A lower bound on the optimal self-concordance parameter of convex cones
نویسنده
چکیده
Let K ⊂ R be a regular convex cone, let e1, . . . , en ∈ ∂K be linearly independent points on the boundary of a compact affine section of the cone, and let x∗ ∈ K be a point in the relative interior of this section. For k = 1, . . . , n, let lk be the line through the points ek and x ∗, let yk be the intersection point of lk with ∂K opposite to ek, and let zk be the intersection point of lk with the linear subspace spanned by all points el, l = 1, . . . , n except ek. We give a lower bound on the self-concordance parameter o of logarithmically homogeneous self-concordant barriers F : K → R on K in terms of the projective cross-ratios qk = (ek, x ∗; yk, zk). The previously known lower bound of Nesterov and Nemirovski can be obtained from our result as a special case. As an application, we construct an optimal barrier for the epigraph of the ∣∣ ⋅ ∣∣∞-norm in R and compute lower bounds on the optimal self-concordance parameters for the power cone and the epigraph of the ∣∣ ⋅ ∣∣p-norm in R.
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