Hulls and boundaries in ${\mathbb{C}}^n$

The paper is concerned with the boundary behaviour of polynomially and rationally convex hulls in pseudoconvex domains in ${\mathbb{C}}^n$. As an application, it is shown that every connected polynomially or rationally convex compact set with $C^1$ boundary is isotopic to the closure of a smoothly bounded strictly pseudoconvex domain that is also polynomially or rationally convex.