# Singular instantons in Eddington-inspired-Born-Infeld gravity

## Abstract

In this work, we investigate O (4)-symmetric instantons within the Eddington-inspired-Born-Infeld gravity theory (EiBI) . We discuss the regular Hawking-Moss instanton and find that the tunneling rate reduces to the General Relativity (GR) value, even though the action value is different by a constant. We give a thorough analysis of the singular Vilenkin instanton and the Hawking-Turok instanton with a quadratic scalar field potential in the EiBI theory. In both cases, we find that the singularity can be avoided in the sense that the physical metric, its scalar curvature and the scalar field are regular under some parameter restrictions, but there is a curvature singularity of the auxiliary metric compatible with the connection. We find that the on-shell action is finite and the probability does not reduce to its GR value. We also find that the Vilenkin instanton in the EiBI theory would still cause the instability of the Minkowski space, similar to that in GR, and this is observationally inconsistent. This result suggests that the singularity of the auxiliary metric may be problematic at the quantum level and that these instantons should be excluded from the path integral.

- Authors:

- Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei, 10617, Taiwan (China)

- Publication Date:

- OSTI Identifier:
- 22679959

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 03; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; BORN-INFELD THEORY; GENERAL RELATIVITY THEORY; GRAVITATION; INSTABILITY; INSTANTONS; METRICS; MINKOWSKI SPACE; PROBABILITY; SCALAR FIELDS; SINGULARITY; SYMMETRY; TUNNEL EFFECT

### Citation Formats

```
Arroja, Frederico, Chen, Che-Yu, Chen, Pisin, and Yeom, Dong-han, E-mail: arroja@phys.ntu.edu.tw, E-mail: b97202056@gmail.com, E-mail: pisinchen@phys.ntu.edu.tw, E-mail: innocent.yeom@gmail.com.
```*Singular instantons in Eddington-inspired-Born-Infeld gravity*. United States: N. p., 2017.
Web. doi:10.1088/1475-7516/2017/03/044.

```
Arroja, Frederico, Chen, Che-Yu, Chen, Pisin, & Yeom, Dong-han, E-mail: arroja@phys.ntu.edu.tw, E-mail: b97202056@gmail.com, E-mail: pisinchen@phys.ntu.edu.tw, E-mail: innocent.yeom@gmail.com.
```*Singular instantons in Eddington-inspired-Born-Infeld gravity*. United States. doi:10.1088/1475-7516/2017/03/044.

```
Arroja, Frederico, Chen, Che-Yu, Chen, Pisin, and Yeom, Dong-han, E-mail: arroja@phys.ntu.edu.tw, E-mail: b97202056@gmail.com, E-mail: pisinchen@phys.ntu.edu.tw, E-mail: innocent.yeom@gmail.com. Wed .
"Singular instantons in Eddington-inspired-Born-Infeld gravity". United States.
doi:10.1088/1475-7516/2017/03/044.
```

```
@article{osti_22679959,
```

title = {Singular instantons in Eddington-inspired-Born-Infeld gravity},

author = {Arroja, Frederico and Chen, Che-Yu and Chen, Pisin and Yeom, Dong-han, E-mail: arroja@phys.ntu.edu.tw, E-mail: b97202056@gmail.com, E-mail: pisinchen@phys.ntu.edu.tw, E-mail: innocent.yeom@gmail.com},

abstractNote = {In this work, we investigate O (4)-symmetric instantons within the Eddington-inspired-Born-Infeld gravity theory (EiBI) . We discuss the regular Hawking-Moss instanton and find that the tunneling rate reduces to the General Relativity (GR) value, even though the action value is different by a constant. We give a thorough analysis of the singular Vilenkin instanton and the Hawking-Turok instanton with a quadratic scalar field potential in the EiBI theory. In both cases, we find that the singularity can be avoided in the sense that the physical metric, its scalar curvature and the scalar field are regular under some parameter restrictions, but there is a curvature singularity of the auxiliary metric compatible with the connection. We find that the on-shell action is finite and the probability does not reduce to its GR value. We also find that the Vilenkin instanton in the EiBI theory would still cause the instability of the Minkowski space, similar to that in GR, and this is observationally inconsistent. This result suggests that the singularity of the auxiliary metric may be problematic at the quantum level and that these instantons should be excluded from the path integral.},

doi = {10.1088/1475-7516/2017/03/044},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 03,

volume = 2017,

place = {United States},

year = {Wed Mar 01 00:00:00 EST 2017},

month = {Wed Mar 01 00:00:00 EST 2017}

}