Our observable universe, despite its apparent stability, may only be in a state of temporary lull, fraught with the risk of sudden collapse. The current understanding of the vacuum as the lowest energy state might be erroneous; there could exist an even more stable, lower-energy state. A publication in the journal Physical Review Letters highlights this new research. Theoretically, the transition of even a small region of space into this hypothetical state would lead to its exponential expansion at the speed of light, rewriting the fundamental laws of physics. Welcome to the concept of false vacuum decay—one of the most terrifying ideas in quantum theory. Physicists from Tsinghua University have developed a way to simulate this process under laboratory conditions. The impetus for the research is that in some theoretical models, false vacuum decay signifies the complete annihilation of our universe. The study lies at the intersection of quantum theory and general relativity, making it a potential tool for resolving fundamental contradictions between these two fields. General relativity perfectly describes physical processes on cosmological scales and at high speeds. However, in the microworld, at the quantum level, its applicability is limited. Quantum field theory, which studies the interaction of quantum fields and particles, is more suitable for describing subatomic phenomena. In their respective domains of applicability, both theories work flawlessly. But in extreme conditions where they overlap, a complexity arises. The absence of a single, comprehensive theory compels scientists to explore these points of contact. Quantum field theory predicts that an absolute vacuum does not exist. What we consider a vacuum is actually a quantum field in a state of minimum energy. If the energy landscape of the field has several local minima, these represent “false vacuums,” from which spontaneous tunneling into a more stable, “true” state with even lower energy is possible. Similarly, if one imagines a landscape with multiple lakes, there might be a deeper basin beneath some of them. A tunnel breach from the upper lake to the lower one would cause the water to flow. In the case of the cosmic vacuum, such a process would mean a small region of space transitioning into a low-energy state, forming a “bubble.” Upon reaching a critical size, this bubble would begin to expand at a speed close to the speed of light, transforming everything in its path. False vacuum decay is a process situated at the intersection of quantum mechanics (the initial tunneling) and general relativity (the large-scale expansion). Neither theory alone can fully describe this phenomenon. In the laboratory experiment, the researchers did not manipulate the real vacuum. Instead, they used a ring of Rydberg atoms as a model. Rydberg atoms are highly excited atoms with greatly expanded electron shells, possessing unusual properties useful for experiments. By creating a ring of an even number of mutually repulsive Rydberg atoms, where spin states were arranged symmetrically, the scientists broke this symmetry using lasers. This created two energetically close states—an analogue of the false and true vacuum. The excited ring then spontaneously “decayed” into a more stable state, with the speed depending on the laser power. This mimics the formation of a quantum bubble facilitating the transition to the true vacuum. The experiment confirms theoretical models of false vacuum decay, creating a new platform for investigating the interaction between quantum physics and general relativity. Perhaps in the future, it will help in assessing the real danger of a sudden transformation of our universe.
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