Let $\Delta = \lambda x.(x)x$ and consider $\Omega = (\Delta)\Delta$. Then $\Omega$ is exactly the only $\lambda$-term of the form $(\lambda x.t)v$ such that $(\lambda x.t)v=t\{v\ /\ x\}$.
Does someone have references about this statement ? I could not find something enough relevant in my ressources or in my lectures material.
Thanks in advance !
