Topological bands in two-dimensional networks of metamaterial elements

We show that topological frequency band structures emerge in two-dimensional electromagnetic lattices of metamaterial components without the application of an external magnetic field. The topological nature of the band structure manifests itself by the occurrence of exceptional points in the band structure or by the emergence of one-way guided modes. Based on an EM network with nearly flat frequency bands of nontrivial topology, we propose a coupled-cavity lattice made of superconducting transmission lines and cavity QED components which is described by the Janes-Cummings-Hubbard model and can serve as simulator of the fractional quantum Hall effect

Three-Dimensional Nanotransmission Lines at Optical Frequencies: A Recipe for Broadband Negative-Refraction Optical Metamaterials

Here we apply the optical nanocircuit concepts to design and analyze in detail a three-dimensional (3-D) plasmonic nanotransmission line network that may act as a negative-refraction broadband metamaterial at infrared and optical frequencies. After discussing the heuristic concepts at the basis of our theory, we show full-wave analytical results of the expected behavior of such materials, which show increased bandwidth and relative robustness to losses. The possibility and constraints of getting a 3-D fully isotropic response is also explored and conditions for minimal losses and increased bandwidth are discussed. Full-wave analytical results for some design examples employing realistic plasmonic materials at infrared and optical frequencies are also presented, and a case of sub-wavelength imaging system using a slab of this material is numerically investigated.Comment: 70 pages, 15 figure

Automated synthesis of transmission lines loaded with complementary split ring resonators (CSRRs) and open complementary split ring resonators (OCSRRs) through aggressive space mapping (ASM)

This paper is focused on the application of space mapping optimization to the automated synthesis of transmission lines loaded with complementary split ring resonators (CSRRs) and open complementary split ring resonators (OCSRRs). These structures are of interest for the implementation of resonant-type metamaterial transmission lines and for the design of planar microwave circuits based on such complementary resonators. The paper presents a method to generate the layouts of CSRR- and OCSRR-loaded microstrip lines from the elements of their equivalent circuit models. Using the so-called aggressive space mapping, a specific implementation that uses quasi-Newton type iteration, we have developed synthesis algorithms that are able to provide the topology of these CSRR and OCSRR-loaded lines in few steps. The most relevant aspect, however, is that this synthesis process is completely automatic, i.e., it does not require any action from the designers, other than initiating the algorithm. Moreover, this technique can be translated to other electrically small planar elements described by lumped element equivalent circuit models.This work has been partially supported by MICIIN-Spain (Projects TEC2010-17512 METATRANSFER, TEC2010-21520-C04-01 AVANSAT, CONSOLIDER EMET CSD2008-00066, and Grant AP2008-04707), Generalitat de Catalunya (Project 2009SGR-421), and MITyC-Spain (Project TSI-020100-2010-169 METASINTESIS). Ferran Martin is in debt to ICREA for supporting his work through an ICREA Academia Award (calls 2008 and 2013).Selga, J.; Rodríguez Pérez, AM.; Orellana, M.; Boria Esbert, VE.; Martín, F. (2014). Automated synthesis of transmission lines loaded with complementary split ring resonators (CSRRs) and open complementary split ring resonators (OCSRRs) through aggressive space mapping (ASM). Applied Physics A. 117(2):557-565. https://doi.org/10.1007/s00339-014-8703-xS5575651172G.V. Eleftheriades, K.G. 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Microsatellite diversity of the Nordic type of goats in relation to breed conservation: how relevant is pure ancestry?

In the last decades, several endangered breeds of livestock species have been re-established effectively. However, the successful revival of the Dutch and Danish Landrace goats involved crossing with exotic breeds and the ancestry of the current populations is therefore not clear. We have generated genotypes for 27 FAO-recommended microsatellites of these landraces and three phenotypically similar Nordic-type landraces and compared these breeds with central European, Mediterranean and south-west Asian goats. We found decreasing levels of genetic diversity with increasing distance from the south-west Asian domestication site with a south-east-to-north-west cline that is clearly steeper than the Mediterranean east-to-west cline. In terms of genetic diversity, the Dutch Landrace comes next to the isolated Icelandic breed, which has an extremely low diversity. The Norwegian coastal goat and the Finnish and Icelandic landraces are clearly related. It appears that by a combination of mixed origin and a population bottleneck, the Dutch and Danish Land-races are separated from the other breeds. However, the current Dutch and Danish populations with the multicoloured and long-horned appearance effectively substitute for the original breed, illustrating that for conservation of cultural heritage, the phenotype of a breed is more relevant than pure ancestry and the genetic diversity of the original breed. More in general, we propose that for conservation, the retention of genetic diversity of an original breed and of the visual phenotype by which the breed is recognized and defined needs to be considered separately

Model Order Reduction in Fluid Dynamics: Challenges and Perspectives

This chapter reviews techniques of model reduction of fluid dynamics systems. Fluid systems are known to be difficult to reduce efficiently due to several reasons. First of all, they exhibit strong nonlinearities — which are mainly related either to nonlinear convection terms and/or some geometric variability — that often cannot be treated by simple linearization. Additional difficulties arise when attempting model reduction of unsteady flows, especially when long-term transient behavior needs to be accurately predicted using reduced order models and more complex features, such as turbulence or multiphysics phenomena, have to be taken into consideration. We first discuss some general principles that apply to many parametric model order reduction problems, then we apply them on steady and unsteady viscous flows modelled by the incompressible Navier-Stokes equations. We address questions of inf-sup stability, certification through error estimation, computational issues and — in the unsteady case — long-time stability of the reduced model. Moreover, we provide an extensive list of literature references