Uniqueness in Discrete Tomography: Three Remarks and a Corollary

  • Authors:
  • Peter Gritzmann;Barbara Langfeld;Markus Wiegelmann

  • Affiliations:
  • gritzman@ma.tum.de;langfeld@math.uni-kiel.de;markuswiegelmann@t-online.de

  • Venue:
  • SIAM Journal on Discrete Mathematics
  • Year:
  • 2011

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Abstract

Discrete tomography is concerned with the retrieval of finite point sets in some $\mathbbm{R}^d$ from their X-rays in a given number $m$ of directions $u_1,\ldots, u_m$. In the present paper we focus on uniqueness issues. The first remark gives a uniform treatment and extension of known uniqueness results. In particular, we introduce the concept of $J$-additivity and give conditions when a subset $J$ of possible positions is already determined by the given data. As a by-product, we settle a conjecture of Brunetti and Daurat on planar lattice convex sets. Remark 2 resolves a problem of Kuba posed in 1997 on the uniqueness in the case $d=m=3$ with $u_1,u_2,u_3$ being the standard unit vectors. Remark 3 determines the computational complexity of finding a smallest set $J$ of positions whose disclosure yields uniqueness. As a corollary, we obtain a hardness result for $0$-$1$-polytopes.