Constraining Primordial Non-Gaussianities from the WMAP2 2-1 Cumulant   Correlator Power Spectrum
  We measure the 2-1 cumulant correlator power spectrum $C^{21}_l$, a degenerate bispectrum, from the second data release of the Wilkinson Microwave Anisotropy Probe (WMAP). Our high resolution measurements with SpICE span a large configuration space ($\simeq 168\times999$) corresponding to the possible cross-correlations of the maps recorded by the different differencing assemblies. We present a novel method to recover the eigenmodes of the correspondingly large Monte Carlo covariance matrix. We examine its eigenvalue spectrum and use random matrix theory to show that the off diagonal terms are dominated by noise. We minimize the $\chi^2$ to obtain constraints for the non-linear coupling parameter $f_{NL} = 22 \pm 52 (1\sigma)$. 
Gang Chen and Istvan Szapudi