Related papers: Stochastic evolution of scalar fields with continu…
An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant $\Lambda$ should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary…
If the expansion of the early Universe was not close to de Sitter, the statistical imprints of the primordial density perturbation on the cosmic microwave background can be quite different from those derived in slow-roll inflation. In this…
The revision of the Author's results with respect to possibility of existence of the so-called Euclidian cycles in cosmological evolution of a system of Higgs scalar fields has been performed. The assumption of non-negativity of the…
Stochastic effects in multi-field inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inflationary $e$-folds. Solving the resulting partial…
We point out that a light scalaron dynamically emerges if scalar fields have a sizable non-minimal coupling to the Ricci scalar as in the Higgs inflation model. We support this claim in two ways. One is based on the renormalization group…
A phenomenological model of an ideal fluid with a scalar charge is formulated, on the basis of which a model with a neutral fluid and a vacuum-field model with rules of transition between them are constructed. A qualitative analysis of the…
This work explores the possibility of inflation in a scale-symmetric extension of the Standard Model Higgs sector, where the Higgs field $\phi_1$ is coupled to a singlet scalar, the dilaton $\phi_0$. The two-scalar theory is formulated…
Quantization implies independent degrees of freedom that do not appear in the classical theory, given by fluctuations, correlations, and higher moments of a state. A systematic derivation of the resulting dynamical systems is presented here…
The large-scale magnetic fields arising from the quantum mechanical fluctuations of the hypercharge are investigated when the evolution of the gauge coupling is combined with a sufficiently long inflationary stage. In this framework the…
To understand mechanisms leading to inflation and late acceleration of the Universe it is important to see how one or a set of quantum fields may evolve such that the classical energy-momentum tensor behave similar to a cosmological…
We derive an uncertainty relation for the energy density and pressure of a quantum scalar field in a time-dependent, homogeneous and isotropic, classical background, which implies the existence of large fluctuations comparable to their…
Recently a Hamiltonian formulation for the evolution of the universe dominated by multiple oscillatory scalar fields was developed by the present author and was applied to the investigation of the evolution of cosmological perturbations on…
In new Higgs inflation the Higgs kinetic terms are non-minimally coupled to the Einstein tensor, allowing the Higgs field to play the role of the inflaton. The new interaction is non-renormalizable, and the model only describes physics…
We consider the effect of a period of inflation with a high energy density upon the stability of the Higgs potential in the early universe. The recent measurement of a large tensor-to-scalar ratio, $r_T \sim 0.16$, by the BICEP-2 experiment…
If the inflaton is a heavy scalar field, it may equilibrate slower than some other degrees of freedom, e.g. non-Abelian gauge bosons. In this case, perturbations in the inflaton field and in a thermal plasma coexist from a given moment…
Most high-energy constructions that realise a phase of cosmic inflation contain many degrees of freedom. Yet, cosmological observations are all consistent with single-field embeddings. We show how volume selection effects explain this…
Cosmological $\alpha$-attractors stand out as particularly compelling models to describe inflation in the very early universe, naturally meeting tight observational bounds from cosmic microwave background (CMB) experiments. We investigate…
We study the entanglement entropy resulting from tracing out local degrees of freedom of a quantum scalar field in an expanding universe. It is known that when field modes become superhorizon during inflation they evolve to increasingly…
The evolution of gauge invariant second-order scalar perturbations in a general single field inflationary scenario are presented. Different second order gauge invariant expressions for the curvature are considered. We evaluate…
For variable gravity models the strength of gravity, as measured by Newton's ``constant'' or the Planck mass, depends on the value of a scalar field, the cosmon. We discuss two simple four-parameter models with a quadratic or constant…