Can ambipolar diffusion solve the cosmic lithium problem?

Recent WMAP observations indicate that the primordial abundance of lithium should have been 2-4 times higher than the value measured in low-metallicity stars. We show that this discrepancy can be explained by the process of ambipolar diffusion in protostellar clouds, which leads to depletion of elements with low ionization potential, such as lithium and sodium. In high-metallicity stars, [Fe/H]>~-1, the depletion of lithium due to this process is found to be negligible, but for [Fe/H]<~-1.5 the lithium abundance falls by a factor of ~3, consistent with WMAP observations.