6 research outputs found
Radiation and Relaxation of Oscillons
We study oscillons, extremely long-lived localized oscillations of a scalar
field, with three different potentials: quartic, sine-Gordon model and in a new
class of convex potentials. We use an absorbing boundary at the end of the
lattice to remove emitted radiation. The energy and the frequency of an
oscillon evolve in time and are well fitted by a constant component and a
decaying, radiative part obeying a power law as a function time. The power
spectra of the emitted radiation show several distinct frequency peaks where
oscillons release energy. In two dimensions, and with suitable initial
conditions, oscillons do not decay within the range of the simulations, which
in quartic theory reach 10^8 time units. While it is known that oscillons in
three-dimensional quartic theory and sine-Gordon model decay relatively
quickly, we observe a surprising persistence of the oscillons in the convex
potential with no sign of demise up to 10^7 time units. This leads us to
speculate that an oscillon in such a potential could actually live infinitely
long both in two and three dimensions.Comment: 16 pages, 28 eps figure
Semilocal Cosmic String Networks
We report on a large scale numerical study of networks of semilocal cosmic
strings in flat space in the parameter regime in which they are perturbatively
stable. We find a population of segments with an exponential length
distribution and indications of a scaling network without significant loop
formation. Very deep in the stability regime strings of superhorizon size grow
rapidly and ``percolate'' through the box. We believe these should lead at late
times to a population of infinite strings similar to topologically stable
strings. However, the strings are very light; scalar gradients dominate the
energy density and the network has thus a global texture-like signature. As a
result, the observational constraints, at least from the temperature power
spectrum of the CMB, on models predicting semilocal strings, should be closer
to those on global textures or monopoles, rather than on topologically stable
gauged cosmic strings.Comment: 5 pages, 3 figures; extended discussion about initial conditions;
matches published versio
Numerical Investigations of Oscillons in 2 Dimensions
Oscillons, extremely long-living localized oscillations of a scalar field,
are studied in theories with quartic and sine-Gordon potentials in two spatial
dimensions. We present qualitative results concentrating largely on a study in
frequency space via Fourier analysis of oscillations. Oscillations take place
at a fundamental frequency just below the threshold for the production of
radiation, with exponentially suppressed harmonics. The time evolution of the
oscillation frequency points indirectly to a life time of at least 10 million
oscillations. We study also elliptical perturbations of the oscillon, which are
shown to decay. We finish by presenting results for boosted and collided
oscillons, which point to a surprising persistence and soliton-like behaviour.Comment: Matches the published version (12 pages, 34 figures
Oscillons and Domain Walls
Oscillons, extremely long-lived localized oscillations of a scalar field, are
shown to be produced by evolving domain wall networks in quartic theory in two
spatial dimensions. We study the oscillons in frequency space using the
classical spectral function at zero momentum, and obtain approximate
information of their velocity distribution. In order to gain some insight onto
the dilute oscillon 'gas' produced by the domain walls, we prepare a denser gas
by filling the simulation volume with oscillons boosted in random directions.
We finish the study by revisiting collisions between oscillons and between an
oscillon and a domain wall, showing that in the latter case they can pass
straight through with minimal distortion.Comment: 11 pages, 28 eps figure