UMN-TH-3037/12

FTPI-MINN-12/10

March 2012

Standard Big Bang Nucleosynthesis at the baryon density determined by the microwave anisotropy spectrum predicts an excess of ^ { 7 } { Li } 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 ^ { 7 } { Li } 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 .