Physlib.QFT.QED.AnomalyCancellation.VectorLike

For any natural number $n \in \mathbb{N}$, the sum of $n$ with itself is equal to two times $n$, that is, $n + n = 2n$.

For any natural number $n$, it holds that $n + 1 + n = 2n + 1$.

For a pure $U(1)$ gauge theory with an even number of fermions $2n$, a charge assignment $S = (q_0, q_1, \dots, q_{2n-1}) \in \mathbb{Q}^{2n}$ is defined to be **vector-like** if, when the charges are sorted in non-decreasing order as $x_0 \le x_1 \le \dots \le x_{2n-1}$, they satisfy the condition $x_i = -x_{n+i}$ for all $i \in \{0, 1, \dots, n-1\}$.