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active 15 featured hot week month

27

votes

2

answers

932

views

+100

A curious process with positive integers

co.combinatorics computational-complexity

modified 19 hours ago Mikhail Tikhomirov 2,249

5

votes

2

answers

1k

views

Does this multiplicative function have a name? If so, what is known about it?

nt.number-theory reference-request analytic-number-theory arithmetic-functions

modified 2 days ago GH from MO 56.7k

7

votes

2

answers

538

views

Eigenvalues of Laplace-Beltrami on half sphere

reference-request ap.analysis-of-pdes sp.spectral-theory harmonic-functions

modified yesterday Liviu Nicolaescu 24.7k

9

votes

3

answers

277

views

Cardinality of families of subsets of $\mathbb{N}$ whose intersections are finite

co.combinatorics set-theory infinite-combinatorics

answered Oct 17 at 13:16 Kapil Hari Paranjape 66

19

votes

2

answers

502

views

References for Riemann surfaces

reference-request complex-geometry riemann-surfaces

answered 6 hours ago Balazs 1,911

9

votes

2

answers

378

views

Lower density of numbers not summable by consecutive integers

nt.number-theory

modified Oct 14 at 15:18 Martin Sleziak 2,784

8

votes

3

answers

234

views

Matrix determinant inequality proof without using information theory

linear-algebra inequalities

answered yesterday Suvrit 23.5k

8

votes

2

answers

406

views

Is taking the positive part of a measure a continuous operation?

fa.functional-analysis measure-theory

modified yesterday Jochen Wengenroth 7,097

8

votes

1

answer

353

views

Do commutative rings without unity have the IBN property?

ac.commutative-algebra

modified 2 days ago Keith Kearnes 5,924

11

votes

2

answers

271

views

Is there any significance to Bousfield localization in the non-derived context?

at.algebraic-topology ct.category-theory homotopy-theory triangulated-categories

answered Oct 17 at 9:16 Tyler Lawson 38k

6

votes

1

answer

323

views

Classification of smooth algebraic surfaces with a smooth morphism to $\Bbb P^1$

ag.algebraic-geometry algebraic-surfaces

modified Oct 16 at 22:15 Ariyan Javanpeykar 5,141

5

votes

1

answer

216

views

Are Gray codes in $\{0,1\}^n$ isomorphic?

graph-theory hamiltonian-paths gray-codes

modified yesterday Keith Kearnes 5,924

12

votes

1

answer

480

views

Reference for the algebro-geometric proof of Matsumoto theorem

ag.algebraic-geometry reference-request kt.k-theory-and-homology algebraic-k-theory

modified Oct 16 at 10:13 Aolong Li 103

5

votes

1

answer

288

views

$BG$ the stack, $BG$ the simplicial presheaf

ag.algebraic-geometry simplicial-stuff stacks

modified yesterday HuynA 60

7

votes

1

answer

887

views

What is the current status of the Arnold conjecture?

sg.symplectic-geometry symplectic-topology

answered Oct 15 at 10:21 Carlo Beenakker 70.1k

5

votes

1

answer

394

views

Are there enough meromorphic functions on a compact analytic manifold?

ag.algebraic-geometry cv.complex-variables complex-geometry

modified 21 hours ago Margaret Friedland 2,955

6

votes

1

answer

336

views

Enhancing Grothendieck's universes and Grothendieck's axiom: Feferman's universe

ct.category-theory set-theory foundations

modified yesterday Jxt921 413

2

votes

1

answer

193

views

Does $\sum_{n=1}^\infty \frac{\mu(n)}{n^s}$ converge for $\sigma > \frac{1}{2}$?

nt.number-theory cv.complex-variables analytic-number-theory dirichlet-series

modified Oct 17 at 5:50 GH from MO 56.7k

3

votes

2

answers

235

views

Number of self avoiding paths on a grid graph?

co.combinatorics graph-theory random-walks

modified Oct 16 at 22:17 Kostya_I 2,553

8

votes

1

answer

279

views

Seeking a more symmetric realization of a configuration of 10 planes, 25 lines and 15 points in projective space

co.combinatorics projective-geometry hyperplane-arrangements

answered yesterday Noam D. Elkies 55.2k

12

votes

1

answer

211

views

Equivalence of surjections from a surface group to a free group

gr.group-theory gt.geometric-topology free-groups

answered Oct 15 at 5:42 Jean Raimbault 1,758

3

votes

3

answers

328

views

mixing theorem with definition (definition with proof)

soft-question exposition

modified yesterday Francois Ziegler 19k

5

votes

2

answers

149

views

Definition of unitary representation of $\mathbf G(\mathbb A_k)$

rt.representation-theory automorphic-forms unitary-representations adeles

modified Oct 15 at 21:20 Abdelmalek Abdesselam 10.6k

0

votes

1

answer

282

views

Two reasons why the Collatz conjecture could fail

nt.number-theory collatz-conjecture

modified 1 hour ago YCor 26k

5

votes

1

answer

369

views

English translation of “Les aspects probabilistes du contrôle stochastique”

reference-request terminology stochastic-calculus stochastic-diff-equations translation

modified 2 days ago Ali Taghavi 55

9

votes

2

answers

209

views

Explicit proof that $c_0$-module $\ell_\infty$ is not projective

fa.functional-analysis banach-algebras

modified Oct 17 at 13:34 Uri Bader 6,289

4

votes

1

answer

419

views

What happened to TituRel?

mathematical-software

modified yesterday Carlo Beenakker 70.1k

4

votes

4

answers

188

views

partial alternating sum involving binomial coefficients

co.combinatorics

answered Oct 15 at 8:16 Aaron Meyerowitz 23.6k

6

votes

2

answers

235

views

Product of arithmetic progressions

arithmetic-progression

answered yesterday Empy2 121

3

votes

2

answers

181

views

Casimir operator of a given Lie algebra and relation with its matrix representation

gr.group-theory rt.representation-theory mp.mathematical-physics lie-algebras invariant-theory

modified Oct 16 at 3:02 Mike Miller 3,174

6

votes

1

answer

225

views

Cohomology of neighborhood of $\mathbb{C}\mathbb{P}^1$ in $\mathbb{C}\mathbb{P}^n$

ag.algebraic-geometry cv.complex-variables complex-geometry complex-manifolds

answered Oct 16 at 18:23 Misha Verbitsky 4,942

7

votes

2

answers

165

views

A link between hooks and contents: Part II

reference-request co.combinatorics combinatorial-identities elementary-proofs

modified Oct 14 at 17:13 darij grinberg 17.7k

7

votes

1

answer

245

views

Relation between Fourier coefficients and Satake parameters

nt.number-theory automorphic-forms l-functions

modified Oct 15 at 3:00 Desiderius Severus 2,166

3

votes

1

answer

243

views

Vandermonde determinant: modulo

nt.number-theory elementary-proofs

modified yesterday darij grinberg 17.7k

3

votes

1

answer

186

views

Generating function for 3 -core partitions: Part II

co.combinatorics soft-question partitions elementary-proofs

answered Oct 15 at 6:06 Gjergji Zaimi 60.5k

4

votes

1

answer

106

views

Generating function for $3$-core partitions

co.combinatorics soft-question partitions elementary-proofs

modified Oct 14 at 17:53 T. Amdeberhan 16.6k

3

votes

1

answer

223

views

Constant “periodization” of a function

real-analysis sequences-and-series

answered Oct 15 at 6:46 Dirk 6,999

4

votes

1

answer

220

views

Trivialization of Pontryagin square on oriented $4$-manifolds

at.algebraic-topology gt.geometric-topology classifying-spaces fibration

modified Oct 16 at 8:32 Zheyan Wan 343

2

votes

1

answer

171

views

Is there a finitely additive measure on R which is not sigma-additive?

measure-theory

answered yesterday Roberto Frigerio 2,479

5

votes

2

answers

193

views

Making the Fourier transform quantitative

fa.functional-analysis ap.analysis-of-pdes harmonic-analysis sobolev-spaces

answered Oct 15 at 10:22 Sönke Hansen 1,781

6

votes

1

answer

175

views

A class number estimate

algebraic-number-theory binary-quadratic-forms

modified 2 days ago Will Jagy 19.2k

6

votes

1

answer

220

views

The outer automorphism of the dihedral group $D_4$ and quartic polynomials

nt.number-theory algebraic-number-theory invariant-theory

modified Oct 16 at 12:35 GNiklasch 1,880

6

votes

1

answer

220

views

Cokernel of map of étale sheaves

ag.algebraic-geometry algebraic-groups sheaf-theory etale-cohomology

modified Oct 17 at 15:13 R. van Dobben de Bruyn 9,741

1

vote

1

answer

168

views

Embedding problem for 3-manifolds attacked via 4-manifolds

differential-topology 3-manifolds 4-manifolds

modified 2 days ago YCor 26k

3

votes

1

answer

91

views

Density of numbers $n$ which are co-prime with their $\phi$-value

nt.number-theory analytic-number-theory

modified 13 hours ago Martin Sleziak 2,784

2

votes

1

answer

191

views

An orientable compact even dimensional manifolds whose all even cohomologies do not vanish but it does not admit any symplectic structure

dg.differential-geometry sg.symplectic-geometry

modified Oct 15 at 22:25 Chris Gerig 9,092

17

votes

0

answers

304

views

Does $\mathrm{SL}_{n}(\mathbb{Z}/p^{2})$ have the same number of conjugacy classes as $\mathrm{SL}_{n}(\mathbb{F}_{p}[t]/t^{2})$?

gr.group-theory rt.representation-theory finite-groups conjugacy-classes

modified Oct 15 at 8:35 A Stasinski 1,748

8

votes

1

answer

236

views

Find an integer coprime to sequence sum

nt.number-theory

modified Oct 16 at 17:05 Gerhard Paseman 8,025

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