User Costel Gabriel Bontea - Mathematics Stack Exchange

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	21 reputation	bio	website		visits	member for	1 year, 2 months
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77

115

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A challenge by R. P. Feynman: give counter-intuitive theorems that can be translated into everyday language

aug 6 at 1:40 John 1

42

48

votes

39

answers

5

kviews

What are some examples of a mathematical result being counterintuitive?

intuition big-list

may 5 at 7:12 Gastón Burrull 1,281

18

37

votes

5

answers

784

views

Why are the solutions of polynomial equations so unconstrained over the quaternions?

polynomials roots quaternions abstract-algebra

may 7 '12 at 6:46 Marc van Leeuwen 23.9k

35

31

votes

9

answers

3

kviews

How to effectively study math?

soft-question education self-learning learning

apr 6 at 2:21 amWhy 54.6k

16

28

votes

2

answers

2

kviews

The square roots of the primes are linearly independent over the field of rationals

abstract-algebra prime-numbers field-theory

oct 7 at 23:05 Community♦ 1

8

21

votes

6

answers

838

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Importance of rigor

soft-question math-history

aug 19 at 0:14 Argon 9,258

12

21

votes

17

answers

1

kviews

Mathematical toys?

reference-request big-list popular-math

may 14 '12 at 6:16 user31284 97

6

20

votes

2

answers

998

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Proving an “amazing” claim regarding $\zeta( 3)$ and Apéry's proof

sequences-and-series special-functions power-series riemann-zeta

jun 8 '12 at 19:32 Peter Tamaroff 25.6k

4

14

votes

3

answers

929

views

Why doesn't 0 being a prime ideal in Z imply that 0 is a prime number?

number-theory abstract-algebra terminology definition ring-theory

mar 15 '11 at 22:45 Community♦ 1

5

13

votes

2

answers

466

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Different formulations of Class Field Theory

algebraic-number-theory

may 25 '11 at 12:37 ogerard 823

23

12

votes

19

answers

7

kviews

Does .99999… = 1?

algebra-precalculus decimal-expansion

may 9 at 13:01 badp 537

5

12

votes

9

answers

2

kviews

How Can One Prove $\cos(\pi/7) + \cos(3 \pi/7) + \cos(5 \pi/7) = 1/2$

trigonometry proof-strategy popular-math

sep 19 at 19:37 Chris's wise sister 11.5k

2

12

votes

2

answers

422

views

Is there a proper subgroup $H$ of $(\mathbb{R},+)$ such that $[\mathbb{R}:H]$ is finite?

group-theory

jan 29 '12 at 7:10 Pierre-Yves Gaillard 8,477

3

10

votes

2

answers

301

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Is there an infinite simple group with no element of order $2$?

group-theory finite-groups simple-groups

may 2 '12 at 13:55 user1729 3,344

4

10

votes

3

answers

2

kviews

In how many ways can a number be expressed as a sum of consecutive numbers?

combinatorics number-theory

may 2 '12 at 20:20 Ilmari Karonen 8,226

4

10

votes

3

answers

318

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Show $\langle a^m \rangle \cap \langle a^n \rangle = \langle a^{\operatorname{lcm}(m, n)}\rangle$

abstract-algebra group-theory cyclic-groups

apr 3 at 23:31 leo 2,695

5

9

votes

3

answers

650

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Galois Group of $(x^3-5)(x^2-3)$

abstract-algebra field-theory galois-theory

may 13 '12 at 12:11 Community♦ 1

5

9

votes

1

answer

386

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Interpretations of the first cohomology group

group-theory group-cohomology

dec 27 '11 at 22:15 mt_ 3,978

3

9

votes

1

answer

620

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If $f$ is measurable and $fg$ is in $L^1$ for all $g \in L^q$, must $f \in L^p$?

functional-analysis measure-theory integration

sep 30 '11 at 2:04 robjohn♦ 59.5k

3

9

votes

3

answers

323

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Reducibility of $P(X^2)$

polynomials field-theory

may 13 '12 at 10:42 Ewan Delanoy 8,393

2

8

votes

2

answers

281

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Showing a UFD which is not a PID must have a nonprincipal maximal ideal.

commutative-algebra ring-theory

may 7 '12 at 23:14 Community♦ 1

5

7

votes

2

answers

601

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Is there a systematic way of finding the conjugacy class and/or centralizer of an element?

abstract-algebra group-theory

jan 25 '12 at 14:55 Community♦ 1

2

7

votes

1

answer

281

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Fraction field of the formal power series ring in finitely many variables

commutative-algebra

feb 15 at 0:34 YACP 9,120

4

7

votes

2

answers

548

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What exactly is a tensor product?

abstract-algebra tensor-products quantum-groups

may 13 '12 at 17:40 Michael Hardy 48k

4

7

votes

1

answer

163

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If $K=K^2$ then every automorphism of $\mbox{Aut}_K V$, where $\dim V< \infty$, is the square of some endomorphism.

linear-algebra field-theory

may 11 '12 at 22:50 Lierre 2,882

2

7

votes

1

answer

192

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Algebraic Extensions and Separability

field-theory finite-fields

may 9 '12 at 15:23 BenjaLim 16.7k

3

6

votes

2

answers

247

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Why is this extension of Galois?

field-theory galois-theory

may 28 '12 at 19:54 Jyrki Lahtonen 30.7k

4

6

votes

1

answer

435

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How to count number of bases and subspaces of a given dimension in a vector space over a finite field?

linear-algebra

may 9 '12 at 4:37 Yuval Filmus 25.9k

1

6

votes

1

answer

258

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Why $E$ is the algebraic closure of $K$?

field-theory

may 10 '12 at 0:53 Makoto Kato 11.3k

3

6

votes

4

answers

354

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what is the fraction field of $R[[x]]$, the power series over some ring?

commutative-algebra power-series

may 4 '12 at 12:38 Hagen 3,347

Costel Gabriel Bontea

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