Relational expansion and insertion signs

The insertion sign is fixed: the first-order dressing is $-{{\mathsf{X}}_1}^{\mu }{\partial }_{\mu }{\varphi }_0$. The five contributions to (eq:A2) are iterated scalar propagation, the second-order scalar vertex, the mixed term, the second-order inverse-coordinate term, and the quadratic Taylor term. None may be omitted. The off-shell expansion (eq:Phi0)–(eq:Phi2) and the on-shell evaluation (eq:A1)–(eq:A2) are different objects: the first is a functional on $\mathcal{C}$, the second its value on the switched solution.