# Robust Inflation from fibrous strings

## Abstract

Successful inflationary models should (i) describe the data well; (ii) arise generically from sensible UV completions; (iii) be insensitive to detailed fine-tunings of parameters and (iv) make interesting new predictions. We argue that a class of models with these properties is characterized by relatively simple potentials with a constant term and negative exponentials. We here continue earlier work exploring UV completions for these models — including the key (though often ignored) issue of modulus stabilisation — to assess the robustness of their predictions. We show that string models where the inflaton is a fibration modulus seem to be robust due to an effective rescaling symmetry, and fairly generic since most known Calabi-Yau manifolds are fibrations. This class of models is characterized by a generic relation between the tensor-to-scalar ratio r and the spectral index n{sub s} of the form r∝(n{sub s}−1){sup 2} where the proportionality constant depends on the nature of the effects used to develop the inflationary potential and the topology of the internal space. In particular we find that the largest values of the tensor-to-scalar ratio that can be obtained by generalizing the original set-up are of order r≲0.01. We contrast this general picture with specific popular models,more »

- Authors:

- Department of Physics & Astronomy, McMaster University,1280 Main Street West, Hamilton ON (Canada)
- (Canada)
- Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy)
- (Italy)
- Physics Department, University of Colorado,Boulder, CO 80309 (United States)
- Abdus Salam International Center for Theoretical Physics,Strada Costiera 11, Trieste 34014 (Italy)
- (United Kingdom)

- Publication Date:

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

- OSTI Identifier:
- 22572078

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2016; Journal Issue: 05; Other Information: PUBLISHER-ID: JCAP05(2016)032; OAI: oai:repo.scoap3.org:15612; 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:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COSMOLOGICAL INFLATION; COSMOLOGY; INFLATIONARY UNIVERSE; MATHEMATICAL MANIFOLDS; SCALARS; STRING MODELS; STRING THEORY; TENSORS

### Citation Formats

```
Burgess, C.P., Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo ON, Cicoli, M., INFN, Sezione di Bologna, Bologna, Abdus Salam International Center for Theoretical Physics,Strada Costiera 11, Trieste 34014, Alwis, S. de, Quevedo, F., and DAMTP, University of Cambridge,Wilberforce Road, Cambridge, CB3 0WA.
```*Robust Inflation from fibrous strings*. United States: N. p., 2016.
Web. doi:10.1088/1475-7516/2016/05/032.

```
Burgess, C.P., Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo ON, Cicoli, M., INFN, Sezione di Bologna, Bologna, Abdus Salam International Center for Theoretical Physics,Strada Costiera 11, Trieste 34014, Alwis, S. de, Quevedo, F., & DAMTP, University of Cambridge,Wilberforce Road, Cambridge, CB3 0WA.
```*Robust Inflation from fibrous strings*. United States. doi:10.1088/1475-7516/2016/05/032.

```
Burgess, C.P., Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo ON, Cicoli, M., INFN, Sezione di Bologna, Bologna, Abdus Salam International Center for Theoretical Physics,Strada Costiera 11, Trieste 34014, Alwis, S. de, Quevedo, F., and DAMTP, University of Cambridge,Wilberforce Road, Cambridge, CB3 0WA. Fri .
"Robust Inflation from fibrous strings". United States.
doi:10.1088/1475-7516/2016/05/032.
```

```
@article{osti_22572078,
```

title = {Robust Inflation from fibrous strings},

author = {Burgess, C.P. and Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo ON and Cicoli, M. and INFN, Sezione di Bologna, Bologna and Abdus Salam International Center for Theoretical Physics,Strada Costiera 11, Trieste 34014 and Alwis, S. de and Quevedo, F. and DAMTP, University of Cambridge,Wilberforce Road, Cambridge, CB3 0WA},

abstractNote = {Successful inflationary models should (i) describe the data well; (ii) arise generically from sensible UV completions; (iii) be insensitive to detailed fine-tunings of parameters and (iv) make interesting new predictions. We argue that a class of models with these properties is characterized by relatively simple potentials with a constant term and negative exponentials. We here continue earlier work exploring UV completions for these models — including the key (though often ignored) issue of modulus stabilisation — to assess the robustness of their predictions. We show that string models where the inflaton is a fibration modulus seem to be robust due to an effective rescaling symmetry, and fairly generic since most known Calabi-Yau manifolds are fibrations. This class of models is characterized by a generic relation between the tensor-to-scalar ratio r and the spectral index n{sub s} of the form r∝(n{sub s}−1){sup 2} where the proportionality constant depends on the nature of the effects used to develop the inflationary potential and the topology of the internal space. In particular we find that the largest values of the tensor-to-scalar ratio that can be obtained by generalizing the original set-up are of order r≲0.01. We contrast this general picture with specific popular models, such as the Starobinsky scenario and α-attractors. Finally, we argue the self consistency of large-field inflationary models can strongly constrain non-supersymmetric inflationary mechanisms.},

doi = {10.1088/1475-7516/2016/05/032},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 05,

volume = 2016,

place = {United States},

year = {Fri May 13 00:00:00 EDT 2016},

month = {Fri May 13 00:00:00 EDT 2016}

}