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.subfields() not working in Sage 6.2; any workaround?

asked 2016-05-03 15:20:09 -0600

samuelbloom gravatar image

Running Sage 6.2, the .subfields() command is not working when applied to an octic number field. Is there any workaround?

(I'm using institutional resources, but they're having trouble updating the Sage version. Hence this question.)

The screenshot is linked below. (Awkward formatting because of the karma system; sorry!) math.umd.edu/~bloom/sagescreenshot.png

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answered 2016-05-03 17:39:14 -0600

tmonteil gravatar image

updated 2016-05-03 18:48:29 -0600

It should work:

sage: NumberField(x^8-2*x^7+4*x^5-4*x^4+3*x^2-2*x+1,'b').subfields()
[
(Number Field in b0 with defining polynomial x, Ring morphism:
  From: Number Field in b0 with defining polynomial x
  To:   Number Field in b with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  Defn: 0 |--> 0, None),
(Number Field in b1 with defining polynomial x^2 + 1, Ring morphism:
  From: Number Field in b1 with defining polynomial x^2 + 1
  To:   Number Field in b with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  Defn: b1 |--> -b^7 + 2*b^6 - 3*b^4 + 3*b^3 - 2*b + 1, None),
(Number Field in b2 with defining polynomial x^4 - 2*x^3 + x^2 + 1, Ring morphism:
  From: Number Field in b2 with defining polynomial x^4 - 2*x^3 + x^2 + 1
  To:   Number Field in b with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  Defn: b2 |--> -b^7 + 2*b^6 - 4*b^4 + 3*b^3 + b^2 - 2*b + 1, None),
(Number Field in b3 with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1, Ring morphism:
  From: Number Field in b3 with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  To:   Number Field in b with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  Defn: b3 |--> b, Ring morphism:
  From: Number Field in b with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  To:   Number Field in b3 with defining polynomial x^8 - 2*x^7 + 4*x^5 - 4*x^4 + 3*x^2 - 2*x + 1
  Defn: b |--> b3)
]

If your home directory is sufficiently large, i suggest to install your own recent version of Sagemath until your institution updates it. You do not need to have root access for that. What is the output of the following commands (from a terminal):

uname -a
cat /etc/issue
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Asked: 2016-05-03 15:20:09 -0600

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Last updated: May 03 '16