TY - JOUR
T1 - Oscillatory attractors
T2 - A new cosmological phase
AU - Bains, Jasdeep S.
AU - Hertzberg, Mark P.
AU - Wilczek, Frank
N1 - Publisher Copyright:
© 2017 IOP Publishing Ltd and Sissa Medialab srl.
PY - 2017/5/4
Y1 - 2017/5/4
N2 - In expanding FRW spacetimes, it is usually the case that homogeneous scalar fields redshift and their amplitudes approach limiting values: Hubble friction usually ensures that the field relaxes to its minimum energy configuration, which is usually a static configuration. Here we discover a class of relativistic scalar field models in which the attractor behavior is the field oscillating indefinitely, with finite amplitude, in an expanding FRW spacetime, despite the presence of Hubble friction. This is an example of spontaneous breaking of time translation symmetry. We find that the effective equation of state of the field has average value ( w)=-1, implying that the field itself could drive an inflationary or dark energy dominated phase. This behavior is reminiscent of ghost condensate models, but in the new models, unlike in the ghost condensate models, the energy-momentum tensor is time dependent, so that these new models embody a more definitive breaking of time translation symmetry. We explore (quantum) fluctuations around the homogeneous background solution, and find that low k-modes can be stable, while high k-modes are typically unstable. We discuss possible interpretations and implications of that instability.
AB - In expanding FRW spacetimes, it is usually the case that homogeneous scalar fields redshift and their amplitudes approach limiting values: Hubble friction usually ensures that the field relaxes to its minimum energy configuration, which is usually a static configuration. Here we discover a class of relativistic scalar field models in which the attractor behavior is the field oscillating indefinitely, with finite amplitude, in an expanding FRW spacetime, despite the presence of Hubble friction. This is an example of spontaneous breaking of time translation symmetry. We find that the effective equation of state of the field has average value ( w)=-1, implying that the field itself could drive an inflationary or dark energy dominated phase. This behavior is reminiscent of ghost condensate models, but in the new models, unlike in the ghost condensate models, the energy-momentum tensor is time dependent, so that these new models embody a more definitive breaking of time translation symmetry. We explore (quantum) fluctuations around the homogeneous background solution, and find that low k-modes can be stable, while high k-modes are typically unstable. We discuss possible interpretations and implications of that instability.
KW - Cosmology of theories beyond the SM
KW - dark energy theory
KW - inflation
KW - physics of the early universe
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U2 - 10.1088/1475-7516/2017/05/011
DO - 10.1088/1475-7516/2017/05/011
M3 - Article
AN - SCOPUS:85035207675
SN - 1475-7516
VL - 2017
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
IS - 5
M1 - 011
ER -