J. Aust. Math. Soc.  82 (2007), 297-313
Extending abelian groups to rings

Lynn M. Batten
  School of Computing and Mathematics
  Deakin University
  221 Burwood Highway
  Burwood Vic 3125
  Australia
  lmbatten@deakin.edu.au
Robert S. Coulter
  Department of Mathematical Sciences
  520 Ewing Hall
  University of Delaware
  Newark, Delaware 19716
  USA
  coulter@math.udel.edu
and
Marie Henderson
  307/60 Willis Street
  Te Aro (Wellington), 6001
  New Zealand
  marie.henderson@ssc.govt.nz


Abstract
For any abelian group G and any function $f: G \rightarrow G$ we define a commutative binary operation or `multiplication' on G in terms of f. We give necessary and sufficient conditions on f for G to extend to a commutative ring with the new multiplication. In the case where G is an elementary abelian p-group of odd order, we classify those functions which extend G to a ring and show, under an equivalence relation we call weak isomorphism, that there are precisely six distinct classes of rings constructed using this method with additive group the elementary abelian p-group of odd order p2.
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