On Friday, May 1, 2015 at 3:04:45 AM UTC-7, John Wiltshire-Gordon wrote:
>
> According to the documentation for commutative_dga, a differential graded
> algebra is graded by integers. However, if I attempt to give a generator
> negative degree, I get an error. For example,
>
> A = GradedCommutativeAlgebra(QQ, 'x, y', degrees=(-1, -1))
>
> returns the error
>
> ValueError: the degree weights must be all positive integers
>
> I'd appreciate any help!
>
I agree that this happens and that it is far from ideal. I think the best
way around it is to introduce a second grading so that the total degree is
positive:
sage: A.<x,y> = GradedCommutativeAlgebra(QQ, degrees=((-1,2), (-1,2)))
You won't care about the second grading mathematically, but Sage will treat
these elements as having total degree 1, which ought to make it happy.
--
John
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