First principles study of topological invariants of Weyl points in continuous media

In recent years there has been a great interest in topological photonics and protected edge states. Here, we present a first principles method to compute topological invariants of three-dimensional gapless phases. Our approach allows to calculate the topological charges of Weyl points through the efficient numerical computation of gap Chern numbers, which relies solely on the photonic Green's function of the system. We particularize the framework to the Weyl points that are found to emerge in a magnetized plasma due to the breaking of time reversal symmetry. We discuss the relevance of modelling nonlocality when considering the topological properties of continuous media such as the magnetized plasma. We find that for some of the considered material models the charge of the Weyl point can be expressed in terms of a difference of the gap Chern numbers of two-dimensional material subcomponents. Our theory may be extended to other three-dimensional topological phases, or to Floquet systems.Comment: 13 pages, 11 figure

Transformation optics approach to singular metasurfaces

Surface plasmons dominate the optical response of metal surfaces, and their nature is controlled by surface geometry. Here we study metasurfaces containing singularities in the form of sharp edges and characterized by three quantum numbers despite the two-dimensional nature of the surface. We explore the nature of the plasmonic excitations, their ability to generate large concentrations of optical energy, and the transition from the discrete excitation spectrum of a nonsingular surface to the continuous spectrum of a singular metasurface

Theory of strong coupling between quantum emitters and propagating surface plasmons

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).Here we present the theoretical foundation of the strong coupling phenomenon between quantum emitters and propagating surface plasmons observed in two-dimensional metal surfaces. For that purpose, we develop a quantum framework that accounts for the coherent coupling between emitters and surface plasmons and incorporates the presence of dissipation and dephasing. Our formalism is able to reveal the key physical mechanisms that explain the reported phenomenology and also determine the physical parameters that optimize the strong coupling. A discussion regarding the classical or quantum nature of this phenomenon is also presented. © 2013 American Physical Society.This work was supported by the Spanish MINECO (Contracts No.MAT2011-22997, No.MAT2011-28581-C02, and No. CSD2007-046-NanoLight.es) and CAM (Contract No. S-2009/ESP-1503). A. G.-T. and P. A.-H acknowledge FPU Grants No. AP2008-00101 and No. AP2008-00021, respectively, from the Spanish Ministry of Education. This work has been partially funded by the European Research Council (ERC-2011-AdG Proposal No. 290981).S-2009/ESP-1503/Q&C LIGHTPeer Reviewe

El maná en la tradición bíblica

Esta investigación busca presentar una visión coherente de conjunto del desarrollo de la tradición del maná y de sus contenidos teológicos a lo largo de la Sagrada Escritura. En ella se han estudiado los pasajes bíblicos, procedentes de diversos libros del Antiguo y del Nuevo Testamento, ligados a esa tradición (de modo especial Ex 16,1-36; Nm 11, 4-35; Sal 78, 1-72; Sb 16, 15-29 y Jn 6, 22-59). Cada uno de ellos ha sido analizado de acuerdo con la metodología histórico-crítica y valorado teológicamente en una perspectiva canónica global. En la investigación realizada se han identificado y analizado cuatro motivos teológicos ligados a la tradición del maná: el motivo del desierto; el de la revelación de Dios; el de la fidelidad de Dios; y el de la vida. También se ha afrontado el estudio de seis cuestiones específicas relacionadas con esa tradición: qué es el maná, cómo es, quién es el agente principal de su envío, quienes son sus beneficiarios, para qué es enviado y cómo se ha trasmitido su tradición junto a las de las codornices y la roca que da agua. El estudio de los desarrollos de la tradición del maná hasta llegar al Nuevo Testamento ha permitido observar que en Jn 6,58, al tratar del misterio del pan de vida, se ofrece una respuesta a la pregunta «man hu»? de Ex 16,15 que aúna la mayor parte de los motivos teológicos que se habían ido asociando a esta tradición a lo largo de los siglosThe dissertation seeks to present a consistent view of the development of the tradition of the manna as a whole and of its theological content throughout Sacred Scripture. It studies biblical passages from a various Old and New Testament books that are linked to that tradition (particularly Ex 16,1-36; Nm. 11, 4-35; Sal 78,1-72; Sb 16,15-29 and Jn 6,22-59). Each one of the passages is analized in accordance with the historical-critical methods and judged theologically within an overall canonical perspective. The research identifies and anlyzes four theological motifs linked to the manna tradition: the desert motif, the revelation of God, the fidelity of God, that of life. The dissertation also studies six specific issues related to that tradition: what is the manna, how is the manna, who is the principal agent of its sending, who are its beneficiaries, what is it sent for and its development together with the tradition of the quails and of the rock as the spring of water. The study of the developments of the manna tradition up to the New Testament observes that Jn. 6,58, whilst speaking of the mystery of the bread of life, offers an answer to the questions of «man hu»? in Ex 16,15. This reply brings together the greater part of the theological motifs that had been associated with this tradition throughout the centuries

Superradiance mediated by Graphene Surface Plasmons

We demonstrate that the interaction between two emitters can be controlled by means of the efficient excitation of surface plasmon modes in graphene. We consider graphene surface plasmons supported by either two-dimensional graphene sheets or one-dimensional graphene ribbons, showing in both cases that the coupling between the emitters can be strongly enhanced or suppressed. The super- and subradiant regimes are investigated in the reflection and transmission configurations. Importantly, the length scale of the coupling between emitters, which in vacuum is fixed by the free space wavelength, is now determined by the wavelength of the graphene surface plasmons that can be extremely short and be tuned at will via a gate voltage

Nonlocal effects in singular plasmonic metasurfaces

A local model of the dielectric response of a metal predicts that singular surfaces, such as sharp-edged structures, have a continuous absorption spectrum and extreme concentration of energy at the singularity. Here, we show that nonlocality drastically alters this picture: The spectrum is now discrete and the energy concentration, though still substantial, is greatly reduced

Epigenetic repression of ROR2 has a Wnt-mediated, pro-tumourigenic role in colon cancer

Background: Wnt factors control cell differentiation through semi-independent molecular cascades known as the beta-catenin-dependent (canonical) and -independent (non-canonical) Wnt signalling pathways. Genetic and epigenetic alteration of components of the canonical Wnt signalling pathway is one of the primary mechanisms underlying colon cancer. Despite increasing evidence of the role of the non-canonical pathways in tumourigenesis, however, the underlying molecular mechanisms are poorly understood. Results: Here we report that the receptor tyrosine kinase-like orphan receptor 2 (ROR2), a transmembrane receptor for Wnt factors that activates non-canonical pathways, is frequently repressed by aberrant promoter hypermethylation in human colon cancer cell lines and primary tumours. By restoring ROR2 activity in colon cancer cells harbouring ROR2 promoter hypermethylation, we show that the role of ROR2 in colon cancer cells is mediated, at least in part, by canonical Wnt and that its epigenetic-dependent loss can be pro-tumourigenic. Conclusions: Our data show the importance of epigenetic alterations of ROR2 in colon cancer, highlighting the close interconnection between canonical and non-canonical Wnt signalling pathways in this type of tumour