User Seva

49 votes

4 answers

6k views

The maximum of a polynomial on the unit circle

asked May 6, 2011 at 9:17

37 votes

4 answers

2k views

"Circular" domination in ${\mathbb R}^4$

asked Nov 23, 2013 at 19:05

28 votes

2 answers

2k views

Erdős-Szekeres for first differences

asked Mar 3, 2012 at 17:27

26 votes

1 answer

793 views

The maximal "nearly convex" function

asked Feb 9, 2012 at 17:28

21 votes

1 answer

1k views

Does $\binom{2n}{n} \equiv 2 \pmod p$ ever hold?

asked Oct 10, 2014 at 11:35

21 votes

2 answers

1k views

The chromatic number of the union of two graphs

asked Nov 20, 2021 at 8:46

19 votes

0 answers

533 views

Why $\gcd \{ {\rm ord}_p(q)\colon q\mid p-1 \}$ likes to be large?

asked Oct 29, 2014 at 12:01

19 votes

4 answers

693 views

The rank of a perturbed triangular matrix

asked May 12, 2017 at 9:50

19 votes

1 answer

872 views

Is the norm of a $0-1$ matrix (almost) attained on a $0-1$ vector?

asked Oct 29, 2010 at 19:11

18 votes

1 answer

862 views

What are the products $\prod_{A\subset{\mathbb F}_p\colon |A|=n} \sum_{a\in A} \zeta^a$ equal to?

asked Jan 23, 2015 at 10:52

17 votes

8 answers

9k views

The first eigenvalue of a graph - what does it reflect?

asked May 1, 2011 at 8:22

17 votes

4 answers

1k views

A mixing property for finite fields of characteristic $2$

asked Jul 20, 2012 at 16:54

16 votes

3 answers

1k views

Fano plane drawings: embedding PG(2,2) into the real plane

asked May 14, 2013 at 19:20

15 votes

1 answer

700 views

The hypercube: $|A {\stackrel2+} E| \ge |A|$?

asked Nov 4, 2011 at 17:41

15 votes

0 answers

430 views

The rank of a "triangle-free" matrix

asked Apr 6, 2017 at 11:05

15 votes

1 answer

644 views

Submodules of $({\mathbb Z}/6{\mathbb Z})^n$ intersecting $\{0,1\}^n$ trivially

asked Jan 21, 2017 at 15:03

15 votes

1 answer

968 views

Sets with both additive and multiplicative gaps

asked Jul 21, 2022 at 11:42

14 votes

1 answer

705 views

Generating function of the Thue-Morse sequence

asked Oct 5, 2015 at 7:30

14 votes

2 answers

2k views

Arithmetic progressions in power sequences

asked Oct 24, 2011 at 11:28

14 votes

3 answers

2k views

When does $P(a−b)=0$ for $a≠b$ ensure $P(0)=0$? (Continued.)

asked Feb 13, 2011 at 10:38

14 votes

1 answer

1k views

How to keep subsets disjoint?

asked Apr 11, 2011 at 8:00

13 votes

2 answers

1k views

An expander (?) graph

asked Mar 16, 2013 at 17:36

13 votes

1 answer

1k views

A delicate elementary inequality

asked Oct 1, 2012 at 18:54

13 votes

1 answer

580 views

Is ${\rm lcm}\{{\rm ord}_p(q)\colon q\mid p-1,\ q>2\}>\sqrt p\ \,$?

asked Nov 10, 2014 at 20:01

13 votes

0 answers

975 views

Pointwise (Hadamard) matrix product and the rank

asked Mar 24, 2017 at 19:08

13 votes

1 answer

446 views

Near-linear mappings from $\mathbb F_p$ to $\mathbb R$

asked Jan 26, 2018 at 7:23

13 votes

2 answers

489 views

Roots of lacunary polynomials over a finite field

asked Aug 17, 2018 at 14:31

12 votes

0 answers

443 views

Around the Erdős-Ginzburg-Ziv theorem

asked Feb 13, 2021 at 10:34

11 votes

1 answer

741 views

Quadratic reciprocity for three primes?

asked Jan 15, 2020 at 19:53

11 votes

0 answers

329 views

"Small" zero divisors in $\mathbb C[\mathbb Z/p\mathbb Z]$

asked Mar 5, 2018 at 20:09

Stack Exchange Network

129 Questions

The maximum of a polynomial on the unit circle

"Circular" domination in ${\mathbb R}^4$

Erdős-Szekeres for first differences

The maximal "nearly convex" function

Does $\binom{2n}{n} \equiv 2 \pmod p$ ever hold?

The chromatic number of the union of two graphs

Why $\gcd \{ {\rm ord}_p(q)\colon q\mid p-1 \}$ likes to be large?

The rank of a perturbed triangular matrix

Is the norm of a $0-1$ matrix (almost) attained on a $0-1$ vector?

What are the products $\prod_{A\subset{\mathbb F}_p\colon |A|=n} \sum_{a\in A} \zeta^a$ equal to?

The first eigenvalue of a graph - what does it reflect?

A mixing property for finite fields of characteristic $2$

Fano plane drawings: embedding PG(2,2) into the real plane

The hypercube: $|A {\stackrel2+} E| \ge |A|$?

The rank of a "triangle-free" matrix

Submodules of $({\mathbb Z}/6{\mathbb Z})^n$ intersecting $\{0,1\}^n$ trivially

Sets with both additive and multiplicative gaps

Generating function of the Thue-Morse sequence

Arithmetic progressions in power sequences

When does $P(a−b)=0$ for $a≠b$ ensure $P(0)=0$? (Continued.)

How to keep subsets disjoint?

An expander (?) graph

A delicate elementary inequality

Is ${\rm lcm}\{{\rm ord}_p(q)\colon q\mid p-1,\ q>2\}>\sqrt p\ \,$?

Pointwise (Hadamard) matrix product and the rank

Near-linear mappings from $\mathbb F_p$ to $\mathbb R$

Roots of lacunary polynomials over a finite field

Around the Erdős-Ginzburg-Ziv theorem

Quadratic reciprocity for three primes?

"Small" zero divisors in $\mathbb C[\mathbb Z/p\mathbb Z]$