Related papers: Gravitational wave generation in loop quantum cosm…
Primordial gravitational waves are amplified during eras when their wavelengths are pushed outside the cosmological horizon. This occurs in both inflationary and ``pre-big-bang'' or ``bounce'' cosmologies. The spectrum is expressed as a…
Whether or not the primordial gravitational wave (GW) produced during inflation is sufficiently strong to be observable, GWs are necessarily produced from the primordial curvature perturbations in the second order of perturbation. The…
Appearance of cosmic strings in the early Universe is a common manifestation of new physics typically linked to some high energy scale. In this paper, we discuss a different situation, where a model underlying cosmic string formation is…
The primordial spectrum of fluctuations may present a large peak as a result of enhancing features during inflation. This may include, but is not limited to, bumps in the inflaton's potential, phases of ultra-slow-roll or turns in…
We study gravitational waves generated by the cosmological magnetic fields induced via bubble collisions during the electroweak (EW) and QCD phase transitions. The magnetic field generation mechanisms considered here are based on the use of…
In Loop Quantum Gravity mathematically rigorous models of full quantum gravity were proposed. In this paper we study a cosmological sector of one of the models describing quantum gravity with positive cosmological constant coupled to…
We discuss effects of loss of coherence in low energy quantum systems caused by or related to gravitation, referred to as gravitational decoherence. These effects, resulting from random metric fluctuations, for instance, promise to be…
We study the quantum-mechanical generation of gravitational waves during inflation on a brane embedded in a five-dimensional anti-de Sitter bulk. To make the problem well-posed, we consider the setup in which both initial and final phases…
Recent cosmological observations indicate the existence of extra light species, i.e., dark radiation. In this paper we show that signatures of the dark radiation are imprinted in the spectrum of inflationary gravitational waves. If the dark…
In this paper, following the previous study, we evaluate the spectrum of gravitational wave background generated by domain walls which are produced if some discrete symmetry is spontaneously broken in the early universe. We apply two…
We study gravitational wave (GW) production in strongly supercooled cosmological phase transitions, taking particular care of models featuring a complex scalar field with a U$(1)$ symmetric potential. We perform lattice simulations of…
It is sometimes argued that observation of tensor modes from inflation would provide the first evidence for quantum gravity. However, in the usual inflationary formalism, also the scalar modes involve quantised metric perturbations. We…
We reconsider the gravitational wave spectrum induced by scalar perturbations in spatially flat Friedmann-Lema\^itre-Robertson-Walker spacetimes, focusing on the matter- and $\Lambda$-dominated epochs. During matter domination, sub-horizon…
It is shown that rotational cosmological perturbations can be generated in the early Universe, similarly to gravitational waves. The generating mechanism is quantum-mechanical in its nature, and the created perturbations should now be…
Inflation generates gravitational waves, which may be observable in the low multipoles of the cosmic microwave background (cmb) anisotropy but only if the inflaton field variation is at least of order the Planck scale. Such a large…
Gravitational wave (GW) astrophysics is entering a multi-band era with upcoming GW detectors, enabling detailed mapping of the stochastic GW background across vast frequencies. We highlight this potential via a new physics scenario: hybrid…
The standard model of cosmology assumes a homogeneous and isotropic universe that undergoes a period of exponential expansion very early on, named inflation. This stretches quantum fluctuations from the onset of inflation to cosmological…
Gravitational waves provide a unique window into gravity, cosmology, and high-energy physics, enabling the exploration of fundamental phenomena across a wide range of scales. This review presents a coherent and pedagogical framework that…
We study the production of gravitational waves from cosmic domain walls created during phase transition in the early universe. We investigate the process of formation and evolution of domain walls by running three dimensional lattice…
Using techniques from loop quantum gravity, the standard theory of cosmological perturbations was recently generalized to encompass the Planck era. We now apply this framework to explore pre-inflationary dynamics. The framework enables us…