New probes of fundamental physics: Utilising small-scale signatures in the Universe.

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The influx of new and high-quality cosmological data from upcoming cosmic microwave background (CMB) and large-scale structure surveys will provide unique and exciting opportunities to study the fundamental constituents of the Universe in the upcoming few years. In particular, measurements of second-order effects in the CMB will become observationally significant for the fist time as surveys will achieve the necessary precision. Such second-order effects include weak gravitational lensing by large-scale structure; the integrated Sachs-Wolfe and Rees-Sciama effects, which describe the redshift effect on CMB photons due to evolving gravitational potentials along the line of sight; and the Sunyaev-Zel'dovich effect where CMB photons Compton scatter with free electrons in galaxy clusters and the intergalactic medium. In parallel, surveys of the 21cm hydrogen line will achieve sufficient accuracy for cosmological inference. In this talk I will describe how these new cosmological probes provide opportunities to study old fundamental problems. I will focus on two new probes: the moving lens effect on the CMB (Hotinli 2019, PRL) and the velocity acoustic oscillations (`so-called' VAOs) in the 21cm hydrogen. I will describe how these observables can be utilised to constrain a class of early Universe models.