Adiabatic and isocurvature perturbation projections in multi-field inflation
Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling per...
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| Format: | Article |
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IOP Publishing
2013
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| Online Access: | https://eprints.nottingham.ac.uk/42148/ |
| _version_ | 1848796431771500544 |
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| author | Gordon, Chris Saffin, Paul M. |
| author_facet | Gordon, Chris Saffin, Paul M. |
| author_sort | Gordon, Chris |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling perturbations in multi-field inflation is to investigate the projection of the perturbation along and perpendicular to the background fields' trajectory. These correspond to the adiabatic and isocurvature perturbations. However, it is important to note that in general there are no corresponding adiabatic and isocurvature fields. The purpose of this article is to highlight the distinction between a field redefinition and a perturbation projection. We provide a detailed derivation of the evolution of the isocurvature perturbation to show that no assumption of an adiabatic or isocurvature field is needed. We also show how this evolution equation is consistent with the field covariant evolution equations for the isocurvature perturbation in the flat field space limit. |
| first_indexed | 2025-11-14T19:47:53Z |
| format | Article |
| id | nottingham-42148 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| last_indexed | 2025-11-14T19:47:53Z |
| publishDate | 2013 |
| publisher | IOP Publishing |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-421482020-05-04T16:38:30Z https://eprints.nottingham.ac.uk/42148/ Adiabatic and isocurvature perturbation projections in multi-field inflation Gordon, Chris Saffin, Paul M. Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling perturbations in multi-field inflation is to investigate the projection of the perturbation along and perpendicular to the background fields' trajectory. These correspond to the adiabatic and isocurvature perturbations. However, it is important to note that in general there are no corresponding adiabatic and isocurvature fields. The purpose of this article is to highlight the distinction between a field redefinition and a perturbation projection. We provide a detailed derivation of the evolution of the isocurvature perturbation to show that no assumption of an adiabatic or isocurvature field is needed. We also show how this evolution equation is consistent with the field covariant evolution equations for the isocurvature perturbation in the flat field space limit. IOP Publishing 2013-08-12 Article PeerReviewed Gordon, Chris and Saffin, Paul M. (2013) Adiabatic and isocurvature perturbation projections in multi-field inflation. Journal of Cosmology and Astroparticle Physics, 2013 (8). 021/1-021/9. ISSN 1475-7516 Inflation Cosmological perturbation theory https://doi.org/10.1088/1475-7516/2013/08/021 doi:10.1088/1475-7516/2013/08/021 doi:10.1088/1475-7516/2013/08/021 |
| spellingShingle | Inflation Cosmological perturbation theory Gordon, Chris Saffin, Paul M. Adiabatic and isocurvature perturbation projections in multi-field inflation |
| title | Adiabatic and isocurvature perturbation projections in multi-field inflation |
| title_full | Adiabatic and isocurvature perturbation projections in multi-field inflation |
| title_fullStr | Adiabatic and isocurvature perturbation projections in multi-field inflation |
| title_full_unstemmed | Adiabatic and isocurvature perturbation projections in multi-field inflation |
| title_short | Adiabatic and isocurvature perturbation projections in multi-field inflation |
| title_sort | adiabatic and isocurvature perturbation projections in multi-field inflation |
| topic | Inflation Cosmological perturbation theory |
| url | https://eprints.nottingham.ac.uk/42148/ https://eprints.nottingham.ac.uk/42148/ https://eprints.nottingham.ac.uk/42148/ |