On relations for rings generated by algebraic numbers and their conjugates

Verfasser / Beitragende:
[Paulius Drungilas, Artūras Dubickas, Jonas Jankauskas]
Ort, Verlag, Jahr:
2015
Enthalten in:
Annali di Matematica Pura ed Applicata (1923 -), 194/2(2015-04-01), 369-385
Format:
Artikel (online)
ID: 605496676
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024 7 0 |a 10.1007/s10231-013-0380-4  |2 doi 
035 |a (NATIONALLICENCE)springer-10.1007/s10231-013-0380-4 
245 0 0 |a On relations for rings generated by algebraic numbers and their conjugates  |h [Elektronische Daten]  |c [Paulius Drungilas, Artūras Dubickas, Jonas Jankauskas] 
520 3 |a Let $$\alpha $$ α be an algebraic number of degree $$d$$ d with minimal polynomial $$F \in \mathbb {Z}[X]$$ F ∈ Z [ X ] , and let $$\mathbb {Z}[\alpha ]$$ Z [ α ] be the ring generated by $$\alpha $$ α over $$\mathbb {Z}$$ Z . We are interested whether a given number $$\beta \in \mathbb {Q}(\alpha )$$ β ∈ Q ( α ) belongs to the ring $$\mathbb {Z}[\alpha ]$$ Z [ α ] or not. We give a practical computational algorithm to answer this question. Furthermore, we prove that a rational number $$r/t \in \mathbb {Q}$$ r / t ∈ Q , where $$r \in \mathbb {Z}, t \in \mathbb {N}, \gcd (r, t) = 1$$ r ∈ Z , t ∈ N , gcd ( r , t ) = 1 , belongs to the ring $$\mathbb {Z}[\alpha ]$$ Z [ α ] if and only if the square-free part of its denominator $$t$$ t divides all the coefficients of the minimal polynomial $$F \in \mathbb {Z}[X]$$ F ∈ Z [ X ] except for the constant coefficient $$F(0)$$ F ( 0 ) that must be relatively prime to $$t$$ t , namely $$\gcd (F(0),t)=1$$ gcd ( F ( 0 ) , t ) = 1 . We also study the question when the equality $$\mathbb {Z}[\alpha ] = \mathbb {Z}[\alpha ']$$ Z [ α ] = Z [ α ′ ] for algebraic numbers $$\alpha , \alpha '$$ α , α ′ conjugates over $$\mathbb {Q}$$ Q holds. In particular, it is shown that for each $$d \in \mathbb {N}$$ d ∈ N , there are conjugate algebraic numbers $$\alpha , \alpha '$$ α , α ′ of degree $$d$$ d satisfying $$\mathbb {Q}(\alpha ) = \mathbb {Q}(\alpha ')$$ Q ( α ) = Q ( α ′ ) and $$\mathbb {Z}[\alpha ] \ne \mathbb {Z}[\alpha ']$$ Z [ α ] ≠ Z [ α ′ ] . The question concerning the equality $$\mathbb {Z}[\alpha ]=\mathbb {Z}[\alpha ']$$ Z [ α ] = Z [ α ′ ] is answered completely for conjugate quadratic pairs $$\alpha ,\alpha '$$ α , α ′ and also for conjugate pairs $$\alpha , \alpha '$$ α , α ′ of cubic algebraic integers. 
540 |a Fondazione Annali di Matematica Pura ed Applicata and Springer-Verlag Berlin Heidelberg, 2013 
690 7 |a Rings of algebraic numbers  |2 nationallicence 
690 7 |a Conjugate algebraic numbers  |2 nationallicence 
690 7 |a Minimal polynomial  |2 nationallicence 
690 7 |a Polynomials in finite fields  |2 nationallicence 
690 7 |a Algorithms  |2 nationallicence 
700 1 |a Drungilas  |D Paulius  |u Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania  |4 aut 
700 1 |a Dubickas  |D Artūras  |u Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania  |4 aut 
700 1 |a Jankauskas  |D Jonas  |u Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania  |4 aut 
773 0 |t Annali di Matematica Pura ed Applicata (1923 -)  |d Springer Berlin Heidelberg  |g 194/2(2015-04-01), 369-385  |x 0373-3114  |q 194:2<369  |1 2015  |2 194  |o 10231 
856 4 0 |u https://doi.org/10.1007/s10231-013-0380-4  |q text/html  |z Onlinezugriff via DOI 
898 |a BK010053  |b XK010053  |c XK010000 
900 7 |a Metadata rights reserved  |b Springer special CC-BY-NC licence  |2 nationallicence 
908 |D 1  |a research-article  |2 jats 
949 |B NATIONALLICENCE  |F NATIONALLICENCE  |b NL-springer 
950 |B NATIONALLICENCE  |P 856  |E 40  |u https://doi.org/10.1007/s10231-013-0380-4  |q text/html  |z Onlinezugriff via DOI 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Drungilas  |D Paulius  |u Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Dubickas  |D Artūras  |u Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania  |4 aut 
950 |B NATIONALLICENCE  |P 700  |E 1-  |a Jankauskas  |D Jonas  |u Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania  |4 aut 
950 |B NATIONALLICENCE  |P 773  |E 0-  |t Annali di Matematica Pura ed Applicata (1923 -)  |d Springer Berlin Heidelberg  |g 194/2(2015-04-01), 369-385  |x 0373-3114  |q 194:2<369  |1 2015  |2 194  |o 10231