%0 Generic %1 akarsu2019constraints %A Akarsu, Ozgur %A Kumar, Suresh %A Sharma, Shivani %A Tedesco, Luigi %D 2019 %K tifr %T Constraints on Bianchi type-I spacetime extension of the standard $Łambda$CDM model %U http://arxiv.org/abs/1905.06949 %X We consider the simplest anisotropic generalization, as a correction, to the standard $Łambda$CDM model, by replacing the spatially flat Robertson-Walker metric by the Bianchi type-I metric, which brings in a new term $Ømega_\sigma 0a^-6$ (mimicking the stiff fluid) in the average expansion rate $H(a)$ of the Universe. From Hubble and Pantheon data, relevant to the late Universe ($z2.4$), we obtain the constraint $Ømega_\sigma0łesssim10^-3$, 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., $Ømega_\sigma0łesssim10^-15$. 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 $Ømega_\sigma0łesssim10^-23$. We show explicitly that the constraint from BBN renders the expansion anisotropy irrelevant to make a detectable change in the CMB quadrupole temperature, whereas the constraint from the cosmological data provides the temperature change up to $\sim11\;K$.

@misc{akarsu2019constraints, abstract = {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 $\Omega_{\sigma 0}a^{-6}$ (mimicking the stiff fluid) in the average expansion rate $H(a)$ of the Universe. From Hubble and Pantheon data, relevant to the late Universe ($z\lesssim 2.4$), we obtain the constraint $\Omega_{\sigma0}\lesssim10^{-3}$, 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., $\Omega_{\sigma0}\lesssim10^{-15}$. 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 $\Omega_{\sigma0}\lesssim10^{-23}$. We show explicitly that the constraint from BBN renders the expansion anisotropy irrelevant to make a detectable change in the CMB quadrupole temperature, whereas the constraint from the cosmological data provides the temperature change up to $\sim11\;\mu \rm K$.}, added-at = {2019-05-20T05:57:29.000+0200}, author = {Akarsu, Ozgur and Kumar, Suresh and Sharma, Shivani and Tedesco, Luigi}, biburl = {https://www.bibsonomy.org/bibtex/236fe391d84da538c2bd97e1ce09b0d8d/citekhatri}, description = {Constraints on Bianchi type-I spacetime extension of the standard $\Lambda$CDM model}, interhash = {4b4207a83dc0d5ad175d5d10ef6ac866}, intrahash = {36fe391d84da538c2bd97e1ce09b0d8d}, keywords = {tifr}, note = {cite arxiv:1905.06949Comment: 13 pages, 3 figures, 5 tables}, timestamp = {2019-05-20T05:57:29.000+0200}, title = {Constraints on Bianchi type-I spacetime extension of the standard $\Lambda$CDM model}, url = {http://arxiv.org/abs/1905.06949}, year = 2019 }