Higher D or Li: Probes of Physics beyond the Standard Model

TL;DR

This paper discusses discrepancies in Big Bang Nucleosynthesis predictions for lithium-7 and deuterium, proposing that observed variations in D/H may be due to local destruction processes, impacting our understanding of early universe chemistry.

Contribution

It introduces the idea that observed D/H variations are influenced by local destruction, affecting interpretations of primordial abundances and BBN models.

Findings

Systems with D/H ~4×10^{-5} are likely more representative of primordial values.

Deuterium destruction in local environments can explain the dispersion in observed D/H.

Alterations in nuclear processes during BBN can reconcile lithium and deuterium observations.

Abstract

Standard Big Bang Nucleosynthesis at the baryon density determined by the microwave anisotropy spectrum predicts an excess of \li7 compared to observations by a factor of 4-5. In contrast, BBN predictions for D/H are somewhat below (but within ~2 \sigma) of the weighted mean of observationally determined values from quasar absorption systems. Solutions to the \li7 problem which alter the nuclear processes during or subsequent to BBN, often lead to a significant increase in the deuterium abundance consistent with the highest values of D/H seen in absorption systems. Furthermore, the observed D/H abundances show considerable dispersion. Here, we argue that those systems with D/H \simeq 4 \times 10^{-5} may be more representative of the primordial abundance and as a consequence, those systems with lower D/H would necessarily have been subject to local processes of deuterium destruction. This can be accounted for by models of cosmic chemical evolution able to destroy in situ Deuterium due to the fragility of this isotope.