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

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

Nonperturbative dynamics of reheating after inflation: A review

Our understanding of the state of the universe between the end of inflation and big bang nucleosynthesis (BBN) is incomplete. The dynamics at the end of inflation are rich and a potential source of observational signatures. Reheating, the energy transfer between the inflaton and Standard Model fields (possibly through intermediaries) and their subsequent thermalization, can provide clues to how inflation fits in with known high-energy physics. We provide an overview of our current understanding of the nonperturbative, nonlinear dynamics at the end of inflation, some salient features of realistic particle physics models of reheating, and how the universe reaches a thermal state before BBN. In addition, we review the analytical and numerical tools available in the literature to study preheating and reheating and discuss potential observational signatures from this fascinating era.Kavli Institute for Cosmology, CambridgeUnited States. Dept. of Energy (Contract Number DE-SC00012567)Massachusetts Institute of Technology. Center for Theoretical Physic

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