A Match Made in Heaven: Linking Observables in Inflationary Cosmology
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866910129304109056 |
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| author | Stefanyszyn, David Tong, Xi Zhu, Yuhang |
| author_facet | Stefanyszyn, David Tong, Xi Zhu, Yuhang |
| contents | Cosmological correlation functions of inflaton and graviton perturbations are the fundamental observables of early universe cosmology and remain a primary target for observations. In this work, we ask the following question: are these observables independent of one another? We find that in the parity-odd sector of inflationary perturbation theory, the answer is a resounding no! In earlier work we derived a correlator-to-correlator factorisation formula which states that parity-odd correlators factorise into lower-point correlators under some mild assumptions on the underlying theory. In this work, we show that these assumptions are satisfied in dynamical Chern-Simons gravity where the action of minimal inflation is augmented by a coupling between the inflaton and the gravitational Chern-Simons term. Such a theory gives rise to a parity-odd trispectrum of curvature perturbations, and we show that such a trispectrum can be expressed solely in terms of the bispectrum that arises due to the minimal coupling between the inflaton and graviton, and the graviton power spectrum which receives a parity-odd correction in this theory. The trispectrum is quadratic in this mixed inflaton-graviton bispectrum and can therefore be interpreted as a ``double copy". Our final expression for the parity-odd trispectrum is a relatively simple function of the external momenta that is rational and factorised. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_16071 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A Match Made in Heaven: Linking Observables in Inflationary Cosmology Stefanyszyn, David Tong, Xi Zhu, Yuhang High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology Cosmological correlation functions of inflaton and graviton perturbations are the fundamental observables of early universe cosmology and remain a primary target for observations. In this work, we ask the following question: are these observables independent of one another? We find that in the parity-odd sector of inflationary perturbation theory, the answer is a resounding no! In earlier work we derived a correlator-to-correlator factorisation formula which states that parity-odd correlators factorise into lower-point correlators under some mild assumptions on the underlying theory. In this work, we show that these assumptions are satisfied in dynamical Chern-Simons gravity where the action of minimal inflation is augmented by a coupling between the inflaton and the gravitational Chern-Simons term. Such a theory gives rise to a parity-odd trispectrum of curvature perturbations, and we show that such a trispectrum can be expressed solely in terms of the bispectrum that arises due to the minimal coupling between the inflaton and graviton, and the graviton power spectrum which receives a parity-odd correction in this theory. The trispectrum is quadratic in this mixed inflaton-graviton bispectrum and can therefore be interpreted as a ``double copy". Our final expression for the parity-odd trispectrum is a relatively simple function of the external momenta that is rational and factorised. |
| title | A Match Made in Heaven: Linking Observables in Inflationary Cosmology |
| topic | High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2505.16071 |