Institute for Advanced Study/Princeton University Early Universe/Cosmology Lunch Discussion

Abstract 1: I will discuss gravitational waves (GWs) induced by a heavy spectator field that starts to oscillate during inflation. During the oscillation of the spectator field, its effective mass can also oscillate in some potentials. This mass oscillation can resonantly amplify the spectator field fluctuations. I will show that these amplified fluctuations can induce large GWs, which could be investigated by future gravitational wave observations. This kind of induced GWs can be produced even if the spectator field does not have any interaction with other fields except for gravitational interaction. This talk will be based on arXiv:2203.04974.

Abstract 2: Aligned, extended structure is the dominant feature of the cosmic web. From filaments that bridge neighboring galaxy clusters to superclusters extending over hundreds of megaparsecs, these multi-scale structures are complicated to measure yet full of cosmological information. I will present novel ways to apply oriented stacking methods to measure the anisotropic superclustering of gas and galaxies. The methods combine large-scale structure information from optical galaxy survey data (the Dark Energy Survey) with thermal Sunyaev-Zel’dovich maps from Atacama Cosmology Telescope millimeter-wavelength data. This combination yields a 3.5-sigma detection of anisotropic superclustering in the hot gas around galaxy clusters. Improved data from ACT Data Release 6 will enable deeper analysis of these measurements, in particular to compare the relationship of galaxies and gas in filaments and measure the evolution of non-Gaussianities in the late-time universe. I will also discuss future plans to use simulations of the dark matter and baryons to advance this method as a probe of dark energy.