Constraints on dark energy and quintessence with a comoving standard   ruler applied to 2dF quasars
  Structures on very large scales (> 100 Mpc) have negligible peculiar motions, and are thus roughly fixed in comoving space. We looked for significant peaks at very large separation in the two-point correlation function -- corrected for redshift selection effects -- of a well convered subsample of 2378 quasars of the recently released 10k sample of the 2dF quasar survey. Dividing our sample in three redshift intervals, we find a peak at 244/h Mpc, which is perfectly comoving for a restricted set of cosmological parameters, namely Omega_m = 0.25+/-0.15 and Omega_Lambda=0.65+/-0.35 (both at 95% confidence). Assuming a flat Universe, we constrain the quintessence parameter w_Q < -0.35 (95% confidence). We discuss the compatibility of our analysis with possible peaks in the power spectrum. 
Gary A. Mamon (1,2), Boud F. Roukema (3) ((1) IAP, Paris, France (2)   GEPI, Obs. de Paris, (3) Torun Ctr for Cosmology, Uni...