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active 7 featured hot week month

17

votes

3

answers

2k

views

Where to publish a new proof of an old theorem?

journals alternative-proof unpublished

modified yesterday maajdl 1

11

votes

4

answers

2k

views

No Tonelli or Fubini

nt.number-theory reference-request real-analysis sequences-and-series

answered Feb 7 at 22:42 paul garrett 14.3k

13

votes

5

answers

591

views

Applications of logic to group theory?

gr.group-theory lo.logic examples

answered yesterday Misha 22.3k

7

votes

2

answers

573

views

An attempt to generalize the previous inequality

real-analysis cv.complex-variables inequalities sequences-and-series

modified 20 mins ago T. Amdeberhan 7,659

5

votes

2

answers

394

views

Can one permute the positive integers with just the four arithmetical operations? [on hold]

nt.number-theory co.combinatorics

modified yesterday Nathaniel 281

3

votes

1

answer

383

views

seeking proofs: infinite series inequalities

real-analysis cv.complex-variables inequalities sequences-and-series

answered yesterday Cherng-tiao Perng 196

8

votes

1

answer

380

views

Sums of sets in ${[n] \choose k}$

co.combinatorics graph-theory

answered Feb 10 at 3:38 Richard Stanley 23k

5

votes

3

answers

400

views

Etale cohomology with coefficients in $\mathbb{Q}$

ag.algebraic-geometry etale-cohomology galois-cohomology

modified 2 days ago Timo Keller 8,415

7

votes

3

answers

238

views

Is the bordism from disjoint union to connected sum universal for connected manifolds?

reference-request smooth-manifolds manifolds morse-theory cobordism

modified 5 hours ago user80296 581

14

votes

1

answer

363

views

Are $\partial$-exact and $\bar\partial$-exact forms also $\partial\bar\partial$-exact?

dg.differential-geometry complex-geometry cohomology

modified Feb 8 at 13:38 Francesco Polizzi 37.8k

8

votes

1

answer

231

views

What's the point of a Whittaker model?

rt.representation-theory algebraic-groups automorphic-forms reductive-groups p-adic-groups

modified Feb 8 at 10:00 Paul Broussous 3,795

7

votes

2

answers

364

views

The set of complements equal to the complement of set

co.combinatorics set-theory lattices discrete-mathematics posets

modified Feb 10 at 13:30 Ramiro de la Vega 8,109

2

votes

1

answer

194

views

Let $F:\mathscr{A}\to\mathscr{B}$ be an equivalence of Abelian categories. Must $F$ be additive?

ct.category-theory homological-algebra abelian-categories

answered Feb 7 at 14:15 Jason Starr 2,796

4

votes

1

answer

344

views

When is :$\displaystyle n!=x^n-y^n$ , with , $x,y,n$ are positive integers?

nt.number-theory hyperbolic-geometry diophantine-equations gamma-function

modified yesterday T. Amdeberhan 7,659

9

votes

2

answers

182

views

Given a Kirby diagram of a 4-manifold, what's its homotopy 2-type?

homotopy-theory smooth-manifolds 4-manifolds crossed-modules kirby-calculus

modified 2 days ago Joao Faria Martins 91

10

votes

2

answers

172

views

Precise definition/construction of $\text{Sym}(\text{Sym}^2)$?

ac.commutative-algebra

modified 8 mins ago Tom Church 6,541

1

vote

2

answers

196

views

When is the projective limit non-empty?

ct.category-theory

answered yesterday Todd Trimble♦ 37.5k

4

votes

2

answers

86

views

Orthonormal basis in $W^{1,2}([0,1])$

fa.functional-analysis ca.analysis-and-odes ap.analysis-of-pdes real-analysis

modified yesterday Fedor Petrov 27.5k

6

votes

1

answer

212

views

How are material set theory and structural set theory related from the point of view of category theory?

ct.category-theory set-theory math-philosophy foundations

answered Feb 9 at 19:55 Mike Shulman 25k

10

votes

1

answer

193

views

a Hankel matrix of involution numbers

nt.number-theory co.combinatorics linear-algebra enumerative-combinatorics hankel-matrices

modified Feb 9 at 15:23 T. Amdeberhan 7,659

6

votes

1

answer

189

views

Conjugacy of Borel subgroups over arbitrary fields

ag.algebraic-geometry algebraic-groups

modified Feb 10 at 10:51 thierry stulemeijer 440

8

votes

1

answer

176

views

Elementary extensions of direct product

gr.group-theory lo.logic model-theory

modified 23 hours ago Douglas Ulrich 1,012

12

votes

1

answer

261

views

Vectors that are almost orthogonal on average: lower bounds on dimension?

inequalities sphere-packing inner-product

modified 2 days ago kodlu 1,763

6

votes

1

answer

142

views

How to solve the system of PDEs defining Killing vectors

dg.differential-geometry ap.analysis-of-pdes integrable-systems

modified Feb 9 at 20:27 José Figueroa-O'Farrill 23.1k

9

votes

2

answers

322

views

Does $q$-Catalan number count subspaces?

co.combinatorics finite-fields catalan-numbers q-analogs

modified 20 hours ago john mangual 8,322

-3

votes

1

answer

162

views

Example of projective variety that do not contain algebraic curves of genus strictly greater to $1$

ag.algebraic-geometry algebraic-curves schemes projective-geometry genus

modified 20 hours ago Armando j18eos 161

2

votes

2

answers

203

views

Representing $x$ as a linear combination of higher powers $x^n$

approximation-theory

answered Feb 7 at 18:31 Robert Israel 32.3k

3

votes

1

answer

155

views

Elementary divisibility problem [on hold]

nt.number-theory

modified 18 hours ago Max Alekseyev 5,736

2

votes

1

answer

184

views

Volume of $SO(n)\subset\mathbb R^{n^2}$, again

dg.differential-geometry riemannian-geometry

answered 2 days ago Robert Bryant 56.7k

6

votes

1

answer

199

views

What is Mumford's example of a normal complex algebraic surface $X$ with non-torsion elements in $H^2_{et}(X,\mathbb{G}_m)$?

ag.algebraic-geometry reference-request etale-cohomology algebraic-surfaces brauer-groups

modified 11 hours ago Timo Keller 8,415

3

votes

1

answer

116

views

Large gaps in Singer planar difference sets?

nt.number-theory finite-groups finite-fields additive-combinatorics finite-geometry

answered 15 hours ago Lucia 26.1k

9

votes

1

answer

393

views

Algebraic Geometry in Number Theory

ag.algebraic-geometry nt.number-theory algebraic-number-theory big-picture

answered Feb 8 at 13:14 Timo Keller 8,415

3

votes

1

answer

135

views

What do the differential k-forms on a product manifold look like?

dg.differential-geometry differential-forms

answered Feb 8 at 11:11 Stefan Waldmann 4,408

3

votes

1

answer

170

views

Tachikawa conjecture for commutative algebras proven?

rt.representation-theory ac.commutative-algebra homological-algebra

answered yesterday Graham Leuschke 4,433

4

votes

1

answer

123

views

On the isometry group of a self cartesian product of a Riemannian space

dg.differential-geometry lie-groups riemannian-geometry

modified Feb 8 at 19:31 Sebastian Goette 3,674

6

votes

1

answer

89

views

A question about relation of the character degrees of $ G/N $ and $ G $

gr.group-theory

answered 2 days ago Mark Wildon 4,473

3

votes

1

answer

111

views

Terminology for a monoid $H$ s.t. $xy \in H^\times$ only if $x, y \in H^\times$

reference-request ra.rings-and-algebras monoids

modified yesterday Salvo Tringali 2,457

2

votes

3

answers

225

views

Invertibility of an operator of the form $I-B$

fa.functional-analysis

modified 2 days ago user10439561 6

4

votes

1

answer

175

views

Gcd of Fibonacci and Catalan

nt.number-theory co.combinatorics sequences-and-series

modified Feb 7 at 20:06 Joe Silverman 23.4k

4

votes

1

answer

166

views

If monodromy representation is unipotent then special fiber is snc?

ag.algebraic-geometry hodge-theory

modified 2 days ago Donu Arapura 21.3k

6

votes

1

answer

98

views

Existence of $L^\infty$ function on $\mathbb{T}$ whose Fourier series is $\ell^2$ but no better?

ca.analysis-and-odes harmonic-analysis

answered Feb 9 at 7:09 Mateusz Wasilewski 1,648

3

votes

1

answer

250

views

Representing an algebraic cycle by differential forms

ag.algebraic-geometry at.algebraic-topology dg.differential-geometry

modified Feb 10 at 1:47 R. van Dobben de Bruyn 3,418

8

votes

1

answer

177

views

Take a matrix with normalized rows; no column of the inverse has too large a norm

linear-algebra

answered Feb 10 at 2:20 fedja 28.4k

6

votes

1

answer

176

views

What is the smallest cardinality of a set A whose difference A-A contains $n$ consequtive integer numbers?

nt.number-theory additive-combinatorics

answered 12 hours ago Lucia 26.1k

2

votes

1

answer

167

views

A model of smooth projective plane

dg.differential-geometry riemannian-geometry projective-geometry

modified yesterday Robert Bryant 56.7k

9

votes

1

answer

167

views

Further aspects of a Hankel matrix of involution numbers

co.combinatorics linear-algebra symmetric-functions

modified Feb 10 at 14:27 Pietro Majer 31.8k

6

votes

1

answer

166

views

Questions about Mitchell forcing and tree property

reference-request lo.logic set-theory forcing

answered 1 hour ago Yair Hayut 2,654

3

votes

2

answers

124

views

Consecutive rising sequence of largest prime factors

nt.number-theory

answered Feb 9 at 3:28 Noam D. Elkies 47.8k

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