WebCovering spaces: The projective plane RP2 has π1 = Z2. It is also the quotient of the simply-connected space S2 by the antipodal map, which, together with the identity map, … WebLet z be the common point (wedge point). Let x 0 be another point on S 2, and x 1 be another point on S 1. Then let Q = X ∖ x 0, and P = X ∖ x 1. Clearly, X = Q ∪ P, and Q, P both open. Now, π 1 ( Q) = Z, since the punctured sphere is homeomorphic to R 2, which def. retracts to the point z and we are left with just S 1.
general topology - Covering space and Fundamental group
WebThe fact that the sphere $\mathbb S^2$ is actually a twofold cover of the real projective plane shows that that projective plane is not simply connected (in fact the loop formed by "going around" any projective line once cannot be contracted, although going around it twice can be), while the sphere (like any universal cover) is simply connected. WebCovering space of S1 V S1 V S2 has homology group >that is different from 0. You are right, the homology groups in the second dimension of the two spaces are different. This could be seen from a Mayer-Vietoris argument or from a cellular homology computation; covering spaces are not needed for that. Copyright © 2024 by Topology Atlas. assess
Real projective space - Wikipedia
WebProposition 2.3 π0: P× BP−→ P is a trivial principal G-bundle over P. Proof: The diagonal map P−→ P× BPis a section; now apply Proposition 2.2. Note that the trivialization obtained is the map P× G−→ P× BP given by (p,g) 7→ (p,pg). By symmetry, a similar result holds for π00, with the roles of the left and right factors reversed. WebSep 4, 2024 · Consider the quotient space in Example \(7.7.3\). The group here is a group of isometries, since rotations preserve Euclidean distance, but it is not fixed-point free. … WebMay 3, 2024 · 1 Answer Sorted by: 2 Since the sphere is simply connected, the universal cover of S 1 ∨ S 1 ∨ S 2 is the universal cover of S 1 ∨ S 1 with a sphere at every intersection point. Since distinct paths in the universal cover of S 1 ∨ S 1 never intersect, the issue that the OP brings up about two paths coming together never occurs. Share … lanenkaatsen