Diophantine Equation x13βx22x1+1=0 over number fields
Abstract
Let π=β(β(βd)) or β(βd), where d is a positive square-free integer, and denote by πͺK the ring of integers of π. I investigate the solution of the equation x13βx22x1+1=0 where x1β π and x2βπͺK. The case π=β(βd) for dβ‘ 2,3pmod4 faces infinite units that require a separate treatment. Using the arithmetic of the quadratic integer rings β€[βd]], together with norm arguments, divisibility properties, and the explicit structure of its unit group, I prove that the equation has exactly two solutions, namely (x1,x2)=(β1,0) and (1,β2) for π=β(β2) and one solution (β1,0) for π=β(βd) As an application, I consider the family of elliptic curves Cm:Y2=X3βm2X+1, mβπͺK, and deduce that, for every mβ 0,β2 the Mordell--Weil group Cm(π) contains no rational point of order two.
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BibTeX
@misc{khatun2026diophantine,
title = {{Diophantine Equation $x_1^3-x_2^2x_1+1=0$ over number fields}},
author = {Pinki Khatun},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.26079},
eprint = {2607.26079},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.26079},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Diophantine Equation x_1^3βx_2^2x_1+1=0 over number fields
AU - Pinki Khatun
PY - 2026
DA - 2026/09/06
PB - arXiv
DO - 10.48550/arxiv.2607.26079
UR - https://arxiv.org/abs/2607.26079
AB - Let π=β(β(βd)) or β(βd), where d is a positive square-free integer, and denote by πͺ_K the ring of integers of π. I investigate the solution of the equation x_1^3βx_2^2x_1+1=0 where x_1β π and x_2βπͺ_K. The case π=β(βd) for dβ‘ 2,3pmod4 faces infinite units that require a separate treatment. Using the arithmetic of the quadratic integer rings β€[βd]], together with norm arguments, divisibility properties, and the explicit structure of its unit group, I prove that the equation has exactly two solutions, namely (x_1,x_2)=(β1,0) and (1,β2) for π=β(β2) and one solution (β1,0) for π=β(βd) As an application, I consider the family of elliptic curves C_m:Y^2=X^3βm^2X+1, mβπͺ_K, and deduce that, for every mβ 0,β2 the Mordell--Weil group C_m(π) contains no rational point of order two.
ER -