Free five-valued Nelson Algebras

Abstract

Five-valued Nelson algebras are those satisfying the condition: $((x\to z)\to y)\to (((y\to x)\to y)\to y)=1$. We give alternative equations defining these algebras, and determine the structure and number of elements of the free five-valued Nelson algebra with a finite number of free generators.

36 pages, 4 figures, 2 appendices