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The matrix equation aXm+bYn=cI over M2(ℤ)

2022/12/29 by Li, Hongjian, Yuan, Pingzhi
#11D09 #11D41 #15A20 #15A24 #15B36 #FOS: Mathematics #Number Theory (math.NT)

paper · doi:10.48550/arxiv.2212.14139

Abstract

Let ℕ be the set of all positive integers and let a, b, c be nonzero integers such that gcd(a, b, c)=1. In this paper, we prove the following three results: (1) the solvability of the matrix equation aXm+bYn=cI, X, Y∈ M2(ℤ), m, n∈ℕ can be reduced to the solvability of the corresponding Diophantine equation if XY≠ YX and the solvability of the equation axm+byn=c, m, n∈ℕ in quadratic fields if XY=YX; (2) we determine all non-commutative solutions of the matrix equation Xn+Yn=cnI, X, Y∈ M2(ℤ), n∈ℕ, n≥3, and the solvability of this matrix equation can be reduced to the solvability of the equation xn+yn=cn, n∈ℕ, n≥3 in quadratic fields if XY=YX; (3) we determine all solutions of the matrix equation aX2+bY2=cI, X, Y∈ M2(ℤ).

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