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Ordering of solutions for quartics when using Root

Posted 10 years ago

Hello all,

There was a discussion recently regarding quartics and here I want to extend it a little bit with regards to Root objects:

Root[#1^4 A1 + #1^3 A2 + #1^2 A3 + #1 A4 + A5 &, n_root]

The problem I have to solve is a quartic equation in which coefficients vary based on problem input - range for one of the model's parameters. The equation has 4 different roots (related to four different physical quantities) and again based on the input they vary throughout a range of model's parameter as follows:

  1. Four real roots two real
  2. Two complex roots
  3. Four complex roots.

Each root is assigned to a separate variable and in order to solve the problem, roots have to be consistent with variables (certain physical quantities), so to say root #1 should be always in position #1 of Root no matter if it is complex or real. Root numbers solutions from smallest to biggest and that works fine until roots start to become complex, then Root changes its' positions and solution is not physical anymore. Can anyone advise on that?

POSTED BY: Yuriy Ivanov
2 Replies
POSTED BY: Daniel Lichtblau
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