theorem
proved
term proof
null_geodesic_exists_minkowski
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formal statement (Lean)
68theorem null_geodesic_exists_minkowski (ic : InitialConditions) :
69 ∃ geo : NullGeodesic minkowski_tensor,
70 geo.path 0 = ic.position ∧
71 (∀ μ, deriv (fun lam => geo.path lam μ) 0 = ic.direction μ) := by
proof body
Term-mode proof.
72 refine ⟨straight_null_geodesic ic, ?_, ?_⟩
73 · simp [straight_null_geodesic, straight_line]
74 · intro μ; simp [straight_null_geodesic, straight_line]
75