  Free scalar field theory in the sector with a large number of particles can
be interpreted as bosonic string theory on anti-de Sitter space of vanishing
radius. Different ways of writing the field theory Hamiltonian translate to
different ways of reparametrizing the world-sheet sigma coordinate. Adding a
mass term in the field theory corresponds to cutting off the warped AdS
direction, with cut-off inversely proportional to the mass. The string theory
has neither tachyon, nor critical dimension.
