Related papers: Improved estimation of radiated axions from cosmol…

String theory suggests the simultaneous presence of many ultralight axions possibly populating each decade of mass down to the Hubble scale 10^-33eV. Conversely the presence of such a plenitude of axions (an "axiverse") would be evidence…

We calculate the contribution of cosmic strings arising from a phase transition in the early universe, or cosmic superstrings arising from brane inflation, to the cosmic 21 cm power spectrum at redshifts z > 30. Future experiments can…

We study the cosmology of axions in the post-inflationary scenario, where random initial conditions and the ensuing string-domain-wall network generate an isocurvature power spectrum. Axions radiated from strings behave as warm, wave-like…

In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter F_a is several orders of…

Axions, periodic scalar fields coupled to gauge fields through the instanton density, have a rich variety of higher-form global symmetries. These include a two-form global symmetry, which measures the charge of axion strings. As we review,…

We study early and late time signatures of both QCD axion strings and hyperlight axion strings (axiverse strings). We focus on charge deposition onto axion strings from electromagnetic fields and subsequent novel neutralizing mechanisms due…

String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. In this paper, we study conditions on the string compactifications under which axion quintessence can happen. For sufficiently…

Generic cosmological models in non-critical string theory have a time-dependent dilaton background at a late epoch. The cosmological deceleration parameter Q_0 is given by the square of the string coupling, g_s^2, up to a negative sign.…

In the simplest picture, the masses of string axions populating the axiverse depend on two parameters: the supersymmetry breaking scale $M_{\rm susy}$ and the action $S$ of the string instantons responsible for breaking the axion shift…

Inspired by the string axiverse idea, it has been suggested that the recent transition from decelerated to accelerated cosmic expansion is driven by an axion-like quintessence field with a sub-Planckian decay constant. The scenario requires…

We have studied the cosmological evolution of domain wall networks in two, three and four spatial dimensions using high-resolution field theory simulations. The dynamical range and number of our simulations is larger than in previous works,…

We use our model of the small scale structure on cosmic strings to develop further the result of Siemens, Olum, and Vilenkin that the gravitational radiation length scale on cosmic strings is smaller than the previously assumed $\Gamma G\mu…

We simultaneously study gravitational waves (GWs) and free axions emitted from axionic string-wall networks in the early universe using advanced 3D lattice simulations. Our simulations start before the Peccei-Quinn phase transition and end…

In this paper we present the results of numerical simulations intended to study the behavior of non-Abelian cosmic strings networks. In particular we are interested in discussing the variations in the asymptotic behavior of the system as we…

We review the current status of axion cosmology in the light of recent work. We conclude that in the standard scenario, in which a global string network forms at the Peccei-Quinn phase transition, the largest contribution to the axion…

We present the first field-theoretic calculations of the contribution made by cosmic strings to the temperature power spectrum of the cosmic microwave background (CMB). Unlike previous work, in which strings were modeled as idealized…

We consider the cosmological consequences of a network of superconducting cosmic strings. For strong enough current the period of friction domination never ends. Instead a plasma scaling solution is reached. We demonstrate that this gives…

The string axion may provide the most attractive solution to the strong CP problem in QCD. However, the axion energy density easily exceeds the dark matter density in the present universe due to a large decay constant around $10^{16}$ GeV,…

A cosmic string network created during an inflationary stage in the early Universe - here defined as i-string network - is expected to enter a transient stretching regime during inflation, in which its characteristic length is stretched to…

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration has recently reported strong evidence for a stochastic process affecting the 12.5 yr dataset of pulsar timing residuals. We show that the signal can…