OAI/MathematicalPhysics/Transonic/Exterior/Continuation.lean

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  1. theorem OAI.SepticProfile.RegularContinuation.exists_between_lower_equilibrium line 14

    Source documentation

    A strict moving lower fence and an invariant upper equilibrium suffice. An exponential strict upper fence is constructed from the compact Lipschitz constant, rather than assuming a continuation or a separation estimate.

    theorem exists_between_lower_equilibrium {a b c d u0 : ℝ}
        (hab : a≤b) (hcd : c≤d)
        {f : ℝ×ℝ → ℝ} (hf : ContDiffOn ℝ 1 f (Icc a b ×ˢ Icc c d))
        (lo dlo : ℝ → ℝ)
        (hloder : ∀ t ∈ Icc a b, HasDerivAt lo (dlo t) t)
        (hlorange : ∀ t ∈ Icc a b, lo t ∈ Icc c d)
        (hlostrict : ∀ t ∈ Icc a b, dlo t<f (t,lo t))
        (heq : ∀ t ∈ Icc a b, f (t,d)=0)
        (hu0 : lo a≤u0) (hu0d : u0<d) :
        ∃ u : ℝ → ℝ, u a=u0 ∧ ContinuousOn u (Icc a b) ∧
          (∀ t ∈ Icc a b, lo t≤u t ∧ u t<d) ∧
          ∀ t ∈ Icc a b, HasDerivWithinAt u (f (t,u t)) (Icc a b) t := by
    …