128,948 research outputs found
Numerically improved computational scheme for the optical conductivity tensor in layered systems
The contour integration technique applied to calculate the optical
conductivity tensor at finite temperatures in the case of layered systems
within the framework of the spin-polarized relativistic screened
Korringa-Kohn-Rostoker band structure method is improved from the computational
point of view by applying the Gauss-Konrod quadrature for the integrals along
the different parts of the contour and by designing a cumulative special points
scheme for two-dimensional Brillouin zone integrals corresponding to cubic
systems.Comment: 17 pages, LaTeX + 4 figures (Encapsulated PostScript), submitted to
J. Phys.: Condensed Matter (19 Sept. 2000
New four-dimensional integrals by Mellin-Barnes transform
This paper is devoted to the calculation by Mellin-Barnes transform of a
especial class of integrals. It contains double integrals in the position space
in d = 4-2e dimensions, where e is parameter of dimensional regularization.
These integrals contribute to the effective action of the N = 4 supersymmetric
Yang-Mills theory. The integrand is a fraction in which the numerator is a
logarithm of ratio of spacetime intervals, and the denominator is the product
of powers of spacetime intervals. According to the method developed in the
previous papers, in order to make use of the uniqueness technique for one of
two integrations, we shift exponents in powers in the denominator of integrands
by some multiples of e. As the next step, the second integration in the
position space is done by Mellin-Barnes transform. For normalizing procedure,
we reproduce first the known result obtained earlier by Gegenbauer polynomial
technique. Then, we make another shift of exponents in powers in the
denominator to create the logarithm in the numerator as the derivative with
respect to the shift parameter delta. We show that the technique of work with
the contour of the integral modified in this way by using Mellin-Barnes
transform repeats the technique of work with the contour of the integral
without such a modification. In particular, all the operations with a shift of
contour of integration over complex variables of two-fold Mellin-Barnes
transform are the same as before the delta modification of indices, and even
the poles of residues coincide. This confirms the observation made in the
previous papers that in the position space all the Green function of N = 4
supersymmetric Yang-Mills theory can be expressed in terms of UD functions.Comment: Talk at El Congreso de Matematica Capricornio, COMCA 2009,
Antofagasta, Chile and at DMFA seminar, UCSC, Concepcion, Chile, 24 pages;
revised version, Introduction is modified, Conclusion is added, five
Appendices are added, Appendix E is ne
Layer-resolved optical conductivity of Co|Pt multilayers
The complex optical conductivity tensor is calculated for the Co|Pt systems
by applying a contour integration technique within the framework of the
spin-polarized relativistic screened Korringa-Kohn-Rostoker method. It is shown
that the optical conductivity of the Co|Pt multilayer systems is dominated by
contributions arising from the Pt cap and/or substrate layers.Comment: 7 pages (LaTeX), 2 (a,b) figures (Encapsulated PostScript), J. Magn.
Magn. Materials, in pres
Casimir's energy of a conducting sphere and of a dilute dielectric ball
In this paper we sum over the spherical modes appearing in the expression for
the Casimir energy of a conducting sphere and of a dielectric ball (assuming
the same speed of light inside and outside), before doing the frequency
integration. We derive closed integral expressions that allow the calculations
to be done to all orders, without the use of regularization procedures. The
technique of mode summation using a contour integral is critically examined.Comment: references added; typos fixe
Ab-initio calculation of Kerr spectra for semi-infinite systems including multiple reflections and optical interferences
Based on Luttinger's formulation the complex optical conductivity tensor is
calculated within the framework of the spin-polarized relativistic screened
Korringa-Kohn-Rostoker method for layered systems by means of a contour
integration technique. For polar geometry and normal incidence ab-initio Kerr
spectra of multilayer systems are then obtained by including via a 2x2 matrix
technique all multiple reflections between layers and optical interferences in
the layers. Applications to Co|Pt5 and Pt3|Co|Pt5 on the top of a semi-infinite
fcc-Pt(111) bulk substrate show good qualitative agreement with the
experimental spectra, but differ from those obtained by applying the commonly
used two-media approach.Comment: 32 pages (LaTeX), 5 figures (Encapsulated PostScript), submitted to
Phys. Rev.
Evaluation of a technique to generate artificially thickened boundary layers in supersonic and hypersonic flows
The feasibility of using a contoured honeycomb model to generate a thick boundary layer in high-speed, compressible flow was investigated. The contour of the honeycomb was tailored to selectively remove momentum in a minimum of streamwise distance to create an artificially thickened turbulent boundary layer. Three wind tunnel experiments were conducted to verify the concept. Results indicate that this technique is a viable concept, especially for high-speed inlet testing applications. In addition, the compactness of the honeycomb boundary layer simulator allows relatively easy integration into existing wind tunnel model hardware
Ingredients of a Casimir analog computer
We present the basic ingredients of a technique to compute quantum Casimir
forces at micrometer scales using antenna measurements at tabletop, e.g.
centimeter, scales, forming a type of analog computer for the Casimir force.
This technique relies on a correspondence that we derive between the contour
integration of the Casimir force in the complex frequency plane and the
electromagnetic response of a physical dissipative medium in a finite, real
frequency bandwidth
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