Infinite five-square progressions over quadratic extensions of quadratic fields

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Let K1K_1 be a quadratic extension of Q(2)\mathbb{Q}(\sqrt{-2}) and K2K_2 a quadratic extension of Q(2)\mathbb{Q}(\sqrt{2}). An arithmetic progression of squares is non-constant if its terms are not all equal, and is properly defined over a field if that field is the smallest field over which the progression is defined. Two progressions are equivalent in the sense used by the source. Infinite five-square progression conjecture. There are infinitely many non-constant arithmetic progressions of five squares properly defined over a quadratic extension K1K_1 of Q(2)\mathbb{Q}(\sqrt{-2}), respectively over a quadratic extension K2K_2 of Q(2)\mathbb{Q}(\sqrt{2}). Up to equivalence, in the first case every such progression has the form

(a2,b2,2c2,md2,2e2),(a^2,b^2,-2c^2,-m d^2,-2e^2),

where a,b,c,d,e,mZa,b,c,d,e,m\in\mathbb{Z} and m>0m>0 is square-free, so that K1=Q(2,m)K_1=\mathbb{Q}(\sqrt{-2},\sqrt{-m}); in the second case every such progression has the form

(2a2,b2,2c2,m,e2),(2a^2,b^2,2c^2,m,e^2),

where a,b,c,e,mZa,b,c,e,m\in\mathbb{Z} and mm is square-free, so that K2=Q(2,m)K_2=\mathbb{Q}(\sqrt{2},\sqrt{m}).

The claim gives both an infinitude assertion and a classification up to equivalence for five-square arithmetic progressions over the two specified quadratic fields. The supplied parser does not provide evidence that it has been resolved, so its status remains open.

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Sources & referencesView supporting material

Primary source

Enrique González-Jiménez and Nguyen Xuan Tho, “Squares in arithmetic progression over certain non-primitive quartic number fields”, arXiv:2602.01380 (2026).

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