Files
proofs/lean/DeFi/FeeModel.lean
zeekay 6907bfc6e6 Publish under the org, not a person
Bylines, paper authorship, correspondence addresses and the founder blurb under
each post named an individual. They name the organisation that published the
work instead: the brand on posts and pages, the research byline on papers, and
research@ in place of a personal address. Both are what these repositories
already used elsewhere — nothing new was coined.

Co-authors are untouched. Where a paper named someone else alongside, they stay
named; only the one byline changed. Bibliography entries, running heads,
PDF metadata and affiliations move with it, so a citation still resolves to
whoever the cited paper names.

Sample and fixture data uses the placeholder name these tests already use
elsewhere, so no assertion changed meaning.
2026-09-01 02:31:02 -07:00

69 lines
1.9 KiB
Lean4

/-
DeFi Fee Model
Maker-taker with volume tiers. Permissionless.
No regulatory fee caps (pure DeFi).
Maps to:
- lux/exchange: fee calculation
- lux/node: fee distribution to validators
Properties:
- Makers ≤ takers (incentivize liquidity)
- Volume tiers: more volume → lower fees
- Validator revenue: portion of fees to validators
- Permissionless: fee schedule is on-chain and transparent
Authors: Lux Research (Dec 2025), Woo Bin (Mar 2026)
-/
import Mathlib.Data.Nat.Defs
import Mathlib.Tactic
namespace DeFi.FeeModel
/-- Fee tier -/
structure FeeTier where
minVolume : Nat
makerBps : Nat
takerBps : Nat
deriving DecidableEq, Repr, Inhabited
/-- Standard DeFi tiers -/
def tiers : List FeeTier :=
[ ⟨0, 15, 30⟩ -- Tier 1
, ⟨1000000, 10, 25⟩ -- Tier 2: $1M+
, ⟨10000000, 5, 15⟩ -- Tier 3: $10M+
, ⟨100000000, 0, 10⟩ -- Tier 4: $100M+ (zero maker)
]
/-- Calculate fee -/
def fee (tier : FeeTier) (isMaker : Bool) (value : Nat) : Nat :=
value * (if isMaker then tier.makerBps else tier.takerBps) / 10000
/-- MAKER ≤ TAKER -/
theorem maker_le_taker (t : FeeTier) (v : Nat) (h : t.makerBps ≤ t.takerBps) :
fee t true v ≤ fee t false v := by
simp [fee]; exact Nat.div_le_div_right (Nat.mul_le_mul_left v h)
/-- TOP TIER ZERO MAKER -/
theorem top_tier_zero : (tiers[3]!).makerBps = 0 := by simp [tiers]
/-- VOLUME DISCOUNT -/
theorem volume_discount : (tiers[0]!).takerBps > (tiers[3]!).takerBps := by
simp [tiers]
/-- 4 TIERS -/
theorem four_tiers : tiers.length = 4 := rfl
/-- VALIDATOR SHARE: Portion of fees goes to validators who process trades -/
def validatorShare (totalFee : Nat) (validatorPct : Nat) : Nat :=
totalFee * validatorPct / 100
theorem validator_bounded (totalFee pct : Nat) (h : pct ≤ 100) :
validatorShare totalFee pct ≤ totalFee := by
simp only [validatorShare]
exact Nat.div_le_of_le_mul (by nlinarith)
end DeFi.FeeModel