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单词 Kepler-Poinsot Solid
释义

Kepler-Poinsot Solid

The Kepler-Poinsot solids are the four regular Concave Polyhedra with intersecting facialplanes. They are composed of regular Concave Polygons and were unknown to the ancients.Kepler discovered two and described them about 1619. These two were subsequently rediscovered by Poinsot, who also discoveredthe other two, in 1809. As shown by Cauchy, they are stellated forms of the Dodecahedron andIcosahedron.


The Kepler-Poinsot solids, illustrated above, are known as the GreatDodecahedron, Great Icosahedron, Great Stellated Dodecahedron, and Small Stellated Dodecahedron. Cauchy (1813) proved that these four exhaust all possibilities for regular star polyhedra (Ball and Coxeter 1987).


A table listing these solids, their Duals, and Compounds is givenbelow.


PolyhedronDual PolyhedronCompound
Great DodecahedronSmall Stellated DodecahedronGreat Dodecahedron-Small Stellated Dodecahedron Compound
Great IcosahedronGreat Stellated DodecahedronGreat Icosahedron-Great Stellated Dodecahedron Compound
Great Stellated DodecahedronGreat IcosahedronGreat Icosahedron-Great Stellated Dodecahedron Compound
Small Stellated DodecahedronGreat DodecahedronGreat Dodecahedron-Small Stellated Dodecahedron Compound


The polyhedra and fail to satisfy the Polyhedral Formula


where is the number of faces, the number of edges, and the number of faces, despite the fact that theformula holds for all ordinary polyhedra (Ball and Coxeter 1987). This unexpected result led none less than Schläfli(1860) to conclude that they could not exist.


In 4-D, there are 10 Kepler-Poinsot solids, and in -D with , there are none. In 4-D, nine of the solids havethe same Vertices as , and the tenth has the same as . TheirSchläfli Symbols are , , ,, , , , ,, and .


Coxeter et al. (1954) have investigated star ``Archimedean'' polyhedra.

See also Archimedean Solid, Deltahedron, Johnson Solid, Platonic Solid, PolyhedronCompound, Uniform Polyhedron


References

Ball, W. W. R. and Coxeter, H. S. M. Mathematical Recreations and Essays, 13th ed. New York: Dover, pp. 144-146, 1987.

Cauchy, A. L. ``Recherches sur les polyèdres.'' J. de l'École Polytechnique 9, 68-86, 1813.

Coxeter, H. S. M.; Longuet-Higgins, M. S.; and Miller, J. C. P. ``Uniform Polyhedra.'' Phil. Trans. Roy. Soc. London Ser. A 246, 401-450, 1954.

Pappas, T. ``The Kepler-Poinsot Solids.'' The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 113, 1989.

Quaisser, E. ``Regular Star-Polyhedra.'' Ch. 5 in Mathematical Models from the Collections of Universities and Museums (Ed. G. Fischer). Braunschweig, Germany: Vieweg, pp. 56-62, 1986.

Schläfli. Quart. J. Math. 3, 66-67, 1860.


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