Erdős discrepancy problem

E554302

The Erdős discrepancy problem is a famous question in combinatorial number theory that asks whether every infinite ±1 sequence has arbitrarily large discrepancy along some homogeneous arithmetic progression.

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Predicate Object
instanceOf mathematical problem
open problem in mathematics
asksAbout discrepancy of ±1 sequences
homogeneous arithmetic progressions
concerns unboundedness of certain partial sums
coreQuestion whether every infinite ±1 sequence has unbounded discrepancy on some homogeneous arithmetic progression
difficulty hard
difficultyClassification very difficult problem in combinatorial number theory
equivalentFormulation for every ±1 sequence (x_n) and every C > 0 there exist n,d with |x_d + x_{2d} + … + x_{nd}| > C
field combinatorial number theory
discrepancy theory
formulation for every function f: ℕ → {−1, +1} and every C > 0 there exist n,d ∈ ℕ such that |∑_{k=1}^{n} f(kd)| > C
hasConsequence every infinite ±1 sequence has arbitrarily large discrepancy along some homogeneous arithmetic progression
hasOnlinePolymathProject Polymath5
linked to: Polymath Project
hasVariant Erdős discrepancy problem for completely multiplicative functions
implies no infinite ±1 sequence has bounded discrepancy on all homogeneous arithmetic progressions
influencedBy classical problems of Erdős in additive and combinatorial number theory
involvesQuantifiers for all C > 0 there exist n,d ∈ ℕ
motivation understanding irregularities of distribution in sequences
namedAfter Paul Erdős
linked to: Pál Erdős
proposedBy Paul Erdős
linked to: Pál Erdős
publication Terence Tao’s 2016 paper in Journal d’Analyse Mathématique
quantifiesOver all infinite ±1 sequences
all positive integers C
positive integers d
positive integers n
relatedTo Erdős–Turán conjecture
completely multiplicative functions
discrepancy of sequences
multiplicative functions
solutionMethod Fourier analysis
analytic number theory
entropy decrement argument
probabilistic methods
solvedBy Terence Tao
status solved
studiedIn Polymath5 project
linked to: Polymath Project
topic arithmetic progressions
infinite sequences
partial sums
usesConcept discrepancy
homogeneous arithmetic progression
±1 sequence
yearProposed 1930s
yearSolved 2015

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Pál Erdős knownFor Erdős discrepancy problem
Erdős discrepancy problem hasVariant Erdős discrepancy problem for completely multiplicative functions
linked to: Erdős discrepancy problem
Erdős discrepancy problem publication Terence Tao’s 2016 paper in Journal d’Analyse Mathématique
linked to: Erdős discrepancy problem
Erdős–Turán conjecture relatedTo Erdős discrepancy problem