Separating set explained

S

of functions with domain

D

is called a and is said to (or just) if for any two distinct elements

x

and

y

of

D,

there exists a function

f\inS

such that

f(x)f(y).

[1]

X,

with the topology of uniform convergence. It states that any subalgebra of this space of functions is dense if and only if it separates points. This is the version of the theorem originally proved by Marshall H. Stone.[1]

Examples

\Reals

separates the points of

\Reals.

X

is a T1 normal topological space, then Urysohn's lemma states that the set

C(X)

of continuous functions on

X

with real (or complex) values separates points on

X.

X

is a locally convex Hausdorff topological vector space over

\Reals

or

\Complex,

then the Hahn–Banach separation theorem implies that continuous linear functionals on

X

separate points.

Notes and References

  1. .