Century of Λ

Abstract

The cosmological constant was proposed 100 years ago in order to make the model of static Universe, imagined then by most scientists, possible. Today it is the main candidate for the physical essence causing the observed accelerated expansion of our Universe. But, as well as a hundred years ago, its nature is unknown. This paper is devoted to the story of invention of Λ by Albert Einstein in 1917, rejection of it by him in 1931 and returning of it into the great science by other scientists during the century. The aim is to once again emphasize prominent role of cosmological constant in the development of ideas of modern physics and cosmology, focusing on the main points and publications, the choice of which may have a certain part of subjectivity.

Observational Constraints on Tensor Perturbations in Cosmological Models with Dynamical Dark Energy

“…Reconstructed potentials of the dark energy scalar field are shown in Fig. 2 (more details on reconstruction of the potentials for fields with c 2 a = 0 can be found in [9], for quintessential fields with arbitrary c 2 a in [10]; the impact of uncertainties in the cosmological parameters determination on the reconstructed potentials for w = const was analyzed in [11] and for c 2 s = const was estimated in [12]). We see the phantom fields slowly rolling up the potentials for mean values of parameters, their 1σ and 2σ lower confidence limits, as well as the quintessence fields slowly rolling down the potentials for 1σ and 2σ upper confidence limits during the evolution of the Universe from a = 0.001 to 1.…”

Constraints on the dark energy with barotropic equation of state: assessing the importance of different observations

“…• Planck: data on the TT, TE, EE spectra and lensing [8] (the usefulness of EE spectra to distinguish between different subclasses of the dark energy models with barotropic EoS was forecasted in [2,3]);…”

“…One of the simplest alternatives to Λ is the dynamical dark energy in form of the minimally coupled classical scalar field. In previous papers (e. g. [2,3,4]) we have introduced and studied in detail such field with the barotropic equation of state. This model involves both quintessential and phantom subclasses, its equation of state parameter and energy density have the analytical form applicable at any time during the past history of the Universe.…”

Two sides of the same coin: sterile neutrinos and dark radiation. Status and perspectives

“…[2][3][4][5]), while dark energy is phenomenologically very similar to a cosmological constant and it is responsible for the recent acceleration of the Universe expansion (see e.g. [6][7][8][9][10][11]). While we have solid evidence that dark matter and dark energy exist, although we ignore their nature, they may not be the only non-standard "dark" components of the Universe.…”