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### Covariant Derivative gives Error, why? (SAGE 7.5.1)

This simple code gives an Error:

f = function('f')

B=Manifold(2,'B',start_index=1)

polar.<r,phi> = B.chart(R'R:(0,+oo) Phi:(0,2*pi):\Phi')

G = B.riemannian_metric('G')

G[1,1]=diff(f(R),R)

G[2,2]=f(R)^2

nabla=G.connection()

S=B.tensor_field(1,1)

S[1,1]=R^(0.5)

S[2,2]=R^3

S.display()

nabla(S)

Error: TypeError: unable to convert R to an integer

This Error doesn't occur either if I avoid the square root in S[1,1]=R^(0.5), for example by writing S[1,1]=R^(0.4) or if I avoid the dependence of the derivative of f in the first entry of the metric, for example by writing G[1,1]=f(R)^2.

This Error also doesn't occur in older Sage versions, for example Sage 7.1

Thanks a lot for help!

 2 None kcrisman 12002 ●37 ●125 ●245

### Covariant Derivative gives Error, why? (SAGE 7.5.1)

This simple code gives an Error:

f = function('f')function('f')
B=Manifold(2,'B',start_index=1)
B=Manifold(2,'B',start_index=1) polar.<r,phi> polar.<R,Phi> = B.chart(R'R:(0,+oo) Phi:(0,2*pi):\Phi')Phi:(0,2*pi):\Phi')
G = B.riemannian_metric('G')B.riemannian_metric('G')
G[1,1]=diff(f(R),R)
G[1,1]=diff(f(R),R)G[2,2]=f(R)^2
nabla=G.connection()
G[2,2]=f(R)^2S=B.tensor_field(1,1)
S[1,1]=R^(0.5)
nabla=G.connection()S[2,2]=R^3
S.display()
S=B.tensor_field(1,1)nabla(S)
S[1,1]=R^(0.5) S[2,2]=R^3 S.display() nabla(S) Error: TypeError: unable to convert R to an integerinteger


This Error doesn't occur either if I avoid the square root in S[1,1]=R^(0.5), for example by writing S[1,1]=R^(0.4) or if I avoid the dependence of the derivative of f in the first entry of the metric, for example by writing G[1,1]=f(R)^2.

This Error also doesn't occur in older Sage versions, for example Sage 7.1

Thanks a lot for help!