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