  Since their discovery, fluctuations in the initial state of heavy-ion
collisions have been understood as originating mostly from the random positions
of nucleons within the colliding nuclei. We consider an alternative approach
where all the focus is on fluctuations generated by QCD interactions, that we
evaluate at leading logarithmic accuracy in the color glass condensate
effective theory. We validate our approach using BNL Relativistic Heavy Ion
Collider (RHIC) and CERN Large Hadron Collider (LHC) data on anisotropic flow.
In particular, we show that, compared to standard Glauber-inspired
calculations, our formalism provides a better description of the centrality
dependence of the ratio of elliptic flow and triangular flow. It also naturally
explains the evolution of elliptic flow fluctuations between RHIC and LHC
energies.
