A characterization of matrix inequality A≥B≥C via Karcher mean

Averaging complex subspaces via a Karcher mean approach

We propose a conjugate gradient type optimization technique for the computation of the Karcher mean on the set of complex linear subspaces of fixed dimension, modeled by the so-called Grassmannian. The identification of the Grassmannian with Hermitian projection matrices allows an accessible introduction of the geometric concepts required for an intrinsic conjugate gradient method. In particula...

The matrix arithmetic-geometric mean inequality revisited

HUANG, YOU, ABSIL, GALLIVAN: KARCHER MEAN IN ELASTIC SHAPE ANALYSIS 1 Karcher Mean in Elastic Shape Analysis*

In the framework of elastic shape analysis, a shape is invariant to scaling, translation, rotation and reparameterization. Since this framework does not yield a closed form of geodesic between two shapes, iterative methods have been proposed. In particular, path straightening methods have been proposed and used for computing a geodesic that is invariant to curve scaling and translation. Path st...

Matrix sparsification via the Khintchine inequality

Given a matrix A ∈ Rn×n, we present a simple, element-wise sparsification algorithm that zeroes out all sufficiently small elements of A, keeps all sufficiently large elements of A, and retains some of the remaining elements with probabilities proportional to the square of their magnitudes. We analyze the approximation accuracy of the proposed algorithm using a powerful inequality bounding the ...

An Inequality of Ostrowski Type via Pompeiu’s Mean Value Theorem

 (b− a)M, for all x ∈ [a, b] . The constant 14 is best possible in the sense that it cannot be replaced by a smaller constant. In [2], the author has proved the following Ostrowski type inequality. Theorem 2. Let f : [a, b] → R be continuous on [a, b] with a > 0 and differentiable on (a, b) . Let p ∈ R\ {0} and assume that Kp (f ) := sup u∈(a,b) { u |f ′ (u)| } < ∞. Then we have the inequality...