A paper that came to my attention from a Twitter feud on LQG is this paper by Smolin, resulting in me adding a new category to this blog, called ``Loops":
[1608.02932] Holographic relations in loop quantum gravity
This is interesting for two reasons. Firstly, it invokes categorial holography as Smolin terms it, which was introduced by Crane in his paper called Categorial Physics, and secondly, it uses spin networks in an interesting way. The idea is to use punctured 2-surfaces and attribute to them a Hilbert space, and eventually attributing to quantum spinnet a ``bulk" by extending from the punctures. Essentially, stating that there is a map $\mathcal{T}^{p}: \mathcal{H}_{\mathcal{B};j, i}\to \mathcal{H}_{\Sigma ; j, i}$ as noted in the paper. However, I must say something here; one may not need to invoke these constructions in the first place and instead approach a deformation perspective, such as Cauchy slice holography or in general, holography of information if canonical quantum gravity is all we wanted. The feud seems to be very unnecessary and for that matter I don't think there is any need to point fingers saying ``string theory is just conjecture" or ``LQG is just conjecture". If such holography is emergent (as it seems above, but I am no expert) in LQG, then it is very fascinating. Calumny is a dangerous thing and as is the nature of politicising quantum gravity.
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