  The crucial property of particle colliders is their ability to convert (e.g.
electrical) energy into the mass of heavy particles. We have become used to the
extremely low efficiency of this conversion and the severe limitations on the
mass scale of heavy particles which can be reached. In view of this situation,
it appears reasonable to ask whether a perfect conversion machine of this type
(a perfect `collider') exists even in principle and whether there is a highest
mass scale which can be reached by such a machine. It turns out that, with a
number of assumptions, such a machine is conceivable in a world with a
strongly-coupled, approximately scale invariant 4d field theory with 5d gravity
dual. This machine can be realized as a 5d tower built on the IR brane (in
Randall-Sundrum model language). Transporting mass to the tip of this tower is,
under certain conditions, equivalent to producing heavy point-like 4d
particles. Hence, this can be thought of as a perfect `collider'. In the
simple, `pure Randall-Sundrum setting' that we analyse, this machine can only
reach a certain maximal energy scale, which falls as the gravity-dual of the 4d
QFT approaches the strong coupling domain. On these grounds, one might expect
that a no-go theorem (in the spirit of that of Carnot for the conversion of
heat into work) exists for weakly-coupled QFTs. We end with some speculations
about collider efficiencies at weak coupling, involving possibly the concept of
entanglement entropy.
