“…For interacting fermions, γ(T ) is not an analytic function of T 2 ; the leading temperature dependence is instead proportional to T 2 ln(T ) in three dimensions (3D) and T in 2D The T 2 ln T term was first found by Eliashberg in a theoretical study of electrons interacting with acoustic phonons [5], and the possibility of a nonanalytic temperature dependence of γ was subsequently (but apparently independently) inferred from measurements of γ for 3 He by Abel, Wheately and Andersen [1]. The 3 He measurements led to a large literature [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30] which we review in detail below. We note here a few crucial (and seemingly contradictory) results.…”