False Vacuum Bubbles Research Articles

Radiation and false-vacuum bubble dynamics

It is shown that child universes may be detected by an external observer via radiation emitted by a restricted class of black holes associated with a generalization of the model of Blau, Guendelman, and Guth. The equations of motion for false-vacuum bubbles in Vaidya-Mallett metrics are derived and numerically solved. It is demonstrated that the evolution of the bubble differs from the standard Schwarzschild-de Sitter results. The luminosity as measured by an external observer is found to deviate from the normal Hawking luminosity, thus producing a signature for the existence of the child universe.

Can a man-made Universe be created by quantum tunneling without an initial singularity?

Essentially all modern particle theories suggest the possible existence of a false vacuum state – a metastable state with an energy density that cannot be lowered except by means of a very slow phase transition. Inflationary cosmology makes use of such a state to drive the expansion of the big bang, allowing the entire observed universe to evolve from a very small initial mass. A sphere of false vacuum in our present universe, if larger than a certain critical mass, could inflate to form a new universe which would rapidly detach from its parent. A false vacuum bubble of this size, however, cannot be produced classsically unless an initial singularity is present from the outset. We therefore explore the possibility that a bubble of subcritical size, which classically would evolve to a maximum size and collapse, might instead tunnel through a barrier to produce a new universe. We estimate the tunneling rate using semiclassical quantum gravity, and discover some interesting ambiguities in the formalism.

Quantization of false-vacuum bubbles: A Hamiltonian treatment of gravitational tunneling.

We develop the quantization of spherically symmetric gravitational systems using the Dirac formalism and the WKB approximation. The particular application is the nucleation of false-vacuum bubbles, which may have been the origin of the inflationary universe and matter. Consistency between our results and those obtained by the Euclidean method requires that the latter include metrics with degeneracies. Our work also raises several other questions of principle, including the meaning of the wave function and the necessity of topology change. A tentative application of this work to quantum cosmology indicates that the "Hartle-Hawking wave function" is inconsistent.

Black-hole nucleosynthesis and Omega B=1.

Black holes may be produced from false-vacuum bubble implosions at the end of the quantum chromodynamics phase transition. Evaporation of these black holes during the keV era readjusts the abundances of light nuclei. An appropriate mass distribution of black holes gives nuclear abundances broadly consistent with observations even for ${\mathrm{\ensuremath{\Omega}}}_{\mathit{B}}$=1, reconciling a critical baryonic universe with standard-model particle physics.

Cosmological production of black holes.

It is argued that, at a first-order phase transition, false-vacuum bubbles may occasionally collapse to become black holes. If the critical temperature ${\mathit{T}}_{\mathit{c}}$ is less than a TeV, these black holes, which have a mass proportional to ${\mathit{M}}_{\mathrm{Pl}}^{2}$/${\mathit{T}}_{\mathit{c}}$, could survive until today to be the dark matter. Alternatively, evaporation of black holes could give rise to relic particle abundances.

Quantum nucleation of false-vacuum bubbles.

We show that a small bubble of false vacuum can tunnel to the critical size for inflation, and calculate the amplitude in leading WKB approximation. An initially nonsingular space becomes and exterior space plus a baby universe (which contains the bubble), joined by a black-hole singularity. We work in a Hamiltonian formalism; the corresponding Euclidean bounce is shown to have a degenerate vierbein.

Thin walls in regions with vacuum energy

The motion of a thin wall is treated in the case where the regions on either side of the wall have vacuum energy. This treatment generalises previous results involving domain walls in vacuum and also previous results involving the properties of false vacuum bubbles. The equation of state for a domain wall is tau = sigma where tau is the tension in the wall and sigma is the energy density. The authors consider the motion of a more general class of walls having equation of state tau = Gamma sigma with 0<or= Gamma <or=1. Spherically symmetric and planar symmetric walls are examined. They also find the global structure of the wall spacetime.

Comment on "Dynamics of false-vacuum bubbles"

It is pointed out that there is no reason to believe that detachment of the false vacuum is ever achieved for nondegenerate real vacua in view of the instability of nondegenerate Killing horizons to the past of their bifurcation.

Dynamics of false-vacuum bubbles.

The possibility of localized inflation is investigated by calculating the dynamics of a spherically symmetric region of false vacuum which is separated by a domain wall from an infinite region of true vacuum. For a range of initial conditions, the false-vacuum region will undergo inflation. An observer in the exterior true-vacuum region will describe the system as a black hole, while an observer in the interior will describe a closed universe which completely disconnects from the original spacetime. We suggest that this mechanism is likely to lead to an instability of Minkowski space: a region of space might undergo a quantum fluctuation into the false-vacuum state, evolving into an isolated closed universe; the black hole which remains in the original space would disappear by quantum evaporation. The formation of these isolated closed universes may also be relevant to the question of information loss in black-hole formation.

An obstacle to creating a universe in the laboratory

We show that any spherically symmetric false vacuum bubble which forms in an asymptotically flat space and grows beyond a certain critical size must have merged from an initial singularity. Our result requires that the energy-momentum tensor obey the condition T μν k μ k ν ⩾0 for all null k μ, a property which holds at the classical level for almost all theories of matter. For the non-spherical case, we state a necessary condition that a false vacuum bubble must meet in order to avoid an initial singularity. We do not know if this condition can ever be met. The requirement of an initial singularity appears to be an insurmountable obstacle to the creation of an inflationary universe in the laboratory.