Question: Who was the Dutch theoretical physicist that created the 't Hooft η symbol?
Context: The 't Hooft η symbol is a symbol which allows one to express the generators of the SU(2) Lie algebra in terms of the generators of Lorentz algebra.  The symbol is a blend between the Kronecker delta and the Levi-Civita symbol.  It was introduced by Gerard 't Hooft.  It is used in the construction of the BPST instanton. Hendrik Philip "Haas" Visser 't Hooft (September 20, 1905 in Haarlem – July 28, 1977 in Velp) was a Dutch field hockey player who competed in the 1928 Summer Olympics. In theoretical physics, a 't Hooft operator, introduced by Gerard 't Hooft in the 1978 paper "On the phase transition towards permanent quark confinement", is a dual version of the Wilson loop in which the electromagnetic potential "A" is replaced by its electromagnetic dual "A", where the exterior derivative of "A" is equal to the Hodge dual of the exterior derivative of "A".  In d spacetime dimensions, "A" is a (d-3)-form and so the 't Hooft operator is the integral of "A" over a (d-3)-dimensional surface. The holographic principle is a principle of string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region—preferably a light-like boundary like a gravitational horizon.  First proposed by Gerard 't Hooft, it was given a precise string-theory interpretation by Leonard Susskind who combined his ideas with previous ones of 't Hooft and Charles Thorn.  As pointed out by Raphael Bousso, Thorn observed in 1978 that string theory admits a lower-dimensional description in which gravity emerges from it in what would now be called a holographic way. Martinus Justinus Godefriedus "Tini" Veltman (] ; born 27 June 1931) is a Dutch theoretical physicist.  He shared the 1999 Nobel Prize in physics with his former student Gerardus 't Hooft for their work on particle theory. Einstein–Cartan–Evans theory or ECE theory was an attempted unified theory of physics proposed by the Welsh chemist and physicist Myron Wyn Evans (born May 26, 1950), which claimed to unify general relativity, quantum mechanics and electromagnetism.  The hypothesis was largely published in the journal "Foundations of Physics Letters" between 2003 and 2005.  Several of Evans' central claims were later shown to be mathematically incorrect and, in 2008, the new editor of "Foundations of Physics", Nobel laureate Gerard 't Hooft, published an editorial note effectively retracting the journal's support for the hypothesis. 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". Hooft or 't Hooft is a Dutch surname.  Notable people with the surname include: In quantum field theory, the anomaly matching condition by Gerard 't Hooft states that the calculation of any chiral anomaly for the flavor symmetry by using the degrees of freedom of the theory at some energy scale, must not depend on what scale is chosen for the calculation.  It is also known as 't Hooft UV-IR anomaly matching condition, where UV stand for the high-energy limit, and IR for the low-energy limit of the theory. In theoretical physics, the 't Hooft–Polyakov monopole is a topological soliton similar to the Dirac monopole but without any singularities.  It arises in the case of a Yang–Mills theory with a gauge group G, coupled to a Higgs field which spontaneously breaks it down to a smaller group H via the Higgs mechanism.  It was first found independently by Gerard 't Hooft and Alexander Polyakov.
Answer: Gerard 't Hooft