Hilbrand Johannes "Hip" Groenewold (1910–1996) was a Dutch theoretical physicist who pioneered the largely operator-free formulation of quantum mechanics in phase space known as phase-space quantization.
After a visit to Cambridge to interact with John von Neumann (1934–5) on the links between classical and quantum mechanics, and a checkered career working with Frits Zernike in Groningen, then Leiden, the Hague, De Bilt, and several addresses in the North of the Netherlands during World War II, he earned his Ph.D. degree in 1946, under the tutelage of Léon Rosenfeld at Utrecht University.
His 1946 thesis paper [1] laid the foundations of quantum mechanics in phase space, in unwitting parallel with J. E. Moyal.
[3] This observation and his counterexamples contrasting Poisson brackets to commutators have been generalized and codified to what is now known as the Groenewold–Van Hove theorem.
It failed to reach a wide audience, leaving these ideas in obscurity until they were independently discovered decades later.