I'm studying $L^p$ multiplier. While reading the book, it says
"The characteristic function of the unit disk is not an $L^p$ multiplier on $\mathbb{R}^n$ when $n\ge2$ unless $p=2$."
How can I verify this? It says it will be discussed in later section 10.1 which does not exist, the book ends at Chapter 5. There is no section 10.1.