The Effect of Nonlinear Gravity on the Cosmological Background During Preheating
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arXiv
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| Main Authors: | , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915237975818240 |
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| author | Grutkoski, Ryn Macpherson, Hayley J. Giblin Jr, John T. Frieman, Joshua |
| author_facet | Grutkoski, Ryn Macpherson, Hayley J. Giblin Jr, John T. Frieman, Joshua |
| contents | We use numerical relativity to study the violent preheating era at the end of inflation. This epoch can result in highly nonlinear fluctuations in density and gravitational potential which feed back onto the averaged expansion rate -- an effect known as backreaction. Usually, simulations of preheating use the Friedmann constraint to enforce the Hubble expansion of spacetime during the evolution. In numerical relativity, this is not required and the inhomogeneous spacetime is evolved self-consistently. For a 'vanilla' preheating model, we find a violation of the Friedmann constraint at the level of $0.005\%$ over the entire simulation. This violation increases to $\sim10\%$ as we sample smaller scales in the simulation domain. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_08939 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The Effect of Nonlinear Gravity on the Cosmological Background During Preheating Grutkoski, Ryn Macpherson, Hayley J. Giblin Jr, John T. Frieman, Joshua Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We use numerical relativity to study the violent preheating era at the end of inflation. This epoch can result in highly nonlinear fluctuations in density and gravitational potential which feed back onto the averaged expansion rate -- an effect known as backreaction. Usually, simulations of preheating use the Friedmann constraint to enforce the Hubble expansion of spacetime during the evolution. In numerical relativity, this is not required and the inhomogeneous spacetime is evolved self-consistently. For a 'vanilla' preheating model, we find a violation of the Friedmann constraint at the level of $0.005\%$ over the entire simulation. This violation increases to $\sim10\%$ as we sample smaller scales in the simulation domain. |
| title | The Effect of Nonlinear Gravity on the Cosmological Background During Preheating |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2504.08939 |