Show there is a tower of cyclic field extensions of prime degree from $\mathbb{Q}(\sqrt[12]{5})$ to $\mathbb{Q}$

43 Views Asked by At

Of course, it suffices to find tower of Galois extensions of prime degree, as these would have to be cyclic. My first thought was to try extending $\mathbb{Q}$ first by $\sqrt 5$, then $\mathbb{Q}(\sqrt 5)$ by $\sqrt[4]{5}$ and $\mathbb{Q}(\sqrt[4]{5})$ by $\sqrt[12]{5}$, but then the last extension isn't Galois as it's not normal. I tried extending $\mathbb{Q}(\sqrt[4]{5})$ by $\omega_3\sqrt[12]{5}$ where $\omega_3$ denotes the third root of the unit, but of course this gives me a different field at the top of the tower, not $\mathbb{Q}(\sqrt[12]{5})$. In general, I'm clueless on how to find a Galois extension of degree three which doesn't have imaginary numbers.