Physicists have many interesting theories about how our universe might end up, including one that suggests it is not in its most stable state. If it goes to that state, we could all be plunged into quantum oblivion. Delicious, I know. But a new study suggests that this disturbing scenario may be less likely than feared—at least that’s what it is. It is known as false vacuum decay. In this hypothetical scenario, the universe appears stable to us, the local observer. But some calculations suggest that the universe is not in its most stable state, in which it has the lowest possible energy: a true vacuum. If the universe decides to tunnel to a more stable state, reality as we know it would disappear. This cosmic transition would create an apocalyptic quantum bubble that would expand at nearly the speed of light, completely rewriting the rules of physics without warning. However, a research team claims to have identified a mechanism by which the rapid expansion of the early universe triggered quantum effects that locked it into what the team calls a “cosmic lockdown.” So even if the universe really exists in a false vacuum, it is unlikely to decay into anything else, as the team explains in a recent paper published in the Journal of Cosmology and Astroparticle Physics. “The result does not prove that the current state of the universe will remain stable forever nor does it determine the specific probability that the Higgs field [which gives elementary particles their mass] will eventually decay,” the researchers explained in a statement from Syracuse University, where co-author Gregory Kaplanek serves as a postdoctoral researcher. A brief insight into physics. The story begins with the Higgs boson, which assigns mass to an otherwise soup universe. Fundamental particles like the electron gain mass by interacting with this field of particles, and it was from exploring this very useful metric that physicists realized that the universe might not be in its most secure state. stable.” A useful analogy is a ball moving across a landscape. “The valley we are trapped in would be the false vacuum: it seems stable because the ball sits comfortably at the bottom, but it is not the lowest energy state available. The deepest valley is the true vacuum.” And quantum mechanics introduces the “remarkable possibility” that the field passes through this hill, Kaplanek said. This would lead to dramatic changes in particle properties and forces, “fundamentally changing the universe as we know it,” he said. That makes it “important to understand whether there are physical mechanisms that can make a false vacuum more stable,” he added. Quantum interactions The latest findings argue that quantum fields do not exist in isolation. The team’s model evaluates how quantum fields evolve in rapidly expanding space, a setup that Kaplanek clarified was “motivated by and applicable to inflationary cosmology.” From the calculations, the team discovered that the tunneling capabilities of a quantum field are restricted by decoherence, a phenomenon in which quantum systems decay after interacting with their environment, acting more like classical systems. There are two possible scenarios. If the field calculated in the paper were heavier relative to the expansion rate of the universe, the universe would probably approach a true vacuum. If it were lighter, then “the system can’t keep up with the changes” and would likely fall into a false vacuum, Robson Christie, first author of the study and a physicist at the University of Portsmouth in the United Kingdom, told Quantum Insider. No mutes here? Either way, decoherence would help “lock” the system at whatever localized minimum it ended up at. This is due to the quantum Zeno effect, which explains how a monitored quantum system apparently has trouble transitioning from one state to another. In this case, the environment itself “effectively acts as a continuous monitor, because interactions continually transport information about the state of the field to their environment,” Kaplanek told Gizmodo. That said, the team explained that this framework does not completely rule out the possibility of false vacuum decay. Although the model takes into account previously overlooked factors, it remains a simplified iteration that does not consider other relevant elements, such as a changing cosmic expansion rate or the field’s own influence on gravity, the researchers added in the statement. Whether this mechanism currently protects our universe is beyond the scope of the new work, Kaplanek told Gizmodo. That would require a “considerably” more realistic estimate, he added. Still, the new findings offer a mechanism that could stabilize a false vacuum. And hey, if that protects us from quantum silencing, I’ll take it.
