The varying cosmological constant: a new approximation to the Friedmann equations and universe model

ÖZTAŞ A. M., Dil E., Smith M. L.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, cilt.476, sa.1, ss.451-458, 2018 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 476 Sayı: 1
  • Basım Tarihi: 2018
  • Doi Numarası: 10.1093/mnras/sty221
  • Dergi Adı: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.451-458
  • Anahtar Kelimeler: equation of state, cosmological parameters, dark energy, distance scale, cosmology: theory, SUPERNOVAE, LAMBDA
  • Hacettepe Üniversitesi Adresli: Evet

Özet

We investigate the time-dependent nature of the cosmological constant, Lambda, of the Einstein Field Equation (EFE). Beginning with the Einstein-Hilbert action as our fundamental principle we develop a modified version of the EFE allowing the value of Lambda to vary as a function of time, Lambda (t), indirectly, for an expanding universe. We follow the evolving Lambda presuming four-dimensional space-time and a flat universe geometry and present derivations of Lambda (t) as functions of the Hubble constant, matter density, and volume changes which can be traced back to the radiation epoch. The models are more detailed descriptions of the Lambda dependence on cosmological factors than previous, allowing calculations of the important parameters, Omega(m) and Omega(r), to deep lookback times. Since we derive these without the need for extra dimensions or other special conditions our derivations are useful for model evaluation with astronomical data. This should aid resolution of several difficult problems of astronomy such as the best value for the Hubble constant at present and at recombination.