Patterns of alien plant distribution in a river landscape following an extreme flood

AbstractThe availability of suitable patches and gaps in the landscape is a crucial determinant of invasibility for alien plants. The type and arrangement of patches in the landscape may both facilitate and obstruct alien plant invasions, depending on whether alien species perceive the patches as barriers. In February 2000 tropical weather systems caused an extreme flood with an estimated return interval of 90 to 200 years in the Sabie River, South Africa. The impact of the 2000 flood on the Sabie River landscape provides an array of patches that may provide suitable resources for the establishment of alien plants. This study examines the distribution of alien plants in relation to patchiness of the Sabie River landscape. Our hypothesis was that if certain patches in the river landscape do not represent environmental barriers to alien plant invasion, alien species will occur preferentially in these patch types. The Sabie River within Kruger National Park [KNP] was divided into six patch types (zones, channel types, elevations, geomorphic units, substrates and flood imprint types). We then examined the distribution of native and alien woody and herbaceous density and species richness in patches. The density and species richness of alien plants in the Sabie River in KNP is very low when compared to the density and species richness of native plants. Some patches (bedrock distributary and braid bar geomorphic units) contained higher density and richness of alien plants compared to the other patches examined, indicating that these locations in the river landscape offer the resources necessary for alien plant establishment. Individual alien species are also associated with different parts of the river landscape. Failure of large numbers of alien plants to establish after the 2000 flood is most likely due to a combination of factors—the plant specific barriers imposed by landscape patchiness, the high abundance and richness of native vegetation leading to competition, and for some species certainly, the clearing by the management (Working for Water) programme

World-sheet scattering in AdS_5 x S^5 at two loops

We study the AdS_5 x S^5 sigma-model truncated to the near-flat-space limit to two-loops in perturbation theory. In addition to extending previously known one-loop results to the full SU(2|2)^2 S-matrix we calculate the two-loop correction to the dispersion relation and then compute the complete two-loop S-matrix. The result of the perturbative calculation can be compared with the appropriate limit of the conjectured S-matrix for the full theory and complete agreement is found.Comment: 26pages, 3 figure

Finite size giant magnons in the SU(2) x SU(2) sector of AdS_4 x CP^3

We use the algebraic curve and Luscher's mu-term to calculate the leading order finite size corrections to the dispersion relation of giant magnons in the SU(2) x SU(2) sector of AdS_4 x CP^3. We consider a single magnon as well as one magnon in each SU(2). In addition the algebraic curve computation is generalized to give the leading order correction for an arbitrary multi-magnon state in the SU(2) x SU(2) sector.Comment: 19 pages; v2, v3: references added, typos fixe

Semiclassical strings in AdS(3) X S^2

In this paper, we investigate the semiclassical strings in AdS(3)XS^2, in which the string configuration of AdS(3) is classified to three cases depending on the parameters. Each of these has a different anomalous dimension proportional to logS, S^(1/3) and S, where S is a angular momentum on AdS(3). Further we generalize the dispersion relations for various string configuration on AdS(3)XS^2.Comment: 15 pages, added reference

Worldsheet Scattering in AdS_5 x S^5

We calculate the S-matrix in the gauge-fixed sigma-model on AdS_5 x S^5 to the leading order in perturbation theory, and analyze how supersymmetry is realized on the scattering states. A mild nonlocality of the supercharges implies that their action on multi-particle states does not follow the Leibniz rule, which is replaced by a nontrivial coproduct. The plane wave symmetry algebra is thus naturally enhanced to a Hopf algebra. The scattering matrix elements obey the classical Yang-Baxter equation modified by the existence of the coproduct. This structure mirrors that of the large 't Hooft coupling expansion of the S-matrix for the spin chain in the dual super-Yang-Mills theory.Comment: 51 pages, v2: references added, v3: sign in (2.12), (6.19) and (6.21) corrected; v4: discussion of classical YBE is considerably modifie

On the perturbative chiral ring for marginally deformed N=4 SYM theories

For \cal{N}=1 SU(N) SYM theories obtained as marginal deformations of the \cal{N}=4 parent theory we study perturbatively some sectors of the chiral ring in the weak coupling regime and for finite N. By exploiting the relation between the definition of chiral ring and the effective superpotential we develop a procedure which allows us to easily determine protected chiral operators up to n loops once the superpotential has been computed up to (n-1) order. In particular, for the Lunin-Maldacena beta-deformed theory we determine the quantum structure of a large class of operators up to three loops. We extend our procedure to more general Leigh-Strassler deformations whose chiral ring is not fully understood yet and determine the weight-two and weight-three sectors up to two loops. We use our results to infer general properties of the chiral ring.Comment: LaTex, 40 pages, 4 figures, uses JHEP3; v2: minor correction

Scattering in Mass-Deformed N>=4 Chern-Simons Models

We investigate the scattering matrix in mass-deformed N>=4 Chern-Simons models including as special cases the BLG and ABJM theories of multiple M2 branes. Curiously the structure of this scattering matrix in three spacetime dimensions is equivalent to (a) the two-dimensional worldsheet matrix found in the context of AdS/CFT integrability and (b) the R-matrix of the one-dimensional Hubbard model. The underlying reason is that all three models are based on an extension of the psu(2|2) superalgebra which constrains the matrix completely. We also compute scattering amplitudes in one-loop field theory and find perfect agreement with scattering unitarity.Comment: 63 pages, v2: minor corrections, v3: minor improvement

Integrable twists in AdS/CFT

A class of marginal deformations of four-dimensional N=4 super Yang-Mills theory has been found to correspond to a set of smooth, multiparameter deformations of the S^5 target subspace in the holographic dual on AdS_5 x S^5. We present here an analogous set of deformations that act on global toroidal isometries in the AdS_5 subspace. Remarkably, certain sectors of the string theory remain classically integrable in this larger class of so-called gamma-deformed AdS_5 x S^5 backgrounds. Relying on studies of deformed su(2)_gamma models, we formulate a local sl(2)_gamma Lax representation that admits a classical, thermodynamic Bethe equation (based on the Riemann-Hilbert interpretation of Bethe's ansatz) encoding the spectrum in the deformed AdS_5 geometry. This result is extended to a set of discretized, asymptotic Bethe equations for the twisted string theory. Near-pp-wave energy spectra within sl(2)_gamma and su(2)_gamma sectors provide a useful and stringent test of such equations, demonstrating the reliability of this technology in a wider class of string backgrounds. In addition, we study a twisted Hubbard model that yields certain predictions of the dual beta-deformed gauge theory.Comment: v2: references and clarifications added, 46 page

Review of AdS/CFT Integrability, Chapter IV.3: N=6 Chern-Simons and Strings on AdS4xCP3

We review the duality and integrability of N=6 superconformal Chern-Simons theory in three dimensions and IIA superstring theory on the background AdS4xCP3. We introduce both of these models and describe how their degrees of freedom are mapped to excitations of a long-range integrable spin-chain. Finally, we discuss the properties of the Bethe equations, the S-matrix and the algebraic curve that are special to this correspondence and differ from the case of N=4 SYM theory and strings on AdS5xS5.Comment: 22 pages, see also overview article arXiv:1012.3982, v2: references to other chapters updated, v3: references added, v4: brief discussion of giant magnons added, further minor changes, published version, v5: union of v3 and v4 because changes made in v3 were accidentally lost in v

Review of AdS/CFT Integrability, Chapter II.2: Quantum Strings in AdS5xS5

We review the semiclassical analysis of strings in AdS5xS5 with a focus on the relationship to the underlying integrable structures. We discuss the perturbative calculation of energies for strings with large charges, using the folded string spinning in an AdS3 subset of AdS5 as our main example. Furthermore, we review the perturbative light-cone quantization of the string theory and the calculation of the worldsheet S-matrix.Comment: 20 pages, see also overview article arXiv:1012.3982, v2: references to other chapters update