Studies in Rings generalised Unique Factorisation Rings
Studies in Rings generalised Unique Factorisation Rings
Studies in Rings generalised Unique Factorisation Rings
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-18-<br />
Proposition 1038.<br />
For a r<strong>in</strong>g R, the follow<strong>in</strong>g conditions are equivalent.<br />
(a) R is simple left Art<strong>in</strong>ian<br />
( b) R is simple right Art i n i a n<br />
( c) R is simple and semisimple<br />
( d) R =M (D), for some positive <strong>in</strong>teger n and<br />
n<br />
some division r<strong>in</strong>g D.<br />
RING OF FRACTIONS<br />
In the theory of commutative r<strong>in</strong>gs, Loc a l Ls a t i on<br />
at a multiplicative set plays a very important role.<br />
Most<br />
important is the idea of a quotient field, without which<br />
one<br />
can hardly imag<strong>in</strong>e the study of <strong>in</strong>tegral doma<strong>in</strong>s.<br />
A very useful technique <strong>in</strong> commutative theory is the<br />
localisation at. a prime ideal, which ~educes many problems<br />
to the study of local r<strong>in</strong>gs and their maximal ideals.<br />
I-Iowever,<br />
this is not the case with non-commutative<br />
r<strong>in</strong>gs. Although the set of nonzero elements is a multiplicative<br />
set <strong>in</strong> any -doma<strong>in</strong>,<br />
we have examples of doma<strong>in</strong>s<br />
which do not possess a division r<strong>in</strong>g of quotientso<br />
It<br />
was <strong>in</strong> 1930, t~dt o. Ore characterised those non-commutative<br />
doma<strong>in</strong>s which possess division r<strong>in</strong>gs of fractions.<br />
In fact,