Abstract

It has now been over 50 and 25 years since the establishment of the Standard Models of particle physics and cosmology, respectively. Over this time, both have withstood a wide range of experimental tests. Still, several key questions about their ingredients remain, such as the model of inflation, the nature of dark matter, the form of dark energy and the masses of the neutrino species. We will show that line-intensity mapping is uniquely poised to probe all of these questions and also shed light on some of the tensions in current data. Line-intensity mapping (LIM) is an emerging approach to survey the Universe, using relatively low-aperture instruments to scan large portions of the sky and collect the total spectral-line emission from galaxies and the intergalactic medium. Mapping the intensity fluctuations of an array of atomic and molecular emission lines offers a unique opportunity to probe redshifts well beyond the reach of other cosmological observations, access regimes that cannot be explored otherwise, and exploit the enormous potential of cross-correlations with other measurements. Over the next decade, LIM will transition from a pathfinder era of first detections to an early-science era where data from more than a dozen missions will be harvested to yield new insights and discoveries. I will review the primary target lines for these missions and motivate the opportunities for synergy with other observables. I will then briefly survey how each of the Standard Model puzzles above can be uniquely probed with LIM, provided that degeneracies between astrophysics and cosmology are carefully taken into account.