Omittable Planes
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In analogy to omittable lines in the plane, we initiate the study of omittable planes in $3$-space. Given a collection of $n$ planes in real projective $3$-space, a plane $\Pi$ is said to be omittable if $\Pi$ is free of ordinary lines of intersection – in other words, if all the lines of intersection of $\Pi$ with other planes from the collection come at the intersection of three or more planes. We provide two infinite families of planes yielding omittable planes in either a pencil or near-pencil, together with examples having between three and seven omittable planes, examples that we call "sporadic," which do not fit into either of the two infinite families.
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1958 ◽
Vol 10
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pp. 210-219
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1964 ◽
Vol 16
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pp. 637-656
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2013 ◽
Vol 50
(2)
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pp. 409-468
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1916 ◽
Vol 92
(638)
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pp. 265-275
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