User Jos van Nieuwman

7 votes

2 answers

245 views

Prime ideals in $\mathbb{Z}[X], \mathbb{Q}[X], \mathbb{F}_{19}[X]$.

asked Mar 13, 2019 at 23:17

6 votes

1 answer

469 views

On free abelian groups

asked Jan 16, 2020 at 21:00

6 votes

2 answers

308 views

Does my operator $C([0,1]) → C([0,1])$ have an inverse?

asked Jan 17, 2022 at 0:50

6 votes

3 answers

195 views

Does the abelianisation functor $\mathrm{Grp} → \mathrm{AbGrp}$ preserve composition?

asked Jan 5, 2023 at 22:18

4 votes

5 answers

289 views

Category where not every mono is regular

asked Jan 22, 2023 at 6:28

4 votes

3 answers

175 views

Extension of $\zeta_5^2 + \zeta_5^3$ over $ℚ$ is quadratic.

asked Mar 15, 2020 at 21:39

4 votes

1 answer

75 views

Minimal polynomial of $\eta_4$ over $\mathbb{Q}(\eta_2)$.

asked Apr 8, 2020 at 22:41

4 votes

1 answer

251 views

Category where morphism sets are Abelian groups

asked Mar 20, 2019 at 21:52

4 votes

1 answer

91 views

Commutative subring of matrices iff trivial unit group

asked Mar 7, 2019 at 22:44

4 votes

1 answer

235 views

How to write an arbitrary polynomial in $n$ variables

asked Jun 13, 2019 at 20:03

3 votes

1 answer

126 views

Extension of $k$-vector space structure to $k[x]$-module structure

asked Jun 12, 2019 at 21:08

3 votes

0 answers

911 views

Notation for codomain

asked Aug 5, 2019 at 3:15

3 votes

1 answer

190 views

Subgroup generated by two cycles in $S_5$.

asked Aug 17, 2019 at 20:17

3 votes

1 answer

52 views

Number of roots of a separable polynomial over a connected ring does not exceed deg $f$.

asked Oct 5, 2019 at 16:49

3 votes

1 answer

153 views

$\gcd(135-14i, 155+34i)$ with the Euclidean algorithm

asked Jan 16, 2020 at 15:41

3 votes

2 answers

367 views

Preorders as categories vs category of preorders

asked Jan 2, 2023 at 19:46

3 votes

1 answer

118 views

A category is complete iff its opposite is cocomplete, formally.

asked Feb 2, 2023 at 19:17

3 votes

1 answer

99 views

$\int_0^\pi f(x)^2dx = \int_0^\pi f'(x)^2dx$?

asked Jun 12, 2021 at 20:54

3 votes

2 answers

74 views

Conjunction not expressible as conditional

asked Apr 11, 2021 at 8:46

3 votes

1 answer

191 views

Unitaries vs isometries and co-isometries in $C^*$-algebras

asked Jun 20, 2022 at 13:53

3 votes

2 answers

107 views

Solving recurrence relation $a_n = a_{n-1} - a_{n-2}$

asked Aug 14, 2022 at 18:23

2 votes

0 answers

56 views

Metrisability of WOT on unit ball of bounded operators on a Hilbert space

asked Jun 23, 2022 at 17:04

2 votes

0 answers

50 views

General question about adequacy of logical connectives

asked Apr 10, 2021 at 8:11

2 votes

1 answer

191 views

Is there a 'distributional antiderivative'?

asked May 10, 2021 at 22:38

2 votes

1 answer

193 views

Preimages of evenly covered basis gives a basis?

asked Sep 12, 2020 at 21:13

2 votes

1 answer

33 views

Is the function representation $T_{\infty} : U(1) → GL(L^2(S^1))$ unitary?

asked Nov 3, 2020 at 21:25

2 votes

2 answers

155 views

Dualising the Yoneda lemma.

asked May 11, 2023 at 19:15

2 votes

2 answers

83 views

Equaliser of $f$ and $g$ is an isomorphism iff $f = g$

asked Jan 20, 2023 at 21:26

2 votes

1 answer

30 views

Non-trivially intersecting summands implies the space can be decomposed as the intersection of the original summands?

asked Jul 30, 2021 at 1:02

2 votes

2 answers

87 views

Limit of sequence in complete space well-defined?

asked Feb 2, 2020 at 21:17

Stack Exchange Network

133 Questions

Prime ideals in $\mathbb{Z}[X], \mathbb{Q}[X], \mathbb{F}_{19}[X]$.

On free abelian groups

Does my operator $C([0,1]) → C([0,1])$ have an inverse?

Does the abelianisation functor $\mathrm{Grp} → \mathrm{AbGrp}$ preserve composition?

Category where not every mono is regular

Extension of $\zeta_5^2 + \zeta_5^3$ over $ℚ$ is quadratic.

Minimal polynomial of $\eta_4$ over $\mathbb{Q}(\eta_2)$.

Category where morphism sets are Abelian groups

Commutative subring of matrices iff trivial unit group

How to write an arbitrary polynomial in $n$ variables

Extension of $k$-vector space structure to $k[x]$-module structure

Notation for codomain

Subgroup generated by two cycles in $S_5$.

Number of roots of a separable polynomial over a connected ring does not exceed deg $f$.

$\gcd(135-14i, 155+34i)$ with the Euclidean algorithm

Preorders as categories vs category of preorders

A category is complete iff its opposite is cocomplete, formally.

$\int_0^\pi f(x)^2dx = \int_0^\pi f'(x)^2dx$?

Conjunction not expressible as conditional

Unitaries vs isometries and co-isometries in $C^*$-algebras

Solving recurrence relation $a_n = a_{n-1} - a_{n-2}$

Metrisability of WOT on unit ball of bounded operators on a Hilbert space

General question about adequacy of logical connectives

Is there a 'distributional antiderivative'?

Preimages of evenly covered basis gives a basis?

Is the function representation $T_{\infty} : U(1) → GL(L^2(S^1))$ unitary?

Dualising the Yoneda lemma.

Equaliser of $f$ and $g$ is an isomorphism iff $f = g$

Non-trivially intersecting summands implies the space can be decomposed as the intersection of the original summands?

Limit of sequence in complete space well-defined?