Local conditions influence thermal sensitivity of pencil urchin populations (Eucidaris galapagensis) in the Galápagos Archipelago

The responses of ectothermic organisms to changes in temperature can be modified by acclimatization or adaptation to local thermal conditions. Thus, the effect of global warming and the deleterious effects of extreme heating events (e.g., heatwaves) on the metabolism and fitness of ectotherms can be population specific and reduced at warmer sites. We tested the hypothesis that when environmental temperature is greater, grazer populations in the Galápagos are less thermally sensitive (potentially due to acclimatization or adaptation). We quantified the acute thermal sensitivity of four populations of the pencil sea urchin, Eucidaris galapagensis, by measuring individual oxygen consumption across a range of temperatures. Thermal performance curves were estimated for each population and compared to local thermal conditions 2 months prior to collection. Results indicate that E. galapagensis populations were adapted and/or acclimatized to short-term local temperature as populations at warmer sites had substantially higher thermal tolerances. The acute thermal optimum (Topt) for the warmest and coolest site populations differed by 3 °C and the Topt was positively correlated with maximum temperature recorded at each site. Additionally, temperature-normalized respiration rate and activation energy (E) were negatively related to the maximum temperature. Understanding the temperature-dependent performance of the pencil urchin (the most significant mesograzer in this system), including its population specificity, provides insight into how herbivores and the functions they perform might be affected by further ocean heating

Transport properties of ybco thin films near the critical state with no applied field

Transport measurements carried out on twinned ybco films are compared to the predictions of a previously proposed model suggesting that the vortices move along the films twin boundaries that behave as rows of Josephson weak links [P.Bernstein and J.F.Hamet, J.Appl.Phys.95 (2004) 2569]. The obtained results suggest that, except if the films are very thin, the twin boundaries consist of superimposed rows of weak links with mean height,ds, whose mean length along the TBs is an universal function of T/Tc, the reduced temperature. This conclusion yields a general expression for the critical surface current density of the films as a function of T/Tc and of the number of superimposed weak links rows, while the critical current density depends on ds. A comparison of the measurements reported by various authors shows that the nature of the substrate and the growth technique have both a strong effect on ds . The existence of superimposed weak links rows is attributed to extended defects generated by y2o3 inclusions.Comment: 33 pages, 13 figures; accepted for publication in Physica

Nonlinear electrodynamics of p-wave superconductors

We consider the Maxwell-London electrodynamics of three dimensional superconductors in p-wave pairing states with nodal points or lines in the energy gap. The current-velocity relation is then nonlinear in the applied field, cubic for point nodes and quadratic for lines. We obtain explicit angular and depth dependent expressions for measurable quantities such as the transverse magnetic moment, and associated torque. These dependences are different for point and line nodes and can be used to distinguish between different order parameters. We discuss the experimental feasibility of this method, and bring forth its advantages, as well as limitations that might be present.Comment: Fourteen pages RevTex plus four postscript figure

Vortex Dynamics at the transition to the normal state in YBCO films

We propose a description of the vortex dynamics in YBCO films from the critical to the normal states. This description supposes that the vortex motion is thermally activated along the twin boundaries of the films. The discontinuity observed in the current-voltage curves at the transition to the normal state is explained by the sudden increase in the dissipated power rate due to vortex depinning. However, near the critical temperature, this phenomenon does not occur because the vortex activation energy is near zero. We also show how the current at the transition to the normal state can be computed from the current-voltage curves measured at low currents. The predictions of this description are compared to the data published by Gonzalez et al. [Phys.Rev.B68,054514 (2003)]

Gravitational Collapse of Phantom Fluid in (2+1)-Dimensions

This investigation is devoted to the solutions of Einstein's field equations for a circularly symmetric anisotropic fluid, with kinematic self-similarity of the first kind, in $(2+1)$-dimensional spacetimes. In the case where the radial pressure vanishes, we show that there exists a solution of the equations that represents the gravitational collapse of an anisotropic fluid, and this collapse will eventually form a black hole, even when it is constituted by the phantom energy.Comment: 10 page

Determination of the Strong Coupling \boldmath{\as} from hadronic Event Shapes and NNLO QCD predictions using JADE Data

Event Shape Data from $e^+e^-$ annihilation into hadrons collected by the JADE experiment at centre-of-mass energies between 14 GeV and 44 GeV are used to determine the strong coupling $\alpha_S$. QCD predictions complete to next-to-next-to-leading order (NNLO), alternatively combined with resummed next-to-leading-log-approximation (NNLO+NLLA) calculations, are used. The combined value from six different event shape observables at the six JADE centre-of-mass energies using the NNLO calculations is $\alpha_S(M_Z)$= 0.1210 +/- 0.0007(stat.) +/- 0.0021(expt.) +/- 0.0044(had.) +/- 0.0036(theo.) and with the NNLO+NLLA calculations the combined value is $\alpha_S$= 0.1172 +/- 0.0006(stat.) +/- 0.0020(expt.) +/- 0.0035(had.) +/- 0.0030(theo.) . The stability of the NNLO and NNLO+NLLA results with respect to missing higher order contributions, studied by variations of the renormalisation scale, is improved compared to previous results obtained with NLO+NLLA or with NLO predictions only. The observed energy dependence of $\alpha_S$ agrees with the QCD prediction of asymptotic freedom and excludes absence of running with 99% confidence level.Comment: 9 pages, EPHJA style, 4 figures, corresponds to published version with JADE author lis

Electronic resonance states in metallic nanowires during the breaking process simulated with the ultimate jellium model

We investigate the elongation and breaking process of metallic nanowires using the ultimate jellium model in self-consistent density-functional calculations of the electron structure. In this model the positive background charge deforms to follow the electron density and the energy minimization determines the shape of the system. However, we restrict the shape of the wires by assuming rotational invariance about the wire axis. First we study the stability of infinite wires and show that the quantum mechanical shell-structure stabilizes the uniform cylindrical geometry at given magic radii. Next, we focus on finite nanowires supported by leads modeled by freezing the shape of a uniform wire outside the constriction volume. We calculate the conductance during the elongation process using the adiabatic approximation and the WKB transmission formula. We also observe the correlated oscillations of the elongation force. In different stages of the elongation process two kinds of electronic structures appear: one with extended states throughout the wire and one with an atom-cluster like unit in the constriction and with well localized states. We discuss the origin of these structures.Comment: 11 pages, 8 figure

Deconfining Phase Transition as a Matrix Model of Renormalized Polyakov Loops

We discuss how to extract renormalized from bare Polyakov loops in SU(N) lattice gauge theories at nonzero temperature in four spacetime dimensions. Single loops in an irreducible representation are multiplicatively renormalized without mixing, through a renormalization constant which depends upon both representation and temperature. The values of renormalized loops in the four lowest representations of SU(3) were measured numerically on small, coarse lattices. We find that in magnitude, condensates for the sextet and octet loops are approximately the square of the triplet loop. This agrees with a large $N$ expansion, where factorization implies that the expectation values of loops in adjoint and higher representations are just powers of fundamental and anti-fundamental loops. For three colors, numerically the corrections to the large $N$ relations are greatest for the sextet loop, $\leq 25$; these represent corrections of $\sim 1/N$ for N=3. The values of the renormalized triplet loop can be described by an SU(3) matrix model, with an effective action dominated by the triplet loop. In several ways, the deconfining phase transition for N=3 appears to be like that in the $N=\infty$ matrix model of Gross and Witten.Comment: 24 pages, 7 figures; v2, 27 pages, 12 figures, extended discussion for clarity, results unchange

Hadronization effects in event shape moments

We study the moments of hadronic event shapes in $e^+e^-$ annihilation within the context of next-to-next-to-leading order (NNLO) perturbative QCD predictions combined with non-perturbative power corrections in the dispersive model. This model is extended to match upon the NNLO perturbative prediction. The resulting theoretical expression has been compared to experimental data from JADE and OPAL, and a new value for $\alpha_s(M_Z)$ has been determined, as well as of the average coupling $\alpha_0$ in the non-perturbative region below $\mu_I=2$ GeV within the dispersive model: \alpha_s(M_Z)&=0.1153\pm0.0017(\mathrm{exp})\pm0.0023(\mathrm{th}),\alpha_0&=0.5132\pm0.0115(\mathrm{exp})\pm0.0381(\mathrm{th}), The precision of the $\alpha_s(M_Z)$ value has been improved in comparison to the previously available next-to-leading order analysis. We observe that the resulting power corrections are considerably larger than those estimated from hadronization models in multi-purpose event generator programs.Comment: 23 pages, 5 figures, 15 tables. Few minor changes. Version accepted for publication in European Physical Journal C

Constraints on Dark Matter Annihilation in Clusters of Galaxies with the Fermi Large Area Telescope

Nearby clusters and groups of galaxies are potentially bright sources of high-energy gamma-ray emission resulting from the pair-annihilation of dark matter particles. However, no significant gamma-ray emission has been detected so far from clusters in the first 11 months of observations with the Fermi Large Area Telescope. We interpret this non-detection in terms of constraints on dark matter particle properties. In particular for leptonic annihilation final states and particle masses greater than ~200 GeV, gamma-ray emission from inverse Compton scattering of CMB photons is expected to dominate the dark matter annihilation signal from clusters, and our gamma-ray limits exclude large regions of the parameter space that would give a good fit to the recent anomalous Pamela and Fermi-LAT electron-positron measurements. We also present constraints on the annihilation of more standard dark matter candidates, such as the lightest neutralino of supersymmetric models. The constraints are particularly strong when including the fact that clusters are known to contain substructure at least on galaxy scales, increasing the expected gamma-ray flux by a factor of ~5 over a smooth-halo assumption. We also explore the effect of uncertainties in cluster dark matter density profiles, finding a systematic uncertainty in the constraints of roughly a factor of two, but similar overall conclusions. In this work, we focus on deriving limits on dark matter models; a more general consideration of the Fermi-LAT data on clusters and clusters as gamma-ray sources is forthcoming.Comment: accepted to JCAP, Corresponding authors: T.E. Jeltema and S. Profumo, minor revisions to be consistent with accepted versio