On Cross-correlations between Curvature and Isocurvature Perturbations during Inflation

Abstract

We investigate the effects of couplings between curvature and isocurvature perturbations before and around horizon-crossings during cosmological inflation. We consider a generalized two-field inflation model, in which the non-canonical kinetic term allows us arbitrary sound speeds of curvature and isocurvature perturbations. By using the field-theoretical perturbative analysis, we calculate the cross-spectrum between curvature and isocurvature perturbations and the corrections to curvature and isocurvature power spectra due to the presence of couplings between them. Our analysis confirms previous results that the cross-correlations are generated and amplified when perturbations cross the horizons. Moreover, we find the cross-correlation, which was previously shown to be first-order in slow-roll parameter, can be enhanced when the sound speed of isocurvature perturbation is much smaller than that of the curvature perturbation. This is because in this case the isocurvature perturbation exits its horizon much earlier than the curvature perturbation and acts as a nearly constant source on the curvature perturbation.

19 pages, 8 figures. v2 important note and reference added. v3, final version, important comments are added to improve the logic and make the physical meaning of the results clearer, version to appear in JCAP

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Cited by in corpus (18)

• Primordial Non-Gaussianities from Inflation Models
• Quasi-Single Field Inflation and Non-Gaussianities
• On the importance of heavy fields during inflation
• Curvature Perturbation Spectrum in Two-field Inflation with a Turning Trajectory
• Influence of heavy modes on perturbations in multiple field inflation
• Cumulative effects in inflation with ultra-light entropy modes
• Oscillatory features in the curvature power spectrum after a sudden turn of the inflationary trajectory
• Calculating Non-adiabatic Pressure Perturbations during Multi-field Inflation
• Note on Non-Gaussianities in Two-field Inflation
• IR Divergences in Inflation and Entropy Perturbations
• Combined features in the primordial spectra induced by a sudden turn in two-field DBI inflation
• On primordial trispectrum from exchanging scalar modes in general multiple field inflationary models
• Coupling structure of multi-field primordial perturbations
• Dynamics of Cosmological Perturbations in Multi-Speed Inflation
• Loop corrections to primordial fluctuations from inflationary phase transitions
• Testing Two-Field Inflation
• Correlation of isocurvature perturbation and non-Gaussianity
• Cosmological perturbations in the spatially covariant gravity with a dynamical lapse function