Beyond ΛCDM: Problems, solutions, and the road ahead

By P. Bull, Yashar Akrami, J. Adamek, T. Baker, Emilio Bellini, J. Jim'enez, E. Bentivegna, S. Camera, S. Clesse, Jonathan H. Davis and 30 more. 2015

522 citations recorded by the source corpus.

Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/595bfb9d65d79210b74d338b0fb424c698be12ee

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Citations in the corpus

Stellar structure models in modified theories of gravity: Lessons and challenges (2019, background): “It has passed tests ranging from submilimiter to solar system scales [1], has been built in the concordance cosmological model [2], and has received further confirmation from the recent detection of gravitational waves consistently interpreted as emitted out of binary mergers [3], and by the imaging”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “Most of the problems of the two Standard Models motivate the exploration of new physics and modifications of gravity, both in the IR and the UV [18, 19, 20, 21, 22, 23, 24, 25].”
Born–Infeld inspired modifications of gravity (2017, background): “On the other hand, the observation of the accelerated expansion of the universe introduced the necessity of dark energy independently of the cosmological constant problem [25, 298, 124, 120, 16, 89, 224, 17].”
Heavy spin-2 Dark Matter (2016, background): “See [2] for a recent review of its status quo.”
Tension and constraints on modified gravity parametrizations of $G_{\textrm{eff}}(z)$ from growth rate and Planck data (2017, background): “Despite of the vast improvement in quality and quantity of the cosmological observations during the past 18 years, the simplest cosmological model predicting an accelerating expansion of the Universe, known as the ΛCDM [1], has remained viable and consistent with observations [2–4].”