Testing the cosmological Euler equation: viscosity, equivalence principle, and gravity beyond general relativity
We investigate how the cosmological Euler equation can be tested in the presence of viscous dark matter, violations of the equivalence principle (EP), and modifications of gravity, while relying on minimal theoretical assumptions. Extending the analysis of Castello et al. Phys. Rev. D 111, 123559 (2...
Salvato in:
| Autori principali: | , , |
|---|---|
| Natura: | Article (Journal) |
| Lingua: | inglese |
| Pubblicazione: |
15 April, 2026
|
| In: |
Physical review
Year: 2026, Volume: 113, Fascicolo: 8, Pages: 1-26 |
| ISSN: | 2470-0029 |
| DOI: | 10.1103/nth3-y54x |
| Accesso online: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1103/nth3-y54x Verlag, lizenzpflichtig, Volltext: https://link.aps.org/doi/10.1103/nth3-y54x 
|
| Note sull'autore: | Ziyang Zheng, Malte Schneider, and Luca Amendola |
| Riassunto: | We investigate how the cosmological Euler equation can be tested in the presence of viscous dark matter, violations of the equivalence principle (EP), and modifications of gravity, while relying on minimal theoretical assumptions. Extending the analysis of Castello et al. Phys. Rev. D 111, 123559 (2025)., we generalize the observable 𝐸𝑃, which quantifies EP violation, to ˜𝐸𝑃, discuss the degeneracy between bulk and shear viscosities and EP-violating effects, and explicitly show that the EP can still be tested in the small-viscosity limit. In addition, we identify a model-independent observable, 𝐶vis,0, which characterizes the present-day dark matter viscosity and can be measured from relativistic galaxy number counts by cross-correlating two galaxy populations. We perform forecasts for three forthcoming stage-IV surveys: DESI, Euclid, and SKA Phase 2 (SKA2), and find that 𝐶vis,0 can be tightly constrained, at the level of 𝒪(10−6) or better in all cases. Among these surveys, SKA2 provides the tightest constraint, with a 1𝜎 uncertainty of 1.08 ×10−7 on 𝐶vis,0. |
|---|---|
| Descrizione del documento: | Veröffentlicht: 15. April 2026 Gesehen am 09.06.2026 |
| Descrizione fisica: | Online Resource |
| ISSN: | 2470-0029 |
| DOI: | 10.1103/nth3-y54x |