Coupling dependence of jet quenching in hot strongly-coupled gauge theories

Abstract

Previous top-down studies of jet stopping in strongly-coupled QCD-like plasmas with gravity duals have been in the infinite 't Hooft coupling limit lambda -> infinity. They have found that, though a wide range of jet stopping distances are possible depending on initial conditions, the maximum jet stopping distance l_max scales with energy as E^(1/3) at large energy. But it has always been unclear whether the large-coupling and high-energy limits commute. In this paper, we use the string alpha' expansion in AdS-CFT to study the corrections to the lambda=infinity result in powers of 1/lambda. For the particular type of "jets" that we study, we find that (i) the naive expansion in 1/lambda breaks down for certain initial conditions but (ii) the relative corrections to the maximum stopping distance are small when 1/lambda is small. More specifically, we find that the expansion in 1/lambda is well behaved for jets whose stopping distance l_stop is in the range lambda^(-1/6) l_max << l_stop <~ l_max, but the expansion breaks down (and the fate of lambda=infinity results is uncertain) for jets created in such a way that l_stop << lambda^(-1/6) l_max. The analysis requires assessing the effects of all higher-derivative corrections to the supergravity action for the gravity dual.