a field-theory motivated approach to computer algebra

## simplify

Simplify the scalar part of an expression.
When expressions (or sub-expressions) involve scalars, simplification of such expressions can be 'outsourced' to an external scalar computer algebra system, at present either Sympy or Mathematica. The simplify algorithm finds all scalar sub-expressions and runs the simplification algorithm of one of these systems on them.
ex:= (\sin{x}**2 + \cos{x}**2) A_{m};
$$\displaystyle{}\left({\left(\sin{x}\right)}^{2}+{\left(\cos{x}\right)}^{2}\right) A_{m}$$
((\sin(x))**2 + (\cos(x))**2) A_{m}
simplify(_);
$$\displaystyle{}A_{m}$$
A_{m}
By default it will use the Sympy backend, but if you have compiled Cadabra on a system which has Mathematica installed, you can also switch it to use Mathematica instead, by using
kernel(scalar_backend="mathematica")