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The pre-Galactic abundance of lithium offers a unique window into non-thermalcosmological processes. The primordial Li abundance is guaranteed to be presentand probes big bang nucleosynthesis (BBN), while an additional Li component islikely to have been produced by cosmic rays accelerated in large scalestructure formation. Pre-Galactic Li currently can only be observed in lowmetallicity Galactic halo stars, but abundance measurements are plagued withsystematic uncertainties due to modeling of stellar atmospheres and convection.We propose a new site for measuring pre-Galactic Li: low-metallicity,high-velocity clouds (HVCs) which are likely to be extragalactic gas accretedonto the Milky Way, and which already have been found to have deuteriumabundances consistent with primordial. A Li observation in such an HVC wouldprovide the first extragalactic Li measurement, and could shed new light on theapparent discrepancy between BBN predictions and halo star Li abundancedeterminations. Furthermore, HVC Li could at the same time test for thepresence of non-primordial Li due to cosmic rays. The observability ofelemental and isotopic Li abundances is discussed, and candidate sitesidentified.Comment: 10 pages, AASTe

Probing Primordial and Pre-Galactic Lithium with High-Velocity Clouds