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 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.
Highlights
This is accomplished by tiling the reheating surface with a continuous set of cosmological coordinate patches
Comparing the outcome for the two initial separations, we see that a larger ∆xsep yields steeper profiles for R(ξ). This is in agreement with previous work [12], where increasing ∆xsep was found to lead to an increasing slope of the comoving curvature perturbation as seen by instanton-born observers
Using a new method for extracting observables from cosmological simulations, we have extended previous work on predicting observables from cosmic bubble collisions in eternal inflation to the entire collision spacetime
Summary
To construct the bubble collision spacetimes, we use the simulation code described in Ref. [11]. To construct the bubble collision spacetimes, we use the simulation code described in Ref. Within this framework, we assume the SO(2,1) symmetry of the collision spacetime [34] between two Coleman-de Luccia vacuum bubbles [45, 46], allowing us to perform simulations in one space and one time dimension. [11] this was accomplished by evolving a set of geodesics through the simulation to construct a perturbed FRW universe in the synchronous gauge. For single-field models, the comoving gauge is defined by slices of constant field. Which the induced metric on slices of constant field deriving from Eq 2.1 is explicitly the perturbed open FRW metric in comoving gauge
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