I have encountered a problem with factor in SR which can be avoided but it
shows a problem. If I run this code:
var('t',domain='complex')
var('r,x,y',domain='real')
h= r^6+r^4*t^2 + 4*r^4*t*conjugate(t) + r^4*conjugate(t)^2 +
r^2*t^2*conjugate(t)^2 - r^2*t^2 - r^2*conjugate(t)^2 + t^2*conjugate(t)^2
H=h(t=x+I*y).factor()
num=1/2*(H.derivative(x)/H).derivative(x)+1/2*(H.derivative(y)/H).derivative(y)
num.factor()
I get the following error
---------------------------------------------------------------------------ValueError
Traceback (most recent call
last)<ipython-input-1-bfb20671ab22> in <module>() 6 H=h(t=x+I*y).factor()
7
num=Integer(1)/Integer(2)*(H.derivative(x)/H).derivative(x)+Integer(1)/Integer(2)*(H.derivative(y)/H).derivative(y)---->
8 num.factor()
/home/artal/sage/local/lib/python2.7/site-packages/sage/symbolic/expression.pyx
in sage.symbolic.expression.Expression.factor
(build/cythonized/sage/symbolic/expression.cpp:57759)() 11107 cdef GEx
x 11108 cdef bint b> 11109 if dontfactor or not
self.is_rational_expression(): 11110 m = self._maxima_() 11111
name = m.name()
/home/artal/sage/local/lib/python2.7/site-packages/sage/symbolic/expression.pyx
in sage.symbolic.expression.Expression.is_rational_expression
(build/cythonized/sage/symbolic/expression.cpp:15368)() 2030
False 2031 """-> 2032 return all(part.is_polynomial(v) 2033
for part in (self.numerator(), self.denominator()) 2034
for v in part.variables())
/home/artal/sage/local/lib/python2.7/site-packages/sage/symbolic/expression.pyx
in genexpr (build/cythonized/sage/symbolic/expression.cpp:15110)() 2031
""" 2032 return all(part.is_polynomial(v)-> 2033
for part in (self.numerator(), self.denominator()) 2034
for v in part.variables()) 2035
/home/artal/sage/local/lib/python2.7/site-packages/sage/symbolic/expression.pyx
in sage.symbolic.expression.Expression.numerator
(build/cythonized/sage/symbolic/expression.cpp:48252)() 9377
sig_on() 9378 try:-> 9379 ex = self._gobj.numer()
9380 finally: 9381 sig_off()
ValueError: divide: arguments must be polynomials over the rationals
This error does not happen if I erase some terms of h; and some times it gives
the error only if I did not restart the jupyter notebook. Any ideas? Enrique.
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