Winnerless competition in coupled Lotka-Volterra maps

Winnerless competition is analyzed in coupled maps with discrete temporal evolution of the Lotka-Volterra type of arbitrary dimension. Necessary and sufficient conditions for the appearance of structurally stable heteroclinic cycles as a function of the model parameters are deduced. It is shown that under such conditions winnerless competition dynamics is fully exhibited. Based on these conditions different cases characterizing low, intermediate, and high dimensions are therefore computationally recreated. An analytical expression for the residence times valid in the N-dimensional case is deduced and successfully compared with the simulations.J.L.C. and E.D.G. acknowledge support from IVIC-141, L.A.G.-D. acknowledges support from IVIC-1089 and P.V. acknowledges support from MINECO TIN2012-30883

Broadband transverse susceptibility in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22

Producción CientíficaNoncollinear spin systems with magnetically induced ferroelectricity from changes in spiral magnetic ordering have attracted significant interest in recent research due to their remarkable magnetoelectric effects with promising applications. Single phase multiferroics are of great interest for these new multifunctional devices, being Y-type hexaferrites good candidates, and among them the ZnY compounds due to their ordered magnetic behaviour over room temperature. Polycrystalline Y type hexaferrites with composition Ba0.5Sr1.5Zn2Fe2O22 (BSZFO) were sintered in 1050 °C–1250 °C temperature range. Transverse susceptibility measurements carried out on these BSZFO samples in the temperature range 80–350 K with DC fields up to ± 5000 Oe reveal different behaviour depending on the sintering temperature. Sample sintered at 1250 °C is qualitatively different, suggesting a mixed Y and Z phase like CoY hexaferrites. Sintering at lower temperatures produce single phase Y-type, but the transverse susceptibility behaviour of the sample sintered at 1150 °C is shifted at temperatures 15 K higher. Regarding the DC field sweeps the observed behaviour is a peak that shifts to lower values with increasing temperature, and the samples corresponding to single Y phase exhibit several maxima and minima in the 250 K–330 K range at low DC applied field as a result of the magnetic field induced spin transitions in this compound.Ministerio de Ciencia, Innovación y Universidades; Agencia Estatal de Investigación with FEDER (MAT2016-80784-P

Casimir effect in the nonequilibrium steady-state of a quantum spin chain

We present a fully microscopics-based calculation of the Casimir effect in a nonequilibrium system, namely an energy flux driven quantum XX chain. The force between the walls (transverse-field impurities) is calculated in a nonequilibrium steady state which is prepared by letting the system evolve from an initial state with the two halves of the chain prepared at equilibrium at different temperatures. The steady state emerging in the large-time limit is homogeneous but carries an energy flux. The Casimir force in this nonequilibrium state is calculated analytically in the limit when the transverse fields are small. We find that the the Casimir force range is reduced compared to the equilibrium case, and suggest that the reason for this is the reduction of fluctuations in the flux carrying steady state.Comment: 11 page

A transiting super-Earth close to the inner edge of the habitable zone of an M0 dwarf star

We present a super-Earth orbiting close to the inner edge of the habitable zone of the cool dwarf star K2-286 (EPIC 249889081), detected with data from the K2 mission in its $15^{th}$ campaign. The planet has radius of $2.1\pm0.2$ R$_{\oplus}$, near the 1.5 - 2.0 R$_{\oplus}$ gap in the radii distribution. The equilibrium temperature is $347^{+21}_{-11}$ K, cooler than most of the small planets with well measured masses, and the orbital period is $27.359\pm0.005$ days. K2-286, located at a distance of $76.3\pm0.3$ pc, is an M0V star with estimated effective temperature of $3926\pm100$ K, less active than other M dwarf stars hosting exoplanets. The expected radial velocity semi-amplitude induced by the planet on the star is $1.9^{+1.3}_{-1.2}$ m$\cdot$s$^{-1}$, and the amplitude of signals in transit transmission spectroscopy is estimated at $5.0\pm3.0$ ppm. Follow-up observations for mass measurements and transit spectroscopy should be desirable for this relatively bright target ($m_V=12.76, m_{Ks}=9.32$) hosting a transiting super-Earth within the inner edge of the habitable zone.Comment: Accepted for publication in MNRA

Temporal evolution of the Evershed flow in sunspots. II. Physical properties and nature of Evershed clouds

Context: Evershed clouds (ECs) represent the most conspicuous variation of the Evershed flow in sunspot penumbrae. Aims: We determine the physical properties of ECs from high spatial and temporal resolution spectropolarimetric measurements. Methods: The Stokes profiles of four visible and three infrared spectral lines are subject to inversions based on simple one-component models as well as more sophisticated realizations of penumbral flux tubes embedded in a static ambient field (uncombed models). Results: According to the one-component inversions, the EC phenomenon can be understood as a perturbation of the magnetic and dynamic configuration of the penumbral filaments along which these structures move. The uncombed inversions, on the other hand, suggest that ECs are the result of enhancements in the visibility of penumbral flux tubes. We conjecture that the enhancements are caused by a perturbation of the thermodynamic properties of the tubes, rather than by changes in the vector magnetic field. The feasibility of this mechanism is investigated performing numerical experiments of thick penumbral tubes in mechanical equilibrium with a background field. Conclusions: While the one-component inversions confirm many of the properties indicated by a simple line parameter analysis (Paper I of this series), we tend to give more credit to the results of the uncombed inversions because they take into account, at least in an approximate manner, the fine structure of the penumbra.Comment: Accepted for publication in A&

A Novel Mouse Model of Peritoneal Dialysis: Combination of Uraemia and Long-Term Exposure to PD Fluid

Different animal models for peritoneal dialysis (PD) have been used in the past decades to develop PD fluids compatible with patient life and to identify markers of peritoneal fibrosis and inflammation. Only few of those studies have taken into account the importance of uraemia-induced alterations at both systemic and peritoneal levels. Moreover, some animal studies which have reported about PD in a uremic setting did not always entirely succeed in terms of uraemia establishment and animal survival. In the present study we induced uraemia in the recently established mouse PD exposure model in order to obtain a more clinically relevant mouse model for kidney patients. This new designed model reflected both the slight thickening of peritoneal membrane induced by uraemia and the significant extracellular matrix deposition due to daily PD fluid instillation. In addition the model offers the opportunity to perform long-term exposure to PD fluids, as it is observed in the clinical setting, and gives the advantage to knock out candidate markers for driving peritoneal inflammatory mechanisms.Marie Curie actionsPeer Reviewe

Environment of the submillimeter-bright massive starburst HFLS3 at z∼z\sim6.34

We describe the search for Lyman-break galaxies (LBGs) near the sub-millimeter bright starburst galaxy HFLS3 at $z$$=$6.34 and a study on the environment of this massive galaxy during the end of reionization.We performed two independent selections of LBGs on images obtained with the \textit{Gran Telescopio Canarias} (GTC) and the \textit{Hubble Space Telescope} (HST) by combining non-detections in bands blueward of the Lyman-break and color selection. A total of 10 objects fulfilling the LBG selection criteria at $z$$>$5.5 were selected over the 4.54 and 55.5 arcmin$^2$ covered by our HST and GTC images, respectively. The photometric redshift, UV luminosity, and the star-formation rate of these sources were estimated with models of their spectral energy distribution. These $z$$\sim$6 candidates have physical properties and number densities in agreement with previous results. The UV luminosity function at $z$$\sim$6 and a Voronoi tessellation analysis of this field shows no strong evidence for an overdensity of relatively bright objects (m$_{F105W}$$<$25.9) associated with \textit{HFLS3}. However, the over-density parameter deduced from this field and the surface density of objects can not excluded definitively the LBG over-density hypothesis. Moreover we identified three faint objects at less than three arcseconds from \textit{HFLS3} with color consistent with those expected for $z$$\sim$6 galaxies. Deeper data are needed to confirm their redshifts and to study their association with \textit{HFLS3} and the galaxy merger that may be responsible for the massive starburst.Comment: 14 pages, 12 figures, accepted for publication in Ap

The coincidence and angular clustering of Chandra and SCUBA sources

NRC publication: N

The ALHAMBRA Survey: Bayesian Photometric Redshifts with 23 bands for 3 squared degrees

The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical) survey has observed 8 different regions of the sky, including sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a new photometric system with 20 contiguous ~ $300\AA$ filters covering the optical range, combining them with deep $JHKs$ imaging. The observations, carried out with the Calar Alto 3.5m telescope using the wide field (0.25 sq. deg FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to ~700hrs on-target science images. The photometric system was designed to maximize the effective depth of the survey in terms of accurate spectral-type and photo-zs estimation along with the capability of identification of relatively faint emission lines. Here we present multicolor photometry and photo-zs for ~438k galaxies, detected in synthetic F814W images, complete down to I~24.5 AB, taking into account realistic noise estimates, and correcting by PSF and aperture effects with the ColorPro software. The photometric ZP have been calibrated using stellar transformation equations and refined internally, using a new technique based on the highly robust photometric redshifts measured for emission line galaxies. We calculate photometric redshifts with the BPZ2 code, which includes new empirically calibrated templates and priors. Our photo-zs have a precision of $dz/(1+z_s)=1$ for I<22.5 and 1.4% for 22.5<I<24.5. Precisions of less than 0.5% are reached for the brighter spectroscopic sample, showing the potential of medium-band photometric surveys. The global $P(z)$ shows a mean redshift =0.56 for I=0.86 for I<24.5 AB. The data presented here covers an effective area of 2.79 sq. deg, split into 14 strips of 58.5'x15.5' and represents ~32 hrs of on-target.Comment: The catalog data and a full resolution version of this paper is available at https://cloud.iaa.csic.es/alhambra

Electromagnetic Response of Layered Superconductors with Broken Lattice Inversion Symmetry

We investigate the macroscopic effects of charge density waves (CDW) and superconductivity in layered superconducting systems with broken lattice inversion symmetry (allowing for piezoelectricity) such as two dimensional (2D) transition metal dichalcogenides (TMD). We work with the low temperature time dependent Ginzburg-Landau theory and study the coupling of lattice distortions and low energy CDW collective modes to the superconducting order parameter in the presence of electromagnetic fields. We show that superconductivity and piezoelectricity can coexist in these singular metals. Furthermore, our study indicates the nature of the quantum phase transition between a commensurate CDW phase and the stripe phase that has been observed as a function of applied pressure.Comment: 9 pages, 1 figure. Final version. Accepted in Phys.Rev.