Electrical Conductivity and Thermal Dilepton Rates

There is the recent paper thats come up by the Bielefeld group on an accurate calculation of  the vector current correlation function in the deconfined phase. This is the arXived link to the paper: http://arxiv.org/abs/1012.4963 . I happened to present this paper in our journal club in TIFR, so I'll be able to quote a summary pretty easily.
The main methodology adopted in the paper is an accurate calculation of the continuum correlation function. This is essentially done by taking the continuum limit on N_t = 16, 24,36 and 48 lattices. An 1/N_t ² extrapolation is done to get the continuum correlation functions. Note that N_t =16 data are not used in the extrapolation.
The further technology introduced is the Taylor expansion of the vector correlation functions about τT = 1/2. The deviations from the free field correlation functions are studied in detail, leading to the conclusion that for the interacting theory at 1.45 T_c, these ratios are never more than 10% at most for all τ values. Therefore, they conclude that the spectral function ansatz for the free theory, suitably modified to take into account behavior of the interacting theory in the low energy (e.g. smear out the exact δ(ω) function present in the spatial channel of the spectral function into a Breit-Wigner form) and the high-energy (perturbative corrections to the free field results) should describe the data: and it actually does. Doing an MEM over these results see small improvements. Note that the default model used for the MEM analysis are the parameters used to model the spectral functions and determined by fits to the extrapolated continuum correlation function. Using a free theory default model kills of the contribution at the origin and hence gives an unphysical value of the electral conductivity.
A final comment on the results: They conclude that σ/T ~ (0.37 ± 0.01) C_em calculated from the fits, while a more conservative estimate can be made from changing the functional form used to represent the spectral function (and consistent with the MEM error estimate) is 1/3 C_em <~ σ/T <~ 1 C_em. Contrast this with previous estimates: a) by Aarts et al (2007): 0.4 ± 0.1 C_em and b) by S Gupta (2004) ~ 7 C_em.