Probing reheating in a holographic induced gravity tachyon model with latest ACT constraints

Abstract In this study, we explore the reheating phase that follows tachyon inflation within the framework of holographic induced gravity (H-IG). Analytical relations for the reheating temperature $$T_{re}$$ T re and the reheating number of e-folds $$N_{re}$$ N re are derived under the assumption of a constant effective equation of state $$\omega _{re}$$ ω re . A numerical analysis is then performed over a broad range of model parameters namely c (holographic parameter), $$\alpha $$ α (potential parameter), and $$\gamma $$ γ (IG parameter). Incorporating the most recent observational constraints from the Atacama Cosmology Telescope (ACT), which indicate a moderate upward shift in the scalar spectral index, $$n_s$$ n s , relative to the Planck 2018 results, we reassess the viability of tachyon inflation with an exponential potential within this framework. Our analysis shows that when $$\alpha $$ α is large ( $$\alpha \sim 2.5\times 10^{-5})$$ α ∼ 2.5 × 10 - 5 ) , the majority of parameter combinations are consistent with observational constraints, though the best fit for the reheating duration $$N_{re}$$ N re to the data occurs for smaller c ( $$c\sim 1\times 10^{7}$$ c ∼ 1 × 10 7 ) and higher $$\gamma $$ γ ( $$\gamma \sim 0.9$$ γ ∼ 0.9 ) while also satisfying the lower bound on the reheating temperature $$T_{re}$$ T re .