a bit about them, could you guys recommend me a good book on the subject?
Cheers.
 A: Yes, they are studied, if only because the endomorphism ring of a simple module over a (unital) ring $R$ is a division ring or skew-field, if you prefer. The term “non-commutative field” is rarely used.
Wedderburn's theorem says that a semisimple artinian ring is the product of (full) matrix rings over division rings, generally non commutative.
However, the structure of vector spaces over a division ring $D$ is quite easy: $D$ is a semisimple ring and has a unique simple module, up to isomorphisms (the same $D$ as a vector space over itself). So any module over a division ring $D$ is just a direct sum of copies of $D$, just like for vector spaces over fields.
The theorems about linear independence and bases extend to this setting and also the duality for finite dimensional vector spaces.
A: The expression "vector space" is usually reserved to the case when the coefficients form a field.
When the coefficients only form a ring (such as a skew field), the corresponding structure is called a module.
