James Mercer (mathematician)
James Mercer FRS was a mathematician, born in Bootle, close to Liverpool, England.
He was educated at University of Manchester, and then University of Cambridge. He became a Fellow, saw active service at the Battle of Jutland in World War I and, after decades of ill health, died in London.
He proved Mercer's theorem, which states that positive-definite kernels can be expressed as a dot product in a high-dimensional space. This theorem is the basis of the kernel trick, which allows linear algorithms to be easily converted into non-linear algorithms.
