Faint gravitational waves may be from primordial fractures in space-time
The early universe may have been such a violent place that space-time itself fractured like a pane of glass. Those fractures would have released floods of gravitational waves, and a team of astronomers has discovered that we may have already detected these ripples in the fabric of space-time. The team, who reported their results recently in a paper submitted for publication in the Journal of Computational Astrophysics and published on arXiv.org(opens in new tab), claim that they have seen evidence for so-called domain walls in the early universe.
When our universe was incredibly young, it was also incredibly exotic. The four forces of nature were bound up into a single, unified force. We do not know what that force looked like or how it operated, but we know that as the universe cooled and expanded, that unified force fractured into the four familiar forces we have today. First came gravity, then the strong nuclear force splintered off, and lastly, the electromagnetic and weak nuclear forces split from each other.
With each of these splittings, the universe completely remolded itself. New particles arose to replace ones that could exist only in extreme conditions previously. The fundamental quantum fields of space-time that dictate how particles and forces interact with each other reconfigured themselves. We do not know how smoothly or roughly these phase transitions took place, but it's perfectly possible that with each splitting, the universe settled into multiple identities at once.
This fracturing isn't as exotic as it sounds. It happens with all kinds of phase transitions, like water turning into ice. Different patches of water can form ice molecules with different orientations. No matter what, all the water turns into ice, but different domains can have differing molecular arrangements. Where those domains meet walls, or imperfections, fracturing will appear.
https://www.space.com/gravitational-waves-fractures-space-time-early-universe
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