Total Entropy Budget of the Observable Universe Before and After a Density-Limited Bounce
Year: 2026
Type: article
Abstract: Black holes dominate the contents budget by many orders of magnitude, while photons and neutrinos, which dominate textbook discussions of cosmic entropy, are a minor share. The horizon bound sits far above even the black-hole total, so the present contents are nowhere near the maximum the geometry allows. Across an adiabatic bounce the contents total changes only at the few-percent level set by particle creation, so the budget after the bounce is recognisably the budget before it. 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_photons_kB = 5.28e+89; S_neutrinos_kB = 3.59e+89; S_blackholes_kB = 1.05e+99; S_horizon_kB = 2.33e+123; S_total_matter_kB = 1.05e+99; S_total_after_kB = 1.10e+99; fraction_BH = 1. The study is simulated and computed, not measured, and its conclusions are stated at the precision the stated assumptions support.
Author: Aldred, William Alexander
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225779361
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