Coleman-De Luccia Bubble Nucleation

1980Sidney Coleman, Frank De LucciaSpeculativeAlso answers, Ch.02 The Origin of Our UniverseAlso answers, Ch.07 The Fate of the Universe3 primary sources, 3 established

False vacuum decay with gravity. The standard mechanism for bubble nucleation.

Visualisation · Quantum Vacuum Mechanism

false vacuum: A field stuck in a state that looks empty and stable but isn't the lowest-energy one. It can collapse later.
bubble universe: A region of inflating space where inflation ends locally, producing an isolated universe inside the larger inflating bulk.
vacuum decay: The collapse of a false vacuum into its true, lower-energy state. The collapse spreads outward as an expanding bubble.
eternal inflation: A scenario where inflation, once started, never stops in some regions of space. The dominant inflation paradigm since 1986.
scalar field: A field with one value at each point in space, like a temperature map. The inflaton is one example.

§1 · The claim, in one sentence

Coleman and De Luccia worked out in 1980 how a false vacuum decays to a true vacuum in the presence of gravity, producing an expanding bubble universe.

§2 · Why it might be true

In quantum field theory, a vacuum is never truly nothing, it is the lowest-energy state of a field, but the field still has structure and fluctuations. A single field can have multiple vacuum states with different energies. A "false vacuum" is metastable: stable for now, but eventually quantum tunneling lets it decay to a lower minimum.

When a region of false vacuum decays, it nucleates a bubble. The bubble expands at nearly the speed of light. Inside the bubble, the energy difference between vacuum states converts into matter and radiation. The interior looks like a brand-new universe with its own hot beginning.

The family stance

A parent vacuum state with structured fields, energy density, and the full machinery of QFT. The vacuum is "something," not nothing, in the QFT sense.

§2.5 · Evidence

Vacuum decay is well-understood in QFT
Mechanism is mathematically rigorous
Underlies bubble nucleation in Eternal Inflation

§3 · What you'd need to test it

Interior of bubble universe is open, negatively curved FRW universe
Bubble walls expand at nearly light speed
Different bubbles can have different physical constants

§4 · Where it breaks

Mechanism, not origin, parent vacuum still unexplained
No direct observation of bubble walls
Specific cosmological realization requires speculative high-energy physics

Go deeper

Coleman-De Luccia: scalar field V(φ) with metastable false vacuum and lower true vacuum, coupled to gravity. Find an O(4)-symmetric Euclidean bounce solution.

Decay rate per unit four-volume: Γ ~ A·exp(-B/ℏ) where B = S_E[bounce] - S_E[false vacuum]. Gravity modifies B, sometimes stabilizing vacua or enabling new channels (Hawking-Moss instanton).

Lorentzian continuation gives an expanding true-vacuum bubble. The interior is an open FRW universe with negative spatial curvature.

▸§5 · Who built it, and when(3 sources, 3 established)

Variants in this family

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