%0 Journal Article %T The entropic barrier: a simple and optimal universal self-concordant barrier %A S¨¦bastien Bubeck %A Ronen Eldan %J Mathematics %D 2014 %I arXiv %X We prove that the Cram\'er transform of the uniform measure on a convex body in $\mathbb{R}^n$ is a $(1+o(1)) n$-self-concordant barrier, improving a seminal result of Nesterov and Nemirovski. This gives the first explicit construction of a universal barrier for convex bodies with optimal self-concordance parameter. The proof is based on basic geometry of log-concave distributions, and elementary duality in exponential families. %U http://arxiv.org/abs/1412.1587v3