Producing the Deuteron in Stars: Anthropic Limits on Fundamental Constants

Abstract

Stellar nucleosynthesis proceeds via the deuteron (D), but only a small change in the fundamental constants of nature is required to unbind it. Here, we investigate the effect of altering the binding energy of the deuteron on proton burning in stars. We find that the most definitive boundary in parameter space that divides probably life-permitting universes from probably life-prohibiting ones is between a bound and unbound deuteron. Due to neutrino losses, a ball of gas will undergo rapid cooling or stabilization by electron degeneracy pressure before it can form a stable, nuclear reaction-sustaining star. We also consider a less-bound deuteron, which changes the energetics of the $pp$ and $pep$ reactions. The transition to endothermic $pp$ and $pep$ reactions, and the resulting beta-decay instability of the deuteron, do not seem to present catastrophic problems for life.

19 pages, 5 figures. Accepted to JCAP. Revised to match the published version; corrected to better take into account free neutrons

References in corpus (11)

• Big-Bang Nucleosynthesis
• Dependence of nuclear binding on hadronic mass variation
• Stars In Other Universes: Stellar structure with different fundamental constants
• Quark mass variation constraints from Big Bang nucleosynthesis
• Constraints on the variability of quark masses from nuclear binding
• Low-energy theorems for nucleon-nucleon scattering at unphysical pion masses
• Anthropic tuning of the weak scale and of m_u/m_d in two-Higgs-doublet models
• Nuclear Astrophysics of Worlds in the String Landscape
• Low-energy theorems for nucleon-nucleon scattering at $M_{\pi }=450$ MeV
• On the Habitability of Universes without Stable Deuterium
• Binding the Diproton in Stars: Anthropic Limits on the Strength of Gravity

Cited by in corpus (7)

• The Degree of Fine-Tuning in our Universe -- and Others
• Sensitivity of Carbon and Oxygen Yields to the Triple-Alpha Resonance in Massive Stars
• Multiverse Predictions for Habitability: The Number of Stars and their Properties
• Multiverse Predictions for Habitability: Element Abundances
• Anthropics of Aluminum-26 Decay and Biological Homochirality
• Effects of Bound Diprotons and Enhanced Nuclear Reaction Rates on Stellar Evolution
• Multiverse Predictions for Habitability: Stellar and Atmospheric Habitability