Fermi ball
{{Short description|Hypothetical objects created in the early history of the universe}}
In cosmology, Fermi balls are hypothetical objects that may have been created in the early history of the universe by spontaneous symmetry breaking. One paper has described them as "charged SLAC-bag type structures".{{cite arXiv|eprint= hep-ph/9412264|last1= Macpherson|first1= Alick L.|title= Fermi Ball Detection|last2= Pinfold|first2= James L.|date= 1994}} Fermi balls can be modeled as a type of non-topological soliton.
The collapse of Fermi balls is also an active area of research, and it is hypothesized that they collapse to form primordial black holes.{{Cite journal |last=Kawana |first=Kiyoharu |last2=Xie |first2=Ke-Pan |date=January 2022 |title=Primordial black holes from a cosmic phase transition: The collapse of Fermi-balls |url=https://arxiv.org/abs/2106.00111 |journal=Physics Letters B |volume=824 |pages=136791 |doi=10.1016/j.physletb.2021.136791|arxiv=2106.00111 }} This mechanism is initiated after the Yukawa potential begins to play a role after the Fermi balls become unstable.
The concept is named after Enrico Fermi (see Fermion).
Hypothesized explanations for observed phenomena
= Dark matter =
A paper by theoretical physicists at Seoul National University has proposed that Fermi balls may be implicated in the formation of primordial black holes from a cosmic first-order phase transition, as a candidate explanation for dark matter.{{cite journal|arxiv=2106.00111|last1=Kawana|first1=Kiyoharu|last2=Xie|first2=Ke-Pan|title=Primordial black holes from a cosmic phase transition: The collapse of Fermi-balls|journal=Physics Letters B |date=2022|volume=824 |doi=10.1016/j.physletb.2021.136791 |bibcode=2022PhLB..82436791K }}