Space and Physics
PUBLISHED
Of all the possible ways for the universe to end, the one that is the most concerning is known as False Vacuum Decay. While the others are a problem for the far future, this one could be for the here and now, any time or anywhere in the cosmos, without seeing it coming. And the coolest part is that we can simulate it in the lab.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Forget the forever expansion of the heat death scenario or the reversal of it all, which would end in the Big Crunch. Those are end-of-the-universe theories that look at the bigger picture. What if the trouble was not there, but in the quantum world? Then we would be facing the False Vacuum Decay.
The universe likes things in the lowest energy state possible, also known as the ground state or true vacuum. It is possible for higher energy states to be metastable; this means that they can stay in them for an indefinite period, but it is always possible for the states to drop into the true ground state after a disturbance or spontaneously.
Now imagine that all the universe and all its properties, everything we consider the ground state, is not really the ground state. Not a true vacuum. There is something more stable. What might happen at any point is this switch to the real true vacuum, making the false vacuum we inhabit change completely. Bubbles of true vacuum would expand at the speed of light, changing the universe as they move. The actual properties of that universe are unknown, but we wouldn’t be there to experience it.
We do not have any evidence that we live in a false vacuum, and nobody is doing experiments to look at a true vacuum, so there’s no need to worry. Still, the question of the false vacuum decay is fascinating, and a few experiments in the last few years have investigated it. Some looked at the bubble production, others used quantum device to simulate this quantum phenomenon.
In the new experiment, physicists used Rydberg atoms. These are atoms that have been excited, so their electrons move onto higher orbitals, but unlike simple excitations, the orbitals are enormous, making them extremely large compared to other atoms. Sometimes 10,000 to 100,000 times larger than their not excited state.
Their exaggerated size is great for doing a variety of experiments. In this case, these atoms were placed in a ring, each atom next to one with an opposite spin. This alternating pattern creates a great ground state. Using a laser, the team was able to give the atoms a bit more energy, making all their spins aligned. This was the false vacuum state for the Rydberg atom ring. The rate at which the decay back to the ground state happened was seen to depend on the strength of the laser itself.
As mentioned, the experiment did not set out to learn about the false vacuum decay as a possible end of the universe, but as a quantum mechanical scenario. The work showed new insight, and the use of Rydberg atoms in such a geometry opens future possibilities to more complex experiments.
The study is published in Physical Review Letters.
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