Holographic principle (https://en.wikipedia.org/wiki/Holographic_principle) establishes a correlation between a bulk and its boundary. It says, in layman terms, that the amount of information in a bulk or volume is proportional to the area of that volumes surface.
But are there any other types of correlations? Are there other types of holographic principles?
I found a statement on Wikipedia which says:
The holographic principle resolves the black hole information paradox within the framework of string theory. However, there exist classical solutions to the Einstein equations that allow values of the entropy larger than those allowed by an area law, hence in principle larger than those of a black hole. These are the so-called "Wheeler's bags of gold". The existence of such solutions conflicts with the holographic interpretation, and their effects in a quantum theory of gravity including the holographic principle are not yet fully understood.
Does this mean that these solutions change the correspondence/correlation and modify holographic principle? Could we have holographic principles where the amount of information in a volume is proportional to the the square of the surface area, or perhaps where there is not general correlation at all?. Does this create other types of holographic principles?