Report of the Topical Group on Cosmic Frontier 5 Dark Energy and Cosmic Acceleration: Cosmic Dawn and Before for Snowmass 2021

Abstract

This report summarizes the envisioned research activities as gathered from the Snowmass 2021 CF5 working group concerning Dark Energy and Cosmic Acceleration: Cosmic Dawn and Before. The scientific goals are to study inflation and to search for new physics through precision measurements of relic radiation from the early universe. The envisioned research activities for this decade (2025-35) are constructing and operating major facilities and developing critical enabling capabilities. The major facilities for this decade are the CMB-S4 project, a new Stage-V spectroscopic survey facility, and existing gravitational wave observatories. Enabling capabilities include aligning and investing in theory, computation and model building, and investing in new technologies needed for early universe studies in the following decade (2035+).

Light fields during inflation from BOSS and future galaxy surveys

“…where the operators O i (⃗ x) are any locally measurable quantities. Since we typically assume that the matter controls the formation of galaxies, these are usually local products of δ m (⃗ x) or the tidal tensor [54], [1] ) 3 ]| (3) , Tr[Π [1] Π [2] ]| (3) ,…”

“…[n] ij are defined in [52]. 2 In principle, there are an infinite number of operators to consider. At any fixed accuracy, we however understand this as an expansion in powers of the small density contrast, δ n m ≪ 1, and gradients R 2 ∇ 2 ≪ 1, for some fixed scale R. To model the galaxy power spectrum at one-loop order, we consider the following set of operators (up to third order in δ m ) in the bias expansion:…”

“…In table 1, we list the fiducial values of the ΛCDM, non-Gaussian and bias parameters. We set the fiducial values of the three loop biases b δ 2 , b s 2 and b ΠΠ [2] to 0 instead of using the Lagrangian local-in-matter-density model [52] and fit results from halo simulations [55], as we did in figure 2, since we cover a larger redshift range than the fitted bias relations were derived from. This choice should have minimal impact on the results of this paper because the forecasted constraints on the loop biases are large enough for both choices of fiducial values to be consistent with each other.…”

“…The statistics of the primordial density perturbations offer a window into the dynamics of the very early universe [1][2][3], in particular the inflationary epoch [4,5]. While current maps of the universe are consistent with purely Gaussian fluctuations [6], non-Gaussian correlation functions encode the particles and interactions relevant to the origin of structure [5,7,8].…”

“…Due to the limited number of modes remaining to be measured to the cosmic variance limit in the cosmic microwave background (CMB), surveys of the large-scale structure (LSS) of the universe present the best opportunity to improve our understanding of the primordial statistics [2,5,[11][12][13]. With the benefit of three-dimensional information, even current surveys have the raw statistical power to compete with the CMB [14].…”