34

Answers
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11
Geometric meaning of torsion in homotopy groups
10
How should one present curl and divergence in an undergraduate multivariable calculus class?
7
Thom’s Principle: rich structures are more numerous in low dimension
7
A programming language that can only create algorithms with polynomial runtime?
7
When is a Riemannian manifold an open subset of a complete one?
4
Why should I prefer bundles to (surjective) submersions?
4
What is the precise relationship between “prodsimplicial sets” and rooted trees?
4
Clearing misconceptions: Defining “is a model of ZFC” in ZFC
3
Tracking spectral sequence differentials
3
What do people mean by “subcategory”?
3
Subset of the plane that intersects every line exactly twice
3
Theorems for nothing (and the proofs for free)
2
When and why do universal objects have extra properties?
2
Do the empty set AND the entire set really need to be open?
2
How to motivate the skein relations?
2
Is there a category-theoretic definition of the arithmetic Grothendieck group
2
Testing for Riemannian Isometry
2
What is your favorite isomorphism?
2
Efficiently sampling points uniformly from the surface of an n-sphere
2
What is the earliest definition given by a universal mapping property?
2
Homology or cohomology?
2
Conventional names for finite categories
1
Associativity with infinite nesting
1
Are all mathematical theorems necessarily true?
1
Name for “lower/upper bounds” of arbitrary relations?
1
Heuristic explanation of why we lose projectives in sheaves.
1
Boundary of planar region
1
Side-Angle-Side Congruence and the Parallel Postulate
0
Where does the generic triangle live?
0
Exact short sequences of vector spaces
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