latex_name and derivatives in sagemanifolds

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asked 4 years ago

cav_rt
494 ●10 ●24

updated 4 years ago

Hi,

I think there is a small bug on displaying derivatives of tensors w.r.t a parameter with latex_name.

For symbolic expressions,

from sage.manifolds.utilities import ExpressionNice
var('t')
dq1 = function('dq_1', latex_name=r'\dot{q}_1')(t)
L = function('L')(dq1)
ExpressionNice(diff(L,t))

works nicely. However, when I define the same L as a scalar field (or any tensor),

M = manifolds.Minkowski()
L1 = M.scalar_field(L)
L1.derivative().display()

the latex_name is ignored and dq_1 is used instead. The problem does not occur when there is no index in dq.

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answered 4 years ago

eric_g
8544 ●10 ●62 ●168 https://luth.obspm.fr/...

I cannot reproduce the issue with Sage 9.2. Typing the following code

%display latex
var('t')
dq1 = function('dq_1', latex_name=r'\dot{q}_1')(t)
L = function('L')(dq1)
M = manifolds.Minkowski()
L1 = M.scalar_field(L)
L1.derivative().display()

in a Jupyter notebook yields

$\frac{\partial\,L}{\partial \left( \dot{q}_1\left(t\right) \right)} \frac{\partial\dot{q}_1}{\partial t} \mathrm{d} t$

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You are right, probably I was messing up variables and names. Thank you!

cav_rt ( 4 years ago )

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Asked: 4 years ago

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Last updated: Feb 02 '21

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