This quantity is sometimes labelled ∇ ∇ . The following adiabatic equation therefore holds true for the entire interior: P 1 − − γ γ T γ γ = C where γ γ is the adiabatic gamma, which is 5/3 for an ideal monatomic gas. The ideal gas law says: P = N k T / V = ρ ρ k T μ μ H = ( k ρ ρ μ μ H ) γ γ C