 Higgs mechanism. According to a “mechanism” established in a general way in 1964 independently by (i) P. Higgs, (ii) R. Brout and F. Englert, and (iii) G. S. Guralnik, C. R. Hagen and T. W. B. Kibble, in the case that the internal symmetry is promoted to a local one, the Goldstone bosons “disappear” and the gauge bosons acquire a mass. The Goldstone bosons are “eaten up” to give mass to the gauge bosons, and this happens without (explicitly) breaking the gauge invariance of the theory. Note that this mechanism for the mass generation for the gauge fields is also what ensures the renormalizability of theories involving massive gauge fields (such as the Glashow-Weinberg-Salam electroweak theory developed in the second half of the 1960s), as first generally demonstrated by M. Veltman and G. ’t Hooft in the early 1970s. (The Higgs mechanism it at the center of a lively debate among philosophers of physics: see, for example, Smeenk, 2006; Lyre, 2008; Struyve, 2011; Friederich, 2013. For a historical-philosophical analysis, see also Borrelli, 2012.)