User Matt N. - Mathematics Stack Exchange

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	15,230 reputation	bio	website		visits	member for	2 years, 4 months
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6

19

votes

1

answer

603

views

Perturbation trick in the proof of Seifert-van-Kampen

algebraic-topology

may 20 '12 at 16:07 Ronnie Brown 2,964

14

19

votes

2

answers

1

kviews

Convergence a.e. and of norms implies that in Lebesgue space

real-analysis

oct 31 at 4:28 leo 2,695

5

19

votes

1

answer

210

views

When is Stone-Čech compactification the same as one-point compactification?

general-topology compactness

mar 27 at 5:32 Martin Sleziak 20.3k

3

18

votes

1

answer

426

views

What is the smallest value of $n$ for which $\phi(n) \ne \phi(k)$ for any $k<n,$ where $n=4m$?

number-theory totient-function

feb 14 '11 at 16:44 joriki 92.5k

9

17

votes

5

answers

555

views

Fun math outreach/social activities

education recreational-mathematics

jan 25 '11 at 3:27 Mike Spivey 25.9k

12

17

votes

5

answers

1

kviews

Soft Question - Intuition of the meaning of homology groups

general-topology soft-question algebraic-topology homology

may 17 '12 at 16:23 Ronnie Brown 2,964

7

17

votes

4

answers

515

views

Is there a $\sigma$-algebra on $\mathbb{R}$ strictly between the Borel and Lebesgue algebras?

real-analysis measure-theory descriptive-set-theory

jul 23 at 1:13 Asaf Karagila 90.8k

10

17

votes

4

answers

936

views

What are the required backgrounds of Robin Hartshorne's Algebraic Geometry book?

reference-request algebraic-geometry

nov 25 at 11:09 Javier Álvarez 4,794

11

17

votes

9

answers

799

views

What's a good place to learn Lie groups?

reference-request representation-theory lie-groups

mar 10 at 0:17 Alex Youcis 12.4k

9

16

votes

2

answers

746

views

For every infinite $S$, $|S|=|S\times S|$ implies the Axiom of choice

set-theory cardinals axiom-of-choice

aug 9 at 17:02 Asaf Karagila 90.8k

10

16

votes

6

answers

702

views

Difficulty in Mathematical Writing

soft-question proof-writing

dec 30 at 12:29 Matt E 57.8k

14

15

votes

4

answers

4

kviews

When can you switch the order of limits?

real-analysis sequences-and-series limit

jun 14 '11 at 16:07 Martin Sleziak 20.3k

5

15

votes

2

answers

1

kviews

Why can't Cantor sets cover $\mathbb{ R}$?

soft-question real-analysis

oct 25 '10 at 11:23 kahen 8,064

3

15

votes

2

answers

812

views

How useless can the Mayer-Vietoris sequence be in general?

algebraic-topology examples-counterexamples

may 22 '11 at 21:19 Grigory M 6,842

6

15

votes

2

answers

995

views

A question regarding Collatz conjecture

number-theory

may 18 '12 at 18:17 Community♦ 1

6

15

votes

1

answer

1

kviews

Cardinality of Borel sigma algebra

real-analysis measure-theory probability-theory set-theory descriptive-set-theory

oct 8 '11 at 23:22 ccc 1,456

5

15

votes

5

answers

567

views

Can two topological spaces surject onto each other but not be homeomorphic?

general-topology examples-counterexamples

jul 19 at 7:26 Community♦ 1

2

15

votes

2

answers

555

views

Continuity and the Axiom of Choice

analysis set-theory axiom-of-choice

oct 17 at 8:39 Brian M. Scott 154k

2

14

votes

1

answer

445

views

Integral of measurable spaces

measure-theory

mar 28 at 18:52 Community♦ 1

14

votes

3

answers

480

views

RSA in plain English

number-theory prime-numbers cryptography

feb 3 '11 at 14:08 Arturo Magidin 158k

3

14

votes

2

answers

549

views

The set of ultrafilters on an infinite set

general-topology set-theory filters

apr 8 at 21:15 Brian M. Scott 154k

6

13

votes

1

answer

734

views

Cohomology of projective plane

algebraic-topology differential-topology cohomology

mar 28 '11 at 17:00 Mariano Suárez-Alvarez♦ 53.2k

6

13

votes

1

answer

1

kviews

Why is a covering space of a torus $T$ homeomorphic either to $\mathbb{R}^2$, $S^1\times\mathbb{R}$ or $T$?

algebraic-topology

aug 25 '11 at 19:17 Aaron 6,642

2

13

votes

4

answers

517

views

Introduction to Filters in Topology

general-topology online-resources filters

apr 29 at 21:05 Dani 11

18

13

votes

4

answers

635

views

Best books in the genre “______ for Mathematicians”

reference-request big-list teaching

jul 9 at 1:00 PhD 162

4

13

votes

2

answers

2

kviews

Lebesgue measurable but not Borel measurable

measure-theory

feb 4 '11 at 17:53 Miguel 443

5

13

votes

4

answers

484

views

Homotopy groups of $S^2$

algebraic-topology homotopy-theory

jul 21 '11 at 1:33 Peter May 356

2

13

votes

1

answer

135

views

Is $\mathbb{Q}^2$ homeomorphic to $\mathbb{Q}^2\setminus \{0\}$?

general-topology metric-spaces

mar 7 at 19:20 Caloric 575

3

12

votes

0

answers

808

views

When is the image of a null set also null?

general-topology analysis measure-theory

sep 14 at 10:13 Ricardo Buring 144

2

12

votes

2

answers

159

views

Applications of model theory to analysis

real-analysis complex-analysis soft-question model-theory

dec 23 at 8:26 Seirios 8,912

Matt N.

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