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Title: Reconciling tensor and scalar observables in G-inflation

Abstract

The simple m 2Φ2 potential as an inflationary model is coming under increasing tension with limits on the tensor-to-scalar ratio r and measurements of the scalar spectral index n s. Cubic Galileon interactions in the context of the Horndeski action can potentially reconcile the observables. However, we show that this cannot be achieved with only a constant Galileon mass scale because the interactions turn off too slowly, leading also to gradient instabilities after inflation ends. Furthermore, allowing for a more rapid transition can reconcile the observables but moderately breaks the slow-roll approximation leading to a relatively large and negative running of the tilt αs that can be of order n s-1. We show that the observables on CMB and large scale structure scales can be predicted accurately using the optimized slow-roll approach instead of the traditional slow-roll expansion. Upper limits on |αs| place a lower bound of r ≳ 0.005 and, conversely, a given r places a lower bound on |α s|, both of which are potentially observable with next generation CMB and large scale structure surveys.

Authors:
 [1];  [2];  [3];  [2];  [4]
  1. Univ. de Valencia, Burjassot (Spain); Univ. de Valencia-CSIC, Paterna (Spain)
  2. Univ. of Chicago, IL (United States)
  3. Kyoto Univ. (Japan)
  4. Univ. de Valencia-CSIC, Paterna (Spain)
Publication Date:
Research Org.:
Univ. of Chicago, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); MINECO; European Union's Horizon; Marie Sklodowska-Curie Grant; JSPS KEKENHI Grant; National Aeronautic and Space Administration (NASA); Simon Foundation
OSTI Identifier:
1594036
Grant/Contract Number:  
FG02-13ER41958; SC0009924
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2018; Journal Issue: 04; Journal ID: ISSN 1475-7516
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; inflation; cosmological parameters from CMBR

Citation Formats

Ramírez, Héctor, Passaglia, Samuel, Motohashi, Hayato, Hu, Wayne, and Mena, Olga. Reconciling tensor and scalar observables in G-inflation. United States: N. p., 2018. Web. doi:10.1088/1475-7516/2018/04/039.
Ramírez, Héctor, Passaglia, Samuel, Motohashi, Hayato, Hu, Wayne, & Mena, Olga. Reconciling tensor and scalar observables in G-inflation. United States. doi:10.1088/1475-7516/2018/04/039.
Ramírez, Héctor, Passaglia, Samuel, Motohashi, Hayato, Hu, Wayne, and Mena, Olga. Wed . "Reconciling tensor and scalar observables in G-inflation". United States. doi:10.1088/1475-7516/2018/04/039. https://www.osti.gov/servlets/purl/1594036.
@article{osti_1594036,
title = {Reconciling tensor and scalar observables in G-inflation},
author = {Ramírez, Héctor and Passaglia, Samuel and Motohashi, Hayato and Hu, Wayne and Mena, Olga},
abstractNote = {The simple m2Φ2 potential as an inflationary model is coming under increasing tension with limits on the tensor-to-scalar ratio r and measurements of the scalar spectral index ns. Cubic Galileon interactions in the context of the Horndeski action can potentially reconcile the observables. However, we show that this cannot be achieved with only a constant Galileon mass scale because the interactions turn off too slowly, leading also to gradient instabilities after inflation ends. Furthermore, allowing for a more rapid transition can reconcile the observables but moderately breaks the slow-roll approximation leading to a relatively large and negative running of the tilt αs that can be of order ns-1. We show that the observables on CMB and large scale structure scales can be predicted accurately using the optimized slow-roll approach instead of the traditional slow-roll expansion. Upper limits on |αs| place a lower bound of r ≳ 0.005 and, conversely, a given r places a lower bound on |αs|, both of which are potentially observable with next generation CMB and large scale structure surveys.},
doi = {10.1088/1475-7516/2018/04/039},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 04,
volume = 2018,
place = {United States},
year = {2018},
month = {4}
}

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