On extreme points of the diffusion polytope
Here, we consider a class of diffusion problems defined on simple graphs in which the populations at any two vertices may be averaged if they are connected by an edge. The diffusion polytope is the convex hull of the set of population vectors attainable using finite sequences of these operations. A number of physical problems have linear programming solutions taking the diffusion polytope as the feasible region, e.g. the free energy that can be removed from plasma using waves, so there is a need to describe and enumerate its extreme points. We also review known results for the case of the complete graph Kn, and study a variety of problems for the path graph Pn and the cyclic graph Cn. Finall, we describe the different kinds of extreme points that arise, and identify the diffusion polytope in a number of simple cases. In the case of increasing initial populations on Pn the diffusion polytope is topologically an ndimensional hypercube.
 Authors:

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 Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences
 BarIIan Univ., Ramat Gan (Israel). Dept. of Mathematics
 Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences; Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Publication Date:
 Grant/Contract Number:
 AC0209CH11466; 274FG5208NA28553
 Type:
 Accepted Manuscript
 Journal Name:
 Physica. A
 Additional Journal Information:
 Journal Volume: 473; Journal Issue: C; Journal ID: ISSN 03784371
 Publisher:
 Elsevier
 Research Org:
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC24); USDOE National Nuclear Security Administration (NNSA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Combinatorics; Optimization; Diffusion; Plasma; Networks; Algebra
 OSTI Identifier:
 1350094