Portrait of Jacques Hadamard (1865-1963), French mathematician. Educated at the Ecole Normale Superieure in Paris, Hadamard was a gifted student. He influenced many fields in maths, publishing over 300 papers. He proved the Cauchy test for the convergence of a power series, and in 1896 proved the prime number theorem of Gauss and Riemann, probably the most important result so far in the history of number theory. From his work on geodesics, he developed a theory of functionals. This led to functional analysis, relevant in modern quantum field theory. Hadamard was also a gifted and popular lecturer, retiring in 1945 at the ripe age of 80.