On quantum corrections to geodesics in de-Sitter spacetime

We find a coordinate-independent wave-packet solution of the massive Klein-Gordon equation with the conformal coupling to gravity in the de-Sitter universe. This solution can locally be represented through the superposition of positive-frequency plane waves at any space-time point, assuming that the scalar-field mass $M$ is much bigger than the de-Sitter Hubble constant $H$. The solution is also shown to be related to the two-point function in the de-Sitter quantum vacuum. Moreover, we study the wave-packet propagation over cosmological times, depending on the ratio of $M$ and $H$. In doing so, we find that this wave packet propagates like a point-like particle of the same mass if $M \ggg H$, but, if otherwise, the wave packet behaves highly non-classically.Comment: final version published in Eur. Phys. J.

Mechanisms of Microwave Absorption in Carbon Compounds from Shungite

According to SEM, X-ray phase analysis, Raman scattering data features of nanostructural changes in shungite carbon structure were found when processing shungite in 52 % hydrofluoric acid. It is found that conductivity increases up to the values of electrical graphite and absorption of microwave radiation also increases at frequencies up to 40 GHz, which, along with dielectric losses, is due to intense processes of both scattering at laminar carbon structures and absorption of electromagnetic energy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3365

Surface-enhanced optical third-harmonic generation in Ag island films

Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than two orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a 2-D random array of silver nanoparticles.Comment: 4 pages, 2 figure

Vector-field model with compensated cosmological constant and radiation-dominated FRW phase

A special model of a massless vector-field is presented, which has an extra modified-gravity-type interaction term in the action. The cosmology of the model is studied with standard noninteracting relativistic matter added. It is found that this cosmology can have an early phase where the vector-field starts to compensate a (Planck-scale) cosmological constant and a late Friedmann-Robertson-Walker (FRW) phase where the relativistic-matter energy density dominates the dynamic vacuum energy density.Comment: 12 pages, v5: published version (but with a small change in the Note Added