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A simplified cosmological model suggests that interactions with the environment can suppress quantum tunneling, effectively locking fields into the vacuum state they have reached. In cosmology, a vacuum is not empty space but a state where a field sits at a minimum of its energy. There can be local minima called false vacua and a deeper true vacuum. A field trapped in a shallower valley might remain there even if a lower-energy state exists elsewhere.

Researchers Robson Christie, Jaewoo Joo, Greg Kaplanek, Vincent Vennin, and David Wands published a study in the Journal of Cosmology and Astroparticle Physics to investigate which vacuum a field may end up in within an expanding universe. They used the Higgs field as an example, noting that calculations suggest it might sit in a false vacuum while a deeper minimum exists at very large field values. A transition to this deeper state would radically alter the structure of matter and forces.

The study found that while perfect isolation is an idealization, fields continuously interact with their environment, producing decoherence. This phenomenon destroys quantum superpositions, making systems behave more like ordinary classical systems. The research indicates that once a field localizes in one minimum, decoherence tends to keep it there by strongly suppressing tunneling toward the other vacuum.

This effect is termed "cosmic lockdown," interpreted as a manifestation of the quantum Zeno effect where continuous monitoring hinders state changes. Although the environment does not decide the initial choice of vacuum, the field’s relationship with the Hubble scale matters more. Heavy fields likely move toward the true vacuum, while lighter fields may stay in false vacua. Cosmic lockdown could help stabilize such fields, though applying this to the real Higgs field requires more realistic models.