Baker–Matiyasevich–Robinson conjecture on Hilbert’s tenth problem for few variables
Establish that, for n ≥ 3 variables, there is no algorithm to decide whether a polynomial equation f(x_1, …, x_n) = 0 with integer coefficients has a positive integer solution; equivalently, prove that the positive-integer-solutions version of Hilbert’s tenth problem remains undecidable in n ≥ 3 variables.
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Thanks to the negative solution of Hilbert's tenth problem no such algorithm exists for the analogous problem of determining whether there is even a single integral solution to an equation f(x_1, \ldots, x_n) = 0 with f\in Z[x_1, \ldots, x_n] in n\geq 11 variables, and it is a conjecture of Baker, Matiyasevich, and Robinson that the same should hold when n\geq 3, at least with "integral solution" replaced with "positive integral solution".