2020/12/28 by Zhang, Cong, Song, Shicong, Han, Muxin · 1 citation
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Theory (hep-th)
paper · doi:10.48550/arxiv.2012.14242
Given the Loop-Quantum-Gravity (LQG) non-graph-changing Hamiltonian \widehatH[N], the coherent state expectation value ⟨\widehatH[N]⟩ admits an semiclassical expansion in ℓ2\rm p. In this paper, we compute explicitly the expansion of ⟨\widehatH[N]⟩ on the cubic graph to the linear order in ℓ2\rm p, when the coherent state is peaked at the homogeneous and isotropic data of cosmology. In our computation, a powerful algorithm is developed to overcome the complexity in computing ⟨ \widehatH[N] ⟩. In particular, some key innovations in our algorithm substantially reduce the computational complexity in the Lorentzian part of ⟨\widehatH[N]⟩. Moreover, the algorithm developed in the present work makes it possible to compute the expectation value of arbitrary monomial of holonomies and fluxes on one edge up to arbitrary order of ℓ\rm p2.