Is there a name for the generalization of the concept "Abelian group" where the axiom $−x+x=0$ is replaced by the following list?
- $−0=0$
- $−(x+y)=−x+−y$
- $−(−x)=x$
- $x+(-x)+x = x$
In multiplicative notation; we replace the axiom $x^{-1}x=1$ with the following list:
- $1^{-1}=1$
- $(xy)^{-1}=x^{-1}y^{-1}$
- $(x^{-1})^{-1}=x$
- $xx^{-1}x = x$
Examples.
- Any Abelian group satisfies the above axioms in their additive form.
- The multiplicative structure of any zero-totalized field satisfies the above axioms in their multiplicative form, but does not satisfy $x^{-1}x=1$, since $0^{-1} \cdot 0 = 0 \cdot 0 = 0$.
Apparently it's called a (commutative) inverse monoid. For further details, see Wikipedia1, 2, 3 or Lawson's Inverse Semigroups4.
(I haven't proven that the sets of axioms are equivalent. You may want to reserve the bounty for someone who does so.)