Autocorrelation and Kakeya constants
Step functions and finite sets that tighten autocorrelation and sum–difference constants (placeholder)
Open problems and research questions, each a git repository: many come from curated collections and credit them. Routes are branches anyone can start or continue; results count once the checks pass.
Step functions and finite sets that tighten autocorrelation and sum–difference constants (placeholder)
Find a closed form for the critical mass N_c ≈ 11.7008965246 of the Townes soliton, the collapse threshold of the 2D cubic NLS.
Find two non-isometric Euclidean domains with the same Steklov spectrum, or prove that the Steklov spectrum determines the domain.
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Close the gap between 1 - 1/n and about 4 in Smale's mean value inequality for complex polynomials, or find a counterexample.
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Find the sharp constant in the one-dimensional sign uncertainty principle, known only to lie between 0.2025 and 0.3216.
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Find the least possible peak of f*f for a non-negative f of unit mass on [-1/4, 1/4]; it lies between 1.2802 and 1.50286.
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Narrow Grothendieck's constant, the worst ratio between a sign optimization and its vector relaxation, now between 1.7136 and 1.7822.
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Find a non-affine polynomial in n ≥ 8 variables whose graph is a minimal hypersurface, or prove that none exists (Simon's question).
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Find a polygonal domain, possibly with holes, whose k-th Dirichlet eigenvalue lies below 4πk/area, or prove Pólya's 1954 conjecture.
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Prove that loops of length 2π give the curvature Schrödinger operator ground-state energy at least 1, or find a loop that beats the circle.
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Find a closed form for the Ising-class integral C5 = (4/15)∫ t K0(t)^5 dt ≈ 0.6657598002 of Bailey, Borwein and Crandall.
Find a closed form for Feigenbaum's period-doubling constant δ ≈ 4.6692016091, known to 10,000 digits but not proven irrational.