Generating the kernel of a staircase starshaped set from certain staircase convex subsets |
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Authors: | Marilyn Breen |
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Institution: | 1.The University of Oklahoma Norman,Oklahoma,USA |
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Abstract: | Let S be an orthogonal polygon in the plane. Assume that S is starshaped via staircase paths, and let K be any component of Ker S, the staircase kernel of S, where K ≠ S. For every x in S\K, define W
K
(x) = {s: s lies on some staircase path in S from x to a point of K}. There is a minimal (finite) collection W(K) of W
K
(x) sets whose union is S. Further, each set W
K
(x) may be associated with a finite family U
K
(x) of staircase convex subsets, each containing x and K, with ∪{U: U in U
K
(x)} = W
K
(x). If W(K) = {W
K
(x
1), ..., W
K
(x
n
)}, then K ⊆ V
K
≡ ∩{U: U in some family U
K
(x
i
), 1 ≤ i ≤ n} ⊆ Ker S. It follows that each set V
K
is staircase convex and ∪{V
k
: K a component of Ker S} = Ker S. |
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Keywords: | |
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