bipyramid


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bipyramid

[¦bī¦pir·ə‚mid]
(crystallography)
A crystal having the form of two pyramids that meet at a plane of symmetry. Also known as dipyramid.
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6]; here c denotes one of the two apices of the bipyramid BP([P.
over the regular bipyramid over Q is a direct product with the projective line [P.
6] or to a skew bipyramid over a (d - 1)-dimensional smooth Fano polytope with 3(d - 1) - 1 = 3d - 4 vertices.
If the polytope P is not of the type above then, for d = 6, the polytope P is a double skew bipyramid over [P.
The final case in this section differs from the above in that the base vertex of the second skew bipyramid is an apex of the first stage.
36) we show that in this case P, again, must be a skew bipyramid.
In the first two cases the first stage is a proper bipyramid.
P] [member of] H(F, 1) there is only one choice of a double bipyramid where both stages are skew.
1) we show that such a polytope is lattice equivalent to a double proper bipyramid over [P.
Second, [eta] = (6, 6, 2, 2) is essentially reduced to a bipyramid (Assarf et al.
Forming suitable direct sums and (skew) bipyramids gives more smooth Fano d-polytopes with 3d - 1 vertices via