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Abstract:
We perform a thorough examination of the neutrino mass (Mν) constraints achievable by combining future spectroscopic galaxy surveys with cosmic microwave background (CMB) experiments, focusing on the contribution of CMB lensing. CMB lensing can help by breaking the Mν-curvature degeneracy when combined with baryon acoustic oscillation (BAO)-only measurements, but we demonstrate this combination wastes a great deal of constraining power, as the broadband shape of the power spectrum contributes significantly to constraints. We also expand on previous work to demonstrate how cosmology-independent constraints on Mν can be extracted by combining measurements of the scale-dependence in the power spectrum caused by neutrino free-streaming with the full power of future CMB surveys. These free-streaming constraints are independent of the optical depth to the CMB (τ) and generally give stronger constraints alone on Mν than are given by the combination of BAOs and CMB lensing. Finally, we demonstrate that the effect of including the galaxy-CMB lensing cross power spectrum is negligible.