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earned this badge 57 times.
What are some good examples of spectral sequences which degenerate after the first nontrivial differential?
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Are the real numbers isomorphic to a nontrivial ultraproduct of fields?
Awarded Apr 1 at 15:50
What is decategorification?
Awarded Feb 14 at 9:42
What do absolute neighborhood retracts look like?
Awarded Feb 2 at 7:49
Fourier transform on Minkowski space
Awarded Jan 23 at 18:42
What are some toy models for the stable homotopy groups of spheres?
Awarded Dec 4, 2023 at 8:50
Are Berkeley cardinals easier to refute in ZFC than Reinhardt cardinals?
Awarded Nov 22, 2023 at 1:45
What are Koszul dualities?
Awarded Oct 12, 2023 at 14:01
What is a module over a Boolean ring?
Awarded Oct 10, 2023 at 17:25
Does the consistency strength hierarchy coincide with the "arithmetic consequence" hierarchy at ZF + Reinhardt?
Awarded Sep 28, 2023 at 1:28
Which $\ast$-algebras are $C^\ast$-algebras?
Awarded Sep 6, 2023 at 10:32
Is there a condensed / pyknotic refinement of the shape of an $\infty$-topos?
Awarded Jul 5, 2023 at 14:42
Why the stable module category?
Awarded May 24, 2023 at 22:26
If two structures are elementarily equivalent, is there a zigzag of elementary embeddings between them?
Awarded Mar 27, 2023 at 17:45
Is there a rigid analytic geometry proof of the functional equation for the Riemann zeta function?
Awarded Feb 22, 2023 at 20:28
What is the consistency strength of weak Vopenka's principle?
Awarded Feb 14, 2023 at 21:05
Is every category a localization of a poset?
Awarded Jan 31, 2023 at 23:08
Condensed / pyknotic approach to orbifolds?
Awarded Jan 20, 2023 at 6:49
Why do Grothendieck topologies used in algebraic geometry typically involve finiteness conditions?
Awarded Nov 24, 2022 at 9:25
Spectral sequences as deformation theory
Awarded Nov 6, 2022 at 15:20
How exotic can an infinite biproduct in an additive category be?
Awarded Aug 17, 2022 at 16:11
What's with equivariant homotopy theory over a compact Lie group?
Awarded Jul 4, 2022 at 13:30
Conceptual reason why the sign of a permutation is well-defined?
Awarded Mar 9, 2022 at 9:17
When is the category of small (pre)sheaves a(n elementary) topos?
Awarded Feb 20, 2022 at 20:20
$K$-theory backwards
Awarded Jan 29, 2022 at 22:18
When is a homotopy pushout contractible?
Awarded Dec 29, 2021 at 18:11
What is the geometric significance of fibered category theory in topos theory?
Awarded Jun 29, 2021 at 13:51
Are "most" spaces aspherical?
Awarded Apr 27, 2021 at 9:07
Is there anything to the obvious analogy between Joyal's combinatorial species and Goodwillie calculus?
Awarded Apr 9, 2021 at 16:46
Why do Chern classes and Stiefel-Whitney classes satisfy the "same" Whitney sum formula?
Awarded Mar 23, 2021 at 12:58
Condensed / pyknotic sets in terms of forcing over Boolean-valued models of set theory / multiverse concepts?
Awarded Mar 6, 2021 at 22:08
Does every (co)homology functor (in particular, stable homotopy) factor through chain complexes?
Awarded Dec 12, 2020 at 5:42
If a right adjoint to the product functor exists, must it be the diagonal?
Awarded Dec 9, 2020 at 22:35
What are _all_ of the exactness properties enjoyed by stable $\infty$-categories?
Awarded Nov 16, 2020 at 18:49
Do vector spaces without choice satisfy Cantor-Schroeder-Bernstein?
Awarded Oct 25, 2020 at 16:12
Why is Kan's $Ex^\infty$ functor useful?
Awarded Oct 24, 2020 at 21:28
What is the cotangent complex good for?
Awarded Sep 21, 2020 at 6:47
Varieties where every algebra is free
Awarded Sep 18, 2020 at 19:00
Are the ideles literally a Picard group?
Awarded Jul 7, 2020 at 23:25
Is algebraic $K$-theory a motivic spectrum?
Awarded May 26, 2020 at 18:15
Where's the best place for an algebraic geometer to learn some algebraic number theory?
Awarded May 6, 2020 at 7:18
Conceptual reason that monadic functors create limits?
Awarded Feb 18, 2020 at 17:00
Is every "nice" abelian category with enough projectives an additive presheaf category?
Awarded Nov 8, 2019 at 14:25
Is there a general theory of "compactification"?
Awarded Oct 15, 2019 at 13:10
A map of non-pathological topology?
Awarded Jun 7, 2019 at 12:25
Why is the motivic category defined over the site of smooth schemes only?
Awarded Feb 20, 2019 at 4:50
What is the relationship between connective and nonconnective derived algebraic geometry?
Awarded Sep 19, 2018 at 15:30
Does the category of (algebraically closed) fields of characteristic $p$ change when $p$ changes?
Awarded May 12, 2018 at 2:05
Does Con(ZF + Reinhardt) really imply Con(ZFC + I0)?
Awarded Feb 17, 2018 at 21:19
What is the point of pointwise Kan extensions?
Awarded Feb 12, 2018 at 9:56
What was the error in the proof of Roos' theorem?
Awarded Jan 28, 2018 at 2:37
Are "most" operators on an infinite-dimensional complex Banach space "diagonalizable"?
Awarded Sep 30, 2017 at 2:26
In what category is the sum of real numbers a coproduct?
Awarded Sep 28, 2017 at 10:45
Converse to Stokes' Theorem
Awarded Oct 14, 2015 at 0:46
Heuristic argument that finite simple groups _ought_ to be "classifiable"?
Awarded Sep 17, 2012 at 17:19
Errata for Atiyah–Macdonald
Awarded Oct 24, 2010 at 9:35
Basis-free definition of Casimir element?
Awarded Sep 27, 2010 at 23:35

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