Showing that Möbius band can't retract onto the boundary circle
88616
Retraction of the Möbius strip to its boundary
23219
The plane minus $n$ points deformation retracts onto...
2348
Show that the sphere, S, and $\mathbb{R}^2$ is not homeomorphic
66444
Why doesn't the "zig-zag" comb deformation retract onto a point, even though it's contractible?
147310
How does one prove that the Klein bottle cannot be embedded in $R^3$?
82210
Analytic continuation of function continuous on boundary
67383
Prove that $G'$ is not planar.
58000
How can one show that a möbius transformation maps the unit circle to some axis?
95058
Finding a conformal map of slit disk on to unit disk
69945
A PDE exercise from Gilbarg Trudinger. problem 2.2
83596
A simple proof that a polygon circumscribing a circle overestimates its perimeter
3601
A problem about Vandemonde matrix
64481
Characterizing all mobius transformations from unit disk to itself.
92746
$\Delta \mathbf n = -2 \mathbf n$ on the Euclidean sphere
149543
Prove that an annulus is not simply connected?
78085
A non orientable closed surface cannot be embedded into $\mathbb{R}^3$
106298
Prove that some topology is not metrizable