EHestablished
Einstein–Hilbert
S_EH = (1/16πG) ∫ R √−g. Standard GR curvature, plus GHY on ∂M.
Diffeomorphism-invariant field theory on (M, g) with scalar φ, thermodynamic map Y^A : M → 𝒯, and two-form B. ω is closed and cohomologically nontrivial — it is not d(dℳ), because d² = 0.
S_EH = (1/16πG) ∫ R √−g. Standard GR curvature, plus GHY on ∂M.
S_φ = −∫ [½ (∇φ)² + V(φ)] √−g. Sourced by α_φ T_m whenever A depends on φ.
S_Y = −∫ [½ G_AB ∂Y^A ∂Y^B + U(Y)] √−g. Target Christoffel Γ^A_BC enter the EL equation.
S_B = −½ ∫ H ∧ *H with H = dB. Gauge B → B + dΛ leaves H invariant.
S_top = λ_Q ∫ B ∧ F_Q. Metric-independent: no direct T_μν, yet it sources B and Y.
S_m[Ψ_m, Ã = A²(φ, ℳ, 𝒥_Q) g]. Conserved w.r.t. the physical metric, not the Einstein frame.