Zulip Chat Archive
Stream: maths
Topic: intersection of positive and positive definite cones?
Nicholas Wilson (Jan 31 2024 at 00:56):
More of a literature question: Is there a specific name for the function cone that is the intersection of the cone of positive functions and the cone of positive definite functions on a given space?
Yaël Dillies (Jan 31 2024 at 07:28):
What do you mean by positive functions and positive definite functions here?
Nicholas Wilson (Jan 31 2024 at 07:34):
respectively f(x) : ∀ f(x) ≥ 0 (and f is not the zero function), https://en.wikipedia.org/wiki/Positive-definite_function definition 1
Eric Wieser (Jan 31 2024 at 23:42):
The first is 0 < f
in mathlib, I think
Nicholas Wilson (Jan 31 2024 at 23:50):
The definitions are not hard (Positive definite functions are Fourier transforms of positive functions), I just wondered if their intersection of those function cones has a specific name. Both for a literature search to see if there is anything interesting that might apply, but also so that I can use a name consistent with what it already in use (if such a name exists).
Yaël Dillies (Feb 01 2024 at 07:13):
The term I know for positive-definite functions is "nonnegative in Fourier space"
Yaël Dillies (Feb 01 2024 at 07:13):
Never heard of a name for the intersection
Anatole Dedecker (Feb 01 2024 at 08:43):
And the name I know is "functions of positive type"
Last updated: May 02 2025 at 03:31 UTC