Clarkson's inequalities

In mathematics, Clarkson's inequalities, named after James A. Clarkson, are results in the theory of L^p spaces. They give bounds for the L^p-norms of the sum and difference of two measurable functions in L^p in terms of the L^p-norms of those functions individually.

Statement of the inequalities

Let (X, Σ, μ) be a measure space; let f, g : X → R be measurable functions in L^p. Then, for 2 ≤ p < +∞,

${\Vert \frac{f+g}{2}\Vert }_{L^p}^p+{\Vert \frac{f-g}{2}\Vert }_{L^p}^p\le \frac{1}{2}(\Vert f{\Vert }_{L^p}^p+\Vert g{\Vert }_{L^p}^p).$

For 1 < p < 2,

${\Vert \frac{f+g}{2}\Vert }_{L^p}^q+{\Vert \frac{f-g}{2}\Vert }_{L^p}^q\le {(\frac{1}{2}\Vert f{\Vert }_{L^p}^p+\frac{1}{2}\Vert g{\Vert }_{L^p}^p)}^{\frac{q}{p}},$

where

$\frac{1}{p}+\frac{1}{q}=1,$

i.e., q = p ⁄ (p − 1).

References

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External links

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