The large-scale maximum at k \simeq 0.05 h / { Mpc } identified in the power-spectrum of galaxy fluctuations provides a co-moving scale for measuring cosmological curvature .
In shallow 3D surveys the peak is broad , but appears to be well resolved in 1D , at \sim 130 h ^ { -1 } { Mpc } ( k = 0.048 h / { Mpc } ) , comprising evenly spaced peaks and troughs .
Surprisingly similar behaviour is evident at z \sim 3 in the distribution of Lyman-break galaxies , for which we find a 5 \sigma excess of pairs separated by \Delta z \simeq 0.22 \pm 0.02 , equivalent to 85 h ^ { -1 } { Mpc } for \Omega = 1 , increasing to 170 h ^ { -1 } { Mpc } for \Omega = 0 , with a number density contrast of 30 % averaged over 5 independent fields .
The combination , 3.2 \Omega _ { m } - \Omega _ { \Lambda } \simeq 0.7 , matches the local scale of 130 h ^ { -1 } { Mpc } , i.e . \Omega = 0.2 \pm 0.1 or \Omega _ { m } ^ { flat } = 0.4 \pm 0.1 for the matter-dominated and flat models respectively , with an uncertainty given by the width of the excess correlation .
The consistency here of the flat model with SNIa based claims is encouraging , but overshadowed by the high degree of coherence observed in 1D compared with conventional Gaussian models of structure formation .
The appearance of this scale at high redshift and its local prominence in the distribution of Abell clusters lends support to claims that the high- z ‘ spikes ’ represent young clusters .
Finally we show that a spike in the primordial power spectrum of \delta \rho / \rho \simeq 0.3 at k = 0.05 h / { Mpc } has little effect on the CMB , except to exaggerate the first Doppler peak in flat matter-dominated models , consistent with recent observations .