Quintic Forms overp-adic Fields Original Research Article

We prove that a quintic form in 26 variables defined over ap-adic fieldKalways has a nontrivial zero overKif the residue class field ofKhas at least 47 elements. This is in agreement with the theorem of Ax–Kochen which states that a homogeneous form of degreedind2+1 variables defined overQphas a nontrivialQp-rational zero ifpis sufficiently large. The Ax–Kochen theorem gives no results on the bound forp. Ford=1, 2, 3 it has been known for a long time that there is a nontrivialQp-rational zero for all values ofp. Ford=4, Terjanian gave an example of a form in 18 variables overQ2having no nontrivialQ2-rational zero. This is the first result which gives an effective bound for the cased=5.