Puneet Varma (Editor)

Logarithmically concave measure

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In mathematics, a Borel measure μ on n-dimensional Euclidean space R n is called logarithmically concave (or log-concave for short) if, for any compact subsets A and B of R n and 0 < λ < 1, one has

μ ( λ A + ( 1 λ ) B ) μ ( A ) λ μ ( B ) 1 λ ,

where λ A + (1 − λB denotes the Minkowski sum of λ A and (1 − λB.

Examples

The Brunn–Minkowski inequality asserts that the Lebesgue measure is log-concave. The restriction of the Lebesgue measure to any convex set is also log-concave.

By a theorem of Borell, a measure is log-concave if and only if it has a density with respect to the Lebesgue measure on some affine hyperplane, and this density is a logarithmically concave function. Thus, any Gaussian measure is log-concave.

The Prékopa–Leindler inequality shows that a convolution of log-concave measures is log-concave.

References

Logarithmically concave measure Wikipedia