Bmodes and the nature of inflation
Abstract
Observations of the cosmic microwave background do not yet determine whether inflation was driven by a slowlyrolling scalar field or involved another physical mechanism. In this paper we discuss the prospects of using the power spectra of scalar and tensor modes to probe the nature of inflation. We focus on the leading modification to the slowroll dynamics, which entails a sound speed c{sub s} for the scalar fluctuations. We derive analytically a lower bound on c{sub s} in terms of a given tensortoscalar ratio r, taking into account the difference in the freezeout times between the scalar and tensor modes. We find that any detection of primordial Bmodes with r > 0.01 implies a lower bound on c{sub s} that is stronger than the bound derived from the absence of nonGaussianity in the Planck data. For r ∼> 0.1, the bound would be tantalizingly close to a critical value for the sound speed, (c{sub s}){sub *} = 0.47 (corresponding to (f{sub NL}{sup equil}){sub *} = 0.93), which we show serves as a threshold for nontrivial dynamics beyond slowroll. We also discuss how an orderone level of equilateral nonGaussianity is a natural observational target for other extensions of the canonical paradigm.
 Authors:
 D.A.M.T.P., Cambridge University, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)
 Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)
 Deutsches ElektronenSynchrotron DESY, Theory Group, Notkestrasse 85, D22603 Hamburg (Germany)
 Publication Date:
 OSTI Identifier:
 22382032
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 01; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGICAL INFLATION; DETECTION; FREEZING OUT; RELICT RADIATION; SCALAR FIELDS; SCALARS; SPECTRA; TENSORS; VELOCITY
Citation Formats
Baumann, Daniel, Green, Daniel, and Porto, Rafael A., Email: dbaumann@damtp.cam.ac.uk, Email: drgreen@cita.utoronto.ca, Email: rporto@ias.edu. Bmodes and the nature of inflation. United States: N. p., 2015.
Web. doi:10.1088/14757516/2015/01/016.
Baumann, Daniel, Green, Daniel, & Porto, Rafael A., Email: dbaumann@damtp.cam.ac.uk, Email: drgreen@cita.utoronto.ca, Email: rporto@ias.edu. Bmodes and the nature of inflation. United States. doi:10.1088/14757516/2015/01/016.
Baumann, Daniel, Green, Daniel, and Porto, Rafael A., Email: dbaumann@damtp.cam.ac.uk, Email: drgreen@cita.utoronto.ca, Email: rporto@ias.edu. 2015.
"Bmodes and the nature of inflation". United States.
doi:10.1088/14757516/2015/01/016.
@article{osti_22382032,
title = {Bmodes and the nature of inflation},
author = {Baumann, Daniel and Green, Daniel and Porto, Rafael A., Email: dbaumann@damtp.cam.ac.uk, Email: drgreen@cita.utoronto.ca, Email: rporto@ias.edu},
abstractNote = {Observations of the cosmic microwave background do not yet determine whether inflation was driven by a slowlyrolling scalar field or involved another physical mechanism. In this paper we discuss the prospects of using the power spectra of scalar and tensor modes to probe the nature of inflation. We focus on the leading modification to the slowroll dynamics, which entails a sound speed c{sub s} for the scalar fluctuations. We derive analytically a lower bound on c{sub s} in terms of a given tensortoscalar ratio r, taking into account the difference in the freezeout times between the scalar and tensor modes. We find that any detection of primordial Bmodes with r > 0.01 implies a lower bound on c{sub s} that is stronger than the bound derived from the absence of nonGaussianity in the Planck data. For r ∼> 0.1, the bound would be tantalizingly close to a critical value for the sound speed, (c{sub s}){sub *} = 0.47 (corresponding to (f{sub NL}{sup equil}){sub *} = 0.93), which we show serves as a threshold for nontrivial dynamics beyond slowroll. We also discuss how an orderone level of equilateral nonGaussianity is a natural observational target for other extensions of the canonical paradigm.},
doi = {10.1088/14757516/2015/01/016},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 01,
volume = 2015,
place = {United States},
year = 2015,
month = 1
}

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