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".
Ehrenfest theorem The Ehrenfest theorem, named after Paul Ehrenfest, an Austrian theoretical physicist at Leiden University, relates the time derivative of the expectation values of the position and momentum operators "x" and "p" to the expectation value of the force