A smooth symmetric loop, possibly degenerate, has index
ProvedFiniteEnergyPlane.exists_loopAlpha_czIndexOfPath_eq_of_symLoopsymplectic-geometry
Let be a smooth symmetric loop of matrices, not assumed nondegenerate. Then there are integers with such that is the largest winding number of a negative eigenvalue of , is the smallest winding number of a nonnegative eigenvalue, and the fundamental solution has czIndexOfPath equal to .
Role. This extends the identity to degenerate loops, with the lower semicontinuous index, so results on winding windows apply without a nondegeneracy assumption.
Formalization Note. The extremal properties are stated through HasLoopEigenWind.
Preamble
import Definitions.Def_FiniteEnergyPlane_Winding
Formal statement
namespace FiniteEnergyPlane
open scoped ContDiff Real
/-- For a smooth symmetric loop `S∞`, not necessarily nondegenerate, there are integers `a, b` with
`b ∈ {a, a + 1}` such that `a` is the largest winding number of a negative eigenvalue of
`-J₀ ∂ₜ - S∞`, `b` is the smallest winding number of a nonnegative eigenvalue, and the fundamental
solution has `czIndexOfPath` equal to `a + b`. -/
theorem exists_loopAlpha_czIndexOfPath_eq_of_symLoop (Sinf : ℝ → CauchyRiemannIndex.Mat 1)
(hSinf : CauchyRiemannIndex.IsSymLoop Sinf)
(hSinf' : ∀ i j, ContDiff ℝ ∞ (fun t => Sinf t i j)) :
∃ a b : ℤ,
((∃ μ < 0, HasLoopEigenWind Sinf μ a) ∧
∀ μ < 0, ∀ k : ℤ, HasLoopEigenWind Sinf μ k → k ≤ a) ∧
((∃ μ, 0 ≤ μ ∧ HasLoopEigenWind Sinf μ b) ∧
∀ μ, 0 ≤ μ → ∀ k : ℤ, HasLoopEigenWind Sinf μ k → b ≤ k) ∧
(b = a ∨ b = a + 1) ∧
∀ Ψ : ℝ → CauchyRiemannIndex.Mat 1, CauchyRiemannIndex.IsFundamentalSolution Sinf Ψ →
HryniewiczCriterion.czIndexOfPath
(fun τ => Matrix.reindex finSumFinEquiv finSumFinEquiv (Ψ τ)) = a + b := by
sorry
end FiniteEnergyPlane
Source
H. Hofer, K. Wysocki, E. Zehnder, Properties of pseudoholomorphic curves in symplectizations II (1995), Section 3; U. Hryniewicz, J. Symplectic Geom. 12 (2014), arXiv:1105.2077, Section 2.1.1