An international team of scientists has proven that rotating black holes may have additional parameters depending on the absorbed matter.
It is noted that astrophysicists usually classify black holes by mass, charge and rotation speed. The corresponding article was published in Physical Review Letters.
In particular, the calculations of the scientists who conducted the study showed that a black hole may have a scalar field during rapid rotation.
However, according to the description of gravity parameters by Einstein’s Theory of Relativity, black holes cannot have stable additional parameters.
That is, one cannot get additional information about matter that has fallen beyond the event horizon. It is impossible to distinguish a black hole formed by antimatter from a black hole of ordinary matter.
Thus there is no exact mathematical proof of this theorem.