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The Boundary Proposal vs Vilenkin's Tunneling from Nothing

Quantum Tunneling Origin· within family

	The Boundary Proposal Speculative	Vilenkin's Tunneling from Nothing Speculative
Proposed	2024	1982
Key figures	Bjoern Hassfeld, Arthur Hebecker	Alexander Vilenkin
In one sentence	An alternative to Hartle-Hawking and Vilenkin in which the universe begins with a finite spacelike spherical boundary that can dominate over the no-boundary instanton.	Vilenkin proposed in 1982 that the universe quantum-tunneled into existence from a state with no space, no time, no fields, literal nothing.
Predictions	Distinct primordial perturbation spectrum from Hartle-Hawking and Vilenkin proposals Specific signatures in the CMB tied to the boundary geometry	[[Inflation]] begins naturally with high probability after tunneling Universe is initially small, closed, and de Sitter-like No contracting phase before the Bang
Where it breaks	Requires specifying the boundary geometry as input, which some critics view as no improvement over the boundary conditions it replaces. The phenomenological implications are still being worked out and have not yet been compared to Planck data.	Krauss: still requires quantum laws, so not really nothing Hawking & Bousso (1995): catastrophic particle production Penrose: ignores Weyl curvature hypothesis
Key unresolved problem	The input-geometry problem: the proposal has to be handed the size of its starting boundary surface from outside, which critics say just moves the fine-tuning problem somewhere else rather than removing it.	The laws-from-nothing problem: the quantum tunneling that creates the universe still needs quantum laws and a space of possible states to work in, so the proposal has not truly started from nothing.
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The Boundary Proposal

2024 · Speculative

Vilenkin's Tunneling from Nothing

1982 · Speculative

Proposed

2024

1982

Key figures

Bjoern Hassfeld, Arthur Hebecker

Alexander Vilenkin

In one sentence

An alternative to Hartle-Hawking and Vilenkin in which the universe begins with a finite spacelike spherical boundary that can dominate over the no-boundary instanton.

Vilenkin proposed in 1982 that the universe quantum-tunneled into existence from a state with no space, no time, no fields, literal nothing.

Predictions

Distinct primordial perturbation spectrum from Hartle-Hawking and Vilenkin proposals
Specific signatures in the CMB tied to the boundary geometry

[[Inflation]] begins naturally with high probability after tunneling
Universe is initially small, closed, and de Sitter-like
No contracting phase before the Bang

Where it breaks

Requires specifying the boundary geometry as input, which some critics view as no improvement over the boundary conditions it replaces.
The phenomenological implications are still being worked out and have not yet been compared to Planck data.

Krauss: still requires quantum laws, so not really nothing
Hawking & Bousso (1995): catastrophic particle production
Penrose: ignores Weyl curvature hypothesis

Key unresolved problem

The input-geometry problem: the proposal has to be handed the size of its starting boundary surface from outside, which critics say just moves the fine-tuning problem somewhere else rather than removing it.

The laws-from-nothing problem: the quantum tunneling that creates the universe still needs quantum laws and a space of possible states to work in, so the proposal has not truly started from nothing.

Reader vote

0% · 0 votes

100% · 2 votes