Spectral distortion constrained reheating in a holographic induced gravity tachyon model under ACT observations
Keywords:
Tachyon inflation; Holographic induced gravity; Reheating temperature; CMB spectral distortions; ACT constraints; Exponential potential; Equation of stateAbstract
We present a Spectral Distortion Constrained Reheating (SDCR) analysis of tachyon inflation within the holographic induced gravity (H-IG) framework, using the latest observational data from the Atacama Cosmology Telescope (ACT) DR6 combined dataset P-ACT-LB-BK18, which yields ns = 0.9743±0.0034. The model is characterized by three free parameters: the holographic parameter c, the induced gravity (IG) parameter γ, and the potential parameter α governing the exponential tachyon potential. Analytical expressions for the reheating temperature Tre and the reheating e-folds Nre are derived under a constant effective equation of state ωre. We then impose CMB µ-type and y-type spectral distortion bounds as supplementary observational filters on the parameter space, alongside the standard ns constraint. The energy injected into the photon-baryon plasma during reheating is computed for each parameter combination and compared against current FIRAS limits and projected PIXIE-class sensitivities. The Spectral Distortion Constrained Reheating method contracts the viable reheating corridor substantially relative to the base spectral index constraint alone, eliminating lowreheating-temperature branches that would otherwise survive ns filtering. Numerical results show that the observationally preferred configuration corresponds to α ∼2.5×10−5, c ∼1×107, and γ ∼0.9, consistent with instantaneous reheating near Tre ∼ 5×1015 GeV. The spectral distortion filter independently reinforces this conclusion, with µ-distortion constraints ruling out Tre ≲104 GeV for the matter-like equation-of-state branch.
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