On a variant of Hardy inequality between weighted Orlicz spaces
Let M be an N-function satisfying the $\Delta_2$- condition, let $\omega, \vp$ be two other functions, $\omega\ge 0$. We study Hardy-type inequalities \[ \int_{\rp} M(\omega (x)|u(x)|) {\rm exp}(-\vp (x))dx \le C\int_{\rp} M(|u'(x)|) {\rm exp}(-\vp (x))dx, \] where $u$ belongs to some dilation invariant set ${\cal R}$ contained in the space of locally absolutely continuous functions. We give sufficient conditions the triple $(\omega,\vp,M)$ must satisfy in order to have such inequalities valid for $u$ from a given set ${\cal R}$. The set ${\cal R}$ can be smaller than the set of Hardy transforms. Bounds for constants, retrieving classical Hardy inequalities with best constants, are also given.