User Devlin Mallory

39 votes

Accepted

Is matrix $A^TA$ always symmetric?

answered Aug 12, 2013 at 13:38

27 votes

Accepted

Does $\det(A + B) = \det(A) + \det(B)$ hold?

answered Aug 12, 2013 at 18:41

24 votes

Accepted

Prove two graphs are isomorphic

answered Aug 19, 2013 at 13:40

15 votes

Motivation for the concept of "open set" in topology

answered Aug 12, 2013 at 19:37

10 votes

Accepted

Do matrices have a "to the power of" operator?

answered Aug 12, 2013 at 14:16

10 votes

Question about math symbol $\bigsqcup$

answered Aug 4, 2012 at 4:59

8 votes

Accepted

Proving $\|e^A\|\le e^{\|A\|}$

answered Jun 14, 2013 at 22:35

8 votes

What does "topological dual of a Banach space" mean?

answered Aug 7, 2013 at 21:06

5 votes

Accepted

show that $n^2 + (n+1)^2 = 2m^2$ is impossible

answered Aug 7, 2013 at 20:38

5 votes

Intersection of algebraic field extensions.

answered Jul 17, 2013 at 18:08

5 votes

Functions have by definition the property that if $f(x_1)=a$ and $f(x_1)=b$, then $a=b$. What is the name of this property?

answered Sep 26, 2013 at 21:01

5 votes

Accepted

If $\phi: G \rightarrow H$ is a group homomorphism, $N \vartriangleleft G$, then $G/N \cong \phi(G)/\phi(N)$

answered Jun 7, 2016 at 22:23

3 votes

Accepted

$\mathrm{Proj}(A)$ and when does $A_1 = \Gamma(\mathcal{O}(1))$

answered Jun 25, 2018 at 5:18

3 votes

Prove that if $AB$ is invertible then $B$ is invertible.

answered Aug 3, 2013 at 22:33

3 votes

Accepted

What defines the dimension of a representation?

answered Jun 17, 2013 at 17:48

3 votes

Accepted

Hilbert's finiteness theorem over arbitrary fields; reductive groups

answered Jun 18, 2013 at 9:14

3 votes

Accepted

$(P[0,1],\|\|_{\infty})$ be the norm linear space

answered Aug 14, 2013 at 7:24

2 votes

Accepted

An irreducible polynomial of degree $4$ in $\mathbb{Z}_5[x]$

answered Aug 14, 2013 at 9:04

2 votes

Complete Graph Invariant

answered Aug 22, 2013 at 19:40

2 votes

Accepted

Example of a function that's uniformly continuous on a closed interval but not on an open one

answered Jun 15, 2013 at 8:11

2 votes

definition of $\mathbb{N}:=\bigcap Ind$

answered Aug 18, 2013 at 21:34

2 votes

Accepted

Global sections of a tangent sheaf of a blown-up surface.

answered Jan 17, 2020 at 17:06

1 vote

Accepted

definition of cycle theoretic fibre

answered Dec 30, 2020 at 19:59

1 vote

Accepted

Type of a singularity of a composition

answered Jun 7, 2016 at 22:53

1 vote

Rudin Theorem 4.20

answered Aug 7, 2013 at 8:31

1 vote

Finding minimum distance between two sets in $\mathbb R^2$

answered Aug 14, 2013 at 12:39

1 vote

Accepted

How to determine the rank of a linear system of equations involving parameters?

answered Aug 17, 2013 at 17:22

0 votes

Is $D(f)$ the smallest open set of $\operatorname{Spec}B$ such that $D_+(f)\subset D(f)$?

answered Aug 7, 2018 at 17:39

Stack Exchange Network

28 Answers

Is matrix $A^TA$ always symmetric?

Does $\det(A + B) = \det(A) + \det(B)$ hold?

Prove two graphs are isomorphic

Motivation for the concept of "open set" in topology

Do matrices have a "to the power of" operator?

Question about math symbol $\bigsqcup$

Proving $\|e^A\|\le e^{\|A\|}$

What does "topological dual of a Banach space" mean?

show that $n^2 + (n+1)^2 = 2m^2$ is impossible

Intersection of algebraic field extensions.

Functions have by definition the property that if $f(x_1)=a$ and $f(x_1)=b$, then $a=b$. What is the name of this property?

If $\phi: G \rightarrow H$ is a group homomorphism, $N \vartriangleleft G$, then $G/N \cong \phi(G)/\phi(N)$

$\mathrm{Proj}(A)$ and when does $A_1 = \Gamma(\mathcal{O}(1))$

Prove that if $AB$ is invertible then $B$ is invertible.

What defines the dimension of a representation?

Hilbert's finiteness theorem over arbitrary fields; reductive groups

$(P[0,1],\|\|_{\infty})$ be the norm linear space

An irreducible polynomial of degree $4$ in $\mathbb{Z}_5[x]$

Complete Graph Invariant

Example of a function that's uniformly continuous on a closed interval but not on an open one

definition of $\mathbb{N}:=\bigcap Ind$

Global sections of a tangent sheaf of a blown-up surface.

definition of cycle theoretic fibre

Type of a singularity of a composition

Rudin Theorem 4.20

Finding minimum distance between two sets in $\mathbb R^2$

How to determine the rank of a linear system of equations involving parameters?

Is $D(f)$ the smallest open set of $\operatorname{Spec}B$ such that $D_+(f)\subset D(f)$?