Vacuum decay
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Vacuum decay | |
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| Type | Theoretical physical process |
| Field | Quantum field theory; Cosmology; Particle physics |
| Core idea | Transition from a metastable vacuum state to a lower-energy vacuum |
| Assumptions | The current vacuum state may not be the absolute minimum of energy |
| Status | Theoretically possible; no observational evidence |
| Related | Quantum vacuum; False vacuum; Higgs field; Cosmological stability |
Vacuum decay refers to a hypothetical process in which the universe transitions from its current vacuum state to a lower-energy vacuum configuration. In quantum field theory, the vacuum is not simply empty space but a state defined by the lowest available energy of underlying fields.
If the present vacuum is only metastable, a lower-energy state could exist and be reached through quantum tunneling.
Definition
A vacuum state is defined as the lowest-energy configuration of a quantum field. A false vacuum is a local energy minimum that is not the absolute lowest possible state.
Vacuum decay describes the transition from a false vacuum to a true vacuum.
Metastability
In a metastable vacuum, the universe appears stable over long timescales but is not fundamentally permanent. Quantum mechanics permits tunneling through energy barriers even when classical transitions are forbidden.
Such decay would occur spontaneously and unpredictably.
Bubble nucleation
Vacuum decay is typically modeled as the nucleation of a bubble of lower-energy vacuum. This bubble would expand outward at near the speed of light, converting surrounding spacetime to the new vacuum state.
Observers would not receive advance warning.
Physical consequences
The properties of particles, forces, and spacetime itself depend on the vacuum configuration. A transition to a lower-energy vacuum could alter fundamental constants, particle masses, and interaction strengths.
Such a transition would be incompatible with existing structures, including atoms and chemistry.
Higgs field considerations
Measurements of the Higgs field suggest that the current vacuum may be metastable under certain assumptions about particle masses and interactions. These conclusions depend sensitively on parameters such as the top quark mass.
Uncertainty remains regarding the true stability of the vacuum.
Triggering mechanisms
In theory, vacuum decay can occur spontaneously via quantum tunneling. Some speculative discussions consider whether high-energy events could trigger decay, but no known process can induce it deliberately.
Cosmic rays and particle accelerators are not considered credible triggers.
Misconceptions
Vacuum decay is sometimes portrayed as an explosion propagating through space. In reality, it would be a change in the underlying field configuration, not a conventional explosion.
It would not be observable before arrival.
Limits and constraints
No experimental evidence indicates that vacuum decay has occurred or is imminent. Theoretical estimates suggest timescales vastly exceeding the current age of the universe.
Predictions depend on extrapolations of known physics.
Status
Vacuum decay remains a speculative but well-defined concept within quantum field theory. It serves as a tool for understanding vacuum structure and stability rather than as a practical concern.
Its relevance is primarily theoretical.