group of order 2
Cohomology and Extensions
There is, up to isomorphism, a unique simple group of order 2:
it has two elements , where .
This is usually denoted or , because it is the cokernel (the quotient by the image of) the homomorphism
on the additive group of integers. As such is the special case of a cyclic group for and hence also often denoted .
Revised on January 22, 2016 15:05:32
by Urs Schreiber