Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Linear Congruences in several variables with congruence restrictions

C. G. Karthick Babu, Ranjan Bera, B. Sury

Abstract

In this article, we consider systems of linear congruences in several variables and obtain necessary and sufficient conditions as well as explicit expressions for the number of solutions subject to certain restriction conditions. These results are in terms of Ramanujan sums and generalize the results of Lehmer \cite{DNL13} and Bibak et al. \cite{BBVRL17}. These results have analogues over $\mathbb{F}_q[t]$ where the proofs are similar, once notions such as Ramanujan sums are defined in this set-up. We use the recent description of Ramanujan sums over function fields as developed by Zhiyong Zheng \cite{ZZ18}. This is discussed in the last section. We illustrate the formulae obtained for the number of solutions through some examples. Over the integers, such problems have a rich history, some of which seem to have been forgotten - a number of papers written on the topic re-prove known results. The present authors also became aware of some of these old articles only while writing the present article and hence, we recall very briefly some of the old work by H. J. S. Smith, Rademacher, Brauer, Butson and Stewart, Ramanathan, McCarthy, and Spilker \cite{AB26, BS55, PJM76, HR25, KGR44, HJSS61, JS96}.

Linear Congruences in several variables with congruence restrictions

Abstract

In this article, we consider systems of linear congruences in several variables and obtain necessary and sufficient conditions as well as explicit expressions for the number of solutions subject to certain restriction conditions. These results are in terms of Ramanujan sums and generalize the results of Lehmer \cite{DNL13} and Bibak et al. \cite{BBVRL17}. These results have analogues over where the proofs are similar, once notions such as Ramanujan sums are defined in this set-up. We use the recent description of Ramanujan sums over function fields as developed by Zhiyong Zheng \cite{ZZ18}. This is discussed in the last section. We illustrate the formulae obtained for the number of solutions through some examples. Over the integers, such problems have a rich history, some of which seem to have been forgotten - a number of papers written on the topic re-prove known results. The present authors also became aware of some of these old articles only while writing the present article and hence, we recall very briefly some of the old work by H. J. S. Smith, Rademacher, Brauer, Butson and Stewart, Ramanathan, McCarthy, and Spilker \cite{AB26, BS55, PJM76, HR25, KGR44, HJSS61, JS96}.
Paper Structure (14 sections, 7 theorems, 108 equations)

This paper contains 14 sections, 7 theorems, 108 equations.

Table of Contents

  1. Introduction
  2. Ramanujan Sums and DFT
  3. Preliminary Lemmas
  4. Some properties of GCD and LCM
  5. Some applications of Ramanujan Sums and DFT
  6. Solutions of Linear Congruences
  7. Proof of Theorem \ref{['soln of congs thm']}.
  8. Some examples
  9. Proof of Theorem \ref{['Theorem 3']}.
  10. Example
  11. Restricted linear congruences over $\mathbb{F}_q[t]$
  12. Ramanujan Sums and DFT
  13. Proof of the Theorems
  14. Some examples

Key Result

Theorem 1

Let $m_{1}, \dots, m_{k}$ be pairwise coprime integers. The system of congruences above has a solution $x_{1}, \dots, x_{n}$ in integers if and only if, $(m_i, a_{i1}, a_{i2}, \dots, a_{in})|b_{i}$ for each $i \leq k$.

Theorems & Definitions (12)

  • Theorem 1
  • Theorem 2
  • Theorem 3
  • proof
  • proof
  • proof
  • Theorem 4
  • Theorem 5
  • Theorem 6
  • Theorem 7
  • ...and 2 more