Can the Li7 problem be resolved by increasing the dark matter ratio?

[BillSaltLake]

Currently the WMAP results give a baryon:photon ratio of ~6.2x10^-10, and a dark:baryonic mass ratio of ~5. When added to the energy density of photons + neutrinos (+dark energy at later times), the total density is then critical for a flat Universe. The BB nucleosynthesis analysis of the relative abundance of 4He, D, 3He, and 7Li strongly suggest that the baryon:photon ratio is <4.5x10^-10 with 4-5 sigmas confidence level (excluding some kind of likely systematic error in 7Li) See figs 3 and 4 of

http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.2818v1.pdf

If the dark:baryonic mass ratio remains ~5, and we believe the 7Li results, this would put the energy density at the CMB last scattering surface at only ~79% of critical. Can this be fixed simply by increasing the dark:baryonic mass ratio, or is there some independent reason the ratio must be 5?

 

[Chalnoth]

WMAP already constrains the baryon/dark matter ratio incredibly tightly. You just can't change that ratio much without altering the power spectrum of the CMB far outside of WMAP's measurement errors.

What this may be telling us, however, is something interesting about the temperature of the dark matter. If the dark matter has some non-zero temperature, it may potentially have some impact on BBN. However, I strongly suspect that the real answer lies in stellar physics, not in BBN.

 

[twofish-quant]

However, I strongly suspect that the real answer lies in stellar physics, not in BBN.

Same here. My first guess would be that the Li-7 was burned up by Pop III stars. (What pop III stars? Well the same one's that magically produced the heavy elements in quasars.)

It's easier to burn up light elements than to produce them.

 

[Chronos]

I sympathize with Twofish. There is a lot about pop III stars we do not have a handle on [not to mention stellar processes in general]. Obviously, the early universe was more heavily polluted by metallicity than expected by theory.

 

[sardar]

I would say that increasing the dark matter ratio may not necessarily resolve the Li7 problem. While it is true that increasing the dark:baryonic mass ratio would increase the overall energy density and potentially bring it closer to the critical value for a flat universe, there are other factors at play that could affect the abundance of Li7.

Firstly, there could be systematic errors in the measurement of Li7 that are not accounted for in the analysis. This could potentially explain the discrepancy between the observed abundance and the predicted abundance based on the baryon:photon ratio. It is important to thoroughly investigate and address any potential sources of error before making conclusions about the role of dark matter in this problem.

Additionally, there may be other processes at play that affect the abundance of Li7, such as stellar nucleosynthesis or cosmic ray interactions. These processes could also contribute to the observed abundance and should be taken into consideration when trying to resolve the Li7 problem.

Furthermore, while the dark:baryonic mass ratio is currently estimated to be around 5, this value is not set in stone and could potentially change as our understanding of dark matter evolves. It is important to continue studying and researching dark matter in order to better understand its properties and potential effects on the universe.

In summary, while increasing the dark matter ratio may have some impact on the Li7 problem, it is not a straightforward solution and other factors must be considered. Further research and analysis is needed to fully understand the role of dark matter in this issue.