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Good Question

Question score of 25 or more. This badge can be awarded multiple times.

Awarded 8249 times.

Why $PSL_3(\mathbb F_2)\cong PSL_2(\mathbb F_7)$?

Awarded Mar 30 at 22:26

Grigory M

18.2k4 gold badges91 silver badges136 bronze badges

Getting different answers when integrating using different techniques

Awarded Mar 30 at 13:47

Xander Henderson♦

32.9k25 gold badges74 silver badges122 bronze badges

A problem posed by Ramanujan involving $\sum e^{-5\pi n^2}$

Awarded Mar 30 at 9:57

Paramanand Singh♦

93k15 gold badges160 silver badges352 bronze badges

Why are the undefined terms in geometry undefined?

Awarded Mar 28 at 17:20

Xios Tilier

3892 silver badges3 bronze badges

In what sense is $p$-adic Hodge theory related to ordinary (complex) Hodge theory?

Awarded Mar 27 at 2:51

Joachim

5,5231 gold badge38 silver badges62 bronze badges

Do the BAC-CAB identity for triple vector product have some intepretation?

Awarded Mar 26 at 17:55

pppqqq

2,2401 gold badge20 silver badges25 bronze badges

Can 3 integer right angle triangles have the same hypotenuse and the areas of two of them sum to the last?

Awarded Mar 24 at 17:23

Dart

3712 silver badges11 bronze badges

Minkowski plane vs. hyperbolic plane

Awarded Mar 24 at 8:56

TeicDaun

3338 silver badges29 bronze badges

Something interesting that I found about some numbers - and would like to see if it's known

Awarded Mar 23 at 9:48

MathematicalPhysicist

4,4191 gold badge25 silver badges49 bronze badges

Approximate $|x|$ with a smooth function

Awarded Mar 20 at 2:03

Ono

5191 gold badge5 silver badges10 bronze badges

Are there spaces "smaller" than $c_0$ whose dual is $\ell^1$?

Awarded Mar 19 at 7:22

Nirakar Neo

9497 silver badges20 bronze badges

Prove that $X^\ast$ separable implies $X$ separable

Awarded Mar 19 at 7:22

Rudy the Reindeer

48.6k30 gold badges176 silver badges356 bronze badges

A surprisingly difficult fact about bilinear maps

Awarded Mar 18 at 13:36

Robert Trosten

9113 silver badges12 bronze badges

Inverse image of a compact set is compact

Awarded Mar 18 at 13:11

Brian Bi

1,3561 gold badge11 silver badges52 bronze badges

Confusion about Homotopy Type Theory terminology

Awarded Mar 18 at 9:55

Nate

2,2851 gold badge18 silver badges24 bronze badges

Is it possible to construct an ordered field which is also algebraically closed?

Awarded Mar 17 at 16:18

Dan M. Katz

1,9733 gold badges16 silver badges28 bronze badges

Is linear function convex or concave?

Awarded Mar 17 at 15:07

Bodo Hombah

3731 gold badge3 silver badges4 bronze badges

Is the closure of a convex set again a convex set?

Awarded Mar 17 at 15:07

nimeshkiranverma

6942 gold badges7 silver badges12 bronze badges

Do wheels of a car always travel the same distance?

Awarded Mar 17 at 13:43

govindah

8606 silver badges10 bronze badges

Compactly supported function whose Fourier transform decays exponentially?

Awarded Mar 17 at 13:07

Syang Chen

3,5761 gold badge30 silver badges32 bronze badges

Best book on axiomatic set theory.

Awarded Mar 17 at 5:16

Regressor

3871 gold badge4 silver badges6 bronze badges

For any two sets $A,B$ , $|A|\leq|B|$ or $|B|\leq|A|$

Awarded Mar 16 at 21:41

Amr

20.6k5 gold badges60 silver badges126 bronze badges

Uncountable sets of Hausdorff dimension zero

Awarded Mar 16 at 3:12

JavaMan

13.4k2 gold badges42 silver badges62 bronze badges

p-adic Lie groups vs. algebraic groups over $\mathbb{Q}_p$

Awarded Mar 15 at 19:41

the_lar

8007 silver badges16 bronze badges

What is the notation for the set of all $m\times n$ matrices? [duplicate]

Awarded Mar 14 at 18:54

Mirrana

9,34336 gold badges89 silver badges128 bronze badges

Example of a stochastic process which does not have the Markov property

Awarded Mar 13 at 15:32

Roman Starkov

3771 gold badge3 silver badges12 bronze badges

Simplification of expressions containing radicals

Awarded Mar 13 at 14:49

Chris Card

2,1081 gold badge18 silver badges16 bronze badges

How likely are you to win this multi-stage lottery?

Awarded Mar 13 at 0:00

MonitorLizard

3531 silver badge7 bronze badges

Order of an element in a finite cyclic group

Awarded Mar 11 at 20:51

AG.

2,12717 silver badges25 bronze badges

Are there uncountably infinite orders of infinity?

Awarded Mar 11 at 20:51

Seth

3533 silver badges6 bronze badges

How to integrate $\int\frac{1}{\sqrt{1+x^3}}\mathrm dx$?

Awarded Mar 11 at 10:13

awllower

17k5 gold badges49 silver badges98 bronze badges

The double-angle formula for cosine is expressible in terms of (single-angle) cosine alone; not so for sine. Why the asymmetry?

Awarded Mar 10 at 15:11

Kirusanth

7735 silver badges13 bronze badges

Topological vs. Algebraic $K$-Theory

Awarded Mar 10 at 5:16

user02138

17.4k5 gold badges61 silver badges90 bronze badges

What does the discriminant of an algebraic number field mean intuitively?

Awarded Mar 9 at 6:08

Mohan

15.7k20 gold badges90 silver badges140 bronze badges

Probability questions that have answer $\frac{1}{2}$ but resist intuitive explanation.

Awarded Mar 9 at 3:37

Dan

40.3k5 gold badges83 silver badges247 bronze badges

What is the lowest degree polynomial that turns a circle into a nontrivial knot?

Awarded Mar 8 at 21:05

Zoe Allen

7,99013 silver badges42 bronze badges

Show that holomorphic $f_1, . . . , f_n $ are constant if $\sum_{k=1}^n \left| f_k(z) \right|$ is constant.

Awarded Mar 5 at 16:30

user59982

3114 silver badges4 bronze badges

joint distribution, discrete and continuous random variables

Awarded Mar 5 at 16:12

Mia

5611 gold badge6 silver badges12 bronze badges

Of French Gothic architecture and Ramanujan's $\pi\approx \frac{9}{5}+ \sqrt{ \frac{9}{5} } = 3.1416\dots $?

Awarded Mar 4 at 19:05

Tito Piezas III

61.1k8 gold badges135 silver badges322 bronze badges

Can a 4-d creature twist your right hand into a left hand without breaking it?

Awarded Mar 2 at 0:25

Rohit Pandey

7,6173 gold badges36 silver badges75 bronze badges

Is $(k \cdot f)(x) := f(kx)$ the scalar multiplication of some vector space?

Awarded Mar 1 at 8:41

Daron

11.8k2 gold badges26 silver badges46 bronze badges

Are these figures homeomorphic?

Awarded Feb 28 at 2:27

Gustavo

2,62819 silver badges32 bronze badges

Properties and notation of third-order (and higher) partial-derivatives

Awarded Feb 27 at 20:59

SDV

7401 gold badge6 silver badges12 bronze badges

On the definition of the structure sheaf attached to $Spec A$

Awarded Feb 27 at 10:09

Dubious

14.2k12 gold badges65 silver badges153 bronze badges

Simple Proof of the Euler Identity $\exp{i\theta}=\cos{\theta}+i\sin{\theta}$

Awarded Feb 27 at 8:21

Hamza

3,8611 gold badge22 silver badges34 bronze badges

$\varphi$ in $\operatorname{Hom}{(S^1, S^1)}$ are of the form $z^n$

Awarded Feb 26 at 21:45

Rudy the Reindeer

48.6k30 gold badges176 silver badges356 bronze badges

Reflection between Two Parallel Cylinders

Awarded Feb 25 at 18:19

Kuru Kurumi

4113 silver badges6 bronze badges

Principal submatrices of a positive definite matrix

Awarded Feb 25 at 5:57

Drew

4611 gold badge5 silver badges10 bronze badges

Fundamental group of complement of $n$ lines through the origin in $\mathbb{R}^3$

Awarded Feb 25 at 0:48

Edward Hughes

5,5054 gold badges41 silver badges74 bronze badges

Prove that the closure of complement, is the complement of the interior

Awarded Feb 24 at 13:17

Jeybe

1,2821 gold badge12 silver badges18 bronze badges

The Frobenius Coin Problem

Awarded Feb 23 at 23:45

John

5511 gold badge6 silver badges13 bronze badges

The Cantor set is homeomorphic to infinite product of $\{0,1\}$ with itself - cylinder basis - and it topology

Awarded Feb 23 at 1:17

nate

2,2093 gold badges24 silver badges37 bronze badges

Difference between Increasing and Monotone increasing function

Awarded Feb 22 at 8:47

Umesh shankar

11.8k5 gold badges33 silver badges73 bronze badges

The Identity Theorem for real analytic functions

Awarded Feb 21 at 0:27

Yui

4114 silver badges9 bronze badges

How to find exponential objects and subobject classifiers in a given category

Awarded Feb 19 at 23:06

Jak

2632 silver badges6 bronze badges

Eigenvalues of matrix with entries that are continuous functions

Awarded Feb 18 at 7:36

ampeo

5456 silver badges9 bronze badges

Closed immersions are stable under base change

Awarded Feb 17 at 10:07

PeterM

5,7111 gold badge39 silver badges75 bronze badges

Last nonzero digit of $(\dots((2018\underset{! \text{ occurs }1009\text{ times}}{\underbrace{!)!)!\dots)!}}$

Awarded Feb 16 at 16:21

Hussain-Alqatari

5,8443 gold badges17 silver badges44 bronze badges

Vector spaces of the same finite dimension are isomorphic

Awarded Feb 16 at 8:53

Bysshed

1,9631 gold badge18 silver badges32 bronze badges

Determining if an arbitrary point lies inside a triangle defined by three points?

Awarded Feb 14 at 15:11

Casey

4492 gold badges8 silver badges15 bronze badges

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