Constraints on a Bianchi type I spacetime extension of the standard Lambda CDM model


Akarsu Ö., Kumar S., Sharma S., Tedesco L.

PHYSICAL REVIEW D, cilt.100, sa.2, 2019 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 100 Sayı: 2
  • Basım Tarihi: 2019
  • Doi Numarası: 10.1103/physrevd.100.023532
  • Dergi Adı: PHYSICAL REVIEW D
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • İstanbul Teknik Üniversitesi Adresli: Evet

Özet

We consider the simplest anisotropic generalization, as a correction, to the standard Lambda CDM model, by replacing the spatially flat Robertson-Walker metric by the Bianchi type-I metric, which brings in a new term Omega sigma s(0) a(-6) (mimicking the stiff fluid) in the average expansion rate Hoathorn of the Universe. From Hubble and Pantheon data, relevant to the late Universe (z less than or similar to 2.4), we obtain the constraint Omega sigma 0 less than or similar to 10(-3), in line with the model-independent constraints. When the baryonic acoustic oscillations and cosmic microwave background (CMB) data are included, the constraint improves by 12 orders of magnitude, i.e., Omega sigma 0 less than or similar to 10(-15). We find that this constraint could alter neither the matter-radiation equality redshift nor the peak of the matter perturbations. Demanding that the expansion anisotropy has no significant effect on the standard big bang nucleosynthesis (BBN), we find the constraint Omega sigma 0 less than or similar to 10(-23). We show explicitly that the constraint from BBN renders the expansion anisotropy irrelevant to make a significant change in the CMB quadrupole temperature, whereas the constraint from the cosmological data in our model provides the temperature change up to similar to 11 mK, though it is much beyond the CMB quadrupole temperature.