Let $f : X \to Y$ be a D1519: Constant map from $X$ to $Y$ such that

(i)	$M_Y = (Y, \mathcal{F}_Y)$ is a D1108: Measurable space
(ii)	$\sigma_{\text{pullback}} \langle f \rangle$ is a D1730: Pullback sigma-algebra on $X$ under $f$ with respect to $M_Y$

Then \begin{equation} \sigma_{\text{pullback}} \langle f \rangle = \{ \emptyset, X \} \end{equation}