Editing Openai/6897769e-4ee4-800f-aba5-69cca34f701c (section)

==== Mainstream fact: a massless spin-2 field in QFT, when coupled consistently, leads to nonlinear equations equivalent to Einstein’s GR (Weinberg, Feynman and later spin-2 derivations). Also modern amplitude methods show a precise relationship between gauge theory (spin-1) and gravity (spin-2) — the double-copy idea (gravity ≈ gauge ⊗ gauge). arXiv<ref>{{cite web|title=arXiv|url=https://arxiv.org/html/2403.08637v1|publisher=arxiv.org|access-date=2025-12-16}}</ref>Physical Review Links<ref>{{cite web|title=Physical Review Links|url=https://link.aps.org/doi/10.1103/PhysRevLett.105.061602|publisher=Physical Review Links|access-date=2025-12-16}}</ref> ====

Two complementary QAT ideas for spin-2 emergence:
# Composite / second-order field from photon absorption+re-emission. - An absorption (spin-1 in) + emission (spin-1 out) at a boundary, if treated together as a coherent, second-order process averaged over many events, can produce a symmetric rank-2 response on the shell (two vector indices → a tensor). Intuitively: two vector directions (incoming and outgoing) combine to a symmetric bilinear object — the same mathematical type as a spin-2 field. - If these pairings are universal (every mass/current participates similarly) then the resulting effective field couples universally → matches why gravity couples to stress-energy. This is the QAT version of “spin-2 from paired spin-1 events.”
# Double-copy evidence (modern QFT): - In scattering amplitudes the graviton amplitude is (roughly) the “square” of gauge amplitudes: gauge × gauge → gravity. This provides a formal mechanism where two gauge (spin-1) degrees can be reassembled into spin-2 dynamics; so the idea “two photons combine into a gravity-like effective field” has active, modern theoretical support in the amplitude literature. Physical Review Links<ref>{{cite web|title=Physical Review Links|url=https://link.aps.org/doi/10.1103/PhysRevLett.105.061602|publisher=Physical Review Links|access-date=2025-12-16}}</ref>arXiv<ref>{{cite web|title=arXiv|url=https://arxiv.org/abs/2203.13013|publisher=arxiv.org|access-date=2025-12-16}}</ref>

So in QAT language: the tensorial curvature seen in GR could be the emergent, effective field generated by an organized pattern (coherent sum) of photon-exchange events across the many atomic shells in matter. The boundary stress of these exchanges gives a rank-2 object that sources curvature.

Important caution: turning this conceptual picture into a rigorous derivation (explicit field operator built from EM fields that transforms as a symmetric rank-2 tensor and reproduces GR) is a hard QFT problem. The double-copy results are encouraging (they show spin-2 can come from “square” gauge structures), but a full non-perturbative derivation mapping QAT boundary processes to Einstein’s equations is an open project. Physical Review Links<ref>{{cite web|title=Physical Review Links|url=https://link.aps.org/doi/10.1103/PhysRevLett.105.061602|publisher=Physical Review Links|access-date=2025-12-16}}</ref>arXiv<ref>{{cite web|title=arXiv|url=https://arxiv.org/html/2403.08637v1|publisher=arxiv.org|access-date=2025-12-16}}</ref>