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Apeirotope


An apeirotope or infinite polytope is a polytope which has infinitely many facets. There are two main geometric classes of apeirotope:

In general, a honeycomb in n dimensions is an infinite example of a polytope in n + 1 dimensions.

Tilings of the plane and close-packed space-fillings of polyhedra are examples of honeycombs in two and three dimensions respectively.

A line divided into infinitely many finite segments is an example of an apeirogon.

A skew apeirogon in two dimensions forms a zig-zag line in the plane. If the zig-zag is even and symmetrical, then the apeirogon is regular.

Skew apeirogons can be constructed in any number of dimensions. In three dimensions, a regular skew apeirogon traces out a helical spiral and may be either left- or right-handed.

There are three regular skew apeirohedra, which look rather like polyhedral sponges:

There are thirty regular apeirohedra in Euclidean space. These include those listed above, as well as (in the plane) polytopes of type: {∞,3}, {∞,4}, {∞,6} and in 3-dimensional space, blends of these with either an apeirogon or a line segment, and the "pure" 3-dimensional apeirohedra (12 in number)


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