Lably
Skip to content

Dichromatic symmetry

Two-colour symmetry (examples, history and dimensional counts)

  • 4 min read
  • 3 chapters

Related on Lably

Through Reflection symmetry

Examples

A simple example is to take a white object, such as a triangle, and apply a colour change resulting in a black triangle. Applying the colour change once more yields the original white triangle.

The colour change, here termed an anti-identity operation (1'), yields the identity operation (1) if performed twice.

Another example is to construct an anti-mirror reflection (m') from a mirror reflection (m) and an anti-identity operation (1') executed in either order.

The m' operation can then be used to construct the antisymmetry point group 3m' of a dichromatic triangle.

There are no mirror reflection (m) operations for the dichromatic triangle, as there would be if all the smaller component triangles were coloured white. However, by introducing the anti-mirror reflection (m') operation the full dihedral D3 symmetry is restored. The six operations making up the dichromatic D3 (3m') point group are:

  • identity (e)
  • rotation by 2π/3 (r)
  • rotation by 4π/3 (r2)
  • anti-mirror reflection (m')
  • combination of m' with r (m'r)
  • combination of m' with r2 (m'r2).

Note that the vertex numbers do not form part of the triangle being operated on - they are shown to keep track of where the vertices end up after each operation.

Sign in to keep reading

2 more chapters are free with a Lably account.

More in Topics in mathematics