Controlling single-photon transport in waveguides with finite cross-section

We study the transverse-size effect of a quasi-one-dimensional rectangular waveguide on the single-photon scattering on a two-level system. We calculate the transmission and reflection coefficients for single incident photons using the scattering formalism based on the Lippmann-Schwinger equation. When the transverse size of the waveguide is larger than a critical size, we find that the transverse mode will be involved in the single-photon scattering. Including the coupling to a higher traverse mode, we find that the photon in the lowest channel will be lost into the other channel, corresponding to the other transverse modes, when the input energy is larger than the maximum bound-state energy. Three kinds of resonance phenomena are predicted: single-photon resonance, photonic Feshbach resonance, and cutoff (minimum) frequency resonance. At these resonances, the input photon is completely reflected.Comment: 9 pages, 6 figure

Catastrophic Photo-z Errors and the Dark Energy Parameter Estimates with Cosmic Shear

We study the impact of catastrophic errors occurring in the photometric redshifts of galaxies on cosmological parameter estimates with cosmic shear tomography. We consider a fiducial survey with 9-filter set and perform photo-z measurement simulations. It is found that a fraction of 1% galaxies at z_{spec}~0.4 is misidentified to be at z_{phot}~3.5. We then employ both chi^2 fitting method and the extension of Fisher matrix formalism to evaluate the bias on the equation of state parameters of dark energy, w_0 and w_a, induced by those catastrophic outliers. By comparing the results from both methods, we verify that the estimation of w_0 and w_a from the fiducial 5-bin tomographic analyses can be significantly biased. To minimize the impact of this bias, two strategies can be followed: (A) the cosmic shear analysis is restricted to 0.5<z<2.5 where catastrophic redshift errors are expected to be insignificant; (B) a spectroscopic survey is conducted for galaxies with 3<z_{phot}<4. We find that the number of spectroscopic redshifts needed scales as N_{spec} \propto f_{cata}\times A where f_{cata}=1% is the fraction of catastrophic redshift errors (assuming a 9-filter photometric survey) and A is the survey area. For A=1000 {deg}^2, we find that N_{spec}>320 and 860 respectively in order to reduce the joint bias in (w_0,w_a) to be smaller than 2\sigma and 1\sigma. This spectroscopic survey (option B) will improve the Figure of Merit of option A by a factor \times 1.5 thus making such a survey strongly desirable.Comment: 25 pages, 9 figures. Revised version, as accepted for publication in Ap

Infrared Optical Properties of Ferropericlase (Mg1-xFexO): Experiment and Theory

The temperature dependence of the reflectance spectra of magnesium oxide (MgO) and ferropericlase (Mg1-xFexO, for x=0.06 and x=0.27) have been measured over a wide frequency range (~50 to 32000 cm-1) at 295 and 6 K. The complex dielectric function has been determined from a Kramers-Kronig analysis of the reflectance. The spectra of the doped materials resembles pure MgO in the infrared region, but with much broader resonances. We use a shell model to calculate the dielectric function of ferropericlase, including both anharmonic phonon-phonon interactions and disorder scattering. These data are relevant to understanding the heat conductivity of ferropericlase in the earth's lower mantle.Comment: 17 pages, 6 figure

Modelling and control of the flame temperature distribution using probability density function shaping

This paper presents three control algorithms for the output probability density function (PDF) control of the 2D and 3D flame distribution systems. For the 2D flame distribution systems, control methods for both static and dynamic flame systems are presented, where at first the temperature distribution of the gas jet flames along the cross-section is approximated. Then the flame energy distribution (FED) is obtained as the output to be controlled by using a B-spline expansion technique. The general static output PDF control algorithm is used in the 2D static flame system, where the dynamic system consists of a static temperature model of gas jet flames and a second-order actuator. This leads to a second-order closed-loop system, where a singular state space model is used to describe the dynamics with the weights of the B-spline functions as the state variables. Finally, a predictive control algorithm is designed for such an output PDF system. For the 3D flame distribution systems, all the temperature values of the flames are firstly mapped into one temperature plane, and the shape of the temperature distribution on this plane can then be controlled by the 3D flame control method proposed in this paper. Three cases are studied for the proposed control methods and desired simulation results have been obtained

Dynamics of Phase Behavior of a Polymer Blend Under Shear Flow

We study the dynamics of the phase behavior of a polymer blend in the presence of shear flow. By adopting a two fluid picture and using a generalization of the concept of material derivative, we construct kinetic equations that describe the phase behavior of polymer blends in the presence of external flow. A phenomenological form for the shear modulus for the blend is proposed. The study indicates that a nonlinear dependence of the shear modulus of the blend on the volume fraction of one of the species is crucial for a shift in the stability line to be induced by shear flow.Comment: 16 pages, late