User Katlus - Mathematics Stack Exchange

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	1,982 reputation	bio	website		visits	member for	1 year, 1 month
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9

votes

5

answers

273

views

Prove that every set with more than one element has a permutation without fixed points

elementary-set-theory axiom-of-choice

may 3 '12 at 19:50 Asaf Karagila 90.7k

2

7

votes

1

answer

137

views

Constructing a choice function in a complete & separable metric space

oct 10 at 6:01 Hagen von Eitzen 42.1k

6

votes

0

answers

105

views

What are 'weak' forms of Urysohn's lemma, which do not require choice?

general-topology axiom-of-choice

jan 16 at 23:49 Katlus 1,982

6

votes

2

answers

110

views

If limit of $|f|$ is divergent to $\infty$, then is $f$ divergent to either $\infty$ or $-\infty$?

real-analysis

dec 13 at 0:05 Marc van Leeuwen 23.8k

1

6

votes

5

answers

1

kviews

If $\gcd(a,b)=1$, then $\gcd(a^n,b^n)=1$

elementary-number-theory

jul 5 at 4:18 Community♦ 1

6

votes

1

answer

170

views

Complete ordered field

field-theory ordered-fields

jun 19 '12 at 13:07 Martin Sleziak 20.3k

6

votes

2

answers

228

views

Operations on ordinal numbers

elementary-set-theory ordinals

may 17 '12 at 6:16 Martin Sleziak 20.3k

2

5

votes

4

answers

249

views

What is a formal definition of series?

analysis

apr 16 at 6:10 user18921 3,395

5

votes

4

answers

107

views

Complement of co-dense set.

general-topology baire-category

feb 24 at 5:28 Asaf Karagila 90.7k

5

votes

1

answer

563

views

Proving that the set of algebraic numbers is countable without AC

set-theory axiom-of-choice

feb 16 at 14:00 lanjarote 1

5

votes

3

answers

45

views

How do i prove that $C_c(X)$ is a vector space?

real-analysis

jan 16 at 17:24 Ilya 14.2k

5

votes

1

answer

139

views

Why uniform closure $\mathscr{B}$ of an algebra $\mathscr{A}$ of bounded complex functions is uniformly closed?

real-analysis axiom-of-choice

dec 17 at 18:54 Katlus 1,982

5

votes

2

answers

133

views

How to convert $\int_{0}^{\infty} \sin (t^2) dt$ to a limit of a series? [duplicate]

real-analysis

dec 9 at 15:56 Michael Hardy 47.9k

5

votes

2

answers

129

views

$f'$ is bounded $\Rightarrow$ $f$ is bounded?

real-analysis

nov 22 at 12:18 Gautam Shenoy 2,309

2

5

votes

1

answer

175

views

Set theorist as a physicist or physicist as a set theorist?

soft-question set-theory advice mathematical-physics

nov 12 at 23:28 Asaf Karagila 90.7k

1

5

votes

2

answers

258

views

If every infinite subset has a limit point in a metric space $X$, then $X$ is separable (in ZF)

general-topology set-theory axiom-of-choice

aug 8 at 15:40 JDH 18.5k

5

votes

1

answer

87

views

Finite ordinal to the power a = a

elementary-set-theory ordinals

jun 4 '12 at 9:20 Daniel Briggs 225

1

4

votes

1

answer

155

views

Totally bouded,sequentially compact,complete,bounded,closed,equicontinuous$\Rightarrow$ compact?

general-topology metric-spaces axiom-of-choice

may 15 at 10:04 Community♦ 1

2

4

votes

3

answers

285

views

What is your definition for neighborhood in topology?

general-topology terminology

jan 19 at 18:00 Mathemagician1234 3,744

4

votes

0

answers

76

views

When $K$ is compact, if $S\subset C_b(K)$ is closed,bounded and equicontinuous, then $S$ is compact? (ZF)

real-analysis axiom-of-choice

dec 27 at 10:07 saz 5,422

4

votes

2

answers

239

views

What is your definition of Riemann-Stieltjes Integral?

real-analysis

nov 24 at 17:55 kahen 8,054

1

4

votes

3

answers

675

views

Every open set in $\mathbb{R}$ is the union of an at most countable collection of disjoint segments

general-topology

nov 11 at 3:32 Cameron Buie 27.5k

4

votes

2

answers

157

views

Solovay's Model and Choice

set-theory axiom-of-choice

oct 11 at 8:54 Martin Sleziak 20.3k

4

votes

1

answer

197

views

Epsilon numbers

elementary-set-theory ordinals

sep 1 at 9:00 Community♦ 1

4

votes

4

answers

199

views

(ZF) If $\mathbb{R}^k$ is a countable union of closed sets, then at least one has a nonempty interior

general-topology set-theory axiom-of-choice baire-category

aug 13 at 13:50 Asaf Karagila 90.7k

4

votes

3

answers

303

views

Does there exist a bijection between empty sets?

elementary-set-theory

may 4 '12 at 17:11 Arturo Magidin 158k

3

votes

2

answers

100

views

How do I define Polynomial ring $R[x]$ over a commutative ring $R$ with unity?

abstract-algebra

feb 5 at 7:52 Community♦ 1

1

3

votes

0

answers

91

views

What is the usual construction of Lebesgue measure?

real-analysis measure-theory

jan 24 at 20:55 Katlus 1,982

3

votes

4

answers

113

views

Why 'equality almost everywhere' is transitive?

measure-theory

jan 13 at 13:54 uncookedfalcon 2,499

3

votes

1

answer

316

views

Helly's selection theorem (For sequence of monotonic functions)

real-analysis

dec 26 at 7:46 Katlus 1,982

Katlus

203 Questions