One hundred years of the cosmological constant: from “superfluous stunt” to dark energy

Abstract

We present a centennial review of the history of the term known as the cosmological constant. First introduced to the general theory of relativity by Einstein in 1917 in order to describe a universe that was assumed to be static, the term fell from favour in the wake of the discovery of the expanding universe, only to make a dramatic return in recent times. We consider historical and philosophical aspects of the cosmological constant over four main epochs; (i) the use of the term in static cosmologies (both Newtonian and relativistic): (ii) the marginalization of the term following the discovery of cosmic expansion: (iii) the use of the term to address specific cosmic puzzles such as the timespan of expansion, the formation of galaxies and the redshifts of the quasars: (iv) the re-emergence of the term in today's Λ-CDM cosmology. We find that the cosmological constant was never truly banished from theoretical models of the universe, but was marginalized by astronomers for reasons of convenience. We also find that the return of the term to the forefront of modern cosmology did not occur as an abrupt paradigm shift due to one particular set of observations, but as the result of a number of empirical advances such as the measurement of present cosmic expansion using the Hubble Space Telescope, the measurement of past expansion using type SN 1a supernovae as standard candles, and the measurement of perturbations in the cosmic microwave background by balloon and satellite. We give a brief overview of contemporary interpretations of the physics underlying the cosmic constant and conclude with a synopsis of the famous cosmological constant problem.

$$H_0$$ tension: clue to common nature of dark sector?

“…The Hubble-Lemaître law originally was established for a sample of nearby galaxies, which are members of the Local Group. For them the empirical Hubble-Lemaître law seemed to confirm the FLRW equations, however, later it became clear that not only the galaxies have their peculiar velocities but the Local Group itself is gravitationally bounded to a larger configuration; see [14]. In other words, that law was observed at scales for which it should not be observed.…”

Century of Λ

“…5 Λ: vacuum, inflation, clusters of galaxies and quasars Despite Einstein's scepticism about the possibility of realisation of cosmological constant in the nature, it continued to live its own life in the minds of physicists and cosmologists. Georges Lemaître, Richard Tolman, Willem de Sitter, Arthur Eddington and other remained its supporters (for more details see [O'Raifeartaigh 2018]). In 1934 G. Lemaître has suggested that since the energy associated with it is Lorentz invariant, then the cosmological constant is the vacuum energy density [Lemaître 1934].…”

“…In this paper, devoted to the century of cosmological constant, we briefly review the motivation of its including in general relativity, using it for interpretation of the cosmological observations and the unsuccessful attempts to give it some fundamental meaning. The comprehensive historical review of the story of the cosmological constant one can find in the recent papers [O'Raifeartaigh 2017, O'Raifeartaigh 2018 as well as the complete list of publications devoted to it. a e-mail: bnovos@gmail.com 2 "Cosmological Considerations on the General Theory of Relativity"…”

A Possible Solution for the Cosmological Constant Problem

“…The well-known Weinberg review of 1989 [12] referenced about one hundred papers dealing with the problem of the cosmological constant. After the discovery of the acceleration of the expansion of the Universe, many thousands of articles were published [14]. However the vacuum fluctuations may not contribute to the cosmological constant [15].…”