James Mercer (mathematician)

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James Mercer FRS[1] (15 January 1883 – 21 February 1932) was a mathematician, born in Bootle, close to Liverpool, England.[2]

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.


  1. ^ Hobson, E. W. (1933). "James Mercer. 1883-1932". Obituary Notices of Fellows of the Royal Society. 1 (2): 164–165. doi:10.1098/rsbm.1933.0016.
  2. ^ O'Connor, John J.; Robertson, Edmund F., "James Mercer", MacTutor History of Mathematics Archive, University of St Andrews