Direct reconstruction of dynamical dark energy from observational Hubble parameter data

Abstract

Reconstructing the evolution history of the dark energy equation of state parameter w(z) directly from observational data is highly valuable in cosmology, since it contains substantial clues in understanding the nature of the accelerated expansion of the Universe. Many works have focused on reconstructing w(z) using Type Ia supernova data, however, only a few studies pay attention to Hubble parameter data. In the present work, we explore the merit of Hubble parameter data and make an attempt to reconstruct w(z) from them through the principle component analysis approach. We find that current Hubble parameter data perform well in reconstructing w(z); though, when compared to supernova data, the data are scant and their quality is worse. Both ΛCDM and evolving w(z) models can be constrained within 10% at redshifts z 1.5 and even 5% at redshifts 0.1 z 1 by using simulated H(z) data of observational quality.

A Unified Model of Dark Energy Based on the Mandelstam-Tamm Uncertainty Relation

“…4. Taking into account that age of the Universe in the standard cosmology is, roughly speaking, inversely proportional to the present-day value of the Hubble parameter, T * ≈ 1/H 0 , we see that our relation (10) predicts that T ≈ (T * /τ ) T * . Since T * ≈ 4•10 17 s, and τ = 5•10 −44 s, this age in our model will be increased by (T * /τ ) ≈ 10 61 times.…”

“…While in the standard cosmology the Hubble parameter either remains constant with time (when evolution is determined by the Λ-term) or decays as α/t (where α = 1/2 when radiation dominates, and α = 2/3 when a non-relativistic matter dominates), our equation(8)predicts the inverse square-root dependence H(t) ∝ 1/ √ t, i.e., again some intermediate case between the two extremal situations. Taking into account that age of the Universe in the standard cosmology is, roughly speaking, inversely proportional to the present-day value of the Hubble parameter,T * ≈ 1/H 0 , we see that our relation(10) predicts that T ≈ (T * /τ ) T * . Since T * ≈ 4·10 17 s, and τ = 5·10 −44 s, this age in our model will be increased by (T * /τ ) ≈ 10 61 times.…”

“…At last, one of hot topics of cosmology in the recent years is a systematic discrepancy in the values of the present-day Hubble parameter H 0 derived by the various methods (namely, by the employment of supernovae Ia and Cepheids as the "standard candles", on the one hand, and by the analysis of CMB spectrum, on the other hand) [7,8]. Since in the second case the resulting value of H 0 substantially depends on the expansion history of the Universe R(t), the most of the recent attempts to resolve the abovementioned discrepancy were based on the empirical modifications of the equation of state of the Dark Energy [9][10][11][12]. In this sense, the substantially modified temporal dependence (9), naturally following from our model, might be an additional option for such attempts.…”

A Cosmological Scenario from the Starobinsky Model within the f(R,T) Formalism

“…Particularly, in standard cosmology, derived from GR, the dark energy and dark matter should compose ∼ 95% of the universe (Hinshaw et al (2013)), but their nature is still dubious (Dil (2017); Behrouz et al (2017); Germani (2017); Jennen & Pereira (2016); Evslin (2016); Liu et al (2016); Rinaldi (2017); Zhang (2017); Albert et al (2017)).…”

Can the Dark-Matter Deficit in the High-Redshift Galaxies Explain the Persistent Discrepancy in Hubble Constants?

“…[5,6]. Yet another popular explanation is a modification of the dark-energy equation-of-state parameter w (where p = wρ) [7,8,9,10]; though the resulting values w < −1 look quite suspicious from the viewpoint of general physical principles. 1 However, from our point of view, the spread in values of H 0 can have a much more straightforward explanation, following from the recent observations of the rotation curves in distant galaxies [12,13]: it was found that the amount of dark matter is considerably less in the vicinity of galaxies located at large redshifts, z = 0.6−2.6.…”