BPS Skyrme neutron stars in generalized gravity

We study the coupling of nuclear matter described by the BPS Skyrme model to generalized gravity. Concretely, we consider the Starobinsky model which provides the leading-order correction to the Einstein-Hilbert action. Static solutions describing neutron stars are found both for the full field theory and for the mean-field approximation. We always consider the full Starobinsky model in the nonperturbative approach, using appropriately generalized shooting methods for the numerical neutron star calculations. Many of our results are similar to previous investigations of neutron stars for the Starobinsky model using other models of nuclear matter, but there are some surprizing discrepancies. The "Newtonian mass" relevant for the surface redshift, e.g., results larger than the ADM mass in our model, in contrast to other investigations. This difference is related to the particularly high stiffness of nuclear matter described by the BPS Skyrme model and offers an interesting possibility to distinguish different models of nuclear matter within generalized gravity.Comment: LaTex, 28 pages, 13 figures; v2: minor change

Luneburg lens in silicon photonics

The Luneburg lens is an aberration-free lens that focuses light from all directions equally well. We fabricated and tested a Luneburg lens in silicon photonics. Such fully-integrated lenses may become the building blocks of compact Fourier optics on chips. Furthermore, our fabrication technique is sufficiently versatile for making perfect imaging devices on silicon platforms. (C) 2011 Optical Society of AmericaPublisher PDFPeer reviewe

Caracterización farmacológica del efecto vasodilatador de extractos de bayas de calafate y de sus tres principales antocianinas glicosiladas

Calafate (Berberis microphylla) es una planta nativa de la Patagonia de Chile y Argentina, sus bayas son de color púrpura oscuro y posee la mayor capacidad antioxidante entre frutas comerciales y endémicas de Chile. Las bayas tienen alto contenido de compuestos fenólicos que incluyen varias antocianinas, flavonoles y ácidos fenólicos. Dado que la etnomedicina une las bayas chilenas con un efecto clínico benéfico, propusimos que los extractos de bayas de calafate tienen propiedades vasodilatadoras relacionadas a la variada naturaleza de sus compuestos. Con este propósito, extractos hidroalcohólicos de calafate (0.1-300 μg/mL) y 3 principales antocianinas glicosiladas (1nM-10 μM), fueron evaluadas en la red vascular mesentérica de rata previa contracción con noradrenalina, se determinó la dependencia del endotelio y producción de óxido nítrico. Extractos de calafate inducen una respuesta dilatadora concentración-dependiente (EC50 3.7 μg/mL); la respuesta máxima de vasodilatación (75-80%) se alcanzó con 10-30 μg/mL. La vasodilatación fue significativamente reducida por la remoción del endotelio (saponina 0.1%) (70 a 30%) e inhibición de eNOS con 150 μM de L-NNA (70 a 10%). El perfil químico del extracto (HPLC-ESI-MS/MS) identificó delfinidina (D3G), petunidina y malvidina como 3-glucósidos, las principales antocianinas del extracto. Las 3 antocianinas provocaron una relajación vascular endotelio-dependiente con diferente potencia y similar eficacia (40-50%). La principal antocianina D3G es más potente pero menos efectiva que los extractos de calafate, lo cual explica parcialmente que otros compuestos no antocianos del extracto enmascaran la respuesta inducida por D3G pero incrementan la eficacia del extractoFil: Calfío, C.. Universidad de Santiago de Chile.Fil: Huidobro-Toro, JP. Universidad de Santiago de Chile

The Cellular Prion Protein Prevents Copper-Induced Inhibition of P2X4 Receptors

Although the physiological function of the cellular prion protein (PrPC) remains unknown, several evidences support the notion of its role in copper homeostasis. PrPC binds Cu2+ through a domain composed by four to five repeats of eight amino acids. Previously, we have shown that the perfusion of this domain prevents and reverses the inhibition by Cu2+ of the adenosine triphosphate (ATP)-evoked currents in the P2X4 receptor subtype, highlighting a modulatory role for PrPC in synaptic transmission through regulation of Cu2+ levels. Here, we study the effect of full-length PrPC in Cu2+ inhibition of P2X4 receptor when both are coexpressed. PrPC expression does not significantly change the ATP concentration-response curve in oocytes expressing P2X4 receptors. However, the presence of PrPC reduces the inhibition by Cu2+ of the ATP-elicited currents in these oocytes, confirming our previous observations with the Cu2+ binding domain. Thus, our observations suggest a role for PrPC in modulating synaptic activity through binding of extracellular Cu2+

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

Constrained instantons and kink-antikink collisions

We show that constrained $CP^1$ instantons, combined with the Relativistic Moduli Space approach, can accurately describe kink-antikink collisions in the $\phi^4$ model.Comment: 8 pages, 5 figure

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

Multikink scattering in the ϕ6 model revisited

Antikink-kink (KK) collisions in the ¯ ϕ6 model exhibit resonant scattering although the ϕ6 kinks do not support any bound states to which energy could be transferred. In P. Dorey et al. [Kink-Antikink Collisions in the ϕ6 Model, Phys. Rev. Lett. 107, 091602 (2011)] it was conjectured that, instead, energy is transferred to a collective bound mode of the full KK configuration. Here we present further strong evidence for this ¯ conjecture. Further, we construct a collective coordinate model (CCM) for KK scattering based on this ¯ collective bound mode trapped between the KK pair which allows us to reproduce the full dynamics of ¯ KK¯ scattering with striking accuracy. We also study kink-antikink (KK) scattering and its description by a ¯ CCM. In this case a significant role of radiation is discovered

Reversible dynamics of single quantum emitters near metal-dielectric interfaces

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).Here we present a systematic study of the dynamics of a single quantum emitter near a flat metal-dielectric interface. We identify the key elements that determine the onset of reversibility in these systems by using a formalism suited for absorbing media and through an exact integration of the dynamics. Moreover, when the quantum emitter separation from the surface is small, we are able to describe the dynamics within a pseudomode description that yields analytical understanding and allows more powerful calculations.Work supported by the Spanish MINECO (MAT2011-22997, MAT2011-28581-C02, CSD2007-046-NanoLight.es) and CAM (S-2009/ESP-1503). A.G.-T. acknowledges funding by the EU integrated project SIQS. P.A.-H. acknowledges a FPU grant (AP2008-00021) from the Spanish Ministry of Education. This work has been partially funded by the European Research Council (ERC-2011-AdG Proposal No. 290981).Peer Reviewe