Author(s):

Lieb, Élliott H; Seiringer, Robert; Yngvason, Jakob

Article Title: 
Poincaré inequalities in punctured domains

Affiliation 

Abstract: 
The classic Poincaré inequality bounds the L qnorm of a function f in a bounded domain Ω ⊂ ℝ n in terms of some L pnorm of its gradient in Ω. We generalize this in two ways: In the first generalization we remove a set Τ from Ω and concentrate our attention on Λ = Ω \ Τ. This new domain might not even be connected and hence no Poincaré inequality can generally hold for it, or if it does hold it might have a very bad constant. This is so even if the volume of Τ is arbitrarily small. A Poincaré inequality does hold, however, if one makes the additional assumption that f has a finite L p gradient norm on the whole of Ω, not just on Λ. The important point is that the Poincaré inequality thus obtained bounds the L qnorm of f in terms of the L p gradient norm on Λ (not Ω) plus an additional term that goes to zero as the volume of Τ goes to zero. This error term depends on Τ only through its volume. Apart from this additive error term, the constant in the inequality remains that of the 'nice' domain Ω. In the second generalization we are given a vector field A and replace ∇ by ∇ + iA(x) (geometrically, a connection on a U(1) bundle). Unlike the A = 0 case, the infimum of ∥(∇ + iA)f∥ p over all f with a given ∥f∥ q is in general not zero. This permits an improvement of the inequality by the addition of a term whose sharp value we derive. We describe some open problems that arise from these generalizations.

Journal Title:

Annals of Mathematics

Volume: 
158

Issue 
3

ISSN:

0003486X

Publisher:

Princeton University Press

Date Published:

20031101

Start Page: 
1067

End Page:

1080

URL: 

DOI: 
10.4007/annals.2003.158.1067

Open access: 
yes (repository) 