In mathematics, especially differential topology, the Gromoll–Meyer sphere is a special seven-dimensional exotic sphere with several unique properties.
It is named after Detlef Gromoll and Wolfgang Meyer, who first described it in detail in 1974, although it was already found by John Milnor in 1956.
consider the complex variety: A description of the Gromoll–Meyer sphere is the intersection with a small sphere around the origin.
) acts on the second symplectic group
A description of the Gromoll–Meyer sphere is the biquotient space: