Related papers: Axion String Constraints
Theories in which the Peccei-Quinn phase transition occurs after inflation tend to suffer from problematic domain walls. One possible solution involves a small, explicit breaking ot the symmetry. But this raises other potential issues. We…
We investigate two cosmological axion problems (isocurvature fluctuations and domain-wall formation) in chaotic inflationary universe. It is believed that these problems are solved if potential for the Peccei-Quinn scalar field is very…
We develop an analytical model to study the production spectrum of loops in the cosmic string network. In the scaling regime, we find two different scales corresponding to large (one order below horizon) and small (few orders below horizon)…
We present the properties of a cosmic superstring network in the scenario of flux compactification. An infinite family of strings, the (p,q)-strings, are allowed to exist. The flux compactification leads to a string tension that is periodic…
Cosmic strings, a hot subject in the 1980's and early 1990's, lost its appeal when it was found that it leads to inconsistencies in the power spectrum of the measured cosmic microwave background temperature anisotropies. However,…
Cosmic strings are one-dimensional topological defects which could have been formed in the early stages of our Universe. They triggered a lot of interest, mainly for their cosmological implications: they could offer an alternative to…
Particle emission, in addition to gravitational radiation from cosmic string loops, affects the resulting loop distribution and hence the corresponding observational consequences of cosmic strings. Here we focus on two models in which loops…
Gravitational wave signatures from cosmic strings are analyzed numerically. Cosmic string networks form during phase transistions in the early universe and these networks of long cosmic strings break into loops that radiate energy in the…
We study Goldstone boson (or axion) radiation from global $U(1)$-strings making direct quantitative comparisons between numerical scalar field theory simulations and linearized analytic calculations in the dual antisymmetric tensor…
Cosmological constraints on moduli, whose coupling to matter is stronger than Planck mass suppressed coupling, are derived. In particular, moduli are considered to be produced by oscillating loops of cosmic strings and constraints are…
We evaluate the efficiency of axion production from spatially random initial conditions in the axion field, so a network of axionic strings is present. For the first time, we perform numerical simulations which fully account for the large…
Cosmic strings are linear concentrations of energy that form whenever phase transitions in the early universe break axial symmetries as originally shown by Kibble. They are the result of frustrated order in the quantum fields responsible…
We study the evolution of abelian-Higgs string networks in numerical simulations. These are compared against a modified velocity-dependent one scale model for cosmic string network evolution. This incorporates the contributions of loop…
If the axion exists and if the initial axion field value is uncorrelated at causally disconnected points, then it should be possible to predict the efficiency of cosmological axion production, relating the axionic dark matter density to the…
I report recent studies on the evolution of perturbations in the context of the ``pre-big-bang" scenario typical of string cosmology, with emphasis on the formation of a stochastic background of relic photons and gravitons, and its possible…
The dynamics of saxion in a supersymmetric axion model and its effect on the axion production is studied in detail. We find that the axion production is very efficient when the saxion oscillation amplitude is much larger than the…
If the QCD axion solves the strong CP problem then light axion-like-particles (ALPs) are expected to be ubiquitous in string theory - the string axiverse. Such ALPs can be the QCD axion and constitute dark matter (DM) or radiation,…
It is difficult to construct a post-inflation QCD axion model that solves the axion quality problem (and hence the Strong CP problem) without introducing a cosmological disaster. In a post-inflation axion model, the axion field value is…
Using recent simulation results, we provide the mass and speed spectrum of cosmic string loops. This is the quantity of primary interest for many phenomenological signatures of cosmic strings, and it can be accurately predicted using…
A brief discussion is presented assessing the achievements and challenges of string phenomenology: the subfield dedicated to study the potential for string theory to make contact with particle physics and cosmology. Building from the well…