Understanding the Euclidean Algorithm for Finding GCDs in Q[sqrt 3]

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Discussion Overview

The discussion centers on finding the greatest common divisor (GCD) of two numbers, specifically 12 and 35, within the number field Q[sqrt 3]. Participants explore the applicability of the Euclidean algorithm in this context and raise questions about the nature of factorization in related number fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about the method to find the GCD of 12 and 35 in Q[sqrt 3].
  • Another participant questions whether Z[sqrt 3] is a unique factorization domain and discusses potential methods for finding GCDs over the integers.
  • A participant describes Q[sqrt 3] as consisting of numbers in the form (a + b sqrt3)/2, where a and b are rational integers.
  • One participant expresses uncertainty about starting the Euclidean algorithm due to the nature of the numbers involved being rational primes.
  • Another participant challenges the relevance of rational integers in the context of the Euclidean algorithm over Q[sqrt 3].
  • A participant notes that while 24 and 49 have no common factors in rational numbers, there may be a quadratic integer factor in Q[sqrt 3], raising questions about identifying such factors.
  • One participant suggests reviewing the argument for the Euclidean algorithm to build confidence or identify specific issues with its application.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the Euclidean algorithm in Q[sqrt 3] and the nature of factorization in this number field. No consensus is reached regarding the method for finding the GCD or the implications of rational integers in this context.

Contextual Notes

Participants reference the structure of Q[sqrt 3] and the nature of numbers within it, but there are unresolved questions about the specific conditions under which the Euclidean algorithm can be applied and the definitions of factors in this number field.

squelchy451
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Hi.

I need to find the GCD of two numbers in Q[sqrt 3]. Let's suppose these two numbers are 12 and 35. How would you go about finding the GCD of those in Q[sqrt 3]?

thanks~
 
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Is Z[sqrt 3] a unique factorization domain? (Or are the integers [itex]\mathbb{Z}[(1 + \sqrt{3}) / 2][/itex]?) I confess I haven't memorized my small number fields.

Anyways, what ways might you find the GCD over the integers? Would any of those work in this number field?
 
Q[sqrt 3] is all the numbers in the form (a + b sqrt3)/2 where a and b are rational integers, both even or both odd.
 
I COULD use the euclidean algorithm, but I wouldn't know where to start, as these numbers are rational primes, and I need to find solutions in Q[sqrt 3]
 
Sure, 12 is a rational integer. But that doesn't matter, does it? What part of the Euclidean algorithm over Q(sqrt 3) prevents it from working with algebraic integers that happen to also be rational integers?
 
I know what you are trying to say but in terms of rational numbers, there are no factors in common between 24 and 49, but according to this problem, there might be a factor that is a quadratic integer in Q[sqrt3]. The question is which numbers do we know is a factor or not? Since 3 is not congruent to 1 sqrt3, the integers are in the form a + b sqrt3, where a and b are rational integers.
 
There are some typos in your post...

If you are unsure about the Euclidean algorithm (or any other method for finding GCDs), then why not review the argument why it works? That way, you will either gain confidence that it works, or find a specific reason why it should not.
 

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