Dark Matter Collapse into Supermassive Black Holes via Instantaneous Convergence
The existence of supermassive black holes (SMBHs) in the early universe presents a major challenge to conventional formation theories. Observations of quasars less than a billion years after the Big Bang imply that either black holes grew at rates exceeding standard accretion limits or that they originated from unusually massive seeds. One possible explanation involves the role of dark matter in producing such seeds shortly after the Big Bang.
Dark matter is generally thought to be collisionless and non-radiative, meaning it cannot lose kinetic energy through electromagnetic processes like baryonic matter. This property prevents it from gradually clumping on small scales. However, immediately after the Big Bang, the overall density of both baryonic and dark matter was far higher than at later times. Under such conditions, even collisionless dark matter could, through gravitational amplification of density fluctuations, be compressed into regions exceeding the Schwarzschild limit.
If a large enough mass of dark matter were to converge into a small enough region at the same time, the local density could surpass the threshold needed for black hole formation, even if the particles retained significant momentum. This is because the Schwarzschild criterion — R ≤ 2GM/c² — depends only on total mass-energy and confinement volume, not on the thermal state of the matter. The result would be an instantaneous gravitational collapse into a black hole without requiring any dissipative cooling.
In the high-density early universe, such events could occur naturally. Primordial density peaks might have caused vast amounts of dark matter to gravitationally focus into small regions nearly simultaneously. The resulting primordial black holes (PBHs) could be massive enough to serve as direct seeds for SMBHs. These PBHs, forming within the first fractions of a second to a few minutes after the Big Bang, would then have had ample cosmic time to grow — either through continued dark matter accretion or by capturing baryonic matter once the latter decoupled from radiation.
This mechanism could help explain why recent observations reveal quasars powered by billion-solar-mass SMBHs less than a billion years after the Big Bang. Instead of requiring a slow, Eddington-limited growth from stellar-mass black holes, the existence of massive PBHs in the early universe would allow for a rapid buildup to the SMBH regime within a relatively short cosmological period.
While the likelihood of such instantaneous mass convergence in the present universe is extremely low due to its much lower mean density, the early universe’s conditions make the process more plausible. If confirmed, this would link dark matter’s initial distribution to one of the most striking features of cosmic evolution: the surprisingly early emergence of the largest gravitational objects known.
