On disjunction of equations in the semigroup language with no constants
Аrtеm N. Shevlyakov · arXiv (Cornell University) · 2013
A semigroup $S$ is an equational domain if any finite union of algebraic sets over $S$ is algebraic. We prove that every nontrivial semigroup in the standard language $\{\cdot\}$ is not an equational domain.