How the Universe Might Have Frozen into Being

The problem with simple beginnings

For a long time, people thought the basic building blocks of reality were tiny points called particles. But a newer idea says particles might not be basic at all. They might be ripples and knots in a deeper substance made of long, string-like objects. This is called the string-net idea, which pictures space as a tangle of long objects with particles as their ends or ripples.

The string-net idea works well in flat sheets. But our world has three dimensions of space. Two researchers named Walker and Wang found a way to make it work in three dimensions. Their model uses a kind of math called category theory, which studies how objects connect and transform, to describe how the strings tangle and join.

There is still a big problem. The simple versions of this idea make left and right look the same. But our universe does not look the same in a mirror. The weak force, which causes radioactivity, only works on left-handed particles. So the simple string-net idea cannot be right.

Why simple models fail

The math that describes these string-nets comes in different sizes. Small sizes are called low-rank. People have listed all the small sizes up to the fourth level. None of them are complex enough to make the particles we see. This empty space of simple answers is called the Low-Rank Desert.

To get the mirror-asymmetry of our world, the math must satisfy a strict rule. The rule says a certain count of chiral features must be three more than a multiple of twenty-four. The smallest answer that works is three. This may be why our universe has three generations of particles: the electron family, the muon family, and the third heavy-electron family.

So the search must turn to high-rank math. The paper focuses on one candidate at the forty-second level. This comes from a specific group of symmetries called the binary tetrahedral group, which is a set of twenty-four ways to rotate a shape with four triangular faces.

Three model universes

The paper builds three computer models of a cooling early universe. All three use a set of kinetic equations that track how defects in the string-net liquid form and vanish as the temperature drops.

Universe A uses a low-rank control at the sixth level. It fails badly. The defects do not clear out. The universe ends in what the paper calls a Glassy Freeze. Some defects stay forever. The vacuum stays messy.

Universe B uses the high-rank candidate at the forty-second level. It succeeds completely. All defects vanish. The vacuum becomes perfectly clean. But this is too clean. No matter remains at all.

Universe C uses the same high-rank math but with one interaction channel turned down. This version keeps some stable dark matter while clearing away the visible particles. It matches what we see: a mostly empty space with some invisible matter left over.

What this means and what it misses

The paper says dark matter may be a natural leftover from this freezing process. The visible particles cleared away because they could meet and cancel with their opposites. The dark particles could not, so they stayed.

The paper also says the masses and mixing patterns of particles may record the history of how the universe cooled. The three generations are like tree rings showing the age of the process.

However, the paper leaves out something important. The model treats the whole universe as one mixed soup. It ignores where things are in space. In a real three-dimensional universe, defects might get trapped in walls or strings that form between cooling regions. This is called the Kibble-Zurek mechanism. The paper says its results are a best case, and real space might make defect clearing harder.

The paper also does not model how the universe expands in detail. It adds a simple dilution term but does not derive cosmic expansion from the string-nets themselves. And it does not explain why any matter survived at all in the visible world. Some extra process, perhaps matter-antimatter imbalance, would be needed to stop total cancellation.

Words used here

String-net

A way of picturing the vacuum as a tangle of long objects, where particles are the ends or ripples of those objects.

Rank

A measure of how many distinct types of knot or tangle exist in the math; higher rank means more complexity.

Chiral

A thing that differs from its mirror image, like a left hand and a right hand.

Defect

A place where the ordered pattern of the string-net is broken, which acts like a particle.

Dark matter

Invisible stuff that pulls on galaxies with gravity but does not emit light.

Learn more in plain language

• Phase transitionWikipedia (English, more technical)
• Topological orderWikipedia (English, more technical)
• Cosmic inflationWikipedia (English, more technical)
• Quantum entanglementSimple English Wikipedia
• Chronology of the universeWikipedia (English, more technical)
• String-net liquidWikipedia (English, more technical)