Fundamental Physics from Future Spectroscopic Surveys

Late Time Modification of Structure Growth and the S8 Tension

8 May 2024, 08:40

10m

Auditorium (Building 50)

Session 9

Speaker

Dr Meng-Xiang Lin (University of Pennsylvania)

Description

The $S_8$ tension between low-redshift galaxy surveys and the primary CMB signals a possible breakdown of the $\mathrm{\Lambda }$CDM model.
Recently differing results have been obtained using low-redshift galaxy surveys and the higher redshifts probed by CMB lensing, motivating a possible time-dependent modification to the growth of structure.
We investigate a simple phenomenological model in which the growth of structure deviates from the $\mathrm{\Lambda }$CDM prediction at late times, in particular as a simple function of the dark energy density. Fitting to galaxy lensing, CMB lensing, BAO, and Supernovae datasets, we find significant evidence - 2.5 - 3$\sigma$, depending on analysis choices - for a non-zero value of the parameter quantifying a deviation from $\mathrm{\Lambda }$CDM.
The preferred model, which has a slower growth of structure below $z\sim 1$, improves the joint fit to the data over $\mathrm{\Lambda }$CDM.
While the overall fit is improved, there is weak evidence for galaxy and CMB lensing favoring different changes in the growth of structure.
The upcoming large-scale structure surveys can further test this model.

Presentation materials

Lin_MX_LBL_2024.05.08.pdf