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About this paper

Marco Dessalvi, Massimo Bartoletti, Alberto Lluch-Lafuente

This research formally integrates trading fees into Constant-Product Market Maker models, leveraging Lean 4 for machine-checked analysis. It establishes that split swaps are suboptimal for traders and derives distinct closed-form solutions for market equilibrium and maximum arbitrage profit in fee-adjusted AMMs.

Key insights

  • Trading fees fundamentally alter the additivity property of AMM swap functions, causing a single large swap to yield greater gain than multiple split swaps for a trader.
  • In fee-adjusted AMMs, the swap amount that brings the market to equilibrium (aligning internal and external rates) is generally distinct from and suboptimal for maximizing an arbitrageur's profit.
  • Core structural properties of Constant-Product Market Makers, such as output-boundedness and strict monotonicity, are preserved even when trading fees are incorporated into the model.

Summary by alphaXiv.

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