theorem boltzmann_eq_rpow {x : Fin J → ℝ} (hx : ∀ j, 0 < x j)
(ρ : ℝ) (j : Fin J) :
Real.exp (-ρ * negEnergy x j) = x j ^ ρ := by
unfold negEnergy
rw [show -ρ * -Real.log (x j) = Real.log (x j) * ρ from by ring]
exact (rpow_def_of_pos (hx j) ρ).symm### The Boltzmann-Escort Identification