Alphabeta Math
TheoremStatement: Literature-sourcedProof: AI-adaptedSession-authored (Fable 5 assisted)precheck passaudited 2026-08-16
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A space admitting a universal covering is semilocally simply connected

Statement

If a space admits a universal covering, then it is semilocally simply connected. No local path-connectedness hypothesis is required.

Facts & Assumptions

Given: The objects, hypotheses, and choice principles stated above.

[F1]

A universal covering space of B is a covering map p:B~B whose total space B~ is simply connected (def-covering-map-and-evenly-covered-neighbourhoods, def-simply-connected). (Universal covering spaces).

[F2]

A space X is semilocally simply connected at xX when there is a neighbourhood U of x and a basepoint-preserving inclusion (U,x)(X,x) whose induced map on fundamental groups is trivial (def-neighbourhood-top, def-induced-homomorphism-on-fundamental-groups, def-based-loops-and-fundamental-group). It is semilocally simply connected when this holds at every point. The neighbourhood need not itself be simply connected. (Semilocally simply connected spaces with explicit basepoint convention).

[F3]

For a covering p:(E,e0)(B,b0), the induced homomorphism p:π1(E,e0)π1(B,b0) is injective. (A covering map induces an injective homomorphism on fundamental groups).

[F4]

A topological space X is simply connected when it is nonempty and path-connected (def-path-connected) and, for every x0X, the group π1(X,x0) has exactly one element. (Simply connected topological spaces).

Proof

technique · direct
1.1

At a basepoint choose an evenly covered neighbourhood and a lift of that point.

givenF2F1
2.1

Any loop in the neighbourhood lifts to a loop in its sheet.

step 1.1F2
3.1

The induced fundamental-group map of the universal cover is injective and its domain group is trivial, so the inclusion-induced class downstairs is trivial.

step 2.1F2F3F1
4.1

No local path-connectedness is needed for this necessity direction.

step 3.1F4F2
5.1

The preceding construction and implications establish the assertion.

step 4.1

Depends on

Used by

Dependency tree · next 3 levels

Direct dependencies and their dependencies through the next three levels: 35 results over 14 levels. An arrow runs from a result to what uses it, and this result sits at the bottom with a heavier outline. Click the chart to enlarge it.

Sources