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Title: Effective field theory of degenerate higher-order inflation

Abstract

We extend the effective field theory of inflation to a general Lagrangian constructed from Arnowitt-Deser-Misner variables that encompasses the most general interactions with up to second derivatives of the scalar field whose background breaks temporal diffeomorphism invariance. Degeneracy conditions, corresponding to 8 distinct types -- only one of which corresponds to known degenerate higher-order scalar-tensor models -- provide necessary conditions for eliminating the Ostrogradsky ghost in a covariant theory at the level of the quadratic action in unitary gauge. Novel implications of the degenerate higher-order system for the Cauchy problem are illustrated with the phase space portrait of an explicit inflationary example: not all field configurations lead to physical solutions for the metric even for positive potentials; solutions are unique for a given configuration only up to a branch choice; solutions on one branch can apparently end at nonsingular points of the metric and their continuation on alternate branches lead to nonsingular bouncing solutions; unitary gauge perturbations can go unstable even when degenerate terms in the Lagrangian are infinitesimal. The attractor solution leads to an inflationary scenario where slow-roll parameters vary and running of the tilt can be large even with no explicit features in the potential far from themore » end of inflation, requiring the optimized slow-roll approach for predicting observables.« less

Authors:
ORCiD logo;
Publication Date:
Research Org.:
Univ. of Chicago, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP)
OSTI Identifier:
1615960
Alternate Identifier(s):
OSTI ID: 1734900
Grant/Contract Number:  
FG02-13ER41958; SC0009924
Resource Type:
Published Article
Journal Name:
Physical Review. D.
Additional Journal Information:
Journal Name: Physical Review. D. Journal Volume: 101 Journal Issue: 8; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Alternative gravity theories; Cosmology; Inflation

Citation Formats

Motohashi, Hayato, and Hu, Wayne. Effective field theory of degenerate higher-order inflation. United States: N. p., 2020. Web. doi:10.1103/PhysRevD.101.083531.
Motohashi, Hayato, & Hu, Wayne. Effective field theory of degenerate higher-order inflation. United States. https://doi.org/10.1103/PhysRevD.101.083531
Motohashi, Hayato, and Hu, Wayne. Thu . "Effective field theory of degenerate higher-order inflation". United States. https://doi.org/10.1103/PhysRevD.101.083531.
@article{osti_1615960,
title = {Effective field theory of degenerate higher-order inflation},
author = {Motohashi, Hayato and Hu, Wayne},
abstractNote = {We extend the effective field theory of inflation to a general Lagrangian constructed from Arnowitt-Deser-Misner variables that encompasses the most general interactions with up to second derivatives of the scalar field whose background breaks temporal diffeomorphism invariance. Degeneracy conditions, corresponding to 8 distinct types -- only one of which corresponds to known degenerate higher-order scalar-tensor models -- provide necessary conditions for eliminating the Ostrogradsky ghost in a covariant theory at the level of the quadratic action in unitary gauge. Novel implications of the degenerate higher-order system for the Cauchy problem are illustrated with the phase space portrait of an explicit inflationary example: not all field configurations lead to physical solutions for the metric even for positive potentials; solutions are unique for a given configuration only up to a branch choice; solutions on one branch can apparently end at nonsingular points of the metric and their continuation on alternate branches lead to nonsingular bouncing solutions; unitary gauge perturbations can go unstable even when degenerate terms in the Lagrangian are infinitesimal. The attractor solution leads to an inflationary scenario where slow-roll parameters vary and running of the tilt can be large even with no explicit features in the potential far from the end of inflation, requiring the optimized slow-roll approach for predicting observables.},
doi = {10.1103/PhysRevD.101.083531},
journal = {Physical Review. D.},
number = 8,
volume = 101,
place = {United States},
year = {Thu Apr 23 00:00:00 EDT 2020},
month = {Thu Apr 23 00:00:00 EDT 2020}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1103/PhysRevD.101.083531

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Cited by: 10 works
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