%0 Journal Article %T Symmetries Shared by the Poincar¨¦ Group and the Poincar¨¦ Sphere %A Young S. Kim %A Marilyn E. Noz %J Symmetry %D 2013 %I MDPI AG %R 10.3390/sym5030233 %X Henri Poincar¨¦ formulated the mathematics of Lorentz transformations, known as the Poincar¨¦ group. He also formulated the Poincar¨¦ sphere for polarization optics. It is shown that these two mathematical instruments can be derived from the two-by-two representations of the Lorentz group. Wigner¡¯s little groups for internal space-time symmetries are studied in detail. While the particle mass is a Lorentz-invariant quantity, it is shown to be possible to address its variations in terms of the decoherence mechanism in polarization optics. %K Poincar¨¦ group %K Poincar¨¦ sphere %K Wigner¡¯s little groups %K particle mass %K decoherence mechanism %K two-by-two representations %K Lorentz group %U http://www.mdpi.com/2073-8994/5/3/233