Often in my studies (economics) the assumption of a "well-behaved" function will be invoked. I don't exactly know what that entails (I think twice continuously differentiability is one of the requirements), nor do I know why this is necessary (though I imagine the why will depend on each case).
Can someone explain it to me, and if there is an explanation of the why as well, I would be grateful. Thanks!
EDIT: To give one example where the term appears, see this Wikipedia entry for utility functions, which says at one point:
In order to simplify calculations,
various assumptions have been made of
utility functions.
CES (constant elasticity of substitution, or
isoelastic) utility
Exponential utility
Quasilinear utility
Homothetic preferences
Most utility functions
used in modeling or theory are
well-behaved. They are usually
monotonic, quasi-concave, continuous
and globally non-satiated.
I might be wrong, but I don't think "well-behaved" means monotonic, quasi-concave, continuous and globally non-satiated. What about twice differentiable?
