Which field of science was the Belgian scientist, Robert Brout involved in?

Robert Brout (June 14, 1928 – May 3, 2011) was a Belgian theoretical physicist who made significant contributions in elementary particle physics. He was a Professor of Physics at Université Libre de Bruxelles where he had created, together with François Englert, the Service de Physique Théorique.

In addition to this work on elementary particle physics, in 1978, Brout, in collaboration with F. Englert and E. Gunzig, was awarded the first prize gravitational award essay for their original proposal of cosmic inflation as the condition of the cosmos prior to the adiabatic expansion, (i.e. the conventional big bang), after cosmogenesis.

Awards

Brout was awarded the 2010 J. J. Sakurai Prize for Theoretical Particle Physics (with Guralnik, Hagen, Kibble, Higgs, and Englert) by The American Physical Society "For elucidation of the properties of spontaneous symmetry breaking in four-dimensional relativistic gauge theory and of the mechanism for the consistent generation of vector boson masses."

Robert Brout contributed greatly to the theory behind the Higgs Boson (an elementary particle in the Standard Model of particle physics), for which the 2013 Nobel Prize was awarded. In a 2014 interview with BBC's 'The Life Scientific' Peter Higgs says of the 2013 Nobel Prize that "I think it's good that they restricted the prize to the two of us, because, by implication, they're recognizing Robert Brout as the third who couldn't be awarded the prize.