  We study the classical analog of the quantum metric tensor and its scalar
curvature for two well-known quantum physics models. First, we analyze the
geometry of the parameter space for the Dicke model with the aid of the
classical and quantum metrics and find that, in the thermodynamic limit, they
have the same divergent behavior near the quantum phase transition, as opposed
to their corresponding scalar curvatures which are not divergent there. On the
contrary, under resonance conditions, both scalar curvatures exhibit a
divergence at the critical point. Second, we present the classical and quantum
metrics for the Lipkin-Meshkov-Glick model in the thermodynamic limit and find
a perfect agreement between them. We also show that the scalar curvature is
only defined on one of the system's phases and that it approaches a negative
constant value. Finally, we carry out a numerical analysis for the system's
finite sizes, which clearly shows the precursors of the quantum phase
transition in the metric and its scalar curvature and allows their
characterization as functions of the parameters and of the system's size.
