Snowmass2021 Theory Frontier White Paper: Data-Driven Cosmology

Abstract

Over the past few decades, astronomical and cosmological data sets firmly established the existence of physics beyond the Standard Model of particle physics by providing strong evidence for the existence of dark matter, dark energy, and non-zero neutrino mass. In addition, the generation of primordial perturbations most likely also relies on physics beyond the Standard Model of particle physics. Theory work, ranging from models of the early universe in string theory that that led to novel phenomenological predictions to the development of effective field theories to large-scale cosmological simulations that include the physics of galaxy evolution, has played a key role in analyzing and interpreting these data sets and in suggesting novel paths forward to isolate the origins of this new physics. Over the next decade, even more sensitive surveys are beginning to take data and are being planned. In this white paper, we describe key areas of the theory program that will be needed to optimize the physics return on investment from these new observational opportunities.

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

“…In this section, we will highlight a few concrete examples where theoretical and analysis techniques are essential and require future investment. See [1,2,36,[240][241][242] and reference therein for a more thorough discussion of the theoretical implications described below.…”

“…The current leading scenario for the origin of structure in our Universe is cosmic inflation, a period of accelerated expansion prior to the hot big bang, as discussed in the dedicated Snowmass 2021 White Papers [1,2], also see [3,4]. Quantum fluctuations during inflation were blown up to large scales, and manifest as density perturbations in the hot particle plasma that followed -these perturbations are visible in the primordial power spectrum.…”

“…Measurements to date determine the scale of the background evolution f , which in the case of conventional slow roll inflation is given by the speed of the background scalar field, f 2 = | φ|. The spectral tilt, n s , encodes the time evolution of inflationary parameters such as ≡ − Ḣ/H 2 1. Future probes of inflation target three parameters, A t , f NL and A lin .…”

Toward accurate measurement of property-dependent galaxy clustering: II. Tests of the smoothed density-corrected $V_{\rm max}$ method

“…Massive amounts of data from deeper in the sky will provide new insights into the physics of galaxy formation, as well as the nature of dark matter and dark energy (Hahn et al 2022). Galaxy two-point statistics, being one of the most fundamental tools, will continue to play a crucial role in future data analysis (Valluri et al 2022;Amin et al 2022), as they have in the past (Zehavi et al 2011;Nuza et al 2013;Skibba et al 2014;Samushia et al 2014;Guo et al 2014;Planck Collaboration et al 2016;Shi et al 2018). Due to different systematics, it is still difficult to reliably measure small-scale property-dependent galaxy clustering at the present time.…”

The MegaMapper: A Stage-5 Spectroscopic Instrument Concept for the Study of Inflation and Dark Energy

“…The mechanisms driving the accelerated expansion of the Universe in its very first moments (Inflation) and at late times (Dark Energy) represent some of the most important open problems in fundamental physics, and have been the subject of several of the Snowmass Community Science White Papers [e.g., [1][2][3][4][5]. We refer readers to those papers, and the questions therein, which have informed the development of the MegaMapper concept.…”