  A constraint of vanishing energy-momentum tensor is motivated by a variety of
perspectives on quantum gravity. We demonstrate in a concrete example how this
constraint leads to a metric-independent theory in which quantum gravity
emerges as a nonperturbative artifact of regularization-scale physics. We
analyze a scalar theory similar to the Dirac-Born-Infeld (DBI) theory with
vanishing gauge fields, with the DBI Lagrangian modulated by a scalar
potential. In the limit of a large number of scalars, we explicitly demonstrate
the existence of a composite massless spin-2 graviton in the spectrum that
couples to matter as in Einstein gravity. We comment on the cosmological
constant problem and the generalization to theories with fermions and gauge
fields.
