Mathematicians from the University of California at Berkeley have found a condition for the existence of naked singularities in black holes, in which the laws of physics are violated. This conclusion casts doubt on the strong principle of cosmic censorship, whereby a naked singularity should be inaccessible to any observer. Writes about this publication Science Alert.
The naked singularity is a hypothetical region of space-time predicted by Einstein's general theory of relativity (GR), where the principle of causality is violated. In other words, this is the point at which an infinitely distant future or past can be observed. However, the principle of strong cosmic censorship, proposed by physicist Roger Penrose, assumes that cosmic singularities exist either entirely in the past (for example, in the case of the Big Bang), or always in the future and therefore unattainable for any observer. Physicist Stephen Hawking introduced the weak principle of cosmic censorship, according to which naked singularities can be present in the present, but "closed" by the event horizons of black holes.
Hawking believes that theoretically there may be an observer who is able to get into a naked singularity, but he will not be able to tell anyone about what he saw, because for this he needs to leave the black hole, which is impossible.
The principle of strong cosmic censorship "closes" the singularity for an astronaut who has gone beyond the event horizon. Its very presence changes the solutions of the equations of general relativity in such a way that the observer will never see the singularity until his death.
Mathematicians have studied the conditions under which an astronaut can fall into the area of causality violation. They considered a special kind of hypothetical black holes, described by the Reissner-Nordstrom-de Sitter metric. These objects, in addition to the event horizon, have an inner Cauchy horizon - a border beyond which determinism is violated, that is, it is impossible to predict the fate of any objects that have got there. Strong cosmic censorship prevents the Cauchy horizon from remaining stable and thus prevents the observation of a singularity at the center of a black hole.
It is shown that the extremely high charge of the Reissner-Nordstrom-de Sitter holes and their gravity stabilize the Cauchy horizon in the expanding Universe. As a result, an observer who has fallen behind the Cauchy horizon will be cut off from his own past, and his fate will become uncertain. This violates the principle of strong cosmic censorship.