26 research outputs found
Generating the Observed Baryon Asymmetry from the Inflaton Field
We propose a mechanism by which the inflaton can generate baryogenesis, by
taking the inflaton to be a complex scalar field with a weakly broken global
symmetry and present a new version of the Affleck-Dine mechanism. The smallness
of the breaking is motivated both by technical naturalness and a requirement
for inflation. We study inflation driven by a quadratic potential for
simplicity and discuss generalizations to other potentials. We compute the
inflationary dynamics and find that a conserved particle number is obtained
towards the end of inflation. We then explain in detail the later decay to
baryons. We present two promising embeddings in particle physics: (i) using
high dimension operators for a gauge singlet; we find this leads to the
observed asymmetry for decay controlled by the ~ grand unified theory scale and
this is precisely the regime where the effective field theory applies. (ii)
using a colored inflaton, which requires small couplings. We also point out two
observational consequences: a possible large scale dipole in the baryon
density, and a striking prediction of isocurvature fluctuations whose amplitude
is found to be just below current limits and potentially detectable in future
data.Comment: 18 pages (double column format), 4 figures, v2: Some clarifications,
more references, updated to resemble version published in PR
Zipping and Unzipping of Cosmic String Loops in Collision
In this paper the collision of two cosmic string loops is studied. After
collision junctions are formed and the loops are entangled. We show that after
their formation the junctions start to unzip and the loops disentangle. This
analysis provides a theoretical understanding of the unzipping effect observed
in numerical simulations of a network of cosmic strings with more than one type
of cosmic strings. The unzipping phenomena have important effects in the
evolution of cosmic string networks when junctions are formed upon collision,
such as in a network of cosmic superstrings.Comment: references added, typos corrected, PRD versio
On the Instability of the Lee-Wick Bounce
It was recently realized that a model constructed from a Lee-Wick type scalar
field theory yields, at the level of homogeneous and isotropic background
cosmology, a bouncing cosmology. However, bouncing cosmologies induced by
pressure-less matter are in general unstable to the addition of relativistic
matter (i.e. radiation). Here we study the possibility of obtaining a bouncing
cosmology if we add radiation coupled to the Lee-Wick scalar field. This
coupling in principle would allow the energy to flow from radiation to matter,
thus providing a drain for the radiation energy. However, we find that it takes
an extremely unlikely fine tuning of the initial phases of the field
configurations for a sufficient amount of radiative energy to flow into matter.
For general initial conditions, the evolution leads to a singularity rather
than a smooth bounce.Comment: 17 pages, 9 figure
Effects of a Thermal Bath of Photons on Embedded String Stability
We compute the corrections of thermal photons on the effective potential for
the linear sigma model of QCD. Since we are interested in temperatures lower
than the confinement temperature, we consider the scalar fields to be out of
equilibrium. Two of the scalar field are uncharged while the other two are
charged under the U(1) gauge symmetry of electromagnetism. We find that the
induced thermal terms in the effective potential can stabilize the embedded
pion string, a string configuration which is unstable in the vacuum. Our
results are applicable in a more general context and demonstrate that embedded
string configurations arising in a wider class of field theories can be
stabilized by thermal effects. Another well-known example of an embedded string
which can be stabilized by thermal effects is the electroweak Z-string. We
discuss the general criteria for thermal stabilization of embedded defects.Comment: 6 pages, formatting changed, a few typos correcte
Lensing and CMB Anisotropies by Cosmic Strings at a Junction
The metric around straight arbitrarily-oriented cosmic strings forming a
stationary junction is obtained at the linearized level. It is shown that the
geometry is flat. The sum rules for lensing by this configuration and the
anisotropies of the CMB are obtained.Comment: 17 pages, 2 figure
A Radiation Bounce from the Lee-Wick Construction?
It was recently realized that matter modeled by the scalar field sector of
the Lee-Wick Standard Model yields, in the context of a homogeneous and
isotropic cosmological background, a bouncing cosmology. However, bouncing
cosmologies induced by pressure-less matter are in general unstable to the
addition of relativistic matter (i.e. radiation). Here we study the possibility
of obtaining a bouncing cosmology if we add not only radiation, but also its
Lee-Wick partner, to the matter sector. We find that, in general, no bounce
occurs. The only way to obtain a bounce is to choose initial conditions with
very special phases of the radiation field and its Lee-Wick partner.Comment: 11 page