Vela Mathematics Program: problems

Problem ledger

declared openerdos:256

declared open · formalizederdos:509

∀ {M : Type u} [inst : MetricSpace M] (S : Set M), S.Nonempty → ∀ (r : ℝ) (ι : Type v) (bdc : Erdos509.BoundedDiscCover S r ι), 0 < r

analysisN/A2 sources

declared open · formalizederdos:510

sorry ↔ ∃ c, ∃ (_ : 0 < c), ∀ᶠ (N : ℕ) in Filter.atTop, ∀ (A : Finset ℕ), 0 ∉ A → A.card = N → ∃ θ, ∑ n ∈ A, Real.cos (↑n * θ) < -c * √↑N

analysisN/A2 sources

declared open · formalizederdos:513

sorry = ⨆ f, Filter.liminf (fun r => Erdos513.ratio r ↑f) Filter.atTop

analysisN/A3 sources

declared openerdos:514

For a transcendental entire function, how fast can

|f(z)|

be forced to grow along a path to infinity, and how short can such a path be in terms of the maximum modulus

M(r, f)

analysisN/A4 sources

declared open · formalizederdos:517

sorry ↔ ∀ {f : ℂ → ℂ} {n : ℕ → ℕ}, HasFabryGaps n → ∀ {a : ℕ → ℂ}, (∀ (k : ℕ), a k ≠ 0) → (∀ (z : ℂ), HasSum (fun k => a k * z ^ n k) (f z)) → ∀ (z : ℂ), {x | f x = z}.Infinite

analysisN/A3 sources

declared open · formalizederdos:521

False ↔ Erdos521.Claim

analysispolynomialsprobabilityN/A4 sources

declared open · formalizederdos:522

For

P_n(z) = \sum_{k=0}^n \varepsilon_k z^k

with independent uniform signs, does the number

R_n

of roots in

|z| \le 1

satisfy

R_n/(n/2) \to 1

almost surely? The manuscript proves the strong law with

R_n = n/2 + O_\omega(n^{149/150})

analysispolynomialsprobabilityN/A4 sources

declared openerdos:524

Erdős problem 524

analysisprobabilitypolynomialsN/A3 sources

declared open · $250erdos:671

For triangular arrays of nodes

a_i^n\in[-1,1]

let

\mathcal{L}^nf

be the Lagrange interpolation polynomials of a continuous

f

, with fundamental polynomials

p_i^n

. Is there a choice of nodes such that for every continuous

f

there is some

x

where

\limsup_n \sum_i\lvert p_{i}^n(x)\rvert=\infty

and yet

\mathcal{L}^nf(x) \to f(x)

? Is there a choice with

\limsup_n \sum_i\lvert p_{i}^n(x)\rvert=\infty

for every

x

, yet for every continuous

f

some

x

has

\mathcal{L}^nf(x)\to f(x)

? Both questions are claimed resolved in the affirmative.

analysisN/A3 sources

declared open · formalizederdos:906

Is there an entire non-zero function

f:\mathbb{C}\to \mathbb{C}

such that, for any infinite sequence

n_1<n_2<\cdots

, the set

\{ z: f^{(n_k)}(z)=0 \textrm{ for some }k\geq 1\}

is everywhere dense? The literal question is trivial for polynomials, so the claims address the transcendental entire case, in the affirmative.

analysisiterated functionsN/A5 sources

declared open · formalizederdos:973

True ↔ ∃ C > 1, ∀ n ≥ 2, ∃ z, z 1 = 1 ∧ (∀ i ∈ Finset.Icc 1 n, 1 ≤ ‖z i‖) ∧ ∀ k ∈ Finset.Icc 2 (n + 1), ‖∑ i ∈ Finset.Icc 1 n, z i ^ k‖ < C ^ (-↑n)

analysisN/A2 sources

declared openerdos:995

Erdős problem 995

analysisdiscrepancyN/A2 sources

declared open · formalizederdos:996

Let

n_1<n_2<\cdots

be a lacunary sequence of integers and

f\in L^2([0,1])

with

n

th Fourier partial sum

f_n

. Is there an absolute constant

C>0

such that if

\| f-f_n\|_2 \ll (\log\log\log n)^{-C}

then

\frac{1}{N}\sum_{k\leq N}f(\{\alpha n_k\})\to\int_0^1 f

for almost every

\alpha

? A preprint answers this negatively via a dyadic spike-block counterexample.

analysisN/A4 sources

declared open · formalizederdos:1002

sorry ↔ ∃ g, Monotone g ∧ Filter.Tendsto g Filter.atBot (nhds 0) ∧ Filter.Tendsto g Filter.atTop (nhds 1) ∧ ∀ (c : ℝ), Filter.Tendsto (fun n => (MeasureTheory.volume {α | α ∈ Set.Ioo 0 1 ∧ (fun α n => 1 / Real.log ↑n * ∑ k ∈ Finset.Icc 1 n, (1 / 2 - Int.fract (α * ↑k))) α n ≤ c}).toReal) Filter.atTop (nhds (g c))

analysisdiophantine approximationN/A2 sources

declared open · formalizederdos:1038

Among all nonconstant monic polynomials

f

whose roots lie in

[-1, 1]

, determine

\inf_f |\{x \in \mathbb{R} : |f(x)| < 1\}|

analysisN/A4 sources

declared openerdos:1039

For

f(z) = \prod_{i=1}^n (z - z_i)

with all

|z_i| \le 1

, let

\rho(f)

be the radius of the largest disc contained in

\{z : |f(z)| < 1\}

. Is

\rho(f) \gg 1/n

? The worst case is now known to be

\Theta(1/n)

, with the explicit bound

\rho(f) \ge (\log 2)/n

analysisN/A3 sources

declared openerdos:1040

For a closed infinite set

F \subseteq \mathbb{C}

, let

\mu(F)

be the infimum of

|\{z : |f(z)| < 1\}|

over monic polynomials with zeros in

F

. Is

\mu(F)

determined only by the transfinite diameter of

F

analysisN/A3 sources

declared openerdos:1045

Erdős problem 1045

analysisN/A

declared openerdos:1117

Erdős problem 1117

analysisN/A

declared openerdos:1120

Erdős problem 1120

analysisN/A

declared openerdos:1131

Erdős problem 1131

analysispolynomialsN/A2 sources

declared openerdos:1132

Erdős problem 1132

analysispolynomialsN/A2 sources

declared open · formalizederdos:1133

Must every sufficiently large node set admit bounded labels that force any polynomial fitting almost all labels at degree below

(1+\varepsilon)n

to have arbitrarily large uniform norm? Claimed via Beurling density for Bernstein spaces.

analysispolynomialsN/A4 sources

declared open · formalizederdos:1150

True ↔ ∃ c > 0, ∀ᶠ (n : ℕ) in Filter.atTop, ∀ (P : Polynomial ℂ), (∀ i ≤ P.natDegree, P.coeff i = -1 ∨ P.coeff i = 1) → P.natDegree = n → ⨆ z, ‖Polynomial.eval (↑z) P‖ > (1 + c) * √↑n

analysispolynomialsN/A2 sources

declared openerdos:1151

Let

\mathcal{L}^nf

be the Lagrange interpolation polynomials of a continuous

f

on the Chebyshev nodes. Prove that, for any closed

A\subseteq [-1,1]

, there exists a continuous function

f

such that

A

is the set of limit points of

\mathcal{L}^nf(x)

analysispolynomialsN/A3 sources

declared openerdos:1152

Erdős problem 1152

analysispolynomialsN/A

Problems · Vela Mathematics Program

Problem ledger

Search problems.science