Can dark matter be composed, even partly, of black holes?

A recent hypothesis says that dark matter comprises a large number of compact objects such as primordial black holes.

Dark Matter Vs Dark Energy:

• Dark matter works like an attractive force, a kind of cosmic cement that holds our universe together.
  • This is because dark matter does interact with gravity, but it doesn’t reflect, absorb, or emit light.
  • Meanwhile, dark energy is a repulsive force, a sort of anti-gravity that drives the universe’s ever-accelerating expansion.
• Dark energy is the far more dominant force of the two, accounting for roughly 68 percent of the universe’s total mass and energy.
  • Dark matter makes up 27 percent. And the rest, a measly 5 percent is all the regular matter we see and interact with every day.
• In short, dark matter slows down the expansion of the universe, while dark energy speeds it up.

What is the recent proposition?

• When the universe was very young, hot and dense – soon after the Big Bang, it must have had quantum fluctuations of its density.
• This, in turn, would have caused some regions to become extremely dense, and therefore, to collapse under their own gravity to form the primordial black holes.
• While we have no conclusive evidence of spotting these objects, some of the binary black hole mergers detected by the LIGO gravitational wave detectors might be primordial black holes.
• The question is open there is good reason to believe that primordial black holes did form in the young universe.

Observing dark matter: Gravitational Lensing

• The paper explores what happens when such objects get in the way of gravitational waves traveling towards the Earth from the distance.
• It invokes a phenomenon called gravitational lensing that is used regularly in astronomy.