The historical starting point is Kaluza–Klein theory.
Theodor Kaluza showed that applying five-dimensional General Relativity produces the four-dimensional equations of gravity together with electromagnetism. Oskar Klein then treated the extra spatial dimension as compact and microscopic; his original estimate was about 10−30 cm. Our Galaxy → Atom length transform independently is of order 1030.
Later higher-dimensional theories generalized this basic idea into what became modern string theory. General Relativity predicts black holes characterized macroscopically by mass, angular momentum, and—when present—electric charge. For fixed mass there are limiting values of angular momentum or charge; saturating the bound gives an extremal black hole.
The ordinary black-hole solution contains a point dividing by zero and an event horizon around it from which light cannot escape. In the extremal limit, the near-horizon geometry replaces the point dividing by zero with an infinitely long throat. Extremal solutions have zero Hawking temperature in the standard treatment and therefore no ordinary thermal Hawking radiation. With Hawking radiation we have an unresolved information paradox; without it, the trade-off is we violate the 2nd law of thermodynamics. The latter is acceptable within this ontology because thermodynamics is itself treated as a local, averaged description of specular billiards that can fail at the fractal scale boundary.
The photonic interpretation proposed here takes the exremal throat literally as a transfer channel: matter and energy entering one black hole (near equator) must reappear through another (at polar jets) so that matter and energy are never created or destroyed. The conventional General Relativity discussion distinguishes black-hole and white-hole regions in maximally extended solutions; this model instead proposes a black-hole → black-hole transfer.
A 2025 Nature Astronomy study by Fender, Motta and collaborators found no correlation between reported black-hole spin estimates and the speeds of the fastest stellar-mass black-hole jets. Read the study. The observation itself establishes the lack of the expected spin-speed correlation; it is clearly evidence that the jets are a non-local phenomenon.