Merger Rate Decline (Z>2)

Galaxy merger rates reconstructed from morphological disturbance statistics and pair counts show a pronounced decline at z > 2 that is steeper than ΛCDM's halo merger tree predictions. In the standard model, merger rates are set by halo-halo collision cross sections within the growing large-scale structure, and these rates should rise continuously toward higher redshift as halos are more closely packed and velocities are higher. The observed steeper decline of visible mergers above z~2 appears to contradict this expectation, suggesting that either the morphological indicators of merging become unreliable at high redshift or that the physical merger rate itself was suppressed in the early universe. Successive Collision Theory resolves this through the angular momentum inheritance framework. The high angular momentum inherited from the original collision event imparts large centrifugal support to early galaxies, increasing their effective radii and dispersing their orbital velocity distributions in ways that reduce the geometrical cross section for close galaxy-galaxy encounters.

More specifically, the early post-collision universe in SCT is dominated by rapidly rotating, angularly supported gas and stellar systems with high specific angular momentum. The orbital parameters of galaxies within their parent halos are set by the inherited angular momentum, which preferentially produces nearly circular orbits rather than the radial infall orbits that drive mergers. As the tensor mesh dissipates over cosmic time from z~2 to the present, the effective gravitational binding weakens at the halo level, reducing the circular orbit speed and allowing more radial orbits to develop — increasing the merger rate at late times relative to early times. The observed merger rate decline above z~2 is thus a temporal signature of the angular momentum inheritance: at early times the inherited angular momentum dominates orbital geometry and suppresses mergers; at late times the decaying mesh reduces centrifugal support and mergers become more frequent, explaining the observed rise in merger rate from z~2 to the present.