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| Natura: | Preprint |
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2026
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| Accesso online: | https://arxiv.org/abs/2605.28752 |
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| _version_ | 1866911726043136000 |
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| author | Chen, Chong-Bin |
| author_facet | Chen, Chong-Bin |
| contents | We revisit the resulting bispectrum of inflation with kinetic-coupled vector fields by organizing the dynamics in terms of $h$, which measures the vector kinetic contribution relative to that of the scalar field. We evaluate the bispectrum in the strong-vector regime and derive a low-energy effective field theory (EFT) for the large-$h$ regime. For $h\gg1$, the entropic perturbation becomes heavy and can be integrated out; the remaining curvature mode has an imaginary sound speed and undergoes transient growth before horizon crossing. In contrast to $h\ll1$ regime, where transfer from the vector sector persists outside the horizon and produces a local-type contribution enhanced as $h^2N_K^3$, we find that in addition to the known flattened-enhanced signals scaling as $h^3$, a flattened-enhanced signal scaling as $h^2$ and a pronounced local projection scaling as $h$ are present. Their competition yields a local-dominated signal for intermediate $h$ and a flattened-dominated signal at larger $h$. The bispectrum therefore distinguishes vector-supported inflationary dynamics even for an exactly isotropic background. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_28752 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Inflation with vector fields revisited: non-Gaussianities Chen, Chong-Bin High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We revisit the resulting bispectrum of inflation with kinetic-coupled vector fields by organizing the dynamics in terms of $h$, which measures the vector kinetic contribution relative to that of the scalar field. We evaluate the bispectrum in the strong-vector regime and derive a low-energy effective field theory (EFT) for the large-$h$ regime. For $h\gg1$, the entropic perturbation becomes heavy and can be integrated out; the remaining curvature mode has an imaginary sound speed and undergoes transient growth before horizon crossing. In contrast to $h\ll1$ regime, where transfer from the vector sector persists outside the horizon and produces a local-type contribution enhanced as $h^2N_K^3$, we find that in addition to the known flattened-enhanced signals scaling as $h^3$, a flattened-enhanced signal scaling as $h^2$ and a pronounced local projection scaling as $h$ are present. Their competition yields a local-dominated signal for intermediate $h$ and a flattened-dominated signal at larger $h$. The bispectrum therefore distinguishes vector-supported inflationary dynamics even for an exactly isotropic background. |
| title | Inflation with vector fields revisited: non-Gaussianities |
| topic | High Energy Physics - Theory Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2605.28752 |