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General Q&A about all branches of theoretical and applied mathematics, including closely-adjacent sciences where the central question is about the math.

377 posts RSS
Activity Age Score Random
Filters (None)
81%
+7 −0
Endomorphisms on an entropic structure whose pointwise product is the identity automorphism - entropic idempotent structure?

1 answer  ·  posted 3y ago by Prime Mover‭  ·  last activity 11mo ago by Derek Elkins‭

abstract-algebra
81%
+7 −0
Does this construction always give a topological vector space?

1 answer  ·  posted 3y ago by celtschk‭  ·  last activity 11mo ago by JohnnyJohn‭

topology linear-algebra topological-vector-spaces
66%
+2 −0
Does "shift of terms" in a Faber–Schauder series expansion of f ∈ C[0,1] produce an element of C[0,1]?

0 answers  ·  posted 11mo ago by KamilPrzespolewski‭  ·  edited 11mo ago by KamilPrzespolewski‭

functional-analysis Banach-space
71%
+3 −0
What is an example of a pathological imbedding of a(n allowed) graph into an oriented surface?

1 answer  ·  posted 1y ago by The Amplitwist‭  ·  last activity 11mo ago by The Amplitwist‭

topology graph-theory
60%
+1 −0
How do I unambiguously define the facial circuits in a $2$-cell embedding of a graph into a surface?

1 answer  ·  posted 1y ago by The Amplitwist‭  ·  last activity 11mo ago by The Amplitwist‭

topology graph-theory
44%
+2 −3
Cyclical or “loop” fractals?

2 answers  ·  posted 1y ago by Julius H.‭  ·  last activity 12mo ago by pbloem‭

real-analysis fractal
66%
+2 −0
Seeking a theorem about lattices

1 answer  ·  posted 12mo ago by WheatWizard‭  ·  last activity 12mo ago by Lisanne‭

linear-algebra reference-request free-abelian-group
77%
+5 −0
How to find perfect squares such that their base 9 representation is all 1s?

1 answer  ·  posted 12mo ago by CrSb0001‭  ·  last activity 12mo ago by Lisanne‭

number-theory bases recreational-mathematics
71%
+3 −0
Is it possible to find a solution for any $ae^{bx}+cx+d=0$?

0 answers  ·  posted 12mo ago by CrSb0001‭

calculus recreational-mathematics
71%
+3 −0
Is there a $\Delta$-complex structure on the sphere with less than three $0$-simplices?

1 answer  ·  posted 1y ago by The Amplitwist‭  ·  last activity 1y ago by Derek Elkins‭

algebraic-topology delta-complex
42%
+1 −2
What is the significance of the K-axiom in modal logic S5?

1 answer  ·  posted 1y ago by Julius H.‭  ·  edited 1y ago by xamidi‭

modal-logic proof-theory hilbert-systems axioms
54%
+4 −3
Defining Bayes’s theorem from scratch in ZFC

1 answer  ·  posted 1y ago by Julius H.‭  ·  last activity 1y ago by xamidi‭

set-theory zfc bayes-theorem
50%
+1 −1
Prove that $\forall x\in\Bbb R:\lfloor x^2\rfloor-\lfloor rx\rfloor\ge-1\iff|r|\le2$.

1 answer  ·  posted 1y ago by TheCodidacter, or rather ACodidacter‭  ·  last activity 1y ago by Derek Elkins‭

inequality solution-verification
71%
+3 −0
Using convexity in the proof of Hölder’s inequality

1 answer  ·  posted 1y ago by Snoopy‭  ·  last activity 1y ago by Snoopy‭

real-analysis
66%
+2 −0
Does {7,4|3} have a realization on the Klein quartic?

0 answers  ·  posted 1y ago by WheatWizard‭

polytopes algebraic-geometry
66%
+2 −0
Find length $MP$ in trapezoid

0 answers  ·  posted 1y ago by TheCodidacter, or rather ACodidacter‭  ·  edited 1y ago by TheCodidacter, or rather ACodidacter‭

geometry
22%
+0 −5
What are the Peano axioms?

1 answer  ·  posted 1y ago by Julius H.‭  ·  last activity 1y ago by rmf‭

logic
66%
+2 −0
The Fourier transform of $1/p^3$

1 answer  ·  posted 1y ago by C-T‭  ·  last activity 1y ago by LL 3.14‭

complex-analysis calculus multivariable-calculus integration fourier-analysis
71%
+3 −0
Besov or Triebel-Lizorkin spaces versus Lorentz spaces

0 answers  ·  posted 1y ago by LL 3.14‭  ·  edited 1y ago by LL 3.14‭

interpolation Besov-space functional-analysis
28%
+0 −3
What is a “first-order substructural logic that has a cut-free sequent calculus”?

1 answer  ·  posted 1y ago by Julius H.‭  ·  last activity 1y ago by Dan Doel‭

logic
40%
+0 −1
What is a one-variable fragment of first-order logic?

0 answers  ·  posted 1y ago by Julius H.‭

logic
66%
+2 −0
matrix inverse of $I + A$ where $A$ is skew-symmetric

1 answer  ·  posted 1y ago by Trevor‭  ·  last activity 1y ago by Trevor‭

linear-algebra
42%
+1 −2
Explain derived categories to someone without a strong background in homological algebra [closed]

0 answers  ·  posted 1y ago by Julius H.‭  ·  closed 1y ago by Peter Taylor‭

category-theory
28%
+0 −3
What is a dual object? [closed]

0 answers  ·  posted 1y ago by Julius H.‭  ·  closed 1y ago by Peter Taylor‭

category-theory
66%
+4 −1
is arithmetic finitely consistent?

0 answers  ·  posted 1y ago by Jason‭

proof logic peano-arithmetic incompletness consistency
66%
+2 −0
A program which could derive theorems given formation rules in any modal logic?

1 answer  ·  posted 1y ago by Julius H.‭  ·  edited 1y ago by Peter Taylor‭

computational-mathematics proof-assistants
71%
+3 −0
Concrete examples of set theorists thinking independence proofs only determine provability rather than that a statement is neither true nor false?

1 answer  ·  posted 1y ago by Julius H.‭  ·  last activity 1y ago by Peter Taylor‭

set-theory
50%
+1 −1
What are the “increasingly stable consequences of the large cardinal hierarchy”?

0 answers  ·  posted 1y ago by Julius H.‭

set-theory
66%
+2 −0
Fourier transform of an $L^1$ function is uniformly continuous

1 answer  ·  posted 1y ago by Snoopy‭  ·  edited 1y ago by Snoopy‭

real-analysis fourier-analysis
37%
+1 −3
Are these introductory logic textbooks wrong to teach ‘unless’ = ‘or’? [duplicate]

0 answers  ·  posted 1y ago by 8500 Ward‭  ·  closed as duplicate 1y ago by Peter Taylor‭

logic
66%
+2 −0
For any real number $m$, $ \left|\sum_{n=1}^{\infty}\frac{m}{n^2+m^2}\right|<\frac{\pi}{2} $

1 answer  ·  posted 1y ago by Snoopy‭  ·  last activity 1y ago by Snoopy‭

calculus real-analysis
71%
+3 −0
If both $\lim_{x\to\infty}f(x)$ and $\lim_{x\to\infty}f'(x)$ exist, then $\lim_{x\to\infty}f'(x)=0$.

1 answer  ·  posted 1y ago by Snoopy‭  ·  last activity 1y ago by Snoopy‭

real-analysis
57%
+2 −1
Strange behavior in elections and pie charts

2 answers  ·  posted 1y ago by TheCodidacter, or rather ACodidacter‭  ·  last activity 1y ago by Hudjefa‭

probability
66%
+2 −0
$\sup(A\cdot B) = (\sup A)(\sup B)$ where $A$ and $B$ bounded sets of positive real numbers

3 answers  ·  posted 1y ago by Snoopy‭  ·  edited 1y ago by Snoopy‭

real-analysis supremum-infimum
60%
+1 −0
Why is $ \int_0^{\infty}\left|\frac{\sin x}{x}\right|\ dx=\infty$?

1 answer  ·  posted 1y ago by Snoopy‭  ·  last activity 1y ago by Snoopy‭

real-analysis improper-integral
71%
+3 −0
Is there a $(n_3)$ configuration which is not self-dual?

1 answer  ·  posted 1y ago by WheatWizard‭  ·  last activity 1y ago by Peter Taylor‭

combinatorics
25%
+0 −4
Picking 20 different numbers, in the same draw $\;$ vs. $\;$ picking 10 different numbers, in 2 different draws.

1 answer  ·  posted 1y ago by H7D‭  ·  last activity 1y ago by Olin Lathrop‭

lottery
66%
+2 −0
Is the nth Betti number determined by orientability?

1 answer  ·  posted 1y ago by WheatWizard‭  ·  edited 1y ago by WheatWizard‭

betti-numbers algebraic-topology
80%
+6 −0
What is special about the 11-cell and 57-cell?

1 answer  ·  posted 2y ago by WheatWizard‭  ·  last activity 1y ago by ziggurism‭

polytopes
22%
+0 −5
How can school children intuit why over 100, D is larger? But under 100, D% is larger?

2 answers  ·  posted 2y ago by Chgg Clou‭  ·  last activity 1y ago by Hudjefa‭

high-school-mathematics
75%
+4 −0
Is there a statistical method to identify the type of outliers shown in the pictures attached to my question?

1 answer  ·  posted 2y ago by Ivan Nepomnyashchikh‭  ·  last activity 1y ago by Hudjefa‭

statistics
33%
+0 −2
$\left(\forall \varepsilon >0: |a-b| < \varepsilon\right) \iff a=b$ vs. $\left(\forall \varepsilon > 0: a \le b + \varepsilon \right) \iff a \le b$

1 answer  ·  posted 1y ago by deleted user  ·  edited 1y ago by Peter Taylor‭

inequality
50%
+0 −0
Calculation of limit

0 answers  ·  posted 1y ago by Klein Moretti‭

calculus analysis limits applied-mathematics
25%
+0 −4
How can I improve contrast of red and green, to prove Reverse Triangle Inequality?

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Peter Taylor‭

visualization
37%
+1 −3
Solely by eye, how can 16 year olds visually distinguish $\color{red}{\vec{b} - \vec{r}}$ from $\color{limegreen}{|\vec{b}| - |\vec{r}|}$ ?

2 answers  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Olin Lathrop‭

visualization
40%
+0 −1
While pictorializing $|x - y| < |x + y|$, how can 1 picture simultaneously prove (Reverse) △ Inequalities, $|x-y| ≤ |x|+|y|, |x|-|y| ≤ |x-y|$? [duplicate]

0 answers  ·  posted 1y ago by deleted user  ·  closed as duplicate 1y ago by Peter Taylor‭

visualization
75%
+4 −0
Is it possible to show that a normalised random variable has zero mean and unit variance?

0 answers  ·  posted 1y ago by mr Tsjolder‭  ·  edited 1y ago by mr Tsjolder‭

statistics expectation
33%
+1 −4
25% probability that there was a chance of avoiding injury $\quad$ vs. $\quad$ 25% chance of avoiding injury

2 answers  ·  posted 2y ago by DNB‭  ·  last activity 1y ago by Hudjefa‭

probability
81%
+7 −0
How can I choose a point from a uniform distribution within a regular polygon?

2 answers  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 1y ago by trichoplax‭

plane-geometry applied-mathematics sampling
77%
+5 −0
Notation for one-sided hypothesis testing

1 answer  ·  posted 3y ago by tommi‭  ·  last activity 1y ago by Glen_b‭

statistics notation hypothesis-testing
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