User Daniel Teixeira

6 votes

2 answers

136 views

Give a reason why $\mathbb Z_{64}\times \mathbb Z_4$ and $\mathbb Z_{64}\times \mathbb Z_{2}\times \mathbb Z_{2}$ are not isomorphic.

asked Dec 31, 2020 at 22:14

5 votes

2 answers

357 views

Completeness of the category of enriched categories

category-theory monoidal-categories enriched-category-theory

asked Apr 15, 2020 at 18:48

5 votes

0 answers

144 views

Why do we care about $(\infty,2)$-categories?

algebraic-topology category-theory homotopy-theory

asked Aug 9, 2021 at 18:08

4 votes

2 answers

101 views

Show that $\mathbb{Z}_5[x]/(x^2+x+1)\cong\mathbb{Z}_5[x]/(x^2+x+2)$

abstract-algebra ring-theory polynomial-rings

asked Sep 18, 2018 at 22:18

3 votes

1 answer

257 views

In $\mathbb{Z}[\sqrt{d}]$, $d$ is not divisible by the square of any prime. Why?

abstract-algebra ring-theory

asked Oct 24, 2018 at 18:49

3 votes

1 answer

121 views

Explicit homeomorphism $SL(2,\mathbb{C})\cong SU(2)\times\mathbb{R}^3$.

covering-spaces spin-geometry

asked Jun 28, 2019 at 14:05

3 votes

0 answers

90 views

Linear algebra constructions on vector bundles

linear-algebra differential-geometry vector-bundles

asked Jul 28, 2020 at 14:53

3 votes

0 answers

64 views

Why $T_pM$ instead of $TM_p$?

soft-question smooth-manifolds convention tangent-bundle

asked Sep 16, 2020 at 14:25

3 votes

0 answers

63 views

Why are acyclic fibrations called so?

category-theory soft-question model-categories

asked Sep 18, 2020 at 13:20

3 votes

1 answer

53 views

For $n\geq 3$, does every horn $\Lambda^n_k\to N\mathcal C$ have a filler?

category-theory homotopy-theory simplicial-stuff

asked Dec 14, 2020 at 15:47

2 votes

0 answers

78 views

Localization of a ring at any subset

abstract-algebra category-theory localization

asked Nov 26, 2021 at 20:17

2 votes

0 answers

48 views

Show that $\text{Top}$ is locally Kan.

category-theory homotopy-theory simplicial-stuff

asked Feb 8, 2021 at 14:18

2 votes

0 answers

45 views

Cycles in an acyclic complex of projectives are projectives.

abstract-algebra category-theory homological-algebra projective-module

asked Feb 12, 2021 at 19:21

2 votes

1 answer

125 views

Monoidal categories as categories internal to $\textbf{Cat}$

category-theory monoidal-categories higher-category-theory

asked Apr 12, 2020 at 13:21

2 votes

1 answer

152 views

Are simplicial sets equal if their non-degenerate simplices are the same?

category-theory homotopy-theory simplicial-stuff

asked Dec 9, 2020 at 22:41

2 votes

1 answer

245 views

Show that $\int |f_n-f|\to 0$

real-analysis measure-theory lebesgue-integral

asked Jan 2, 2021 at 18:10

2 votes

1 answer

295 views

Is there an $\infty$-category of spaces?

algebraic-topology category-theory homotopy-theory

asked Jan 13, 2021 at 20:39

2 votes

1 answer

71 views

Canonical model structure on a 2-category

category-theory homotopy-theory model-categories

asked Sep 16, 2020 at 14:48

2 votes

1 answer

38 views

$V^{1,0}$ as a Lagrangian subspace of $V^c$

complex-geometry symplectic-geometry kahler-manifolds

asked Aug 24, 2020 at 20:58

2 votes

1 answer

82 views

Inductive definition of $\infty$-category

category-theory homotopy-theory higher-category-theory

asked Apr 18, 2020 at 14:06

2 votes

1 answer

150 views

A ring is commutative if the solution of $ab=ca$ is always unique [duplicate]

abstract-algebra ring-theory

asked Aug 22, 2018 at 19:41

2 votes

3 answers

431 views

Flat principal bundles over a simply connected manifold are trivial

fiber-bundles connections gauge-theory

asked Oct 16, 2019 at 18:41

2 votes

0 answers

55 views

Surfaces of revolution as vector bundles

smooth-manifolds fiber-bundles

asked Mar 7, 2018 at 14:39

2 votes

0 answers

127 views

Invariance of signature in semi-riemannian manifolds

semi-riemannian-geometry

asked Jun 27, 2018 at 18:27

1 vote

1 answer

35 views

The projection from the time-orientable double cover preserves topological properties.

semi-riemannian-geometry

asked Jun 27, 2018 at 23:59

1 vote

0 answers

195 views

Using the Fourier transform to solve PDEs with non-integrable initial conditions

partial-differential-equations fourier-transform

asked Nov 13, 2017 at 5:03

1 vote

1 answer

37 views

Can a data set of a function $f:\mathbb{R}^n\to\mathbb{R}^k$ decide if it is differentiable?

real-analysis computational-science

asked Apr 20, 2018 at 15:07

1 vote

2 answers

41 views

Let $C\subset E$ be a convex subspace and $a\in E\setminus C$. The point in $C$ closest to $a$ is unique.

linear-algebra

asked Apr 20, 2018 at 19:16

1 vote

0 answers

41 views

Vacuum solutions of Einstein's field equations with $O(n)$ isometry group

reference-request general-relativity semi-riemannian-geometry

asked Jun 27, 2018 at 13:21

1 vote

0 answers

57 views

Definition of tensor product of graded maps

linear-algebra monoidal-categories graded-modules

asked Mar 20, 2020 at 14:37

Stack Exchange Network

current community

your communities

more stack exchange communities

38 Questions

Give a reason why $\mathbb Z_{64}\times \mathbb Z_4$ and $\mathbb Z_{64}\times \mathbb Z_{2}\times \mathbb Z_{2}$ are not isomorphic.

Completeness of the category of enriched categories

Why do we care about $(\infty,2)$-categories?

Show that $\mathbb{Z}_5[x]/(x^2+x+1)\cong\mathbb{Z}_5[x]/(x^2+x+2)$

In $\mathbb{Z}[\sqrt{d}]$, $d$ is not divisible by the square of any prime. Why?

Explicit homeomorphism $SL(2,\mathbb{C})\cong SU(2)\times\mathbb{R}^3$.

Linear algebra constructions on vector bundles

Why $T_pM$ instead of $TM_p$?

Why are acyclic fibrations called so?

For $n\geq 3$, does every horn $\Lambda^n_k\to N\mathcal C$ have a filler?

Localization of a ring at any subset

Show that $\text{Top}$ is locally Kan.

Cycles in an acyclic complex of projectives are projectives.

Monoidal categories as categories internal to $\textbf{Cat}$

Are simplicial sets equal if their non-degenerate simplices are the same?

Show that $\int |f_n-f|\to 0$

Is there an $\infty$-category of spaces?

Canonical model structure on a 2-category

$V^{1,0}$ as a Lagrangian subspace of $V^c$

Inductive definition of $\infty$-category

A ring is commutative if the solution of $ab=ca$ is always unique [duplicate]

Flat principal bundles over a simply connected manifold are trivial

Surfaces of revolution as vector bundles

Invariance of signature in semi-riemannian manifolds

The projection from the time-orientable double cover preserves topological properties.

Using the Fourier transform to solve PDEs with non-integrable initial conditions

Can a data set of a function $f:\mathbb{R}^n\to\mathbb{R}^k$ decide if it is differentiable?

Let $C\subset E$ be a convex subspace and $a\in E\setminus C$. The point in $C$ closest to $a$ is unique.

Vacuum solutions of Einstein's field equations with $O(n)$ isometry group

Definition of tensor product of graded maps