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arXiv · 1812.02110

Emergent 4-dimensional linearized gravity from spin foam model

Muxin Han·Zichang Huang·Antonia Zipfel
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Abstract

Spin Foam Models (SFMs) are covariant formulations of Loop Quantum Gravity (LQG) in 4 dimensions. This work studies the perturbations of SFMs on a flat background. It demonstrates for the first time that smooth curved spacetime geometries satisfying Einstein equation can emerge from discrete SFMs under an appropriate low energy limit, which corresponds to a semiclassical continuum limit of SFMs. In particular, we show that the low energy excitations of SFMs on a flat background give all smooth solutions of linearized Einstein equations (spin-2 gravitons). This indicates that at the linearized level, classical Einstein gravity is indeed the low energy effective theory from SFMs. Thus our result heightens the confidence that covariant LQG is a consistent theory of quantum gravity. As a key technical tool, a regularization/deformation of the SFM is employed in the derivation. The deformation parameter $δ$ becomes a coupling constant of a higher curvature correction term to Einstein gravity from SFM.

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Muxin Han, Zichang Huang, Antonia Zipfel. 2019-04-17. Emergent 4-dimensional linearized gravity from spin foam model. https://doi.org/10.1103/physrevd.100.024060

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