Non-Gaussianity of Tensor Induced Density Perturbations
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arXiv
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| Hauptverfasser: | , , , |
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| Format: | Preprint |
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2025
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| author | Abdelaziz, Mariam Bari, Pritha Matarrese, Sabino Ricciardone, Angelo |
| author_facet | Abdelaziz, Mariam Bari, Pritha Matarrese, Sabino Ricciardone, Angelo |
| contents | We investigate the non-Gaussianity of second-order matter density perturbations induced by primordial gravitational waves (GWs). These tensor-induced scalar modes arise from local fluctuations in the GWs energy density, which is quadratic in tensor perturbations. The resulting second-order density contrast follows a chi-squared distribution, naturally exhibiting significant non-Gaussianity. We compute the bispectrum of these tensor-induced scalar modes and analyze its dependence on various primordial GWs power spectra, including scale-invariant, blue-tilted, Gaussian-bump, and monochromatic sources. We find that the bispectrum shape is inherently sensitive to the underlying GWs spectrum by construction. In particular, Gaussian-bump and monochromatic sources produce a strong signal peaking in the equilateral configuration, similar to the effect of scalar-induced tensor modes. Our findings reveal a new way to probe primordial GWs via galaxy surveys and highlight a unique feature of tensor-induced density perturbations, otherwise mimicking linear ones on sub-horizon scales. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_07063 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Non-Gaussianity of Tensor Induced Density Perturbations Abdelaziz, Mariam Bari, Pritha Matarrese, Sabino Ricciardone, Angelo Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We investigate the non-Gaussianity of second-order matter density perturbations induced by primordial gravitational waves (GWs). These tensor-induced scalar modes arise from local fluctuations in the GWs energy density, which is quadratic in tensor perturbations. The resulting second-order density contrast follows a chi-squared distribution, naturally exhibiting significant non-Gaussianity. We compute the bispectrum of these tensor-induced scalar modes and analyze its dependence on various primordial GWs power spectra, including scale-invariant, blue-tilted, Gaussian-bump, and monochromatic sources. We find that the bispectrum shape is inherently sensitive to the underlying GWs spectrum by construction. In particular, Gaussian-bump and monochromatic sources produce a strong signal peaking in the equilateral configuration, similar to the effect of scalar-induced tensor modes. Our findings reveal a new way to probe primordial GWs via galaxy surveys and highlight a unique feature of tensor-induced density perturbations, otherwise mimicking linear ones on sub-horizon scales. |
| title | Non-Gaussianity of Tensor Induced Density Perturbations |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2504.07063 |