There’s a profound worry underlying the fundamental physics of existence: The Universe may not be quite as stable as we’d ideally like it to be.
Quantum field theory describes invisible quantum fields all around us, producing subatomic vibrations that show up as particles and matter.
These fields tend to seek out the lowest possible energy state, like a marble settling at the bottom of a bowl – and certain fields may have lower to go than they are currently.
In a new study in the Journal of Cosmology and Astroparticle Physics, researchers led by a team from the University of Portsmouth in the UK detail some reassuring discoveries that suggest quantum fields could become effectively locked in place, which could help explain why the Universe has remained stable.
The findings address concerns that via an effect known as quantum tunneling, fields could shift states without warning. The Higgs field, which gives mass to particles including electrons, is one field scientists think may be resting in a ‘false vacuum’.
“In principle, a transition to that deeper minimum would take the Universe into a radically different state, in which the structure of matter and the forces that govern it would be altered,” says physicist Robson Christie from the University of Portsmouth.
frameborder=”0″ allow=”accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” allowfullscreen>
The researchers put together a mathematical model of the Universe as it expands, tracking the behavior of quantum fields as they interacted with each other. It was essentially a simplified simulation of unequal valleys, representing energy states.
Crucial to the model was the setup of one field surrounded by other fields – the surrounding environment. This ties in to the concept of decoherence in quantum computing, where delicate quantum systems can be knocked out of line by interference from the environment.
“Perfect isolation is an idealization,” says computer scientist Greg Kaplanek from Syracuse University in New York.
“Think, for example, of quantum computers: We go to enormous lengths to protect the quantum information stored in these machines from the environment, because even weak interactions with it can quickly alter the quantum state.
“Something similar happens in cosmology: A field is never really alone.”
In a similar way to how a surrounding environment can cause decoherence and a loss of quantum effects in computers, surrounding fields can also limit the possibility of quantum effects (the catastrophic tunneling behavior) in quantum fields, the researchers determined from their model.
The study team calls it “cosmic lockdown”, and it means the valley jumping that physicists were worried about could be strongly suppressed – though not impossible.
The model analysis also found that a quantum field’s mass in relation to the speed of the expansion of the Universe (the Hubble scale) influences the valley the field finds itself in to begin with.
“A field that is heavy compared with the Hubble scale can quickly adjust to the changes as the Universe expands, and in this case it is highly likely to move towards the true vacuum, the deepest energy minimum,” says Christie.
“If the expansion is too rapid compared with the dynamics of the field, the system cannot keep up with the changes. In this case there can remain a significant probability that the field will also end up in the false vacuum.”
The researchers compare it to another known phenomenon, the quantum Zeno effect, which essentially posits that a system doesn’t change state when it starts to be measured or monitored – which the quantum field interactions are doing here.
We can perhaps rest a little easier when it comes to the fate of the Universe, then, though the researchers acknowledge that more complex models are needed to investigate this idea further, and to analyze actual quantum fields like the Higgs field.
“If a mechanism of this kind were relevant in more realistic cosmological situations, then it could help stabilize a field that is already sitting in a false vacuum, but understanding how far this can be applied to the Higgs field will require more realistic models,” says cosmologist David Wands from the University of Portsmouth.
The research has been published in Journal of Cosmology and Astroparticle Physics.
This article was fact-checked by Peter Dockrill and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
