The main ideas, technical concepts and perspectives for a mode resolved
description of the hydrodynamical regime of relativistic heavy ion collisions
are discussed. A background-fluctuation splitting and a Bessel-Fourier
expansion for the fluctuating part of the hydrodynamical fields allows for a
complete characterization of initial conditions, the fluid dynamical
propagation of single modes, the study of interaction effects between modes,
the determination of the associated particle spectra and the generalization of
the whole program to event-by-event correlations and probability distributions.Comment: 6 pages, 1 figure, Plenary contribution to the International
Conference on the Initial Stages of High-Energy Nuclear Collisions 2013
(IS2013
