Let $X$ be a smooth projective curve over an algebarically closed field $k$.
Consider the commutative diagram where the left square is cartesian.
where $S,S'$ are schemes over $k$ and $X_S:=X\times S$ and $X_{S'}:=X\times S'$.
Let $\omega_{X|k}$ be the canonical bundle of $X$ and let $\omega_{X_S/S}:=p^*(\omega_{X|k})$.
- Is it true that $\omega_{X_S/S}$ is a dualizing sheaf for $X_S$?
- Similarly, is $\omega_{X_{S'}/S'}:=g^*(\omega_{X_S/S})$ a dualizing sheaf for $X_{S'}$?
I can see that $\omega_{X_S/S}$ and $\omega_{X_{S'}/S'}$ are canonical line bundles respectively on $X_{S},X_{S'}$, but I couldn't find anything prooving that the canonical bundle coincides with the dualizing sheaf in the case where the base scheme is arbitrary like with $S,S'$.(when it is a field, Hartshorne III, cor 7.12 gives an answer in that special case).
Thank you for your help.
