Opened 4 years ago

#24454 new defect

Strange behaviour of change_ring(CC) for Dirichlet characters

Reported by: mneururer Owned by:
Priority: minor Milestone: sage-8.2
Component: number theory Keywords: dirichlet characters, DirichletGroup
Cc: wuthrich Merged in:
Authors: Michael Neururer Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description

Changing the base ring of a Dirichlet character defined over a number field to the complex numbers does not work. The following code shows some unexpected behaviour:

sage: G = DirichletGroup(5);
sage: G_CC = G.change_ring(CC)
sage: phi = G[1]
sage: phi.change_ring(CC) #NotImplementedError
<repr(<sage.modular.dirichlet.DirichletGroup_class_with_category.element_class at 0x6fe8c3e94b0>) failed: NotImplementedError: order of element not known>
sage: G_CC(phi) #NotImplementedError
<repr(<sage.modular.dirichlet.DirichletGroup_class_with_category.element_class at 0x6fe9012c550>) failed: NotImplementedError: order of element not known>
sage: G_CC[2];
sage: phi.change_ring(CC)
Dirichlet character modulo 5 of conductor 5 mapping 2 |--> 6.12323399573677e-17 + 1.00000000000000*I

It seems that when calling G_CC[2] (or calling any other element of G_CC) some values get cached that make phi.change_ring(CC) work.

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