def from_riemann(cls, riemann, parent_metric=None):
"""
Get Ricci Tensor calculated from Riemann Tensor
Parameters
----------
riemann : ~einsteinpy.symbolic.riemann.RiemannCurvatureTensor
Riemann Tensor
parent_metric : ~einsteinpy.symbolic.metric.MetricTensor or None
Corresponding Metric for the Ricci Tensor.
None if it should inherit the Parent Metric of Riemann Tensor.
Defaults to None.
"""
if not riemann.config == "ulll":
riemann = riemann.change_config(newconfig="ulll",
metric=parent_metric)
if parent_metric is None:
parent_metric = riemann.parent_metric
return cls(
simplify_sympy_array(
sympy.tensorcontraction(riemann.tensor(), (0, 2))),
riemann.syms,
config="ll",
parent_metric=parent_metric,
)
def from_riccitensor(cls, riccitensor, parent_metric=None):
"""
Get Ricci Scalar calculated from Ricci Tensor
Parameters
----------
riccitensor: ~einsteinpy.symbolic.metric.RicciTensor
Ricci Tensor
parent_metric : ~einsteinpy.symbolic.metric.MetricTensor or None
Corresponding Metric for the Ricci Scalar.
Defaults to None.
"""
if not riccitensor.config == "ul":
riccitensor = riccitensor.change_config(newconfig="ul",
metric=parent_metric)
if parent_metric is None:
parent_metric = riccitensor.parent_metric
ricci_scalar = tensorcontraction(riccitensor.tensor(), (0, 1))
return cls(
simplify_sympy_array(ricci_scalar),
riccitensor.syms,
parent_metric=parent_metric,
)
def simplify(self, set_self=True):
"""
Returns a simplified Tensor
Parameters
----------
set_self : bool
Replaces the tensor contained the class with its simplified version, if ``True``.
Defaults to ``True``.
Returns
-------
~einsteinpy.symbolic.tensor.Tensor
Simplified Tensor
"""
if set_self:
self.arr = simplify_sympy_array(self.tensor())
return self.tensor()
# return sympy.simplify(self.tensor()) # this used to work with older sympy versions
return simplify_sympy_array(self.tensor())