English
A covering map is a function that is continuous with discrete fibers and every point has an evenly covered neighborhood.
Русский
Покрывающее отображение — непрерывное отображение с дискретными волокнами и у каждого x есть равномерно покрытое окрестность.
LaTeX
$$$IsCoveringMap\\ f := (\\forall x, IsEvenlyCovered f x (f^{-1}\\{x\\}))$$$
Lean4
/-- A covering map is a continuous function `f : E → X` with discrete fibers such that each point
of `X` has an evenly covered neighborhood. -/
def IsCoveringMap :=
∀ x, IsEvenlyCovered f x (f ⁻¹' { x })