I am trying to define the polynomial ring $\Bbb{Z}[j]$ where $j$ is the 3rd root of unity, i.e. $j = e^{\frac{2}{3} \pi i} \in \Bbb C$.
I tried this:
P.<x> = PolynomialRing(QQ)
j = exp((2/3)*pi*i)
P[j]
But I get the error:
NotImplementedError: ring extension with prescribed embedding is not implemented