The Arrow of Time Across a Symmetric Bounce: A Computed Two-Branch Test

The construction is exactly symmetric at the precision computed: observers on the far branch would record entropy increasing away from the bounce, which from our side reads as increasing toward the past. Each branch has a consistent internal arrow, and neither branch's inhabitants could use thermodynamics alone to determine which side of the bounce they occupy. The computation is performed from stated assumptions in a density-limited bounce, in which the neutron-branch limit density sets a maximum density, a finite bounce temperature, and a minimum horizon size. Headline values from the deposited calculation are: S_min_kB = 1.00e+87; S_plus_age_kB = 1.54e+91; S_minus_age_kB = 1.54e+91; S_plus_1Gyr_kB = 3.01e+89; symmetry_residual = 0; dSdt_today_kB_per_s = 5.31e+73. The study is simulated and computed, not measured, and its conclusions are stated at the precision the stated assumptions support.