Polarization Measures And Nature Of Dark Energy

Polarization measures, on wide angular scales, together with anisotropy data, can fix DE parameters. Here we discuss the sensitivity needed to provide significant limits. Our analysis puts in evidence that a class of models predicts low correlation or anticorrelation between polarization and anisotropy at low l. This class includes open models and models with DE due to a Ratra--Peebles (RP) potential. Results on this point, given in a previous paper of ours, are updated and partially corrected. We outline that, with the sensitivity of experiments like SPOrt or WMAP, high values of Lambda (energy scale in the RP potential) can be excluded. With the sensitivity expected for PLANCK, the selection will extend to much lower Lambda's.