User lanskey

11 votes

1 answer

284 views

Baby Rudin 1.14 is essentially Thales's theorem?

asked Jul 26, 2018 at 23:58

8 votes

1 answer

782 views

Converse Lagrange's Theorem for abelian groups

group-theory abelian-groups

asked Apr 30, 2018 at 22:04

6 votes

2 answers

444 views

Category of multisets

category-theory multisets

asked Aug 20, 2019 at 13:37

4 votes

1 answer

162 views

Finding ring homomorphisms $\mathbb{Z}\to\mathbb{Z}/n\mathbb{Z}$

ring-theory ring-homomorphism

asked Feb 19, 2018 at 1:50

4 votes

1 answer

550 views

Is surjection an epimorphism without the axiom of choice?

category-theory axiom-of-choice epimorphisms

asked Mar 7, 2018 at 11:16

3 votes

0 answers

272 views

Why is $0$ a zero divisor?

ring-theory soft-question terminology

asked May 4, 2018 at 1:32

3 votes

0 answers

103 views

Proof check. Standard form for alternating polynomials

abstract-algebra proof-verification polynomials

asked May 8, 2018 at 13:10

2 votes

1 answer

153 views

Show that $G$ is isomorphic to $\operatorname{Aut}_{G-Set}(G)$

abstract-algebra group-theory group-actions

asked May 4, 2018 at 0:33

2 votes

0 answers

59 views

Compact manifold without boundary is boundary of another manifold [duplicate]

differential-geometry manifolds

asked Feb 25, 2017 at 2:35

2 votes

1 answer

102 views

Contraction map, inequality

real-analysis functional-analysis metric-spaces

asked Aug 18, 2016 at 0:20

1 vote

1 answer

30 views

If $B\triangleleft A\subset G,H\triangleleft G$ and $A/B$ abelian, then $(A\cap H )/(B\cap H)$ is abelian

group-theory

asked Jan 9, 2017 at 7:01

1 vote

1 answer

687 views

Closure of interior of a convex closed set with nonempty interior is the set itself.

general-topology geometry

asked Feb 16, 2017 at 13:57

1 vote

1 answer

150 views

Inversion mapping four points to vertices of a parallelogram.

geometry

asked Feb 17, 2017 at 15:03

1 vote

1 answer

53 views

What are the essentials about classes

soft-question set-theory

asked Mar 10, 2018 at 15:25

1 vote

0 answers

67 views

Integral over an ellipsoid of $z^2\mathrm{d}x\wedge\mathrm{d}y$, Stokes' theorem

integration differential-geometry

asked Feb 22, 2017 at 18:42

1 vote

1 answer

413 views

Nowhere vanishing vector field on Moebius strip

surfaces geometric-topology

asked Sep 17, 2018 at 20:47

1 vote

0 answers

35 views

$\lim\limits_{n\to\infty} n^a x_n$ [duplicate]

real-analysis limits

asked Aug 30, 2019 at 9:29

1 vote

1 answer

51 views

Is the Lie algebra so(2,6) semi-simple?

reference-request lie-algebras semisimple-lie-algebras

asked Sep 12, 2021 at 22:53

0 votes

1 answer

460 views

$\mathbb{Q}(\sqrt d)$ is the smallest subfield of $\mathbb{C}$ containing $\mathbb{Q}$ and $\sqrt d$ using field norm

abstract-algebra ring-theory field-theory

asked Jul 31, 2018 at 19:37

0 votes

1 answer

95 views

continuous function on a circle without holomorphic continuation to the interior

complex-analysis

asked Oct 9, 2017 at 21:02

0 votes

1 answer

209 views

Integral of a 2-form over an ellipsoid.

integration multivariable-calculus differential-geometry

asked Feb 22, 2017 at 1:45

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21 Questions

Baby Rudin 1.14 is essentially Thales's theorem?

Converse Lagrange's Theorem for abelian groups

Category of multisets

Finding ring homomorphisms $\mathbb{Z}\to\mathbb{Z}/n\mathbb{Z}$

Is surjection an epimorphism without the axiom of choice?

Why is $0$ a zero divisor?

Proof check. Standard form for alternating polynomials

Show that $G$ is isomorphic to $\operatorname{Aut}_{G-Set}(G)$

Compact manifold without boundary is boundary of another manifold [duplicate]

Contraction map, inequality

If $B\triangleleft A\subset G,H\triangleleft G$ and $A/B$ abelian, then $(A\cap H )/(B\cap H)$ is abelian

Closure of interior of a convex closed set with nonempty interior is the set itself.

Inversion mapping four points to vertices of a parallelogram.

What are the essentials about classes

Integral over an ellipsoid of $z^2\mathrm{d}x\wedge\mathrm{d}y$, Stokes' theorem

Nowhere vanishing vector field on Moebius strip

$\lim\limits_{n\to\infty} n^a x_n$ [duplicate]

Is the Lie algebra so(2,6) semi-simple?

$\mathbb{Q}(\sqrt d)$ is the smallest subfield of $\mathbb{C}$ containing $\mathbb{Q}$ and $\sqrt d$ using field norm

continuous function on a circle without holomorphic continuation to the interior

Integral of a 2-form over an ellipsoid.