1,133 research outputs found
Bell inequalities from variable elimination methods
Tight Bell inequalities are facets of Pitowsky's correlation polytope and are
usually obtained from its extreme points by solving the hull problem. Here we
present an alternative method based on a combination of algebraic results on
extensions of measures and variable elimination methods, e.g., the
Fourier-Motzkin method. Our method is shown to overcome some of the
computational difficulties associated with the hull problem in some non-trivial
cases. Moreover, it provides an explanation for the arising of only a finite
number of families of Bell inequalities in measurement scenarios where one
experimenter can choose between an arbitrary number of different measurements
Small Chvatal rank
We propose a variant of the Chvatal-Gomory procedure that will produce a
sufficient set of facet normals for the integer hulls of all polyhedra {xx : Ax
<= b} as b varies. The number of steps needed is called the small Chvatal rank
(SCR) of A. We characterize matrices for which SCR is zero via the notion of
supernormality which generalizes unimodularity. SCR is studied in the context
of the stable set problem in a graph, and we show that many of the well-known
facet normals of the stable set polytope appear in at most two rounds of our
procedure. Our results reveal a uniform hypercyclic structure behind the
normals of many complicated facet inequalities in the literature for the stable
set polytope. Lower bounds for SCR are derived both in general and for
polytopes in the unit cube.Comment: 24 pages, 3 figures, v3. Major revision: additional author, new
application to stable-set polytopes, reorganization of sections. Accepted for
publication in Mathematical Programmin
The Hyperdeterminant and Triangulations of the 4-Cube
The hyperdeterminant of format 2 x 2 x 2 x 2 is a polynomial of degree 24 in
16 unknowns which has 2894276 terms. We compute the Newton polytope of this
polynomial and the secondary polytope of the 4-cube. The 87959448 regular
triangulations of the 4-cube are classified into 25448 D-equivalence classes,
one for each vertex of the Newton polytope. The 4-cube has 80876 coarsest
regular subdivisions, one for each facet of the secondary polytope, but only
268 of them come from the hyperdeterminant.Comment: 30 pages, 6 figures; An author's name changed, typos fixe
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