User Achim Krause

7 votes

Accepted

Proof of the equivalence of spectra $(\mathbb{S}^{-1} \otimes \mathbb{S}^{-1})_{h \Sigma_2} \cong \Sigma^{-1} \mathbb{RP}_{-1}^{\infty}$

answered Jun 14 at 14:52

7 votes

Are strict higher categories more general than weak higher categories?

answered Jul 26 at 22:21

7 votes

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Characterization of normed spaces based on violation of parallelogram law

answered Aug 14 at 9:24

6 votes

Schur cover of alternating groups

answered Jun 4 at 9:43

6 votes

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Does there exist a continuous field of directions in $\mathbb R^3$ tangent to every sphere?

answered Jun 25 at 13:58

6 votes

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Filtered homotopy colimits of spectra

answered Oct 27, 2023 at 14:29

6 votes

Is there a clear pattern for the degree $2n$ cohomology group of the $n$'th Eilenberg-MacLane space?

answered Jul 14, 2023 at 11:34

6 votes

Integral versus real (universal) characteristic classes

answered Dec 17, 2013 at 9:52

6 votes

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Trying to relate the fundamental groupoid to vector bundles

answered Jun 1, 2015 at 0:10

6 votes

What is the proof for any non trivial zero?

answered Jan 30, 2023 at 19:20

5 votes

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Reference for the equivalence between chain complexes and sequential diagrams in a stable $\infty$-category

answered Oct 5, 2022 at 21:46

5 votes

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$K_1(\mathbb{Z}_4)$ and $K_1(\mathbb{Z_4}[t])$

answered Apr 26, 2022 at 9:19

5 votes

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Relationship between $H_(X, A)$ and $H_(Y \cup_f X, Y)$? $\pi_(X, A)$ and $\pi_(Y \cup_f X, Y)$?

answered Sep 1, 2015 at 14:51

5 votes

A natural embedding of the total space of tautological bundle over $G(2,n)$ in $G(2,n+1)$

answered Oct 21, 2015 at 7:57

5 votes

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how to prove the $n$-times self-product of a map is null-homotopic

answered Nov 14, 2015 at 10:12

5 votes

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Explicit description of transfer for $K_1$

answered Jun 12 at 10:08

5 votes

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Counting roots of several polynomials modulo a prime

answered Jul 9 at 13:33

5 votes

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Bijection $f:\mathbb{N}\to\mathbb{N}$ such that $f(S)\neq S$ for $S\subseteq \mathbb{N}$ infinite and co-infinite

answered Aug 6 at 8:39

5 votes

Accepted

Realization of a constant simplicial anima

answered Aug 6 at 13:23

4 votes

Does $17x^4+y^2=-1$ have solution in $\Bbb{Q}_2(\sqrt{-5})$?

answered Jul 6, 2023 at 7:59

4 votes

Accepted

When is a p-adic number a $p$th power over the field it generates

answered Sep 4 at 8:12

4 votes

Generating random finite groups

answered Jul 13, 2015 at 13:04

4 votes

Accepted

Infinite play with tape, or covering the integers with prime arithmetic progressions

answered Mar 15, 2014 at 9:20

4 votes

Accepted

Perfect $\mathbb Z_\ell$-modules

answered Jul 11, 2020 at 7:11

4 votes

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Reference for integral extensions of $\mathbb{Z}/p^k\mathbb{Z}$

answered Dec 25, 2020 at 1:28

4 votes

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Finiteness of cohomology group

answered May 19, 2021 at 14:39

3 votes

Twin Primes- Clement conjecture proof

answered Apr 11, 2021 at 23:14

3 votes

Accepted

When aren't products iterated coproducts?

answered Feb 24, 2021 at 9:22

3 votes

Inner product over finite field

answered Feb 4, 2023 at 7:28

3 votes

Presentationally finite group "extensions"

answered Feb 4, 2023 at 15:19

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113 Answers

Proof of the equivalence of spectra $(\mathbb{S}^{-1} \otimes \mathbb{S}^{-1})_{h \Sigma_2} \cong \Sigma^{-1} \mathbb{RP}_{-1}^{\infty}$

Are strict higher categories more general than weak higher categories?

Characterization of normed spaces based on violation of parallelogram law

Schur cover of alternating groups

Does there exist a continuous field of directions in $\mathbb R^3$ tangent to every sphere?

Filtered homotopy colimits of spectra

Is there a clear pattern for the degree $2n$ cohomology group of the $n$'th Eilenberg-MacLane space?

Integral versus real (universal) characteristic classes

Trying to relate the fundamental groupoid to vector bundles

What is the proof for any non trivial zero?

Reference for the equivalence between chain complexes and sequential diagrams in a stable $\infty$-category

$K_1(\mathbb{Z}_4)$ and $K_1(\mathbb{Z_4}[t])$

Relationship between $H_(X, A)$ and $H_(Y \cup_f X, Y)$? $\pi_(X, A)$ and $\pi_(Y \cup_f X, Y)$?

A natural embedding of the total space of tautological bundle over $G(2,n)$ in $G(2,n+1)$

how to prove the $n$-times self-product of a map is null-homotopic

Explicit description of transfer for $K_1$

Counting roots of several polynomials modulo a prime

Bijection $f:\mathbb{N}\to\mathbb{N}$ such that $f(S)\neq S$ for $S\subseteq \mathbb{N}$ infinite and co-infinite

Realization of a constant simplicial anima

Does $17x^4+y^2=-1$ have solution in $\Bbb{Q}_2(\sqrt{-5})$?

When is a p-adic number a $p$th power over the field it generates

Generating random finite groups

Infinite play with tape, or covering the integers with prime arithmetic progressions

Perfect $\mathbb Z_\ell$-modules

Reference for integral extensions of $\mathbb{Z}/p^k\mathbb{Z}$

Finiteness of cohomology group

Twin Primes- Clement conjecture proof

When aren't products iterated coproducts?

Inner product over finite field

Presentationally finite group "extensions"