Let
N(t) := #{(m,n)∈Z2: m2+n2≤t2}
be the number of integer lattice points inside the (closed) disk of radius t centered at the origin. The Gauss circle problem is to find the smallest exponent θ such that, for every ε>0,
N(t) = πt2 + O(tθ+ε).
[CRM2023-def-theta]
We define
C64 := θ,
the Gauss circle problem exponent.
The best established upper bound is due to Huxley:
θ ≤ 208131.
[CRM2023-ub-131-208]
Hardy conjectured the optimal exponent θ=1/2.
[CRM2023-conj-1-2]
The best established range currently is
0 ≤ C64 ≤ 208131.