Why can't we use van-Kampen's theorem directly on the Hawaiian earring?
88723
Why does Van Kampen Theorem fail for the infinite earring space?
81550
Linking two theorems: on algebraic closure and on minimal splitting field
103463
Mantel's Theorem proof verification
5420
Why doesn't Cantor's diagonal argument also apply to natural numbers?
134971
Why doesn't L'Hospital's rule work in this case?
74675
Why is there no natural isomorphism between $V$ and its dual?
108372
Milne Algebraic Geometry - Remark 3.14 confusion
78085
A non orientable closed surface cannot be embedded into $\mathbb{R}^3$
23875
Why is convexity a requirement for Brouwer fixed points? Shouldn't "no holes" be good enough?
121581
Why superposition theorem fails here?
26764
Proving that $\mathbb R^3$ cannot be made into a real division algebra (and that extending complex multiplication would not work)
26644
Does this give a localization of a ring?
76902
Variation on Vandermonde's identity
154841
Computing symmetry/combinatorial factor for a diagram in $\phi^4$ theory
49503
Why does the natural quotient metric works in this case?
64060
Is it possible to obtain a sphere from a quotient of a torus?
121643
Why isn't the zero ring the field with one element?