Can a black hole be a gigantic string? If so, can a it be a enlarged extra dimensional structure inside, something is expanded under the energy in the black hole?
There is exist an opinion, confirmed by some calculations, that the black hole is not singular, it consists of the strings connected in some way. Such object is called a fuzzball. The number of connection options (the organization) of strings in such a structure is equal to the entropy of a black hole (obtained recently), and the dimensions are identical with the radius of the Event horizon (also a well-known concept).