Problems
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For a measurable set Ω⊂ R^3, let E(Ω)=P(Ω)+frac12iint_Ω×Ωdx dy/|x-y|, where P is De Giorgi perimeter, and set V_*=5frac2-2^2/32^2/3-1≈3.51. The conjecture asks for the complete fixed-volume minimization picture. Chodosh and Gianocca prove…
Does a universal summation process recover the degree of a circle map from its Fourier moduli, that is, does ∑_n σ_n,ε n |hat f(n)|^2 → deg f hold for Holder maps below the threshold? No. For every 0 < α < 1/3 there is an f ∈…
VibeMathed records no statement for this problem. See erdosproblems.com for the original.
For the three-dimensional paraboloid P_3 over a prime field in which -1 is not a square, the Fourier extension operator maps L^2 to L^r for r > 176/51 = 3.45098…, improving the exponent by combining a bilinear approach with point-line…
Denjoy's 1932 theorem says a C^1+bv circle diffeomorphism with irrational rotation number has no wandering interval. Whether it is sharp in regularity: for every concave modulus of continuity ω weaker than Lipschitz, there is a C^1+ω…
The Smith-Ward theorem realizes the first k essential matrix ranges of an operator as the matrix ranges of a compact perturbation. The classical Smith-Ward problem asks whether that perturbation can be chosen independently of k,…
Let n_1<n_2<… be a lacunary sequence of integers and f∈ L^2([0,1]) with nth Fourier partial sum f_n. Is there an absolute constant C>0 such that if | f-f_n|_2 ≪ (logloglog n)^-C then 1/N∑_k≤ Nf(α n_k)→∫_0^1 f for almost every α? A preprint…
A Banach space is primary if in every decomposition into two complemented subspaces one summand is isomorphic to the whole. Lechner, Motakis, Müller and Schlumprecht identified the primariness of L_p(L_1) as a prominent remaining open…
The realisation problem asks which unital Banach algebras arise as the Calkin algebra B(X)/K(X) of some Banach space. Recorded in Tarbard's thesis and studied by Horváth and Kania. The paper exhibits a unital Banach algebra that cannot be…
Vinzant conjectured, in a form later restated by Bandeira, that the 4M-4 threshold for injective complex phase retrieval is sharp. Part (1) holds: for A ∈ C^N × M with N = 4M-5 and i.i.d. standard complex Gaussian entries, the phase…
For f(z) = ∏_i=1^n (z - z_i) with all |z_i| ≤ 1, let ρ(f) be the radius of the largest disc contained in z : |f(z)| < 1. Is ρ(f) ≫ 1/n? The worst case is now known to be Θ(1/n), with the explicit bound ρ(f) ≥ (log 2)/n.
Must every sufficiently large node set admit bounded labels that force any polynomial fitting almost all labels at degree below (1+ε)n to have arbitrarily large uniform norm? Claimed via Beurling density for Bernstein spaces.
Let μ be a probability measure on the unit circle with Verblunsky coefficients α. Lukic conjectured that a weighted entropy condition with finitely many critical points is equivalent to a decomposition of α into components localized at…
The unrestricted planar Berenstein conjecture holds that overdetermined Dirichlet-Neumann data characterize the disc. Disproved: a bounded simply connected domain with real-analytic Jordan boundary that is not a disc, carrying a nonzero…
How large can a measurable A ⊆ [0,R]^2 be while avoiding the vertices of upward-oriented axis-aligned right triangles of area 1/2? At most O_c(R^2/(log R)^c), with a matching-shaped lower bound construction.
Does every lattice of density above one admit a Gabor frame with a nice window? No. For every dimension d > 1 there are explicit criteria on lattices Λ ⊂ R^2d with D(Λ) > 1 such that no function with continuous Zak transform generates a…
Near-optimal density thresholds forcing a measurable set in R^d to contain all sufficiently large similar copies of every n-point configuration, answering a question from the Euclidean density theorem literature up to logarithmic factors.
For a closed infinite set F ⊆ C, let μ(F) be the infimum of |z : |f(z)| < 1| over monic polynomials with zeros in F. Is μ(F) determined only by the transfinite diameter of F?
After L^2 normalization, stable phase retrieval holds over the L^2-spans of independent real-valued centered random variables exactly when all but possibly one coordinate satisfies a uniform two-sided L^1 bound. This confirms the…
VibeMathed records no statement for this problem. See erdosproblems.com for the original.