In the very first moments of the universe, everything was hot and dense, in perfect equilibrium. There were no particles as we understand them, let alone any stars or the vacuum that fills space today. The entire space is filled with uniform, intangible, compressed matter. This substance is called primordial plasma, and it is an extreme state of quarks and gluons that are so hot and dense that they cannot form stable nuclei or atoms.
Then, something went wrong. All that monotonous stability has become unstable. Matter triumphs over its strange cousin, antimatter, and begins to rule the entire space. Clouds of matter form and collapse into stars, which in turn form galaxies. Everything we know is beginning to exist.
So, what caused the universe to transition from an invisible state? Scientists are still not sure. But researchers have found a new way to simulate in the lab the kind of flaws that could have caused an imbalance in the early universe. In a new article, scientists show that they can use ultra-cold helium to simulate the first moments of the universe's existence — specifically, a possible condition that might exist after recreating the big **. This is important because the universe is full of what physicists call "symmetry" in the form of equilibrium.
Some of the main examples: The physical equations are the same in both the forward and negative directions of time. This is called time reversal symmetry, which means that physical processes do not depend on the direction of time. The number of positively charged particles in the universe is just enough to cancel out all negatively charged particles. This is the conservation of charge, which means that the total amount of charge does not change.
But sometimes, symmetry is broken. A perfect sphere is balanced on the tip of the needle and will fall to one side or the other. This is called spontaneous symmetry breaking, which means that the ground state of the system no longer has the original symmetry. Two identical sides of a magnet separate into the North and South Poles. This is the magnetic monopole, which is an imaginary particle that has only one pole instead of a pair. Matter triumphed over antimatter early in the universe. This is the matter antimatter asymmetry, which is an unsolved mystery that suggests that there is a mechanism in the universe that prefers matter. Specific elementary particles emerge from the invisible in the early universe and interact with each other through discrete forces. This is the Standard Model of particle physics, which is a theory that describes elementary particles and three fundamental interactions (strong, weak, and electromagnetic).
If we take the existence of the big ** as an established fact, then the universe has undoubtedly undergone some symmetry-breaking transformation," said Jerre Makinen, lead author of the study and a doctoral student at Aalto University in Finland. Need proof? They are all around us. Every table, every chair, every galaxy, and every platypus proves what has transformed the universe from its early flat state to its present complexity. We are here, and not in a homogeneous void to become a possibility. So, there's something that breaks that symmetry.
Physicists call some random fluctuations that break symmetry "topological defects."
You must be curious, what is a topological defect, in fact, it is a phenomenon that breaks symmetry in a physical system, and they are usually formed due to different parts of the system choosing different vacuum states when undergoing a phase transition. There are different types of topological defects, such as point defects, line defects, surface defects, and volume defects, and their formation and properties can be described by mathematical topological theory. Topological defects have important applications and research values in the fields of cosmology, condensed matter physics, and particle physics.
Essentially, topological defects are in a uniform field where some anomalies appear. A disturbance appears suddenly. This may be due to outside interference, such as in experiments. Or it could happen randomly and mysteriously, as scientists suspect happened early in the universe. Once a topological defect is formed, it can stay in a uniform field, like a boulder creating ripples in a smooth flow of water.
Some researchers believe that some particular type of topological defect in the invisible matter of the early universe may have played a role in the initial symmetry-breaking transition of the universe. These defects may include a structure called a "semi-quantum vortex" (which looks a bit like a pattern of energy and matter in a vortex) and a structure called a "wall defined by strings" (a magnetic structure consisting of two one-dimensional "strings" defined by two two-dimensional walls). These spontaneously emerging structures affect the flow of matter in otherwise symmetrical systems, and some researchers suspect that these structures played a role in bringing the universe together into the stars and galaxies we see today. The existence of topological defects can explain some cosmological observations, such as the inhomogeneity of cosmic microwave background radiation and the origin of the cosmic magnetic field.
Researchers have previously created these types of defects in ultracold gases and the magnetic fields of superconductors in the laboratory. But these defects appear individually. Most theories that explain the origin of the modern universe in terms of topological defects involve "compound" defects — that is, multiple defects working together, Makinen said.
Multiple defect synergies generally refer to the interaction between defects of different types or locations in a physical system to enhance or degrade the performance or functionality of the system. For example, in photocatalysts, different defect sites can affect processes such as light absorption, carrier separation, and surface reactions, thereby increasing or decreasing photocatalytic activity and selectivity.
Based on this principle, Makkinen and his collaborators designed an experiment that involved cooling liquid helium to a fraction of a degree above absolute zero and extruding it into tiny chambers. In the darkness of those little boxes, semi-quantum vortices emerge in ultra-cold helium**.
The researchers then changed the conditions of helium so that it underwent a series of phase transitions between two different types of superfluids (or non-viscous fluids). These phase transitions are similar to water changing from a solid to a liquid or gas, but under more extreme conditions.
Phase transitions can lead to symmetry breaks. For example, liquid water is filled with molecules that can be oriented in different directions. But when you freeze the water, the molecules are locked in a specific position. A similar symmetry break occurs in experimental superfluid phase transitions.
However, after the phase change of superfluid helium, the vortex still exists – protected by a wall defined by a string. Together, the vortex and the wall form a composite topological defect and survive the symmetry-breaking phase transition. The researchers write in ** that these objects reflect flaws that some theories suggest were formed in the early universe.
Does this mean that Makkinen and his collaborators have figured out how the symmetry of the early universe was broken? Definitely not. Their model shows only certain aspects of the "grand unification theory," the theory of how the early universe came to be, that can be replicated in the lab — specifically, those that deal with topological flaws. None of these theories are widely accepted by physicists, and this may all be a huge theoretical dead end.
But Makinen's work opens the door to more experiments to explore how these types of flaws may shape the big after-moment. The studies, he said, have certainly taught scientists something new about the quantum realm. An open question is: Will physicists be able to finally relate these details about the tiny quantum world to the behavior of the universe as a whole?
To answer this question, we need more observational data and theoretical calculations, as well as more innovative experiments, to validate or disprove different cosmological models. At present, we are not sure whether the origin and evolution of the universe can be fully explained by the laws of physics, or whether there are some factors that we cannot understand. However, what we can be sure of is that the universe is a place full of mysteries and beauty, and it deserves to be explored and appreciated with the best scientific methods.