Per-Phase Gen Convergence (State-Based Local Argument) #
State-based ("gen") version of LocalArgument.lean. For each m⋆ ∈ M, chains
local_fiberwise_geometry, lyapunov_coercivity_gen,
curv_absorb_assembly_gen, lyapunov_contraction_gen, motion bounds, and
bootstrap_total_displacement_gen
to produce a ball around m⋆ where the Nesterov iterates starting from an arbitrary initial state s₀ (not just v=0) converge geometrically.
State-based version of LocalArgument.lean. The conclusion provides gen bootstrap output:
∃ δ > 0, ∀ s₀ near m⋆ with small Lyapunov →
iterates stay in Ω ∧ Lyapunov decays geometrically with nesterovSeqGen.
theorem
PLAcceleratedNesterovLean.local_convergence_at_base_point_gen
{d : ℕ}
(hd : 0 < d)
(L : NNReal)
(hL : 0 < ↑L)
(μ : ℝ)
(hμ : 0 < μ)
(hμ_le_L : μ ≤ ↑L)
(μ_minus : ℝ)
(hμ_minus : 0 < μ_minus)
(hμ_minus_lt : μ_minus < μ)
(θ : ℝ)
(hθ : 0 < θ)
(hθ_lt1 : θ < 1)
(f : E d → ℝ)
(S : Set (E d))
(hrange : S = argminSet f)
(U : Set (E d))
(hTub_sub : IsTubularNeighborhoodOfSubmanifold S U)
(hPL : PolyakLojasiewicz f μ U)
(hf_C2 : ContDiffOn ℝ 2 f U)
(hf_lip : LipschitzOnWith L (gradient f) U)
(π : E d → E d)
(hπ_on_U : ∀ x ∈ U, π x ∈ S ∧ dist x (π x) = Metric.infDist x S)
(hπ_fix : ∀ x ∈ S, π x = x)
(hπ_in_S : ∀ (x : E d), π x ∈ S)
(hgrad_zero : ∀ x ∈ S, gradient f x = 0)
(mstar : E d)
(hmstar : mstar ∈ S)
:
have η := 1 / ↑L;
have ρ := (1 - √(μ_minus * η)) / (1 + √(μ_minus * η));
have P := fderiv ℝ π mstar;
∃ (Ω : Set (E d)) (δ : ℝ) (r_ball : ℝ) (C_coer : ℝ),
IsOpen Ω ∧ mstar ∈ Ω ∧ Ω ⊆ U ∧ 0 < δ ∧ 0 < r_ball ∧ 0 < C_coer ∧ Metric.ball mstar r_ball ⊆ Ω ∧ (∀ (x : E d), P (P x) = P x) ∧ (∀ (v : E d), ‖P v‖ ≤ ‖v‖) ∧ μ_minus * η < 1 ∧ (∀ (s : NesterovState d),
s.x ∈ Ω →
s.lookahead η ∈ Ω →
‖s.v‖ ^ 2 + μ_minus * ‖normalDispOfState π η s‖ ^ 2 ≤ C_coer * lyapunovOfState P μ_minus π f η s) ∧ ∀ (s₀ : NesterovState d),
s₀.x ∈ Metric.ball mstar δ →
s₀.lookahead η ∈ Metric.ball mstar δ →
lyapunovOfState P μ_minus π f η s₀ ≤ δ ^ 2 →
(∀ (n : ℕ),
(nesterovSeqGen f η ρ s₀ n).x ∈ Ω ∧ (nesterovSeqGen f η ρ s₀ n).lookahead η ∈ Ω) ∧ (∀ (n : ℕ),
(nesterovSeqGen f η ρ s₀ n).x ∈ Metric.ball mstar r_ball ∧ (nesterovSeqGen f η ρ s₀ n).lookahead η ∈ Metric.ball mstar r_ball) ∧ (∀ (n : ℕ),
lyapunovOfState P μ_minus π f η (nesterovSeqGen f η ρ s₀ (n + 1)) ≤ (1 - (1 - θ) * √(μ_minus * η)) ^ (n + 1) * lyapunovOfState P μ_minus π f η s₀) ∧ ∀ (j : ℕ) (t : ℝ),
0 ≤ t →
t ≤ 1 →
π ((nesterovSeqGen f η ρ s₀ j).lookahead η) + t • ((nesterovSeqGen f η ρ s₀ j).lookahead η - π ((nesterovSeqGen f η ρ s₀ j).lookahead η)) ∈ U
Public theorem wrapper for localConvergenceAtBasePointGenProof.