Effective Relativistic Species Through a Bounce: A Bound on Additional Radiation from the Expansion History
Year: 2026
Type: article
Abstract: The effective number of relativistic species, conventionally near 3.044 in the standard model, is a compact summary of how much radiation-like energy the early universe contained beyond photons. At a bounce temperature of 3 MeV the equivalent shift is 0.122, giving an effective count of 3.166 against the observed 2.99 with an uncertainty of 0.17; at 10 MeV the shift falls to 0.011. The species count thus independently disfavours a bounce lying within a small factor of the nucleosynthesis temperature, reinforcing the abundance bounds through a channel that depends on the expansion rate alone rather than on any individual nuclear reaction. Computed from stated assumptions, not measured.
Author: Aldred, William Alexander
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225811681
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