Suppose $f_n(x)$ is a sequence of real-valued functions converging uniformly to a function $f(x)$ and let $\{\epsilon_n\}_{n \in \mathbb{N}}$ be a sequence of positive real numbers converging to $0$.
Is it necessarily true that the sequence of (extended real-valued) functions
$$
g_n(x)\triangleq \frac{1}{\epsilon_n}I_{\{
f_x(x)>\epsilon_n
\}}
$$
converges uniformly to the (extended real-valued) function
\begin{equation}
\begin{aligned}
g(x)\triangleq & \begin{cases}
\infty & \mbox{if} & f(x)>0\\
0 & \mbox{if} & f(x)=0?
\end{cases}
\end{aligned}
\end{equation}
If not what additional conditions must I impose for this to be true?
2026-04-29 11:29:38.1777462178
Uniform convergence of indicators
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No. Consider $\epsilon_n = 2^{-n}$ and $f_n(x) = \frac{1}{n}$. Then $g_n(x) = 2^n$ everywhere, but $g(x) = 0$ everywhere. You need $\epsilon_n$ to converge to $0$ faster than $f_n$ where $f(x)=0$. I don't know of a simple sufficient condition.