Anomalous Light Scattering by Topological PT{\mathcal{PT}}-symmetric Particle Arrays

Robust topological edge modes may evolve into complex-frequency modes when a physical system becomes non-Hermitian. We show that, while having negligible forward optical extinction cross section, a conjugate pair of such complex topological edge modes in a non-Hermitian $\mathcal{PT}$-symmetric system can give rise to an anomalous sideway scattering when they are simultaneously excited by a plane wave. We propose a realization of such scattering state in a linear array of subwavelength resonators coated with gain media. The prediction is based on an analytical two-band model and verified by rigorous numerical simulation using multiple-multipole scattering theory. The result suggests an extreme situation where leakage of classical information is unnoticeable to the transmitter and the receiver when such a $\mathcal{PT}$-symmetric unit is inserted into the communication channel.Comment: 16 pages, 8 figure

Negative Optical Torque

Maxwell noted that light carries angular momentum, and as such it can exert torques on material objects. This was subsequently proved by Beth in 1936. Applications of these opto-mechanical effects were limited initially due to their smallness in magnitude, but later enabled by the invention of laser. Novel and practical approaches for harvesting light for particle rotation have been demonstrated, where the structure is subjected to a positive optical torque along a certain axis21 if the incident angular momentum has a positive projection on the same axis. We report here a counter-intuitive phenomenon of negative optical torque, meaning that incoming photons carrying angular momentum rotate an object in the opposite sense. Surprisingly this can be realized quite straightforwardly in simple planar structures. Field retardation is a necessary condition. The optimal conditions are explored and explained.Comment: 15 pages, 3 figure

Investigating 1d and 1d/1d Modeling Using SWMM

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

The volatility structure of the fixed income market under the HJM framework: A nonlinear filtering approach

ABSTRACT. This paper considers the dynamics for interest rate processes within a multi-factor Heath, Jarrow and Morton (1992) specification. Despite the flexibility of and the notable advances in theoretical research about the HJM models, the number of empirical studies is still inadequate. This paucity is principally because of the difficulties in estimating models in this class, which are not only high-dimensional, but also nonlinear and involve latent state variables. This paper treats the estimation of a fairly broad class of HJM models as a nonlinear filtering problem, and adopts the local linearization filter of Jimenez and Ozaki (2003), which is known to have some desirable statistical and numerical features, to estimate the model via the maximum likelihood method. The estimator is then applied to the interbank offered-rates of the U.S, U.K, Australian and Japanese markets. The two-factor model, with the factors being the level and the slope effect, is found to be a reasonable choice for all of the markets. However, the contribution of each factor towards overall variability of the interest rates and the financial reward each factor claims differ considerably from one market to another

Dynamical coupled-channel model of kaon-hyperon interactions

The pi N --> KY and KY --> KY reactions are studied using a dynamical coupled-channel model of meson-baryon interactions at energies where the baryon resonances are strongly excited. The channels included are: pi N, K \Lambda, and K\Sigma. The resonances considered are: N^* [S_{11}(1650), P_{11}(1710), P_{13}(1720),D_{13}(1700)]; \Delta^* [S_{31}(1900), P_{31}(1910), P_{33}(1920)]; \Lambda ^* [S_{01}(1670), P_{01}(1810)] \Sigma^* [P_{11}(1660), D_{13}(1670)]; and K^*(892). The basic non-resonant \pi N --> KY and KY --> KY transition potentials are derived from effective Lagrangians using a unitary transformation method. The dynamical coupled-channel equations are simplified by parametrizing the pi N -->pi N amplitudes in terms of empirical pi N partial-wave amplitudes and a phenomenological off-shell function. Two models have been constructed. Model A is built by fixing all coupling constants and resonance parameters using SU(3) symmetry, the Particle Data Group values, and results from a constituent quark model. Model B is obtained by allowing most of the parameters to vary around the values of model A in fitting the data. Good fits to the available data for pi^- p to K^0 \Lambda, K^0 \Sigma^0 have been achieved. The investigated kinematics region in the center-of-mass frame goes from threshold to 2.5 GeV. The constructed models can be imbedded into associated dynamical coupled-channel studies of kaon photo- and electro-production reactions.Comment: 35 pages, 11 Figure

Chiral microstructures (spirals) fabrication by holographic lithography

We present an optical interference model to create chiral microstructures (spirals) and its realization in photoresist using holographic lithography. The model is based on the interference of six equally-spaced circumpolar linear polarized side beams and a circular polarized central beam. The pitch and separation of the spirals can be varied by changing the angle between the side beams and the central beam. The realization of the model is carried out using the 325 nm line of a He-Cd laser and spirals of sub-micron size are fabricated in photoresist.Comment: 6 page

Approximate gauge symmetry of composite vector bosons

It can be shown in a solvable field theory model that the couplings of the composite vector bosons made of a fermion pair approach the gauge couplings in the limit of strong binding. Although this phenomenon may appear accidental and special to the vector boson made of a fermion pair, we extend it to the case of bosons being constituents and find that the same phenomenon occurs in more an intriguing way. The functional formalism not only facilitates computation but also provides us with a better insight into the generating mechanism of approximate gauge symmetry, in particular, how the strong binding and global current conservation conspire to generate such an approximate symmetry. Remarks are made on its possible relevance or irrelevance to electroweak and higher symmetries.Comment: Correction of typos. The published versio