English

Some universal quadratic sums over the integers

Number Theory 2020-01-14 v6

Abstract

Let a,b,c,d,e,fNa,b,c,d,e,f\in\mathbb N with ace>0a\ge c\ge e>0, bab\le a and ba(mod2)b\equiv a\pmod2, dcd\le c and dc(mod2)d\equiv c\pmod2, fef\le e and fe(mod2)f\equiv e\pmod2. If any nonnegative integer can be written as x(ax+b)/2+y(cy+d)/2+z(ez+f)/2x(ax+b)/2+y(cy+d)/2+z(ez+f)/2 with x,y,zZx,y,z\in\mathbb Z, then the ordered tuple (a,b,c,d,e,f)(a,b,c,d,e,f) is said to be universal over Z\mathbb Z. Recently, Z.-W. Sun found all candidates for such universal tuples over Z\mathbb Z. In this paper, we use the theory of ternary quadratic forms to show that 44 concrete tuples (a,b,c,d,e,f)(a,b,c,d,e,f) in Sun's list of candidates are indeed universal over Z\mathbb Z. For example, we prove the universality of (16,4,2,0,1,1)(16,4,2,0,1,1) over Z\mathbb Z which is related to the form x2+y2+32z2x^2+y^2+32z^2.

Keywords

Cite

@article{arxiv.1707.06223,
  title  = {Some universal quadratic sums over the integers},
  author = {Hai-Liang Wu and Zhi-Wei Sun},
  journal= {arXiv preprint arXiv:1707.06223},
  year   = {2020}
}

Comments

19 pages, final published version

R2 v1 2026-06-22T20:52:08.075Z