On $p$-adic denseness of quotients of values of integral forms

Fuente: arXiv
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Auteurs principaux: Antony, Deepa, Barman, Rupam, Gajović, Stevan, Širola, Daniel
Format: Preprint
Publié: 2023
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author Antony, Deepa
Barman, Rupam
Gajović, Stevan
Širola, Daniel
author_facet Antony, Deepa
Barman, Rupam
Gajović, Stevan
Širola, Daniel
contents Given $A\subseteq \mathbb{Z}$, the ratio set or the quotient set of $A$ is defined by $R(A):=\{a/b: a, b\in A, b\neq 0\}$. It is an open problem to study the denseness of $R(A)$ in the $p$-adic numbers when $A$ is the set of values attained by an integral form. In this paper, we consider the question of whether this happens for all but finitely many $p$. We prove that if a form is non-singular and has at least three variables, then the ratio set of its values is dense in $\mathbb{Q}_p$ for all sufficiently large $p$. We conjecture that the same statement is true for non-degenerate forms of prime degree having sufficiently many variables, which is indeed the case when the degree is 2, 3, or 5. Still, we give two counterexamples when the assumptions of the conjecture are not satisfied. The first one happens when the number of variables is equal to the degree. The other works for any number of variables but only for composite degrees. Our innovation is to consider the problem in terms of varieties defined by forms, thereby using the tools from algebraic geometry, making their first appearance in this setting. Finally, we construct integral forms such that the ratio set of its values is dense in at least one $\mathbb{Q}_p$ but only in finitely many of them.
format Preprint
id arxiv_https___arxiv_org_abs_2308_08907
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle On $p$-adic denseness of quotients of values of integral forms
Antony, Deepa
Barman, Rupam
Gajović, Stevan
Širola, Daniel
Number Theory
Given $A\subseteq \mathbb{Z}$, the ratio set or the quotient set of $A$ is defined by $R(A):=\{a/b: a, b\in A, b\neq 0\}$. It is an open problem to study the denseness of $R(A)$ in the $p$-adic numbers when $A$ is the set of values attained by an integral form. In this paper, we consider the question of whether this happens for all but finitely many $p$. We prove that if a form is non-singular and has at least three variables, then the ratio set of its values is dense in $\mathbb{Q}_p$ for all sufficiently large $p$. We conjecture that the same statement is true for non-degenerate forms of prime degree having sufficiently many variables, which is indeed the case when the degree is 2, 3, or 5. Still, we give two counterexamples when the assumptions of the conjecture are not satisfied. The first one happens when the number of variables is equal to the degree. The other works for any number of variables but only for composite degrees. Our innovation is to consider the problem in terms of varieties defined by forms, thereby using the tools from algebraic geometry, making their first appearance in this setting. Finally, we construct integral forms such that the ratio set of its values is dense in at least one $\mathbb{Q}_p$ but only in finitely many of them.
title On $p$-adic denseness of quotients of values of integral forms
topic Number Theory
url https://arxiv.org/abs/2308.08907