Brezis–Gallouet inequality

In mathematical analysis, the Brezis–Gallouet inequality, named after Haïm Brezis and Thierry Gallouet, is an inequality valid in 2 spatial dimensions. It shows that a function of two variables which is sufficiently smooth is (essentially) bounded, and provides an explicit bound, which depends only logarithmically on the second derivatives. It is useful in the study of partial differential equations.

Let u ∈ H 2 ( Ω ) where Ω ⊂ R 2 . Then the Brézis–Gallouet inequality states that there exists a constant C such that

where Δ is the Laplacian, and λ 1 is its first eigenvalue.