Let PREFIX-FREE = {$\langle G\rangle$ | G is a CFG where L(G) is prefix-free}. Prove PREFIX-FREE is undecidable.
I've seen several solutions to PREFIX-FREE by reduction to PCP (here).
In my course we've treated PCP and mPCP superficially (not an essential part of the my course's program) and therefore I'm not able to create a reduction with it.
It is possible to create a valid reduction to $A_{TM}$? I was stuck for a but so I need to know if a reduction like that is possibile. I don't need a clue I really need to have the reduction (or the bone of that) in order to to help me understand problems of this type (reductions with CFLs that do not use PCP).