Phantom Dark Energy with a Bounded Hamiltonian [CEA]

Motivated by the apparent discrepancy between Cosmic Microwave Background measurements of the Hubble constant and measurements from Type-Ia supernovae, we construct a model for Dark Energy with equation of state $w = p / \rho < -1$, violating the Null Energy Condition. Naive canonical models of so-called “Phantom” Dark Energy require a negative scalar kinetic term, resulting in a Hamiltonian unbounded from below and associated vacuum instability. We construct a scalar field model for Dark Energy with $w < -1$, which nonetheless has a Hamiltonian bounded from below. We demonstrate that the solution is a cosmological attractor, and the homogeneous solution is therefore a viable model for cosmic Dark Energy with Hubble parameter increasing in time, as suggested by data. Issues, however, remain: despite having a bounded Hamiltonian, the model considered here nonetheless still suffers from the presence of a classical gradient instability.

G. Barenboim and W. Kinney
Fri, 13 Oct 17
48/56