Comment on the Hojman conservation quantities in Cosmology
  We comment upon the application of Hojman's method for the determination of
conservation laws in Cosmology, which has been introduced by Capozziello \&
Roshan (Phys. Lett. B 726 (2013) 471 (arXiv:1308.3910)), and has been applied
recently in the cosmological scenario of a nonminimally coupled scalar field by
Paolella \& Capozziello (Phys. Lett. A (2015), in press (arXiv:1503.00098)). We
apply the Ansatz, $\phi\left( t\right) =\phi\left( a\left( t\right) \right) $,
which was introduced by the cited authors for a minimally-coupled scalar field,
and we study the Lie and Noether point symmetries for the reduced equation. We
show that under this Ansatz the unknown function of the model cannot be
constrained by the requirement of the existence of a conservation law and that
the Hojman conservation quantity which arises for the reduced equation is
nothing more than the functional form of the Noether conservation law of
momentum for the free particle. Finally we show that Hojman's method for
Hamiltonian systems, in which the Hamiltonian function is one of the involved
equations of the system, is equivalent with the application of Noether's
Theorem for generalized transformations.
