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arXiv 0910.5765math.OCcs.DSmath.COmath.FA
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带秩约束的半正定Grothendieck问题

The positive semidefinite Grothendieck problem with rank constraint

Jop Briet, Fernando Mario de Oliveira Filho, Frank Vallentin

摘要:

给定一个正整数n和一个大小为m × m的正半定矩阵A =(A_{ij}),带秩n约束的半正定Grothendieck问题(SDP_n)是最大化\sum_{i=1}^m \sum_{j=1}^m A_{ij} x_i \cdot x_j,其中x_1,.,x_m \in S^{n-1}。本文设计了一个求解SDP_n的多项式时间近似算法,其近似比为γ(n)= \frac{2}{n}(\frac{Γ((n+1)/2)}{Γ(n/2)})^2 = 1 - Θ(1/n).我们证明了在唯一对策猜想的假设下,所得到的逼近比是最优的:不存在多项式时间算法能以大于γ(n)的逼近比逼近SDP_n.本文将已知的多项式时间算法对SDP_1的逼近比从2/π改进为2/(πγ(m))= 2/π+ Θ(1/m),并且当A是具有非负边权的图的Laplacian矩阵时,对SDP_n的逼近比更紧.

英文摘要:

Given a positive integer n and a positive semidefinite matrix A = (A_{ij}) of size m x m, the positive semidefinite Grothendieck problem with rank-n-constraint (SDP_n) is maximize \sum_{i=1}^m \sum_{j=1}^m A_{ij} x_i \cdot x_j, where x_1, ..., x_m \in S^{n-1}. In this paper we design a polynomial time approximation algorithm for SDP_n achieving an approximation ratio of γ(n) = \frac{2}{n}(\frac{Γ((n+1)/2)}{Γ(n/2)})^2 = 1 - Θ(1/n). We show that under the assumption of the unique games conjecture the achieved approximation ratio is optimal: There is no polynomial time algorithm which approximates SDP_n with a ratio greater than γ(n). We improve the approximation ratio of the best known polynomial time algorithm for SDP_1 from 2/πto 2/(πγ(m)) = 2/π+ Θ(1/m), and we show a tighter approximation ratio for SDP_n when A is the Laplacian matrix of a graph with nonnegative edge weights.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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