Θ10
In representation theory, a branch of mathematics, θ10 is a particular unitary representation of the symplectic group Sp4, which has some exceptional properties. The symplectic group Sp4 is the set of 4×4 matrices that preserve a skew-symmetric non-degenerate matrix, but its unitary representations – that is, the ways of realizing that set as a group of linear operators preserving the inner product in a Hilbert space – are often subtle.