The Operator Product Expansion for Radial Lattice Quantization of 3D ϕ⁴ Theory

At its critical point, the three-dimensional lattice Ising model is described by a conformal field theory (CFT), the 3d Ising CFT. Instead of carrying out simulations on Euclidean lattices, we use the Quantum Finite Elements method to implement radially quantized critical ϕ⁴ theory on simplicial lattices approaching R × S². Computing the four-point function of identical scalars, we demonstrate the power of radial quantization by the accurate determination of the scaling dimensions Δ_ε and ΔT as well as ratios of the operator product expansion (OPE) coefficients fσσε and fσσT of the first spin-0 and spin-2 primary operators $ε$ and T of the 3d Ising CFT.