The congruence-spacing conjecture for square roots modulo integers

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For integers aa and bb, consider positive solutions of x2≡a(modb)x^2\equiv a\pmod b. The congruence-spacing conjecture. There exists a constant NN such that, for every aa and bb, there do not exist more than NN solutions

0<x1<x2<⋯<xN<x1+b1/20<x_1<x_2<\cdots<x_N<x_1+b^{1/2}

to this congruence. The source notes that this would imply Rudin's square-counting conjecture for arithmetic progressions, while only weaker logarithmic bounds are proved.

References

Primary source

Javier Cilleruelo and Andrew Granville, “Lattice points on circles, squares in arithmetic progressions and sumsets of squares”, arXiv:math/0608109 (2006).

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