619 research outputs found

### Investigation of the spectra of coupled polaritons on the periodically modulated metallic layer and the narrow regions of anomalous transparency

The paper deals with the theoretical investigation of plane, normally
incident electromagnetic wave transmission through the flat metal film whose
dielectric constant has small periodical sinusoidal modulation in one dimension
parallel to the projection of the electric field onto the film surface. The
dependencies of the film transmittancy on the parameters of the problem
(frequency, modulation depth and absorption) are examined. It is shown that the
film transmittancy increases considerably when the conditions for resonance
interaction of an incident electromagnetic wave with surface plasmon polaritons
(SPPs) are met. It is found that for small but finite absorption there are two
frequencies in the vicinity of which the transmittancy can achieve the values
of the order of unity due to resonances on symmetric and antisymmetric
(relative to the mean plane) SPP modes. It is shown that for each value of
absorption there exists a certain optimal modulation depth, which maximizes the
resonance transparency.Comment: 18 pages, 8 figures, proceeding of conference "Plasmonics: metallic
nanostructures and their optical properties", SPIE's 48-th Annual Meeting,
3-8 August, 2003, San Diego, US

### Tectonics and volcanisms of Mars

Televised images of Mars transmitted from interplanetary stations are used to develop a theory of the structure and development of the planet. Crater chronology, the structure of planetary bodies in the Earth group, and a comparison of the Earth planetary bodies are among the factors included

### Modeling of Return on Pension Funds, Taking into Well-being of Older Generation

The hypothesis that the well-being of the older generation can be improved by increasing the efficiency of pension savings investments into more profitable securities is proposed.A key factor, which increases the return on investment at a constant level of risk, is to diversify risk in the preparation of the portfolio. The well-being of older generations in terms of the need for optimum use of pension savings is considered. Four types of securities with different levels of risk and return, which theoretically can be invested pension funds are taken for analysis. Opportunities for investment securities in the simple and expanded portfolios are determined on the basis of existing legislation. Portfolios with different risk levels are compared. The principle of diversification is used. The curve of return and risk of various possible investment portfolios is simulated. The study is based on statistical methods.The opportunities for investing pension savings in securities with a higher level of profitability while maintaining a constant risk is demonstrated. The study focused on the revision of legislation in the field of investments of the pension funds of the Russian Federation in the stocks and bonds of Russian companies

### On Black Fundamental Strings

We study aspects of four dimensional black holes with two electric charges,
corresponding to fundamental strings with generic momentum and winding on an
internal circle. The perturbative \alpha' correction to such black holes and
their gravitational thermodynamics is obtained.Comment: 17 pages, v2: published versio

### The String Landscape, Black Holes and Gravity as the Weakest Force

We conjecture a general upper bound on the strength of gravity relative to
gauge forces in quantum gravity. This implies, in particular, that in a
four-dimensional theory with gravity and a U(1) gauge field with gauge coupling
g, there is a new ultraviolet scale Lambda=g M_{Pl}, invisible to the
low-energy effective field theorist, which sets a cutoff on the validity of the
effective theory. Moreover, there is some light charged particle with mass
smaller than or equal to Lambda. The bound is motivated by arguments involving
holography and absence of remnants, the (in) stability of black holes as well
as the non-existence of global symmetries in string theory. A sharp form of the
conjecture is that there are always light "elementary" electric and magnetic
objects with a mass/charge ratio smaller than the corresponding ratio for
macroscopic extremal black holes, allowing extremal black holes to decay. This
conjecture is supported by a number of non-trivial examples in string theory.
It implies the necessary presence of new physics beneath the Planck scale, not
far from the GUT scale, and explains why some apparently natural models of
inflation resist an embedding in string theory.Comment: 20 pages, LaTeX, 5 EPS figures; v2: minor correction

### Robustness of Sound Speed and Jet Quenching for Gauge/Gravity Models of Hot QCD

We probe the effectiveness and robustness of a simple gauge/gravity dual
model of the QCD fireball that breaks conformal symmetry by constructing a
family of similar geometries that solve the scalar/gravity equations of motion.
This family has two parameters, one of which is associated to the temperature.
We calculate two quantities, the speed of sound and the jet-quenching
parameter. We find the speed of sound to be universal and robust over all the
geometries when appropriate units are used, while the jet-quenching parameter
varies significantly away from the conformal limit. We note that the overall
structure of the jet-quenching depends strongly on whether the running scalar
is the dilaton or not. We also discuss the variation of the scalar potential
over our family of solutions, and truncate our results to where the associated
error is small.Comment: 21 pages, 9 figures, LaTeX. v2:references added, minor correction to
speed of sound; conclusions unchange

### Excitation of surface plasmon-polaritons in metal films with double periodic modulation: anomalous optical effects

We perform a thorough theoretical analysis of resonance effects when an
arbitrarily polarized plane monochromatic wave is incident onto a double
periodically modulated metal film sandwiched by two different transparent
media. The proposed theory offers a generalization of the theory that had been
build in our recent papers for the simplest case of one-dimensional structures
to two-dimensional ones. A special emphasis is placed on the films with the
modulation caused by cylindrical inclusions, hence, the results obtained are
applicable to the films used in the experiments. We discuss a spectral
composition of modulated films and highlight the principal role of
``resonance'' and ``coupling'' modulation harmonics. All the originating
multiple resonances are examined in detail. The transformation coefficients
corresponding to different diffraction orders are investigated in the vicinity
of each resonance. We make a comparison between our theory and recent
experiments concerning enhanced light transmittance and show the ways of
increasing the efficiency of these phenomena. In the appendix we demonstrate a
close analogy between ELT effect and peculiarities of a forced motion of two
coupled classical oscillators.Comment: 24 pages, 17 figure

### Large Charge Four-Dimensional Extremal N=2 Black Holes with R^2-Terms

We consider N=2 supergravity in four dimensions with small R^2 curvature
corrections. We construct large charge extremal supersymmetric and
non-supersymmetric black hole solutions in all space, and analyze their
thermodynamic properties.Comment: 18 pages. v2,3: minor fixe

### Shear viscosity, instability and the upper bound of the Gauss-Bonnet coupling constant

We compute the dimensionality dependence of $\eta/s$ for charged black branes
with Gauss-Bonnet correction. We find that both causality and stability
constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in
the infinite dimensionality limit. We further show that higher dimensionality
stabilize the gravitational perturbation. The stabilization of the perturbation
in higher dimensional space-time is a straightforward consequence of the
Gauss-Bonnet coupling constant bound.Comment: 16 pages,3 figures+3 tables,typos corrected, published versio

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