The original question was
"Is the relation $\sim$ is a equivalence relation?"
I can mathematically figure it out that this is not.
Since $a$ is not related to $a$, as $a$ satisfies neither of the conditions.
Basically no two pair of integers satisfies this.
My question is,
- Is my approach correct?
- Since no element is mapped to no other element, can we even call it a relation?
No, it is not an equivalence relation since, as you have correctly determined, it is not reflexive.
It is the binary relation $\emptyset$ since $a\not{\sim}b$ for all $a, b\in \Bbb Z$, because $\emptyset\in \mathcal P(\Bbb Z\times \Bbb Z)$.