As physicists continue their struggle to find and explain the origin of dark matter, the approximately 80% of the matter in the universe that we can’t see and so far haven’t been able to detect, researchers have now proposed a model where it is produced before the Big Bang.
As physicists continue their struggle to find and explain the origin of dark matter, the approximately 80% of the matter in the universe that we can’t see and so far haven’t been able to detect, researchers have now proposed a model where it is produced before the Big Bang.
Their idea is that dark matter would be produced during a infinitesimally short inflationary phase when the size of the universe quickly expanded exponentially. The new model was published in Physical Review Letters by three scientists from Texas in the US.
An intriguing idea among cosmologists is that dark matter was produced through its interaction with a thermal bath of some species, and its abundance is created by “freeze-out” or “freeze-in.” In the freeze-out scenario, dark matter is in chemical equilibrium with the bath at the earliest times—the concentration of each does not change with time.
In the freeze-in picture, dark matter never comes into equilibrium with the bath. Such a suppressed interaction between dark matter and the thermal bath could be due to interactions in quantum field theories, either infrared freeze-in or ultraviolet freeze-in.
In UV freeze-in, the temperature of the thermal bath is always lower than the masses of the particles that connect dark matter to the Standard Model of particle physics. (Mass and temperature are both proportional to energy and can be related via fundamental constants.)
The theory of inflation was developed about 45 years ago now, proposing a period of exponentially fast expansion in the very early universe where the universe expanded by a factor of about 1026 in 10-36 seconds. (After that inflation ceased, the universe continued to expand, though not exponentially.
