# Simulating the universe(s) III: observables for the full bubble collision spacetime

## Abstract

This is the third paper in a series establishing a quantitative relation between inflationary scalar field potential landscapes and the relic perturbations left by the collision between bubbles produced during eternal inflation. We introduce a new method for computing cosmological observables from numerical relativity simulations of bubble collisions in one space and one time dimension. This method tiles comoving hypersurfaces with locally-perturbed Friedmann-Robertson-Walker coordinate patches. The method extends previous work, which was limited to the spacetime region just inside the future light cone of the collision, and allows us to explore the full bubble-collision spacetime. We validate our new methods against previous work, and present a full set of predictions for the comoving curvature perturbation and local negative spatial curvature produced by identical and non-identical bubble collisions, in single scalar field models of eternal inflation. In both collision types, there is a non-zero contribution to the spatial curvature and cosmic microwave background quadrupole. Some collisions between non-identical bubbles excite wall modes, giving extra structure to the predicted temperature anisotropies. We comment on the implications of our results for future observational searches. For non-identical bubble collisions, we also find that the surfaces of constant field can readjust in the presence ofmore »

- Authors:

- Department of Physics and Astronomy, York University, Toronto, On, M3J 1P3 (Canada)
- (Canada)
- SCIPP and Department of Physics, University of California, Santa Cruz, CA, 95064 (United States)
- Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

- Publication Date:

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

- OSTI Identifier:
- 22572117

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2016; Journal Issue: 07; Other Information: PUBLISHER-ID: JCAP07(2016)020; OAI: oai:repo.scoap3.org:16438; 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; BUBBLES; COLLISIONS; COSMOLOGICAL INFLATION; COSMOLOGY; DISTURBANCES; GENERAL RELATIVITY THEORY; INFLATIONARY UNIVERSE; LIGHT CONE; PERTURBATION THEORY; POTENTIALS; RELICT RADIATION; SCALAR FIELDS; STRING THEORY

### Citation Formats

```
Johnson, Matthew C., Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Wainwright, Carroll L., Aguirre, Anthony, and Peiris, Hiranya V.
```*Simulating the universe(s) III: observables for the full bubble collision spacetime*. United States: N. p., 2016.
Web. doi:10.1088/1475-7516/2016/07/020.

```
Johnson, Matthew C., Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Wainwright, Carroll L., Aguirre, Anthony, & Peiris, Hiranya V.
```*Simulating the universe(s) III: observables for the full bubble collision spacetime*. United States. doi:10.1088/1475-7516/2016/07/020.

```
Johnson, Matthew C., Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Wainwright, Carroll L., Aguirre, Anthony, and Peiris, Hiranya V. Thu .
"Simulating the universe(s) III: observables for the full bubble collision spacetime". United States.
doi:10.1088/1475-7516/2016/07/020.
```

```
@article{osti_22572117,
```

title = {Simulating the universe(s) III: observables for the full bubble collision spacetime},

author = {Johnson, Matthew C. and Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 and Wainwright, Carroll L. and Aguirre, Anthony and Peiris, Hiranya V.},

abstractNote = {This is the third paper in a series establishing a quantitative relation between inflationary scalar field potential landscapes and the relic perturbations left by the collision between bubbles produced during eternal inflation. We introduce a new method for computing cosmological observables from numerical relativity simulations of bubble collisions in one space and one time dimension. This method tiles comoving hypersurfaces with locally-perturbed Friedmann-Robertson-Walker coordinate patches. The method extends previous work, which was limited to the spacetime region just inside the future light cone of the collision, and allows us to explore the full bubble-collision spacetime. We validate our new methods against previous work, and present a full set of predictions for the comoving curvature perturbation and local negative spatial curvature produced by identical and non-identical bubble collisions, in single scalar field models of eternal inflation. In both collision types, there is a non-zero contribution to the spatial curvature and cosmic microwave background quadrupole. Some collisions between non-identical bubbles excite wall modes, giving extra structure to the predicted temperature anisotropies. We comment on the implications of our results for future observational searches. For non-identical bubble collisions, we also find that the surfaces of constant field can readjust in the presence of a collision to produce spatially infinite sections that become nearly homogeneous deep into the region affected by the collision. Contrary to previous assumptions, this is true even in the bubble into which the domain wall is accelerating.},

doi = {10.1088/1475-7516/2016/07/020},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 07,

volume = 2016,

place = {United States},

year = {Thu Jul 14 00:00:00 EDT 2016},

month = {Thu Jul 14 00:00:00 EDT 2016}

}