Speaker
Description
The upcoming Square Kilometre Array (SKA) will map the large-scale structure of the Universe with unprecedented sensitivity via 21-cm intensity mapping. While standard analyses focus on the power spectrum, non-linear gravitational evolution encodes rich information in higher-order statistics. In this work, we investigate the redshift-space 21-cm bispectrum and its spherical harmonic multipoles as a probe of gravity in the post-reionization epoch (z∼0.3−3). Using tree-level perturbation theory, we model the bispectrum for both ΛCDM and the Hu-Sawicki f(R) modified gravity model, incorporating local Eulerian bias and redshift-space distortions. We forecast the detectability of modified gravity signatures for an SKA-MID-like survey, accounting for thermal noise and cosmic variance. We find that the signal-to-noise ratio is maximized by the lowest order multipoles (ℓ=0,2) in squeezed and stretched triangle configurations. Our results demonstrate that the 21-cm bispectrum on quasi-linear scales (k∼0.4−0.8hMpc−1) offers a potent, complementary test of General Relativity, capable of constraining scale-dependent growth with high statistical significance in the SKA era. The talk is based on the arXiv:2601.18862
