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Poincaré Constant


The Poincaré constant C_P(mu) of a probability measure on R^n is the least constant for which

 Var_mu(f)<=C_P(mu)int||del f||^2dmu

for every sufficiently regular function f, where Var_mu(f)=intf^2dmu-(intfdmu)^2 is its variance. This is the Poincaré inequality for mu.

The Kannan-Lovász-Simonovits conjecture asserts a universal upper bound on C_P(mu) for isotropic logarithmically concave distributions. Bizeul et al. (2026) reported a proof of this bound.

Balasubramanian and Kasiviswanathan (2026) reported a deterministic variational proof of the explicit bound C_P(mu)<=25 for every isotropic logarithmically concave distribution mu, independently of dimension. Balasubramanian and Kasiviswanathan (2026) acknowledge AI assistance and take responsibility for the content. The complete argument has not been independently verified here.


See also

Kannan-Lovász-Simonovits Conjecture, Logarithmically Concave Distribution, Poincaré Inequality, Probability Measure

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References

Balasubramanian, K. and Kasiviswanathan, S. "A Dimension-Free Bound on the Poincaré Constant of Isotropic Log-Concave Measures." 8 Oct 2026. https://arxiv.org/abs/2610.07728v2.Bizeul, P.; Klartag, B.; and Lehec, J. "Presenting a Proof of the Kannan-Lovász-Simonovits Conjecture." 4 Oct 2026. https://arxiv.org/abs/2610.05474.

Cite this as:

Weisstein, Eric W. "Poincaré Constant." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PoincareConstant.html

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