Who was the Dutch theoretical physicist that created the 't Hooft η symbol?
Gerard 't Hooft Gerardus (Gerard) 't Hooft (] ; born July 5, 1946) is a Dutch theoretical physicist and professor at Utrecht University, the Netherlands. He shared the 1999 Nobel Prize in Physics with his thesis advisor Martinus J. G. Veltman "for elucidating the quantum structure of electroweak interactions".
Hilbrand J. Groenewold 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.