Sigma-8 tension is a drag
Abstract
Measurements of weak gravitational lensing at low redshifts (z ≲0.5 - 1 ), quantified by the parameter S8, favor weaker matter clustering than that expected from the standard Λ cold dark matter (Λ CDM ) cosmological model with the parameters determined by cosmic microwave background (CMB) measurements. However, the amplitude of matter clustering at higher redshifts, as probed by lensing of the CMB, is consistent with Λ CDM . In the literature, it has been found that the tension can be resolved by introducing a friction between dark matter and dark energy without altering the tightly constrained expansion history. Here, we show that in order to get a low S8 value consistent with the findings of cosmic shear under Λ CDM , cosmological measurements favor (at ∼3 σ , in this one parameter model) a nonzero drag leading to a suppression of low-redshift power right precisely around the transition from matter to dark-energy domination. Our results hint at a connection between the S8 tension and the long-standing "cosmic coincidence problem." We suggest ways to further probe the scenario.
- Publication:
-
Physical Review D
- Pub Date:
- June 2023
- DOI:
- 10.1103/PhysRevD.107.123538
- arXiv:
- arXiv:2209.06217
- Bibcode:
- 2023PhRvD.107l3538P
- Keywords:
-
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- High Energy Physics - Phenomenology;
- High Energy Physics - Theory
- E-Print:
- 6 pages, 5 figures. Comments welcome! v2: published in PRD. updated to match publish version. Added a new section with an analysis where the DE equation of state is let free to vary. Main conclusions unaffected