New constraints on primordial non-Gaussianity from missing two-loop contributions of scalar induced gravitational waves

2023/11/09 by Zhe Chang, Yuting Kuang, Chang, Zhe +7 · 2 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Pulsars and Gravitational Waves Research #Black Holes and Theoretical Physics

paper · pdf · doi:10.48550/arxiv.2311.05102

Abstract

We analyze the energy density spectrum of \acpSIGW using the NANOGrav 15-year data set, thereby constraining the primordial non-Gaussian parameter f_NL. For the first time, we calculate the seventeen missing two-loop diagrams proportional to f_NLA_ζ³ that correspond to the two-point correlation function ⟨ h^λ,(3)_k h^λ',(2)_k' ⟩ for local-type primordial non-Gaussianity. The total energy density spectrum of \acpSIGW can be significantly suppressed by these two-loop diagrams. If \acpSIGW dominate the \acpSGWB observed in \acPTA experiments, the parameter interval f_NL∈ [-5,-1] is notably excluded based on NANOGrav 15-year data set. After taking into account abundance of \acpPBH and the convergence of the cosmological perturbation expansion, we find that the only possible parameter range for f_NL might be -1≤ f_NL< 0.

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