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Electronic Notes in Discrete Mathematics 36 (2010) 805-812
Valid Inequalities and Convex Hulls for Multilinear Functions
Pietro Belotti 1, Andrew J. Miller 2, 3, Mahdi Namazifar 4
(2010)

We study the convex hull of the bounded, nonconvex set of a product of n variables for any n ≥ 2. We seek to derive strong valid linear inequalities for this set, which we call M_n; this is motivated by the fact that many exact solvers for nonconvex problems use polyhedral relaxations so as to compute a lower bound via linear programming solvers. We present a class of linear inequalities that, together with the well-known McCormick inequalities, defines the convex hull of M_2. This class of inequalities, which we call lifted tangent inequalities, is uncountably infinite, which is not surprising given that the convex hull of M_n is not a polyhedron. This class of inequalities generalizes directly to M_n for n > 2, allowing us to define strengthened relaxations for these higher dimensional sets as well.
1:  Department of Industrial and Systems Engineering [Lehigh] (ISE)
Lehigh University, Bethlehem, USA
2:  Institut de Mathématiques de Bordeaux (IMB)
CNRS : UMR5251 – Université Sciences et Technologies - Bordeaux I – Université Victor Segalen - Bordeaux II
3:  RealOpt (INRIA Bordeaux - Sud-Ouest)
INRIA – Université Sciences et Technologies - Bordeaux I – Université Victor Segalen - Bordeaux II – CNRS : UMR – École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)
4:  Department of Industrial and Systems Engineering [Wisconsin-Madison] (ISyE)
University of Wisconsin-Madison
Computer Science/Operations Research