Séminaire / Seminar GReCO |
| « Cosmological consequences of statistical inhomogeneity and anisotropy » |
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Dipayan Mukherjee |
| The quantum fluctuations during inflation are typically assumed to be statistically homogeneous and isotropic, in accordance with the cosmological principle. In this work, we relax this assumption by allowing the primordial scalar perturbations to acquire a non-zero scale-dependent one-point function: `A primordial mean'. We consider the quantum fluctuations during inflation to originate from a coherent state, instead of the usual Bunch-Davies vacuum, resulting in a primordial mean that breaks statistical homogeneity and isotropy. Consequently, the higher-order correlation functions of primordial scalar perturbations acquire unique features. The cosmic microwave background (CMB) fluctuations specifically probe the statistically anisotropic component of the primordial mean. Notably, the off-diagonal elements in the angular two-point function provide a unique and clean observational probe into the primordial mean. A key consequence of a non-zero primordial mean is the emergence of a non-vanishing three-point correlation (bispectrum) even for a Gaussian field, allowing current constraints on the non-Gaussianity parameter to impose strong limits on the primordial mean. Furthermore, due to these statistical inhomogeneities in the scalar sector, the scalar-induced secondary gravitational waves (SIGW) acquire distinct scale-dependent features in its correlation functions. Statistical anisotropies further lead to possible parity violation and correlation between different polarization modes in the induced tensor perturbations. Therefore, detection of these signatures in cosmological observables would offer probes into the nature of the primordial mean and thus the initial configuration of inflation. |
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Monday 08 September 2025 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |