Compressing a Hadamard matrix

Hadamard matrices are in the news following the recent announcement of a newly discovered Hadamard matrix. I ve written three posts on Hadamard matrices recently, one as a sort of introduction and two on applications: the error correcting code used in the Mariner 9 probe and constructing sphere packings. A Hadamard matrix is an orthogonal matrix [ ] The post Compressing a Hadamard matrix first…