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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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Analysis

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E0120/: Asks whether, for every infinite set of reals, some set of positive measure contains no affine copy of it.

E0225/: Asks whether a trigonometric polynomial with all real roots and maximum modulus one has integral of its absolute value at most 4 over a full period.

E0226/: Asks whether some entire non-linear function sends exactly the rational real numbers to rational values.

E0227/: Asks whether, for a non-polynomial entire function, the limiting ratio of largest coefficient term to maximum modulus, when it exists, must be zero.

E0229/: Asks whether, given sets of complex numbers with no finite limit point, some transcendental entire function has each set among zeros of some derivative.

E0256/: Estimates the largest lower bound for the maximum modulus on the unit circle of a product of terms one minus z to the a-i, over all choices of n exponents.

E0395/: Asks whether random signs on n unit complex numbers give a sum of absolute value at most the square root of two with probability at least about one over n; Erdős asked it with radius one, which fails for every even n.

E0498/: Asks whether at most the middle binomial coefficient of the signed sums of n complex numbers of modulus at least one can lie in one open unit disc.

E0510/: Asks whether every set of N positive integers admits an angle where the sum of the cosines of its members times that angle is below a negative constant times root N; the site's wording over all integers fails at sets containing zero.

E0511/: Asks whether the set where a monic polynomial has modulus below one has boundedly many components of diameter above a fixed constant, whatever the degree.

E0512/: Asks whether the mean absolute value of the exponential sum over a set of N integers is at least of order the logarithm of N.

E0513/: Determines the largest limit inferior of the ratio of the maximal power series term of a transcendental entire function to its maximum modulus on radius r.

E0514/: Asks whether every transcendental entire function has a path to infinity on which it outgrows every power of the variable, how long such a path must be, and whether it can outgrow a fixed function of the maximum modulus.

E0515/: Asks whether every entire nonpolynomial function has a rectifiable path to infinity along which the integral of any negative power of its modulus is finite.

E0516/: Asks whether an entire function of finite order with very sparse exponents has minimum modulus whose logarithm matches that of its maximum modulus.

E0517/: Asks whether an entire power series whose exponents grow faster than linearly in the index must take every complex value infinitely often.

E0519/: Asks whether the largest modulus among the first n power sums of complex numbers, one of which is one, is bounded below by an absolute positive constant.

E0527/: Asks whether, for almost all sign choices, a signed power series with small but not square-summable coefficients converges somewhere on the unit circle.

E0671/: Concerns sequences of Lagrange interpolation polynomials built on nodes in the interval from minus one to one and how they behave as the degree grows.

E0906/: Asks whether there is a transcendental entire function whose derivatives, along any infinite subsequence of orders, have zero sets that together are dense in the plane.

E0907/: Asks whether a real function whose every fixed-shift difference is continuous must be the sum of a continuous function and an additive one.

E0908/: Asks whether a real function whose every fixed-shift difference is measurable splits into measurable, additive and almost-everywhere-shift-invariant parts; the site prints continuous.

E0909/: Asks whether, for each n at least two, there is a space of dimension n whose square also has dimension n.

E0910/: Asks whether every connected set in n-dimensional space has a connected subset that is neither a single point nor homeomorphic to the whole set.

E0967/: Asks whether, for integer sequences whose reciprocals sum finitely, one plus the sum of their reciprocals to the power one plus i t is never zero.

E0973/: Asks whether n complex numbers of modulus at least one, the first equal to one, can keep all their power sums below an exponentially small bound.

E0974/: Asks whether complex numbers whose power sums vanish on infinitely many blocks of n minus one consecutive indices are essentially the nth roots of unity, read as Tijdeman's classification.

E0990/: Asks whether a polynomial's root arguments are equidistributed with error at most the square root of the number of nonzero coefficients times a log factor.

E0996/: Asks how fast a square integrable function's Fourier partial sums must converge for its averages along alpha times a lacunary sequence to equal its integral.

E1038/: Determines the smallest and largest measure of the set where a monic real polynomial with all roots real in minus one to one has absolute value below one.

E1040/: The least area of the region where a monic polynomial with all roots from a fixed closed infinite set of complex numbers has absolute value below one.

E1042/: Asks what can be said about a closed set in the plane of transfinite diameter one that lies inside no closed disc of radius one.

E1043/: Asks whether every monic non-constant complex polynomial has a line onto which the set where its absolute value is at most one projects to measure at most two.

E1044/: Determines the infimum of the largest component boundary length of the region where a polynomial with all roots in the closed unit disc is below one.

E1045/: The maximum product of all pairwise distances among complex numbers that are pairwise at most distance two apart, and whether a regular polygon is optimal.

E1046/: Asks whether the set where a monic complex polynomial has absolute value below one must lie in a disc of radius two whenever that set is connected.

E1047/: Examines a monic polynomial with m distinct roots and a threshold so small that the set where its absolute value is at most that threshold has m components.

E1048/: Asks whether a monic polynomial with all roots of absolute value at most r below two has a component of diameter over two minus r where it is below one.

E1115/: The linear-length asymptotic-path conjecture fails at every finite order, even for functions growing arbitrarily close to the logarithmic-square threshold that guarantees radial paths.

E1116/: Asks whether some meromorphic or entire function has, for every two distinct values, the ratio of their solution counts in growing discs unbounded.

E1117/: Concerns the number of points on the circle of radius r at which a non-monomial entire function attains its maximum modulus.

E1118/: Concerns non-constant entire functions for which the set where the modulus exceeds some constant has finite measure.

E1120/: Asks for the shortest path from zero to the unit circle inside the set where a monic polynomial with all roots in the unit disc has modulus at most one.

E1125/: Asks whether a real function with twice its value at a point at most the sum of its values at two later equally spaced points must be monotonic.

E1126/: Asks whether a function additive for almost all pairs of reals must agree almost everywhere with a function that is additive for all pairs.

E1154/: Asks whether, for every number between zero and one, some ring or field of real numbers has exactly that Hausdorff dimension; yes under the continuum hypothesis by Mauldin's theorem, so the existence cannot be refuted in ZFC.

E1164/: Asks whether the logarithm of the radius of the largest origin-centered disc a planar simple random walk covers by time n has order sqrt(log n) in probability; the site's almost-every wording is corrected, and Révész and Dembo–Peres–Rosen–Zeitouni prove it.

E1165/: Asks the infinitely-often probability of exactly r sites tied for maximum local time in planar simple random walk, for each integer r at least three.

E1166/: Asks whether the number of sites ever favorite by time n in planar simple random walk is eventually bounded by a power of log n almost surely.

E1195/: Concerns sets of real numbers of infinite measure in which no ratio of two distinct elements is an integer.

E1197/: Asks whether, for a set of positive measure and almost every positive x, every large integer multiple of x lies in some integer dilate of the set.

E1215/: Asks whether a constant bounds the length of a path from zero to the unit circle inside the region where such a polynomial has modulus below one.

E1221/: Asks whether, for a sequence on the circle, the de Bruijn–Erdős constants for the largest and smallest sums of r consecutive gaps and for their ratio deviate from their trivial values by more than any constant over r as r grows; a 2026 preprint claims all three parts for distinct points, unrefereed and unreviewed.


Entire and complex functions, real functions and measure, exponential sums and series, and the few purely probabilistic and topological problems that carry no subject co-tag.

Site tags routed here: analysis, combinatorics, iterated functions, number theory, probability, topology.