Loeb, AbrahamWyithe, J. Stuart B.2019-09-272008-04-22Loeb, Abraham, and J. Stuart B. Wyithe. 2008. “Possibility of Precise Measurement of the Cosmological Power Spectrum with a Dedicated Survey of 21 Cm Emission after Reionization.” Physical Review Letters 100 (16). https://doi.org/10.1103/physrevlett.100.161301.0031-90071079-71141092-0145http://nrs.harvard.edu/urn-3:HUL.InstRepos:41417318Measurements of the 21 cm line emission by residual cosmic hydrogen after reionization can be used to trace the power spectrum of density perturbations through a significant fraction of the observable volume of the Universe. We show that a dedicated 21 cm observatory could probe a number of independent modes that is 2 orders of magnitude larger than currently available, and enable a cosmic-variance limited detection of the signature of a neutrino mass similar to 0.05 eV. The evolution of the linear growth factor with redshift could also constrain exotic theories of gravity or dark energy to an unprecedented precision.en-USJournal Article2019-09-2710.1103/PhysRevLett.100.161301