Eternal Inflation: Bubble Universe Nucleation

Eternal Inflation

Nucleation rate Γ 1.0

Bubble wall speed (×c) 0.85

Background expansion H 0.35

Time scale 1.0×

Multiverse State

Scale factor a(t)

1.00

Bubbles nucleated

Collisions

Vol. converted

0.0%

How it works

Eternal inflation describes a false-vacuum background that expands exponentially, ("de Sitter" space, driven by a scalar inflaton field). Its physical volume grows as a(t) = e^Ht. Quantum tunnelling occasionally nucleates a bubble of true vacuum (a "pocket universe" — potentially ours) via the Coleman–De Luccia instanton:

Nucleation rate:  Γ ≈ A · e^(-B)   (per unit spacetime volume)
Scale factor:     a(t) = e^(H·t)
Bubble wall:      R_phys(t) = v_wall · c · (t − t_nucleation)
Comoving radius:  r(t) = R_phys(t) / a(t)

Because the background volume grows faster than any finite nucleation rate can convert it, inflation never globally ends — new bubbles keep forming forever in the ever-growing false vacuum between them, producing an infinite multiverse of disconnected pocket universes.

Γ (nucleation rate) — how often new bubbles tunnel into existence per unit time.
Wall speed — how fast each bubble's true-vacuum boundary expands, close to the speed of light.
Expansion H — the Hubble rate of the background; higher H redshifts old bubbles' comoving size down faster, visually "outrunning" them.
Collisions (orange rings) — when two bubbles' walls meet, they leave a permanent scar. In our own universe such a collision would appear as a disk-shaped anomaly in the cosmic microwave background — a real, actively searched-for observational signature of a multiverse beyond ours.

When the scale factor grows too large the box auto-resets to a fresh comoving patch (the "New Multiverse Patch" button does the same) — inflation itself has no end, so this is a window onto one region of an endless process.

Patch #1

True-vacuum bubble Collision scar False-vacuum background

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