Counting faces of randomly projected polytopes when the projection radically lowers dimension
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TL;DR
This paper develops asymptotic methods to count faces of random high-dimensional polytopes; a seemingly dry and unpromising pursuit that has surprising implications in statistics, probability, information theory, and signal processing with potential impacts in practical subjects like medical imaging and digital communications.
Abstract
Let Q = Q N Q = Q_N denote either the N N -dimensional cross-polytope C N C^N or the N − 1 N-1 -dimensional simplex T N − 1 T^{N-1} . Let A = A n , N A = A_{n,N} denote a random orthogonal projector A : R N ↦ b R n A: \mathbf {R}^{N} \mapsto bR^n . We compare the number of faces f k ( A Q ) f_k(AQ) of the projected polytope A Q AQ to the number of faces of f k ( Q ) f_k(Q) of the original polytope Q Q . We concentrate on the case where n n and
