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GR: Fachverband Gravitation und Relativitätstheorie
GR 7: Cosmo I, Relastro II, GW II
GR 7.3: Vortrag
Mittwoch, 2. April 2025, 14:10–14:30, ZHG008
Resolving σ8 tension with time-varying gravitational constant — •Tilek Zhumabek1, Azamat Mukhamediya2, Hrishikesh Chakrabarty1, and Daniele Malafarina1 — 1Department of Physics, School of Sciences and Humanities, Nazarbayev University, Astana 010000, Kazakhstan — 2Department of Electrical and Computer Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Astana 010000, Kazakhstan
We consider a modified gravity model, dubbed GCDM, with running gravitational constant G(a), to test its imprints on the growth of structure. Using Redshift Space Distortion (RSD) measurement results, we show a tension at the 3 σ level between the best fit ΛCDM and the corresponding Planck18/ΛCDM parameters (w0 = −1, Ωm = 0.31, σ8 = 0.81). Unlike many modified gravity based solutions that overlook the scale dependence and model specific background evolution, we study this problem in the broadest possible context by incorporating both factors into our investigation. We obtain the model specific background quantities and perform a full perturbation analysis of the model to demonstrate a scale dependence in the growth equation. Fixing the scale to k = 0.1 h Mpc−1 and introducing a specific functional form for G(a) with one free parameter, we conducted likelihood analysis of RSD selected data. This analysis reveal that GCDM can bring the tension level within 1 σ while maintaining the deviation from Newton’s gravitational constant at the fifth order.
Keywords: modified gravity; scale dependent structure growth; $\sigma_8$ tension