# singular points of $\alpha_{p}$-torsor and $\mu_{p}$-torsor of curves

Let $X$ be a smooth projective curve over an algebraically closed field of characteristic $p>0$. Suppose that the genus of $X$ is >2. Let $Y$ be a non-trivial $\alpha_{p}$-torsor or $\mu_{p}$-torsor of $X$. Write $S$ for the set of singular points of $Y$.

Is the cardinality $\sharp S>2$ ?

• Over the complex numbers, there are branched covers $X$ of elliptic curves $E$ branched over only one point. Some such model can be defined over some number field, and the reduction of that model over all but finitely many primes is a similar model in positive characteristic. The reduction of the elliptic curve $E$ admits purely inseparable isogenous covers by another elliptic curve $E'$. Defining $Y=E'\times_E X$ for the reductions, $Y$ is singular only over the unique branch point of $X\to E$. – Jason Starr Jul 11 '16 at 19:14
• Just to clarify, choose the branching of $X\to E$ to have one branch point in $E$ and one ramification point in $X$. – Jason Starr Jul 11 '16 at 19:41