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Top new questions this week:

Object of proven finiteness, yet with no algorithm discovered?

I explain my title by two examples in number theory: The rational points on elliptic curve over number fields forms a finitely generated abelian group, so its rank is an integer, but so far we do not ...

ag.algebraic-geometry nt.number-theory at.algebraic-topology  
user avatar asked by J.Li Score of 25
user avatar answered by Joe Silverman Score of 27

Generalized $\infty$-operads are an analog of ??? in $\infty$-category theory

In Section 2.3.2 of Higher Algebra, Lurie introduces the notion of generalized $\infty$-operads. This is a functor $p:\mathcal{O}^\otimes \to \mathcal{F}\mathrm{in}_\ast$ of $\infty$-categories, where ...

ct.category-theory higher-category-theory infinity-categories operads higher-algebra  
user avatar asked by Ken Score of 12

Fermat last theorem : proof of a criterion by Cauchy

In 13 Lectures on Fermat's Last Theorem, Ribenboim states the following theorem (on page 7) attributed to Cauchy: If the first case of Fermat's theorem fails for the exponent $p$, then the sum: $$ 1^{...

reference-request ho.history-overview diophantine-equations bernoulli-numbers  
user avatar asked by RUser4512 Score of 11
user avatar answered by Carlo Beenakker Score of 5

Why is $ULU=NU$ (a refinement of $|N|=q^{n^2-n}$)?

Let $G=GL_n(\mathbb{F}_q)$, $U$, $L$, $N$ the subsets of upper-triangular unipotent, lower-triangular unipotent, all unipotent matrices respectively. Then $ULU=NU$ means that for any $g\in G$ the ...

co.combinatorics matrices finite-fields geometric-representation-theory character-sheaves  
user avatar asked by Anton Mellit Score of 8

If we know the combinatorics of a polyhedron, and all but one of its dihedral angles, does that uniquely determine the remaining dihedral angle?

If we know the combinatorics of a polyhedron, and all but one of its dihedral angles, does that uniquely determine the remaining dihedral angle? I’m happy to assume the polyhedron is simply connected, ...

discrete-geometry euclidean-geometry polyhedra  
user avatar asked by Robin Houston Score of 8
user avatar answered by Dmitrii Korshunov Score of 5

Reference request: Software for producing sounds of drums of specified shapes

Is there software that, when the input is the shape of a drum, will produce the corresponding audible sound?

reference-request ap.analysis-of-pdes sp.spectral-theory  
user avatar asked by Michael Hardy Score of 8
user avatar answered by Carlo Beenakker Score of 12

What kind of commutative rings lift to the sphere?

Suppose $A$ is a commutative ring. By a "lift to the sphere" I mean a commutative ring spectrum $\mathbb{S}_A$ such that $A \simeq \mathbb{S}_A\otimes_{\mathbb{S}} \mathbb{Z}$ as commutative ...

homotopy-theory higher-algebra  
user avatar asked by atticusw Score of 8

Greatest hits from previous weeks:

Most memorable titles

Given the vast number of new papers / preprints that hit the internet everyday, one factor that may help papers stand out for a broader, though possibly more casual, audience is their title. This view ...

soft-question ho.history-overview big-list mathematical-writing math-communication  
user avatar asked by Suvrit Score of 184
user avatar answered by David Roberts Score of 233

Most elementary proof showing that exponential growth wins against polynomial growth

This question is motivated by teaching : I would like to see a completely elementary proof showing for example that for all natural integers $k$ we have eventually $2^n>n^k$. All proofs I know rely ...

inequalities  
user avatar asked by Roland Bacher Score of 51
user avatar answered by Fedor Petrov Score of 55

Why does mathematics seem to have a polarity bias?

Why does mathematics seem to have a polarity bias, i.e., why are products more common than coproducts, algebras more common than coalgebras, limits more common than colimits, monads more common than ...

ct.category-theory soft-question big-picture  
user avatar asked by Cameron Zwarich Score of 27
user avatar answered by David White - gone from MO Score of 25

Example of a good Zero Knowledge Proof

I am working on my zero knowledge proofs and I am looking for a good example of a real world proof of this type. An even better answer would be a Zero Knowledge Proof that shows the statement isn't ...

cryptography computational-complexity  
user avatar asked by George Score of 67
user avatar answered by Ryan O'Donnell Score of 169

Breakthroughs in mathematics in 2023

At the end of 2021, Johnny Cage asked about breakthroughs in 2021 in different mathematical disciplines. A similar question has been asked at the end of 2022, so it looks like Johnny Cage originated a ...

soft-question big-list big-picture  
user avatar asked by Bogdan Grechuk Score of 91
user avatar answered by JoshuaZ Score of 55

Best algebraic geometry textbook? (other than Hartshorne)

I think (almost) everyone agrees that Hartshorne's Algebraic Geometry is still the best. Then what might be the 2nd best? It can be a book, preprint, online lecture note, webpage, etc. One suggestion ...

ag.algebraic-geometry books big-list textbook-recommendation  
user avatar asked by sanokun Score of 249
user avatar answered by Javier Álvarez Score of 242

The "Dzhanibekov effect" - an exercise in mechanics or fiction? Explain mathematically a video from a space station

The question briefly: Can one explain the "Dzhanibekov effect" (see youtube videos from space station or comments below) on the basis of the standard rigid body dynamics using Euler's equations? (Or ...

classical-mechanics ds.dynamical-systems  
user avatar asked by Alexander Chervov Score of 170
user avatar answered by Terry Tao Score of 175

Can you answer these questions?

Evaluating the difference of weighted binomial coefficients

I encountered the following type of sum: $$ \begin{align} \left[ \sum_{k=1}^{t}\binom{k+i-2}{i-1}\binom{t-k+l_1-i}{l_1-i}\sum_{s=k}^{t}\binom{t-s+l_2-j+1}{l_2-j+1}\binom{s+j-3}{j-2} \right] \tag{1} \\ ...

co.combinatorics  
user avatar asked by Haimu Wang Score of 1

End cohomology and space of ends

I have started learning about end cohomology, and as far as I understand, the zeroth end cohomology $H_e^0(M; \mathbb{Z})$ is isomorphic to the zeroth Čech cohomology $\check{H}^0(e(M); \mathbb{Z})$, ...

at.algebraic-topology cohomology manifolds cech-cohomology  
user avatar asked by Random Score of 1

Multivariate normal over cone

Does anyone have any references on how to integrate the multivariate normal distribution over an intersection of closed half spaces? Consider the half spaces $H \triangleq \left \{ \boldsymbol{x} : \...

pr.probability geometric-probability  
user avatar asked by MathIsLife12 Score of 1
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