Generation of Coherent Structures After Cosmic Inflation
  We investigate the nonlinear dynamics of hybrid inflation models, which are
characterized by two real scalar fields interacting quadratically. We start by
solving numerically the coupled Klein-Gordon equations in static Minkowski
spacetime, searching for possible coherent structures. We find long-lived,
localized configurations, which we identify as a new kind of oscillon. We
demonstrate that these two-field oscillons allow for "excited" states with much
longer lifetimes than those found in previous studies of single-field
oscillons. We then solve the coupled field equations in an expanding
Friedmann-Robertson-Walker spacetime, finding that as the field responsible for
inflating the Universe rolls down to oscillate about its minimum, it triggers
the formation of long-lived two-field oscillons, which can contribute up to 20%
of the total energy density of the Universe. We show that these oscillons
emerge for a wide range of parameters consistent with WMAP 7-year data. These
objects contain total energy of about 25*10^20 GeV, localized in a region of
approximate radius 6*10^-26 cm. We argue that these structures could have
played a key role during the reheating of the Universe.
