User Georg Lehner - MathOverflow

31 votes

2 answers

5k views

The philosophy behind local rings

asked Nov 24, 2016 at 16:21

26 votes

1 answer

917 views

The analogy between dualizable categories and compact Hausdorff spaces

asked Jul 8, 2024 at 14:09

25 votes

1 answer

1k views

Examples of $(\infty,1)$-topoi that are not given as sheaves on a Grothendieck topology

asked Jun 26, 2017 at 21:14

25 votes

1 answer

2k views

A geometric theory of Blueprints? (Algebras over the field with one element)

asked Dec 12, 2015 at 22:04

20 votes

3 answers

3k views

Alternate proofs of Hilberts Basis Theorem

asked Nov 7, 2015 at 11:56

14 votes

3 answers

2k views

Is there a universal property characterizing the category of compact Hausdorff spaces?

asked Jan 26, 2023 at 12:17

14 votes

1 answer

1k views

Relating two different approaches to the Atiyah-Hirzebruch Spectral Sequence

asked Mar 2, 2018 at 21:04

13 votes

2 answers

830 views

Proving Kashiwara–Schapira's micro-local cutoff lemma $\infty$-categorically

asked Feb 24 at 18:15

11 votes

1 answer

2k views

The set of subgroups of $F_2$

asked Jul 13, 2016 at 16:30

10 votes

1 answer

477 views

Definition of $Fun^G( \mathcal C, \mathcal D)$ in the setting of quasicategories

asked Feb 7, 2019 at 11:11

10 votes

0 answers

439 views

"Generalized theory of polynomials" for a given commutative Lawvere Theory

asked Jul 22, 2015 at 13:03

10 votes

1 answer

415 views

In what sense is the double negation topology functorial?

asked Jul 24, 2025 at 13:23

8 votes

2 answers

609 views

A lattice/topos-theoretic construction of the Boolean algebra of measurable subsets modulo nullsets

asked Jan 23, 2025 at 18:35

8 votes

1 answer

281 views

Finite group such that $K_{-1} (\mathbb Z G)$ has non-trivial torsion

asked Dec 2, 2020 at 16:12

8 votes

0 answers

148 views

The homotopy inverse on Quillen's $S^{-1}S$ construction

asked Jan 30, 2024 at 9:24

7 votes

1 answer

436 views

Commuting homotopy colimits and arbitrary products in spaces

asked Aug 22, 2023 at 13:31

7 votes

1 answer

270 views

Idempotent $H$-structures / Higher join-semilattices are discrete?

asked Jun 29, 2025 at 8:10

7 votes

1 answer

317 views

When is the category of sheaves on a site compactly assembled/a continuous category?

asked Oct 14, 2024 at 20:25

5 votes

0 answers

192 views

Resources on a smooth topos containing complex analytic/holomorphic geometry

asked Jan 21, 2016 at 21:28

5 votes

0 answers

252 views

Realizing the 0-th Postnikov truncation of a spectrum in the category of orthogonal/symmetric spectra

asked Mar 29, 2018 at 15:03

4 votes

1 answer

587 views

The "$\infty$"-column in the periodic table of n-categories

asked Aug 26, 2015 at 13:37

4 votes

0 answers

122 views

How to describe a concrete generator of $\widetilde{K_0(\mathbb{Z}[C_{23}])} \cong \widetilde{K_0(\mathbb{Z}[\zeta_{23}])}$

asked Aug 7, 2023 at 8:36

4 votes

1 answer

214 views

Injectivity of assembly in A-theory for $BC_2 = \mathbb R P^\infty$ in degree $4$

asked Jan 8, 2022 at 7:50

3 votes

0 answers

134 views

Constructive formula for Haar measure of a compact subset

asked Aug 21, 2025 at 19:49

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24 Questions

The philosophy behind local rings

The analogy between dualizable categories and compact Hausdorff spaces

Examples of $(\infty,1)$-topoi that are not given as sheaves on a Grothendieck topology

A geometric theory of Blueprints? (Algebras over the field with one element)

Alternate proofs of Hilberts Basis Theorem

Is there a universal property characterizing the category of compact Hausdorff spaces?

Relating two different approaches to the Atiyah-Hirzebruch Spectral Sequence

Proving Kashiwara–Schapira's micro-local cutoff lemma $\infty$-categorically

The set of subgroups of $F_2$

Definition of $Fun^G( \mathcal C, \mathcal D)$ in the setting of quasicategories

"Generalized theory of polynomials" for a given commutative Lawvere Theory

In what sense is the double negation topology functorial?

A lattice/topos-theoretic construction of the Boolean algebra of measurable subsets modulo nullsets

Finite group such that $K_{-1} (\mathbb Z G)$ has non-trivial torsion

The homotopy inverse on Quillen's $S^{-1}S$ construction

Commuting homotopy colimits and arbitrary products in spaces

Idempotent $H$-structures / Higher join-semilattices are discrete?

When is the category of sheaves on a site compactly assembled/a continuous category?

Resources on a smooth topos containing complex analytic/holomorphic geometry

Realizing the 0-th Postnikov truncation of a spectrum in the category of orthogonal/symmetric spectra

The "$\infty$"-column in the periodic table of n-categories

How to describe a concrete generator of $\widetilde{K_0(\mathbb{Z}[C_{23}])} \cong \widetilde{K_0(\mathbb{Z}[\zeta_{23}])}$

Injectivity of assembly in A-theory for $BC_2 = \mathbb R P^\infty$ in degree $4$

Constructive formula for Haar measure of a compact subset