Kavli Affiliate: Tom Melia
| First 5 Authors: David E. Kaplan, Tom Melia, Surjeet Rajendran, ,
| Summary:
In this and a companion paper, we show that quantum field theories with gauge
symmetries permit a broader class of classical dynamics than typically assumed.
In this article, we show that the dynamics extracted from the path integral or
Hamiltonian formulation of general relativity allows for classical states that
do not satisfy the full set of Einstein’s equations. This amounts to loosening
the Hamiltonian and momentum constraints that are imposed on the initial state.
Nevertheless, the quantum theory permits gauge invariant time evolution of
these states. The time evolution of these states is such that at the classical
level the full set of Einstein’s equations would appear to hold, with the
physical effects of these states being attributable to an auxiliary,
covariantly conserved energy-momentum tensor with no internal degrees of
freedom. We derive the generalized Einstein equations for these states and show
that a homogeneous and isotropic initial background state contributes to
expansion identical to cold dark matter. The inhomogeneous components of this
state could source curvature perturbations that grow linearly at linear order.
This auxiliary contribution to Einstein’s equations could have either sign and
thus provide a trivial way to violate the null energy condition, enabling novel
gravitational dynamics such as cosmic bounces and wormholes.
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