# Magnon inflation: slow roll with steep potentials

## Abstract

We find multi-scalar effective field theories (EFTs) that can achieve a slow inflationary roll despite having a scalar potential that does not satisfy G{sup ab}∂{sub a}V∂{sub b}V≪V{sup 2}/M{sub p}{sup 2} (where G{sub ab} is the target-space metric). They evade the usual slow-roll conditions on V because their kinetic energies are dominated by single-derivative terms rather than the usual two-derivative terms. Single derivatives dominate during slow roll and so do not require a breakdown of the usual derivative expansion that underpins calculational control in much of cosmology. The presence of such terms requires some sort of UV Lorentz-symmetry breaking during inflation (besides the usual cosmological breaking). Chromo-natural inflation provides one particular example of a UV theory that can generate the multi-field single-derivative terms we consider, and we argue that the EFT we find indeed captures the slow-roll conditions for its background evolution. We also show that our EFT can be understood as a multi-field generalization of the single-field Cuscuton models. The multi-field case introduces a new feature, however: the scalar kinetic terms define a target-space 2-form, F{sub ab}, whose antisymmetry gives new ways for slow roll to be achieved.

- Authors:

- Department of Physics, University of Illinois at Urbana-Champaign,Urbana, IL 61801 (United States)
- Theoretical Physics Department, CERN,CH-1211 Geneva 23 (Switzerland)
- Physics & Astronomy, McMaster University,Hamilton, ON, L8S 4M1 (Canada)
- (Canada)
- Department of Theoretical Physics, University of Geneva,24 Quai Ansermet, Geneva, CH-1211 (Switzerland)

- Publication Date:

- Sponsoring Org.:
- SCOAP3, CERN, Geneva (Switzerland)

- OSTI Identifier:
- 22572178

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2016; Journal Issue: 11; Other Information: PUBLISHER-ID: JCAP11(2016)009; OAI: oai:repo.scoap3.org:17883; cc-by Article funded by SCOAP3. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 License. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COSMOLOGICAL INFLATION; COSMOLOGY; INFLATIONARY UNIVERSE; INFLATONS; KINETIC ENERGY; POTENTIALS; QUANTUM FIELD THEORY; ULTRAVIOLET DIVERGENCES

### Citation Formats

```
Adshead, Peter, Blas, Diego, Burgess, C.P., Hayman, Peter, Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, and Patil, Subodh P..
```*Magnon inflation: slow roll with steep potentials*. United States: N. p., 2016.
Web. doi:10.1088/1475-7516/2016/11/009.

```
Adshead, Peter, Blas, Diego, Burgess, C.P., Hayman, Peter, Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, & Patil, Subodh P..
```*Magnon inflation: slow roll with steep potentials*. United States. doi:10.1088/1475-7516/2016/11/009.

```
Adshead, Peter, Blas, Diego, Burgess, C.P., Hayman, Peter, Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, and Patil, Subodh P.. Fri .
"Magnon inflation: slow roll with steep potentials". United States.
doi:10.1088/1475-7516/2016/11/009.
```

```
@article{osti_22572178,
```

title = {Magnon inflation: slow roll with steep potentials},

author = {Adshead, Peter and Blas, Diego and Burgess, C.P. and Hayman, Peter and Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 and Patil, Subodh P.},

abstractNote = {We find multi-scalar effective field theories (EFTs) that can achieve a slow inflationary roll despite having a scalar potential that does not satisfy G{sup ab}∂{sub a}V∂{sub b}V≪V{sup 2}/M{sub p}{sup 2} (where G{sub ab} is the target-space metric). They evade the usual slow-roll conditions on V because their kinetic energies are dominated by single-derivative terms rather than the usual two-derivative terms. Single derivatives dominate during slow roll and so do not require a breakdown of the usual derivative expansion that underpins calculational control in much of cosmology. The presence of such terms requires some sort of UV Lorentz-symmetry breaking during inflation (besides the usual cosmological breaking). Chromo-natural inflation provides one particular example of a UV theory that can generate the multi-field single-derivative terms we consider, and we argue that the EFT we find indeed captures the slow-roll conditions for its background evolution. We also show that our EFT can be understood as a multi-field generalization of the single-field Cuscuton models. The multi-field case introduces a new feature, however: the scalar kinetic terms define a target-space 2-form, F{sub ab}, whose antisymmetry gives new ways for slow roll to be achieved.},

doi = {10.1088/1475-7516/2016/11/009},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 11,

volume = 2016,

place = {United States},

year = {Fri Nov 04 00:00:00 EDT 2016},

month = {Fri Nov 04 00:00:00 EDT 2016}

}