Suppose we have a family of objects $\Xi \to S$ over a base smooth projective scheme $S$. Take a closed point $p\in S$ and consider the tangent space to $S$ at $p$. Can one construct an "induced family" over this tangent space (or probably rather over its projectivized space) starting from $ \Xi$ ? what interpretation could one give to this? a second-order deformation?



does there exist a family of objects over the tangent space to the base space of a family of objects?
Imagine that $S$ is an open subset of some fine moduli space which does not contain any rational curves. This does happen although I don't know any examples. Then any family over an affine space will have to be constant, so the answer would be no.


On the other hand, of course there is formal family over the completion of $S$ at the given point $p$ ($\hat{S}\_p = \lim Spec (\mathcal{O}\_{S, p}/\mathfrak{m}\_{S, p}^n)$), which looks like the infinitesimal neighborhood of $0$ in the tangent space ($\hat{T}\_0 = Spf(k[[t\_1, \ldots, t\_s]])$ where the $t\_i$ form a basis of the dual of $T= T\_{p} S$). I think morally this might play the role of what you want.


