Diagnostics of plasma photoemission at strong coupling

Abstract

We compute the spectrum of photons emitted by the finite-temperature large-N SU(N) ${\cal {N}}=4$ supersymmetric Yang-Mills plasma coupled to electromagnetism, at strong yet finite 't Hooft coupling. We work in the holographic dual description, extended by the inclusion of the full set of ${\cal{O}}(\alpha'^3)$ type IIB string theory operators that correct the minimal supergravity action. We find that, as the t' Hooft coupling decreases, the peak of the spectrum increases, and the momentum of maximal emission shifts towards the infra-red, as expected from weak-coupling computations. The total number of emitted photons also increases as the 't Hooft coupling weakens.