Pathways to link biodiversity and ecosystem functioning: from monitoring to complex ecological interactions studies

Abstract Environmental changes have been rapidly increasing in the last decades, causing unprecedented shifts in biodiversity. The impacts of biodiversity changes on ecosystem processes depend on the traits of affected species and their functional redundancy at the community level. The generated data on biodiversity-functioning in marine environments are still fragmentary and predictions on how species, communities and ecosystems will respond to the ongoing global changes are still uncertain. This selection of manuscripts presents the efforts of researchers around the world towards a better understanding on the mechanisms driving biodiversity and functioning patterns in marine ecosystems. The issue is composed of studies about first records of diversity and single species patterns in overlooked marine communities, effects of pollution in shaping species composition, foundation species and the impact of their loss on local communities, and the relevance of ecological interactions and species’ traits in structuring marine food webs. We conclude that more field and experimental studies combined to modelling are needed for understanding mechanisms that currently determine the structure and functioning of ecosystems and for improving predictions under global change scenarios

Bell inequalities stronger than the CHSH inequality for 3-level isotropic states

We show that some two-party Bell inequalities with two-valued observables are stronger than the CHSH inequality for 3 \otimes 3 isotropic states in the sense that they are violated by some isotropic states in the 3 \otimes 3 system that do not violate the CHSH inequality. These Bell inequalities are obtained by applying triangular elimination to the list of known facet inequalities of the cut polytope on nine points. This gives a partial solution to an open problem posed by Collins and Gisin. The results of numerical optimization suggest that they are candidates for being stronger than the I_3322 Bell inequality for 3 \otimes 3 isotropic states. On the other hand, we found no Bell inequalities stronger than the CHSH inequality for 2 \otimes 2 isotropic states. In addition, we illustrate an inclusion relation among some Bell inequalities derived by triangular elimination.Comment: 9 pages, 1 figure. v2: organization improved; less references to the cut polytope to make the main results clear; references added; typos corrected; typesetting style change

Non-perturbative gauge/gravity correspondence in N=2 theories

We derive the exact supergravity profile for the twisted scalar field emitted by a system of fractional D3 branes at a Z2 orbifold singularity supporting N=2 quiver gauge theories with unitary groups and bifundamental matter. At the perturbative level this twisted field is "dual" to the gauge coupling but it is corrected non-perturbatively by an infinite tower of fractional D-instantons. The explicit microscopic description allows to derive the gravity profile from disk amplitudes computing the emission rate of the twisted scalar field in terms of chiral correlators in the dual gauge theory. We compute these quantum correlators using multi-instanton localization techniques and/or Seiberg-Witten analysis. Finally, we discuss a non-perturbative relation between the twisted scalar and the effective coupling of the gauge theory for some simple choices of the brane set ups.Comment: 42 pages. 3 figures, PDFLaTe

A review of effects of ultraviolet light on the visual system

An accumulation of epidemiologic and experimental studies support the notion that ultraviolet radiation may be hazardous to the human eye. This review will examine the role and effects of ultraviolet radiation on the visual system as well as present some prescribing considerations for the eye professional with regards to ultraviolet radiation

N=2 Instanton Effective Action in Omega-background and D3/D(-1)-brane System in R-R Background

We study the relation between the ADHM construction of instantons in the Omega-background and the fractional D3/D(-1)-branes at the orbifold singularity of C \times C^2/Z_2 in Ramond-Ramond (R-R) 3-form field strength background. We calculate disk amplitudes of open strings connecting the D3/D(-1)-branes in certain R-R background to obtain the D(-1)-brane effective action deformed by the R-R background. We show that the deformed D(-1)-brane effective action agrees with the instanton effective action in the Omega-background.Comment: 35 pages, no figures, references adde

Quantum Heisenberg Chain with Long-Range Ferromagnetic Interactions at Low Temperature

A modified spin-wave theory is applied to the one-dimensional quantum Heisenberg model with long-range ferromagnetic interactions. Low-temperature properties of this model are investigated. The susceptibility and the specific heat are calculated; the relation between their behaviors and strength of the long-range interactions is obtained. This model includes both the Haldane-Shastry model and the nearest-neighbor Heisenberg model; the corresponding results in this paper are in agreement with the solutions of both the models. It is shown that there exists an ordering transition in the region where the model has longer-range interactions than the HS model. The critical temperature is estimated.Comment: 17 pages(LaTeX REVTeX), 1 figure appended (PostScript), Technical Report of ISSP A-274

Charge form factor of π\pi and KK mesons

The charge form factor of $\pi$ and $K$ mesons is evaluated adopting a relativistic constituent quark model based on the light-front formalism. The relevance of the high-momentum components of the meson wave function, for values of the momentum transfer accessible to $CEBAF$ energies, is illustrated. The predictions for the elastic form factor of $\pi$ and $K$ mesons are compared with the results of different relativistic approaches, showing that the measurements of the pion and kaon form factors planned at $CEBAF$ could provide information for discriminating among various models of the meson structure.Comment: 8 pages, latex, 4 figures available as separate .uu fil

Strange Mesonic Transition Form Factor in the Chiral Constituent Quark Model

The form factor $g_{\rho \pi}^{(S)}(Q^{2})$ of the strange vector current transition matrix element $$ is calculated within the chiral quark model. A strange vector current of the constituent $U$- and D-quarks is induced by kaon radiative corrections and this mechanism yields the nonvanishing values of $g_{\rho\pi}^{(S)}(0)$. The numerical result at the photon point is consistent with the one given by the $\phi$-meson dominance model, but the fall-off in the $Q^{2}$-dependence is faster than the monopole form factor. Mesonic radiative corrections are also examined for the electromagnetic $\rho$-to-$\pi$ and $K^{*}$-to-$K$ transition amplitudes.Comment: LaTex 11 pages, 2 PostScript figure