TY - JOUR

T1 - No two non-real conjugates of a Pisot number have the same imaginary parts

AU - Dubickas, Artūras

AU - Hare, Kevin

AU - Jankauskas, Jonas

PY - 2017/3

Y1 - 2017/3

N2 - We show that the number α=(1+3+25√−−−−−−−√)/2 with minimal polynomial x4−2x3+x−1 is the only Pisot number whose four distinct conjugates α1,α2,α3,α4 satisfy the additive relation α1+α2=α3+α4. This implies that there exists no two non-real conjugates of a Pisot number with the same imaginary part and also that at most two conjugates of a Pisot number can have the same real part. On the other hand, we prove that similar four term equations α1=α2+α3+α4 or α1+α2+α3+α4=0 cannot be solved in conjugates of a Pisot number α. We also show that the roots of the Siegel's polynomial x3−x−1 are the only solutions to the three term equation α1+α2+α3=0 in conjugates of a Pisot number. Finally, we prove that there exists no Pisot number whose conjugates satisfy the relation α1=α2+α3.

AB - We show that the number α=(1+3+25√−−−−−−−√)/2 with minimal polynomial x4−2x3+x−1 is the only Pisot number whose four distinct conjugates α1,α2,α3,α4 satisfy the additive relation α1+α2=α3+α4. This implies that there exists no two non-real conjugates of a Pisot number with the same imaginary part and also that at most two conjugates of a Pisot number can have the same real part. On the other hand, we prove that similar four term equations α1=α2+α3+α4 or α1+α2+α3+α4=0 cannot be solved in conjugates of a Pisot number α. We also show that the roots of the Siegel's polynomial x3−x−1 are the only solutions to the three term equation α1+α2+α3=0 in conjugates of a Pisot number. Finally, we prove that there exists no Pisot number whose conjugates satisfy the relation α1=α2+α3.

KW - Pisot numbers

KW - Linear equations

KW - Additive relations

KW - Mahler's measure

M3 - Article

VL - 86.2017

SP - 935

EP - 950

JO - Mathematics of computation

JF - Mathematics of computation

SN - 1088-6842

IS - 304

ER -