Forward regressive

Let $\mathbb{T}$ be a time scale. Let $p \colon \mathbb{T} \rightarrow \mathbb{C}$. We say that $p$ is forward regressive if for all $t \in \mathbb{T}^{\kappa}$ $$1+\mu(t)p(t)\neq 0.$$ We use the notation $\mathcal{R}(\mathbb{T},Y)$ for forward regressive functions with domain $\mathbb{T}$ and codomain $Y$.