Jacques Hadamard

He studied at the École Normale Supérieure.
After the Dreyfus affair, which involved him personally, he became politically active and became a staunch supporter of Jewish causes.

He introduced the idea of well-posed problem in the theory of partial differential equations. He also gave his name to the Hadamard inequality on volumes, and the Hadamard matrix, on which the Hadamard transform is based. The Hadamard gate in quantum computing uses this matrix.

In his book Psychology of Invention in the Mathematical Field, Hadamard uses introspection to describe mathematical thought processes. In sharp opposition to authors who identify language and cognition, he describes his own mathematical thinking as largely wordless, often accompanied by mental images that condense the overall idea of a proof.

One of his students was André Weil.

Writings