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Wormhole Nucleation from Anti-de Sitter vs The Boundary Proposal

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	Wormhole Nucleation from Anti-de Sitter Speculative	The Boundary Proposal Speculative
Proposed	2024 / 2026	2024
Key figures	Panos Betzios, Olga Papadoulaki, George Lavrelashvili, Jean-Luc Lehners	Bjoern Hassfeld, Arthur Hebecker
In one sentence	A wave function for the universe in which a Euclidean wormhole, anchored in an anti-de Sitter region, gives birth to an expanding universe that begins with inflation.	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.
Predictions	A small shift and faint oscillations in the [[cosmic microwave background]] on the largest angular scales, with a size set by the wormhole's charge Short-wavelength fluctuations identical to those of standard inflation, so the signature appears only on the largest scales Wormholes with small charge give a longer phase of inflation than wormholes with large charge	Distinct primordial perturbation spectrum from Hartle-Hawking and Vilenkin proposals Specific signatures in the CMB tied to the boundary geometry
Where it breaks	Lavrelashvili and Lehners find that no-boundary instantons still dominate the overall probability, which weakens the case that wormholes are the preferred beginning. The universe needs a parent anti-de Sitter or flat region to emerge from, which moves the question of origins back one step. The predicted signal sits on the largest scales of the sky, where there are too few independent patches to measure it precisely.	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.
Key unresolved problem	Which beginning wins: the wormhole, or the no-boundary instanton it turns into at zero charge. Current calculations still favour no-boundary overall, so the wormhole route needs a reason to be selected.	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.
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Wormhole Nucleation from Anti-de Sitter

2024 / 2026 · Speculative

The Boundary Proposal

2024 · Speculative

Proposed

2024 / 2026

2024

Key figures

Panos Betzios, Olga Papadoulaki, George Lavrelashvili, Jean-Luc Lehners

Bjoern Hassfeld, Arthur Hebecker

In one sentence

A wave function for the universe in which a Euclidean wormhole, anchored in an anti-de Sitter region, gives birth to an expanding universe that begins with inflation.

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.

Predictions

A small shift and faint oscillations in the [[cosmic microwave background]] on the largest angular scales, with a size set by the wormhole's charge
Short-wavelength fluctuations identical to those of standard inflation, so the signature appears only on the largest scales
Wormholes with small charge give a longer phase of inflation than wormholes with large charge

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

Where it breaks

Lavrelashvili and Lehners find that no-boundary instantons still dominate the overall probability, which weakens the case that wormholes are the preferred beginning.
The universe needs a parent anti-de Sitter or flat region to emerge from, which moves the question of origins back one step.
The predicted signal sits on the largest scales of the sky, where there are too few independent patches to measure it precisely.

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.

Key unresolved problem

Which beginning wins: the wormhole, or the no-boundary instanton it turns into at zero charge. Current calculations still favour no-boundary overall, so the wormhole route needs a reason to be selected.

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.

Reader vote

No votes yet