theorem
proved
term proof
dsic_agent_one
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formal statement (Lean)
171theorem dsic_agent_one (v₁ b₀ : ℝ) (b₁' : ℝ) :
172 utility₁ v₁ b₀ b₁' ≤ utility₁ v₁ b₀ v₁ := by
proof body
Term-mode proof.
173 unfold utility₁
174 by_cases h_truth : b₀ ≥ v₁
175 · -- Truthful: agent 1 loses (since b₀ ≥ v₁), utility = 0.
176 rw [if_pos h_truth]
177 by_cases h_dev : b₀ ≥ b₁'
178 · -- Deviation also loses, utility = 0.
179 rw [if_pos h_dev]
180 · -- Deviation wins (b₁' > b₀), utility = v₁ - b₀.
181 -- Since v₁ ≤ b₀, we get utility ≤ 0.
182 rw [if_neg h_dev]
183 linarith
184 · -- Truthful: agent 1 wins (since v₁ > b₀), utility = v₁ - b₀ > 0.
185 rw [if_neg h_truth]
186 by_cases h_dev : b₀ ≥ b₁'
187 · -- Deviation loses, utility = 0 ≤ v₁ - b₀.
188 rw [if_pos h_dev]
189 push_neg at h_truth
190 linarith
191 · -- Deviation also wins, utility = v₁ - b₀ (same).
192 rw [if_neg h_dev]
193
194/-! ## §4. The pivot identity and σ-conservation -/
195
196/-- **PIVOT IDENTITY.** Under truthful bidding, the winner's payment
197equals the loser's valuation: the externality the winner imposes on
198the displaced agent. -/