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A Slightly Lifted Convex Relaxation for Nonconvex Quadratic Programming with Ball Constraints
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A Slightly Lifted Convex Relaxation for Nonconvex Quadratic Programming with Ball Constraints

Samuel Burer
03/02/2023
DOI: 10.48550/arxiv.2303.01624
url
https://doi.org/10.48550/arxiv.2303.01624View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

Abstract

Globally optimizing a nonconvex quadratic over the intersection of $m$ balls in $\mathbb{R}^n$ is known to be polynomial-time solvable for fixed $m$. Moreover, when $m=1$, the standard semidefinite relaxation is exact, and when $m=2$, it has recently been shown that an exact relaxation can be constructed via a disjunctive semidefinite formulation based on essentially two copies of the $m=1$ case. However, there is no known explicit, tractable, exact convex representation for $m \ge 3$. In this paper, we construct a new, polynomially sized semidefinite relaxation for all $m$, and we demonstrate empirically that it is quite strong compared to existing relaxations, although still not exact for all objectives. The key idea is a simple lifting of the original problem into dimension $n+1$. Related to this construction, we also show that nonconvex quadratic programming over $\|x\| \le \min \{ 1, g + h^T x \}$, which arises for example as a substructure in the alternating current optimal power flow problem, has an exact semidefinite representation.
Mathematics - Optimization and Control

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