Signals from Fermionic inflationary cosmology with Yukawa interaction
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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_ | 1866911216610312192 |
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| author | Sui, Lin-Hong Li, Dan Sun, Jia-Ze Li, Xi-Bin |
| author_facet | Sui, Lin-Hong Li, Dan Sun, Jia-Ze Li, Xi-Bin |
| contents | We investigate an inflationary model wherein the Dirac field $ψ$ is directly coupled to a scalar inflaton $ϕ$ via a Yukawa interaction $gϕ\barψψ$ and examine the resulting observational implications. Within the slow-roll approximation, we derive analytical solutions of the Dirac equations during inflation. The analytical result on the fermion pair density $\langle n\rangle$ indicates that the Yukawa interaction strength $g$ is to characterize the degree of non-adiabaticity. For large value of the dimensionless effective mass $\tilde m=(m+gϕ)/H$, i.e. $\tilde m\gtrsim 1$, the tensor-to-scalar ratio $r$ is suppressed by a factor of approximately $1/(1+2.95π^2g^2)$. This condition is also characterized by a significant backreaction. Conversely, if $\tilde m \ll 1$, the value of $r$ remains consistent with that observed in standard cold inflation. Our analysis is performed under the assumption of the highest inflationary energy scales compatible with current observational constraints. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_15609 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Signals from Fermionic inflationary cosmology with Yukawa interaction Sui, Lin-Hong Li, Dan Sun, Jia-Ze Li, Xi-Bin General Relativity and Quantum Cosmology We investigate an inflationary model wherein the Dirac field $ψ$ is directly coupled to a scalar inflaton $ϕ$ via a Yukawa interaction $gϕ\barψψ$ and examine the resulting observational implications. Within the slow-roll approximation, we derive analytical solutions of the Dirac equations during inflation. The analytical result on the fermion pair density $\langle n\rangle$ indicates that the Yukawa interaction strength $g$ is to characterize the degree of non-adiabaticity. For large value of the dimensionless effective mass $\tilde m=(m+gϕ)/H$, i.e. $\tilde m\gtrsim 1$, the tensor-to-scalar ratio $r$ is suppressed by a factor of approximately $1/(1+2.95π^2g^2)$. This condition is also characterized by a significant backreaction. Conversely, if $\tilde m \ll 1$, the value of $r$ remains consistent with that observed in standard cold inflation. Our analysis is performed under the assumption of the highest inflationary energy scales compatible with current observational constraints. |
| title | Signals from Fermionic inflationary cosmology with Yukawa interaction |
| topic | General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2510.15609 |