theorem
proved
tactic proof
weighted_Jlog_average
show as:
view Lean formalization →
formal statement (Lean)
145private theorem weighted_Jlog_average {N : ℕ} (c : Configuration N) :
146 (∑ i ∈ (Finset.univ : Finset (Fin N)), (1 / (N : ℝ)) * Jlog (Real.log (c.entries i))) =
147 (1 / (N : ℝ)) * total_defect c := by
proof body
Tactic-mode proof.
148 calc
149 (∑ i ∈ (Finset.univ : Finset (Fin N)), (1 / (N : ℝ)) * Jlog (Real.log (c.entries i)))
150 = ∑ i ∈ (Finset.univ : Finset (Fin N)), (1 / (N : ℝ)) * defect (c.entries i) := by
151 apply Finset.sum_congr rfl
152 intro i _
153 unfold Jlog defect J Jcost
154 rw [Real.exp_log (c.entries_pos i)]
155 _ = (1 / (N : ℝ)) * total_defect c := by
156 unfold total_defect
157 rw [← Finset.mul_sum]
158
159/-- Jensen lower bound: fixed log-charge implies a defect lower bound. -/