355 research outputs found
From inflation to dark energy in the non-minimal modified gravity
We consider the modified gravity non-minimally coupled with matter Lagrangian
for the description of early-time and late-time universe. Such ()
gravity in the absence of non-minimal coupling is viable theory which passes
the local tests and reproduces the CDM era. For qualitatively similar
choice of non-minimal gravitational coupling function it is shown that the
unified description of early-time inflation and late-time cosmic acceleration
is possible. It is interesting that matter (scalar) which supports the
inflationary era is gravitationally screened at late times. Hence, it may be
effectively invisible at current universe.Comment: LaTeX file, 10 pages, based on the talk given by S.D. Odintsov at
ICGA8 conference, Nara, Japa
On the Definition of Effective Permittivity and Permeability For Thin Composite Layers
The problem of definition of effective material parameters (permittivity and
permeability) for composite layers containing only one-two parallel arrays of
complex-shaped inclusions is discussed. Such structures are of high importance
for the design of novel metamaterials, where the realizable layers quite often
have only one or two layers of particles across the sample thickness. Effective
parameters which describe the averaged induced polarizations are introduced. As
an explicit example, we develop an analytical model suitable for calculation of
the effective material parameters and
for double arrays of electrically small electrically polarizable scatterers.
Electric and magnetic dipole moments induced in the structure and the
corresponding reflection and transmission coefficients are calculated using the
local field approach for the normal plane-wave incidence, and effective
parameters are introduced through the averaged fields and polarizations. In the
absence of losses both material parameters are purely real and satisfy the
Kramers-Kronig relations and the second law of thermodynamics. We compare the
analytical results to the simulated and experimental results available in the
literature. The physical meaning of the introduced parameters is discussed in
detail.Comment: 6 pages, 5 figure
Quasiclassical calculations of BBR-induced depopulation rates and effective lifetimes of Rydberg nS, nP and nD alkali-metal atoms with n < 80
Rates of depopulation by blackbody radiation (BBR) and effective lifetimes of
alkali-metal \textit{nS}, \textit{n}P and \textit{nD} Rydberg states have been
calculated in a wide range of principal quantum numbers at the
ambient temperatures of 77, 300 and 600 K. Quasiclassical formulas were used to
calculate the radial matrix elements of the dipole transitions from Rydberg
states. Good agreement of our numerical results with the available theoretical
and experimental data has been found. We have also obtained simple analytical
formulas for estimates of effective lifetimes and BBR-induced depopulation
rates, which well agree with the numerical data.Comment: 12 pages, 6 figures, 8 tables. Typo in Eq.16 corrected in V2. Typos
in Eq.5 and Eq.9 corrected in V3. Error in calculation of Rb nP_{3/2}
effective lifetimes corrected in V4: see new data in Table II and Table VII,
Erratum to be published in PR
Synthesis of nitroxyl radical by direct nucleophilic functionalization of a C-H bond in the azadiene systems
Cyclic dinitrones underwent nucleophilic substitution of the hydrogen atom in the reaction with a paramagnetic carbanion, the lithium derivative of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide, to give polyfunctional nitronyl nitroxyls. © 2012 Springer Science+Business Media New York
Full light absorption in single arrays of spherical nanoparticles
In this paper we show that arrays of core-shell nanoparticles function as
effective thin absorbers of light. In contrast to known metamaterial absorbers,
the introduced absorbers are formed by single planar arrays of spherical
inclusions and enable full absorption of light incident on either or both sides
of the array. We demonstrate possibilities for realizing different kinds of
symmetric absorbers, including resonant, ultra-broadband, angularly selective,
and all-angle absorbers. The physical principle behind these designs is
explained considering balanced electric and magnetic responses of unit cells.
Photovoltaic devices and thermal emitters are the two most important potential
applications of the proposed designs.Comment: (e.g.: 18 pages, 5 figures
Effect of finite detection efficiency on the observation of the dipole-dipole interaction of a few Rydberg atoms
We have developed a simple analytical model describing multi-atom signals
that are measured in experiments on dipole-dipole interaction at resonant
collisions of a few Rydberg atoms. It has been shown that finite efficiency of
the selective field-ionization detector leads to the mixing up of the spectra
of resonant collisions registered for various numbers of Rydberg atoms. The
formulas which help to estimate an appropriate mean Rydberg atom number for a
given detection efficiency are presented. We have found that a measurement of
the relation between the amplitudes of collisional resonances observed in the
one- and two-atom signals provides a straightforward determination of the
absolute detection efficiency and mean Rydberg atom number. We also performed a
testing experiment on resonant collisions in a small excitation volume of a
sodium atomic beam. The resonances observed for 1 to 4 detected Rydberg atoms
have been analyzed and compared with theory.Comment: 10 pages, 4 figures; equations 8,9,18,19,23,26-31, figures 3 and
4(d), and measurements revised in version
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