Elliptic Flow Fluctuations in Nucleus-Nucleus Collisions

Measurements of elliptic flow in high-energy nucleus-nucleus suggest that in these collisions a strongly interacting medium is formed. The expansion of this medium appears to be well described by ideal hydrodynamics. Further information about the properties of the medium and the hydrodynamic evolution can be obtained by studying not just the average strength of elliptic flow, , but also event-by-event fluctuations in the elliptic flow coefficient, v2. However, the quantitative interpretation of current measurements of v2 fluctuations is complicated by the presence of multi-particle correlations between final state hadrons. We will discuss the status of v2 fluctuation measurements, the influence of non-flow particle correlations and possible approaches to obtain the '' true '' v2 fluctuation strength. (author)