Axion inflation in the regime of homogeneous backreaction
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| Format: | Preprint |
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2025
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| _version_ | 1866914103830773760 |
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| author | Barbon, Matteo Ijaz, Nadir Peloso, Marco |
| author_facet | Barbon, Matteo Ijaz, Nadir Peloso, Marco |
| contents | We investigate the Stochastic Gravitational Wave Background (SGWB) produced in models of axion inflation coupled to gauge fields. Achieving a detectable signal at Pulsar Timing Array, astrometry, or interferometer frequencies requires a sufficiently strong amplification of the gauge fields, at a level that induces significant backreaction on the inflaton background dynamics. Numerical studies based on the approximation of homogeneous backreaction (i.e., neglecting inhomogeneities of the inflaton field) exhibit oscillations in the inflaton velocity, with corresponding peaks in the SGWB spectrum. The most recent lattice simulations have questioned the validity of this regime, showing examples characterized by a rapid increase in the inflaton gradient energy and the breakdown of homogeneous backreaction. We compute this energy density perturbatively within the assumption of homogeneous backreaction, obtaining examples with a detectable SGWB and with an inflaton gradient energy that remains subdominant to the inflaton zero-mode kinetic energy throughout inflation. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_17207 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Axion inflation in the regime of homogeneous backreaction Barbon, Matteo Ijaz, Nadir Peloso, Marco Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology High Energy Physics - Theory We investigate the Stochastic Gravitational Wave Background (SGWB) produced in models of axion inflation coupled to gauge fields. Achieving a detectable signal at Pulsar Timing Array, astrometry, or interferometer frequencies requires a sufficiently strong amplification of the gauge fields, at a level that induces significant backreaction on the inflaton background dynamics. Numerical studies based on the approximation of homogeneous backreaction (i.e., neglecting inhomogeneities of the inflaton field) exhibit oscillations in the inflaton velocity, with corresponding peaks in the SGWB spectrum. The most recent lattice simulations have questioned the validity of this regime, showing examples characterized by a rapid increase in the inflaton gradient energy and the breakdown of homogeneous backreaction. We compute this energy density perturbatively within the assumption of homogeneous backreaction, obtaining examples with a detectable SGWB and with an inflaton gradient energy that remains subdominant to the inflaton zero-mode kinetic energy throughout inflation. |
| title | Axion inflation in the regime of homogeneous backreaction |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology High Energy Physics - Theory |
| url | https://arxiv.org/abs/2510.17207 |