Related papers: Density perturbations in braneworld cosmology and …
We analyse the fate of density perturbation in the Brans-Dicke Theory, giving a general classification of the solutions of the perturbed equations when the scale factor of the background evolves as a power law. We study with details the…
We calculate the spectral distortions from Hawking evaporation of primordial black holes before the epoch of recombination, taking into account emission of all standard model particles, including quark and gluons, and evolving the resulting…
In this paper we present a gauge-invariant formalism for perturbations of the brane-world model developed by the author, A. Ishibashi and O. Seto recently, and analyze the behavior of cosmological perturbations in a spatially flat expanding…
We investigate the evolution of the linear cosmological perturbations in f(R) gravity, an alternative to dark energy for explaining the late-time cosmic acceleration. We numerically calculate the early-time evolution with an approximation…
Based on the formulated and proven similarity properties of cosmological models based on a statistical system of degenerate scalarly charged fermions, as well as the previously identified mechanism of scalar-gravitational instability of…
In this article we provide a new closed relationship between cosmic abundance of primordial gravitational waves and primordial blackholes originated from initial inflationary perturbations for inflection-point models of inflation where…
We construct a concrete model of Horndeski bounce with strong gravity in the past. Within this model we show that the correct spectra of cosmological perturbations may be generated at early contracting epoch, with mild fine-tuning ensuring…
The cross sections of black holes with tidal charge predicted in the context of the Randall--Sundrum brane-world scenario are computed considering the massless scalar field. Results obtained for black holes with different tidal-charge…
In recent years it has become apparent that intriguing phenomenology exists at the threshold of black hole formation in a large class of general relativistic collapse models. This phenomenology, which includes scaling, self-similarity and…
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…
We provide a simple but robust argument that primordial black hole (PBH) production generically does {\em not} exceed astrophysical bounds during the resonant preheating phase after inflation. This conclusion is supported by fully nonlinear…
Previously defined covariant and gauge-invariant perturbation variables, representing, e.g., the fractional spatial energy density gradient on hypersurfaces of constant expansion, are used to simplify the linear perturbation analysis of a…
We investigate the production of primordial black holes (PBHs) and scalar-induced gravitational waves (GWs) for cosmological models in the Horndeski theory of gravity. The cosmological models of our interest incorporate the derivative…
The general motion of spinning test particles to the leading order approximation of spin in the brane-world spacetime is investigated. Analytical integrations for the equations of motion and linear shifts in orbital frequency are obtained.…
Precision measurements of anisotropies in the cosmic microwave background and of the clustering of large-scale structure have supposedly confirmed that the primordial density perturbation has a (nearly) scale-invariant spectrum. However…
For primordial black holes (PBHs) to form a considerable fraction of cold dark matter, the required amplitude of primordial scalar perturbations is quite large ($P_{\zeta}(k) \sim 10^{-2}$) if PBH is formed in radiation epoch. In alternate…
The properties of primordial curvature perturbations on small scales are still unknown while those on large scales have been well probed by the observations of the cosmic microwave background anisotropies and the large scale structure. In…
Primordial black holes (PBHs) can form in the early Universe, for instance during radiation domination, from the collapse of large-amplitude density perturbations shortly after horizon re-entry. This mechanism establishes an approximate…
We investigate cosmological scenarios containing one canonical scalar field with an exponential potential in the context of bouncing models, where the bounce happens due to quantum cosmological effects. The only possible bouncing solutions…
This work discusses scalar-tensor theories of gravity, with a focus on the Brans-Dicke subclass, and one that also takes note of the latter's equivalence with $f(R)$ gravitation theories. A 1+3 covariant formalism is used in this case to…