TY - JOUR
T1 - α -attractor-type double inflation
AU - Maeda, Kei Ichi
AU - Mizuno, Shuntaro
AU - Tozuka, Ryota
N1 - Funding Information:
We would like to thank Renata Kallosh, Shinji Mukohyama, Shi Pi and Yusuke Yamada for useful discussions. We also thank the Yukawa Institute for Theoretical Physics, Kyoto University for the hospitality during the workshop on Gravity and Cosmology 2018 (YITPT-17-02) and the symposium on General Relativity—The Next Generation—(YKIS2018a). This work was supported by JSPS Grant-in-Aid for Scientific Research Grants No. 16K05362 (K. M.), No. JP17H06359 (K. M.) and No. 16K17709 (S. M.).
Publisher Copyright:
© 2018 authors. Published by the American Physical Society.
PY - 2018/12/15
Y1 - 2018/12/15
N2 - We study the background dynamics and primordial perturbation in α-attractor-type double inflation. The model is composed of two minimally coupled scalar fields, where each of the fields has a potential of the α-attractor type. We find that the background trajectory in this double inflation model is given by two almost straight lines connected with a turn in the field space. With this simple background, we can classify the property of the perturbations generated in this double inflation model just depending on whether the turn occurs before the horizon exit for the mode corresponding to the scale of interest or not. In the former case, the resultant primordial curvature perturbation coincides with the one obtained by the single-field α-attractor. On the other hand, in the latter case, it is affected by the multifield effects, like the mixing with the isocurvature perturbation and the change of the Hubble expansion rate at the horizon exit. We obtain the approximated analytic solutions for the background, with which we can calculate the primordial curvature perturbation by the δN formalism analytically, even when the multifield effects are significant. We also impose observational constraints on the model parameters and initial values of the fields in this double inflation model based on the Planck result.
AB - We study the background dynamics and primordial perturbation in α-attractor-type double inflation. The model is composed of two minimally coupled scalar fields, where each of the fields has a potential of the α-attractor type. We find that the background trajectory in this double inflation model is given by two almost straight lines connected with a turn in the field space. With this simple background, we can classify the property of the perturbations generated in this double inflation model just depending on whether the turn occurs before the horizon exit for the mode corresponding to the scale of interest or not. In the former case, the resultant primordial curvature perturbation coincides with the one obtained by the single-field α-attractor. On the other hand, in the latter case, it is affected by the multifield effects, like the mixing with the isocurvature perturbation and the change of the Hubble expansion rate at the horizon exit. We obtain the approximated analytic solutions for the background, with which we can calculate the primordial curvature perturbation by the δN formalism analytically, even when the multifield effects are significant. We also impose observational constraints on the model parameters and initial values of the fields in this double inflation model based on the Planck result.
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U2 - 10.1103/PhysRevD.98.123530
DO - 10.1103/PhysRevD.98.123530
M3 - Article
AN - SCOPUS:85059382779
VL - 98
JO - Physical Review D
JF - Physical Review D
SN - 2470-0010
IS - 12
M1 - 123530
ER -