What do the curly brackets mean in this context?
$$f(x) = 2 \cdot x \cdot 1_{x>0}$$
Is this a condition?
What do the curly brackets mean in this context?
$$f(x) = 2 \cdot x \cdot 1_{x>0}$$
Is this a condition?
The $\Bbb 1_{x>0}$ is the indicator function $^1$ that indicates if $x$ is greater than $0$ or not. $$1_{x>0}=\begin{cases} 1, ~~x>0\\0, ~~x \le 0\end{cases}$$
This makes your function into,
$$f(x)=\begin{cases}2x,~~x>0\\0, ~~x \le0 \end{cases}$$
Footnotes:
$^1$(also called the Characteristic function, denoted by $\chi_A$ is the function that takes $1$ when $x \in A$ and $0$ otherwise.)