The Radial Baryon Acoustic Oscillation Scale in a Bounced Cosmology: Direct Expansion Rates Against Survey Values

The radial baryon acoustic oscillation measurement returns the product of the expansion rate and the sound horizon at the tracer redshift, a direct reading of H(z) against a computed length. In the bounce frame both factors move, the horizon shrinking and the rate rising, and their product at epsilon = 0.10 changes by -3.57 percent at redshift 0.5, -2.45 percent at redshift 1.0, and -1.62 percent at redshift 1.5. Published radial precisions are near 2 to 3 percent in the best bins. The tolerance amplitude from the redshift-one bin is epsilon = 0.103. Combined with the transverse measurement, which responds differently to the same amplitude, the radial mode breaks the degeneracy between a changed horizon and a changed late expansion that either mode alone would leave open. This study is computed from stated assumptions, not measured.