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Arxiv: Explaining JWST star formation history at z \sim 17 by modifying ΛCDM Published: 1/19/2025 6:26:24 PM Updated: 1/19/2025 6:26:24 PM

Paper abstract: Recent cosmological observations indicate a 5\sigma discrepancy between thevalues of the Hubble constant H_0 derived from late and early universeprobes. A further possible tension at the ~ 3\sigma level arises fromdifferent measurements of \sigma_8. These measurements suggest the existenceof new physics. Here, we explore several theories of modified gravity that mayhelp to resolve these cosmological tensions. These include a family ofphenomenological modified theories, where only Newton's gravitational constantand the Einstein-Boltzmann equations are affected. We consider one particularclass of these theories: cosmologies with varying growth index \gamma andvarying dark energy Equation of State (EoS) w_\Lambda. We also consider thenormal branch of the Dvali-Gabadadze-Porrati (nDGP) model as well ask-mouflage gravity, which involves a non-trivially coupled scalar field. Ourmain aim is to narrow down the modified gravity landscape by constraining eachmodel using high-redshift JWST data. Several probes are considered in thiswork: Stellar Mass Function (SMF), Stellar Mass Density (SMD), Star FormationRate Density (SFRD) and Ultra-Violet Luminosity Function (UVLF) along with theEpoch of Reionization (EoR). We find that generally, the choice of r_c\gtrsim10^{3.5} Mpc is preferred for nDGP, while \beta~0.1, K_0\gtrsim 0.9 isfavored for k-mouflage. Moreover, in the context of phenomenological gravity,phantom-like dark energy EoS w_\Lambda<~ -1 is preferred over thequintessence.