10.07.2015 Views

v2007.09.13 - Convex Optimization

v2007.09.13 - Convex Optimization

v2007.09.13 - Convex Optimization

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

306 CHAPTER 5. EUCLIDEAN DISTANCE MATRIXFigure 77: Sphere-packing illustration from [279, kissing number].Translucent balls illustrated all have the same diameter.the kissing number as 12 (Figure 77) while Gregory argued for 13. Theirdispute was finally resolved in 1953 by Schütte & van der Waerden. [220] In2003, Oleg Musin tightened the upper bound on kissing number K in fourdimensions from 25 to K = 24 by refining a method by Philippe Delsartefrom 1973 providing an infinite number [14] of linear inequalities necessaryfor converting a rank-constrained semidefinite program 5.9 to a linearprogram. 5.10 [200]There are no proofs known for kissing number in higher dimensionexcepting dimensions eight and twenty four.Translating this problem to an EDM graph realization (Figure 74,Figure 78) is suggested by Pfender & Ziegler. Imagine the centers of eachsphere are connected by line segments. Then the distance between centersmust obey simple criteria: Each sphere touching the central sphere has a linesegment of length exactly 1 joining its center to the central sphere’s center.All spheres, excepting the central sphere, must have centers separated by adistance of at least 1.From this perspective, the kissing problem can be posed as a semidefiniteprogram. Assign index 1 to the central sphere, and assume a total of N5.9 whose feasible set belongs to that subset of an elliptope (5.9.1.0.1) bounded aboveby some desired rank.5.10 Simplex-method solvers for linear programs produce numerically better results thancontemporary log-barrier (interior-point method) solvers for semidefinite programs byabout 7 orders of magnitude.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!