Cosmographic view on the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>σ</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:math> tensions

Abstract

Measurements of the ${H}_{0}$ and ${\ensuremath{\sigma}}_{8}$ parameters within the standard cosmological model recently highlighted significant statistical tensions between the cosmic microwave background and low-redshift probes, such as local distance ladder, weak lensing, and galaxy clustering surveys. In this work, we frame geometrical distances in a model-independent way by means of cosmographic approximations in the range $z\ensuremath{\in}(0,2.3)$ to take into account a robust dataset composed of baryon acoustic oscillations (BAOs), type Ia supernovae (SN), cosmic chronometer (CC) data, and measurements from redshift space distortions (RSDs). From the joint analysis $\mathrm{BAO}+\mathrm{SN}+\mathrm{CC}+\mathrm{RSD}$, we find an accuracy of $\ensuremath{\sim}1.4%$ and $\ensuremath{\sim}3.7%$ on ${H}_{0}$ and ${\ensuremath{\sigma}}_{8}$, respectively. Our result for ${H}_{0}$ is at $2\ensuremath{\sigma}$ tension with local measurements by the SH0ES team, while our ${\ensuremath{\sigma}}_{8}$ estimate is at $2.6\ensuremath{\sigma}$ tension with Planck-CMB analysis. This inference shows a tension statistically smaller when compared to those estimated via the Lambda cold dark matter ($\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$) model. We also find that the jerk parameter can deviate more than $3\ensuremath{\sigma}$ from the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ prediction. Under the same cosmographic setup, we also present results by considering a SH0ES Gaussian prior on ${H}_{0}$ that allows for improved accuracy of the parameter space of the models. The present work brings observational constraints on ${H}_{0}$ and ${\ensuremath{\sigma}}_{8}$ into a new model-independent perspective, which differs from the predictions obtained within the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ paradigm.

Topics & Concepts