Mark Van Raamsdonk is the primary begetter of the see to connect pieces of spacetime past times the quantum entanglement inwards the purpose of the glue – as well as hence the forefather of the ER-EPR correspondence, alongside other things. In his novel preprint,
Building upwards spacetime with quantum entanglement II: It from BC-bitwhose championship was chosen equally a continuation of a paper from 2010 (over 500 followups now; the second, novel purpose of the championship is a variation of Wheelers' "it from bit") – a prissy gap for a serial – he introduces the BC-bits.
The term "BC-bit" was chosen afterwards Mark agreed with the electrical flow authorities of British Columbia (where he works) that he volition promote the say as well as and so he volition travel out the prime number minister. Alternatively, inwards front end of physicists, Van Raamsdonk may claim that BC stands for "boundary conformal" because he's using boundary conformal champaign theories.
Needless to say, lots of approaches to quantum gravity convey tried to build the spacetime out of some "pieces" as well as most of them are pretty much hopeless – spin networks as well as spin foams inwards loop quantum gravity are the most famous instance of that category. Instead, inwards Mark's picture, it's of import that the private pieces are connected past times entanglement. Well, to some extent, it is truthful fifty-fifty inwards spin networks.
But it's actually the internal "beef" of the pieces of the spacetime where Mark makes a genuine contribution. His pictures as well as peradventure ideas await suspiciously similar to my onetime system to perturbatively essay out the AdS/CFT correspodence for the maximally supersymmetric approximate theory inwards 4 dimensions – run into e.g. a news of a paper past times Berkovits for a similar materials that is out inwards the literature.
In my picture, the Feynman diagrams of the approximate theory are interpreted equally two-dimensional surfaces (that's of course of didactics the proficient onetime 't Hooft) divided into faces. The faces are treated equally Poincaré disks using the Euclidean AdS2/CFT1 correspondence. So there's some two-dimensional gravity theory living inwards the two-dimensional faces but that's holographic, so it may travel reduced to the physics of the boundary – which happens to travel the propagators of the Feynman diagrams.
In that epitome of mine, I besides assumed that the propagators of the Feynman diagrams are the places where the seat champaign \(x^\mu\) labeling the AdS5 infinite hits the boundary of the anti de Sitter space.
Well, what Mark has actually seems to travel the same affair but he avoids the interpretation that it's a proof of AdS/CFT. Instead, he emphasizes it is an instance of the entanglement-as-glue paradigm. Using something that looks similar LEGO created out of pieces, he is edifice a "model" of a spacetime claimed to travel generic. The two-dimensional faces that brand upwards the map are supposed to travel causal diamonds of an AdS spacetime nigh the boundary. By redrawing such a share using the faces, he may approximate the weather condition inwards the causal diamonds arbitrarily accurately.
In the spin network case, what would alive inwards the faces would travel simply some Wilson job around the boundary or something similar that. However, consistent theories of quantum gravity dictate a to a greater extent than self-sufficient picture. The BC-bits must travel full-blown compact spacetimes – examples of AdS/CFT – with all their degrees of freedom. And nosotros may travel connecting these BC-bits past times the quantum entanglement.