+ This is buggy right now::
+
+ sage: J = eja_ln(5)
+ sage: x = J.random_element()
+ sage: x.matrix()*x.vector() == (x**2).vector() # works
+ True
+ sage: u = x.subalgebra_generated_by().random_element()
+ sage: u.matrix()*u.vector() == (u**2).vector() # busted
+ True
+