Which object is theorized to have infinite density and an escape velocity equal to or greater than the speed of light?

A black hole is theorized to be an object that has infinite density and an escape velocity equal to or greater than the speed of light. This concept stems from the solutions to Einstein's equations of general relativity, particularly in relation to the warping of space-time caused by a massive object. When a star exhausts its fuel, it can collapse under its own gravity, resulting in a black hole if the core's mass is sufficiently large. Within the event horizon of a black hole, the gravitational pull is so intense that not even light can escape, which is why they appear 'black' against the universe.

In contrast, a neutron star is incredibly dense and composed mostly of neutrons, but it does not reach the threshold necessary to form a black hole and can still emit light. A red supergiant is a phase in the life cycle of a massive star and will eventually explode as a supernova, but it does not possess the properties of a black hole. A supernova is the explosive end of a massive star and can lead to the formation of a neutron star or a black hole, but is not itself an entity with infinite density. Therefore, the distinct characteristics of black holes make them the correct answer in this context.