Gravity from spontaneous Lorentz violation
  We investigate a class of theories involving a symmetric two-tensor field in
Minkowski spacetime with a potential triggering spontaneous violation of
Lorentz symmetry. The resulting massless Nambu-Goldstone modes are shown to
obey the linearized Einstein equations in a fixed gauge. Imposing
self-consistent coupling to the energy-momentum tensor constrains the potential
for the Lorentz violation. The nonlinear theory generated from the
self-consistent bootstrap is an alternative theory of gravity, containing
kinetic and potential terms along with a matter coupling. At energies small
compared to the Planck scale, the theory contains general relativity, with the
Riemann-spacetime metric constructed as a combination of the two-tensor field
and the Minkowski metric. At high energies, the structure of the theory is
qualitatively different from general relativity. Observable effects can arise
in suitable gravitational experiments.
