# Dark energy from α-attractors: phenomenology and observational constraints

## Abstract

The possibility of linking inflation and late cosmic accelerated expansion using the $$\alpha$$-attractor models has received increasing attention due to their physical motivation. In the early universe, $$\alpha$$-attractors provide an inflationary mechanism compatible with Planck satellite CMB observations and predictive for future gravitational wave CMB modes. Additionally $$\alpha$$-attractors can be written as quintessence models with a potential that connects a power law regime with a plateau or uplifted exponential, allowing a late cosmic accelerated expansion that can mimic behavior near a cosmological constant. In this paper we study a generalized dark energy $$\alpha$$-attractor model. We thoroughly investigate its phenomenology, including the role of all model parameters and the possibility of large-scale tachyonic instability clustering. We confirm the relation that $$1+w\sim 1/\alpha$$ (while the gravitational wave power $$r\sim\alpha$$) so these models predict that a signature should appear in either the primordial B-modes or in late time deviation from a cosmological constant. We constrain the model parameters with current datasets, including the cosmic microwave background (Planck 2015 angular power spectrum, polarization and lensing), baryon acoustic oscillations (BOSS DR12) and supernovae (Pantheon compressed). Our findings demonstrate that expansion histories close to a cosmological constant exist in large regions of the parameter space, not requiring a fine-tuning of the parameters or initial conditions.

- Authors:

- Consejo Superior de Investigaciones Cientificas (CSIC), Madrid (Spain); Institut de Ciencies del Cosmos (UB-IEEC), Barcelona (Spain)
- Univ. of California, Berkeley, CA (United States); Nazarbayev Univ., Astana (Kazakhstan)
- Univ. of California, Berkeley, CA (United States); Univ. Paris-Saclay, Gif-sur-Yvette (France)

- Publication Date:

- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); Ministry of Industry, Science and Innovation of Spain

- OSTI Identifier:
- 1542391

- Grant/Contract Number:
- AC02-05CH11231; SC0007867; BES-2016-077038

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of Cosmology and Astroparticle Physics

- Additional Journal Information:
- Journal Volume: 2018; Journal Issue: 08; Journal ID: ISSN 1475-7516

- Publisher:
- Institute of Physics (IOP)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTRONOMY AND ASTROPHYSICS

### Citation Formats

```
García-García, Carlos, Linder, Eric V., Ruíz-Lapuente, Pilar, and Zumalacárregui, Miguel. Dark energy from α-attractors: phenomenology and observational constraints. United States: N. p., 2018.
Web. doi:10.1088/1475-7516/2018/08/022.
```

```
García-García, Carlos, Linder, Eric V., Ruíz-Lapuente, Pilar, & Zumalacárregui, Miguel. Dark energy from α-attractors: phenomenology and observational constraints. United States. doi:10.1088/1475-7516/2018/08/022.
```

```
García-García, Carlos, Linder, Eric V., Ruíz-Lapuente, Pilar, and Zumalacárregui, Miguel. Fri .
"Dark energy from α-attractors: phenomenology and observational constraints". United States. doi:10.1088/1475-7516/2018/08/022. https://www.osti.gov/servlets/purl/1542391.
```

```
@article{osti_1542391,
```

title = {Dark energy from α-attractors: phenomenology and observational constraints},

author = {García-García, Carlos and Linder, Eric V. and Ruíz-Lapuente, Pilar and Zumalacárregui, Miguel},

abstractNote = {The possibility of linking inflation and late cosmic accelerated expansion using the $\alpha$-attractor models has received increasing attention due to their physical motivation. In the early universe, $\alpha$-attractors provide an inflationary mechanism compatible with Planck satellite CMB observations and predictive for future gravitational wave CMB modes. Additionally $\alpha$-attractors can be written as quintessence models with a potential that connects a power law regime with a plateau or uplifted exponential, allowing a late cosmic accelerated expansion that can mimic behavior near a cosmological constant. In this paper we study a generalized dark energy $\alpha$-attractor model. We thoroughly investigate its phenomenology, including the role of all model parameters and the possibility of large-scale tachyonic instability clustering. We confirm the relation that $1+w\sim 1/\alpha$ (while the gravitational wave power $r\sim\alpha$) so these models predict that a signature should appear in either the primordial B-modes or in late time deviation from a cosmological constant. We constrain the model parameters with current datasets, including the cosmic microwave background (Planck 2015 angular power spectrum, polarization and lensing), baryon acoustic oscillations (BOSS DR12) and supernovae (Pantheon compressed). Our findings demonstrate that expansion histories close to a cosmological constant exist in large regions of the parameter space, not requiring a fine-tuning of the parameters or initial conditions.},

doi = {10.1088/1475-7516/2018/08/022},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 08,

volume = 2018,

place = {United States},

year = {2018},

month = {8}

}

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#### Figures / Tables:

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Figures / Tables found in this record:

*Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.*