  Numerical and experimental data for the heat transfer as function of the
Rossby number Ro in turbulent rotating Rayleigh-B\'enard convection are
presented for Prandtl number Pr=4.38 and Rayleigh number $Ra=2.91\times10^8$ up
to $Ra=4.52\times10^9$. The aspect ratio \Gamma = D/L, where L is the height
and D the diameter of the cylindrical sample, is varied between \Gamma=0.5 and
\Gamma=2.0. Without rotation, where the aspect ratio influences the global
large scale circulation, we see a small aspect-ratio dependence in the Nusselt
number for $Ra=2.91\times10^8$. However, for stronger rotation, i.e. $1/Ro \gg
1/Ro_c$, the heat transport becomes independent of the aspect-ratio. We
interpret this finding as follows: In the rotating regime the heat is mainly
transported by vertically-aligned vortices. Since the vertically-aligned
vortices are local, the aspect ratio has a negligible effect on the heat
transport in the rotating regime. Indeed, a detailed analysis of vortex
statistics shows that the fraction of the horizontal area that is covered by
vortices is independent of the aspect ratio when $1/Ro \gg 1/Ro_c$. In
agreement with the results of Weiss et al. Phys. Rev. Lett., vol 105, 224501
(2010) we find a vortex-depleted area close to the sidewall. Here, we in
addition show that there is also an area with enhanced vortex concentration
next to the vortex-depleted edge region and that the absolute widths of both
regions are independent of the aspect ratio.
