3
$\begingroup$

Suppose I have a class of functions $\mathcal{F}$ with the property that

$\int f(x) g(x) = \int f(x) h(x)$ for all $f \in \mathcal{F}$ implies $g = h$.

What's the correct name for this property? If $g$ and $h$ are in $L^p$, do I say that $\mathcal{F}$ is a seperating set, or that it seperates points in $L^p$, or something else?

If $\mathcal{F}$ is the class of smooth functions with compact support and $g$ and $h$ live in $L^p$, is the implication correct? If so, what's that result called?

  • 0
    I think statement of this form often go under the name "fundamental lemma of the calculus of variations".2011-07-15

1 Answers 1

2

The function $g\mapsto \int fg$ is a linear function. Depending on the topology you impose, it is a continuous linear function. What you are seeing is that $\mathcal F$ has as its closed linear span the entire space (in your case $L^p$).