5 research outputs found
Cosmic Strings Collision in Cosmological Backgrounds
The collisions of cosmic strings loops and the dynamics of junctions
formations in expanding backgrounds are studied. The key parameter controlling
the dynamics of junctions formation, the cosmic strings zipping and unzipping
is the relative size of the loops compared to the Hubble expansion rate at the
time of collision. We study analytically and numerically these processes for
large super-horizon size loops, for small sub-horizon size loops as well as for
loops with the radii comparable to the Hubble expansion rate at the time of
collision.Comment: 24 pages, 13 figure
Fermionic Tachyons as a Source of Dark Energy
A model for the universe on the basis of a self interacting fermionic tachyon
field is investigated here. It is shown that, devising a self interaction
potential of a proper form, the fermionic tachyon field is capable of producing
an accelerating expansion that at late time tends to a constant value which is
in consistence with the cosmological constant. This way the introduced
fermionic tachyon field can be interpreted as the source of dark energy.Comment: 5 figure
Fields Annihilation and Particles Creation in DBI inflation
We consider a model of DBI inflation where two stacks of mobile branes are
moving ultra relativistically in a warped throat. The stack closer to the tip
of the throat is annihilated with the background anti-branes while inflation
proceeds by the second stack. The effects of branes annihilation and particles
creation during DBI inflation on the curvature perturbations power spectrum and
the scalar spectral index are studied. We show that for super-horizon scales,
modes which are outside the sound horizon at the time of branes collision, the
spectral index has a shift to blue spectrum compared to the standard DBI
inflation. For small scales the power spectrum approaches to its background DBI
inflation value with the decaying superimposed oscillatory modulations.Comment: First revision: minor changes, the background spectral index is
corrected, new references are added. Second revision: minor changes, new
references are added, accepted for publication in JCA