 Eilenberg–Mazur swindle

The Eilenberg–Mazur swindle is a technique in category theory and algebraic topology used to show that certain objects can be manipulated in a way that results in unexpected behaviors, particularly in the context of homological algebra. Specifically, it's often applied to demonstrate that certain abelian groups or modules can be considered "equivalent" by constructing a specific kind of isomorphism that leads to counterintuitive results.