Template:Use dmy dates James Mercer FRS<ref>Template:Cite journal</ref> (15 January 1883 – 21 February 1932) was a mathematician, born in Bootle, close to Liverpool, England.<ref>Template:MacTutor Biography</ref>
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 (applied by Aizerman), which allows linear algorithms to be easily converted into non-linear algorithms.