English

On the finiteness of solutions for polynomial-factorial Diophantine equations

Number Theory 2021-05-28 v3

Abstract

We study the Diophantine equations obtained by equating a polynomial and the factorial function, and prove the finiteness of integer solutions under certain conditions. For example, we show that there exists only finitely many ll such that l!l! is represented {by} NA(x)N_A(x), where NAN_A is a norm form constructed from the field norm of a field extension K/QK/\mathbf Q. We also deal with the equation NA(x)=l!SN_A(x)=l!_S, where l!Sl!_S is the Bhargava factorial. In this paper, we also show that the Oesterl\'e-Masser conjecture implies that for any infinite subset SS of Z\mathbf Z and for any polynomial P(x)Z[x]P(x)\in\mathbf Z[x] of degree 22 or more the equation P(x)=l!SP(x)=l!_S has only finitely many solutions (x,l)(x,l). For some special infinite subsets SS of Z\mathbf Z, we can show the finiteness of solutions for the equation P(x)=l!SP(x)=l!_S unconditionally.

Keywords

Cite

@article{arxiv.1903.01076,
  title  = {On the finiteness of solutions for polynomial-factorial Diophantine equations},
  author = {Wataru Takeda},
  journal= {arXiv preprint arXiv:1903.01076},
  year   = {2021}
}

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21 pages