Search

Understanding and predicting interactions between predators and prey and their environment are fundamental for understanding food web structure, dynamics, and ecosystem function in both terrestrial and marine ecosystems.Thus, estimating the conditional associations between species and their environments is important for exploring connections or cooperative links in the ecosystem, which in turn can help to clarify such causal relationships. For this purpose, a relevant and practical statistical method is required to link presence/absence observations with biomass, abundance, and physical quantities obtained as continuous real values.These data are sometimes sparse in oceanic space and too short as time series data. To meet this challenge, we provide an approach based on applying categorical data analysis to present/absent observations and real-number data.This approach consists of a two-step procedure for categorical data analysis:1) finding the appropriate threshold to discretize the real-number data for applying an independent test;and 2) identifying the best conditional probability model to investigate the possible associations among the data based on a statistical information criterion.We conduct a simulation study to validate our proposed approach. Furthermore, the approach is applied to two datasets: 1) one collected during an international synoptic krill survey in the Scotia Sea west of the Antarctic Peninsula to investigate associations among krill, fin whale (Balaenoptera physalus),surface temperature, depth, slope in depth, and temperature gradient; 2) the other collected by ecosystem surveys conducted during August-September in 2014 - 2017 to investigate associations among common minke whales, the predatory fish Atlantic cod, and their main prey groups in Arctic Ocean waters to the west and north of Svalbard, Norway.

Integral invariants in maximally supersymmetric Yang-Mills theories are discussed in spacetime dimensions $4\leq D\leq 10$ for $SU(k)$ gauge groups. It is shown that, in addition to the action, there are three special invariants in all dimensions. Two of these, the single- and double-trace $F^4$ invariants, are of Chern-Simons type in $D=9,10$ and BPS type in $D\leq 8$, while the third, the double-trace of two derivatives acting on $F^4$, can be expressed in terms of a gauge-invariant super-$D$-form in all dimensions. We show that the super-ten-forms for $D=10$ $F^4$ invariants have interesting cohomological properties and we also discuss some features of other invariants, including the single-trace $d^2 F^4$, which has a special form in $D=10$. The implications of these results for ultra-violet divergences are discussed in the framework of algebraic renormalisation., Comment: 20 pages, 1 table

We discuss the conditions for extra supersymmetry of the N=(2,2) supersymmetric vector multiplets described in arXiv:0705.3201 [hep-th] and in arXiv:0808.1535 [hep-th]. We find (4,4) supersymmetry for the semichiral vector multiplet but not for the Large Vector Multiplet., Comment: 15 pages

We discuss additional supersymmetries for N = (2, 2) supersymmetric non-linear sigma models described by left and right semichiral superfields., Comment: 11 pages. Talk presented by U.L. at "30th Winter School on Geometry and Physics" Srni, Czech Republic January 2010.

The $\alpha'^2$ deformation of D=10 SYM is the natural generalisation of the $F^4$ term in the abelian Born-Infeld theory. It is shown that this deformation can be extended to $\alpha'^4$ in a way which is consistent with supersymmetry. The latter requires the presence of higher-derivative and commutator terms as well as the symmetrised trace of the Born-Infeld $\alpha'^4$ term., Comment: 27 pages. Minor changes to text; references added.

We describe the conditions for extra supersymmetry in N=(2,2) supersymmetric nonlinear sigma models written in terms of semichiral superfields. We find that some of these models have additional off-shell supersymmetry. The (4,4) supersymmetry introduces geometrical structures on the target-space which are conveniently described in terms of Yano f-structures and Magri-Morosi concomitants. On-shell, we relate the new structures to the known bi-hypercomplex structures., Comment: 20 pages; v2: significant corrections, clarifications, and reorganization; v3: discussion of supersymmetry vs twisted supersymmetry added, relevant signs corrected.

We investigate the target space geometry of supersymmetric sigma models in two dimensions with Euclidean signature, and the conditions for N=2 supersymmetry. For a real action, the geometry for the N=2 model is not the generalized Kahler geometry that arises for Lorentzian signature, but is an interesting modification of this which is not a complex geometry., Comment: 13 pages

The projective superspace formulation for four-dimensional N = 2 matter-coupled supergravity presented in arXiv:0805.4683 makes use of the variant superspace realization for the N = 2 Weyl multiplet in which the structure group is SL(2,C) x SU(2) and the super-Weyl transformations are generated by a covariantly chiral parameter. An extension to Howe's realization of N = 2 conformal supergravity in which the tangent space group is SL(2,C) x U(2) and the super-Weyl transformations are generated by a real unconstrained parameter was briefly sketched. Here we give the explicit details of the extension., Comment: 17 pages, no figure; V2: comments and references added, published version

This paper presents a projective superspace formulation for 4D N = 2 matter-coupled supergravity. We first describe a variant superspace realization for the N = 2 Weyl multiplet. It differs from that proposed by Howe in 1982 by the choice of the structure group (SO(3,1) x SU(2) versus SO(3,1) x U(2)), which implies that the super-Weyl transformations are generated by a covariantly chiral parameter instead of a real unconstrained one. We introduce various off-shell supermultiplets which are curved superspace analogues of the superconformal projective multiplets in global supersymmetry and which describe matter fields coupled to supergravity. A manifestly locally supersymmetric and super-Weyl invariant action principle is given. Off-shell locally supersymmetric nonlinear sigma models are presented in this new superspace., Comment: 26 pages, LaTeX, no figures; V2: comments and references added, version published in JHEP; V3: typo in eq. (2.7e) corrected

We discuss two dimensional N-extended supersymmetry in Euclidean signature and its R-symmetry. For N=2, the R-symmetry is SO(2)\times SO(1,1), so that only an A-twist is possible. To formulate a B-twist, or to construct Euclidean N=2 models with H-flux so that the target geometry is generalised Kahler, it is necessary to work with a complexification of the sigma models. These issues are related to the obstructions to the existence of non-trivial twisted chiral superfields in Euclidean superspace., Comment: 8 pages

We investigate the topological theory obtained by twisting the N=(2,2) supersymmetric nonlinear sigma model with target a bihermitian space with torsion. For the special case in which the two complex structures commute, we show that the action is a Q-exact term plus a quasi-topological term. The quasi-topological term is locally given by a closed two-form which corresponds to a flat gerbe-connection and generalises the usual topological term of the A-model. Exponentiating it gives a Wilson surface, which can be regarded as a generalization of a Wilson line. This makes the quantum theory globally well-defined., Comment: 16 pages, Appendix added, the version to appear in JHEP

A kappa-symmetric action for coincident D-branes is presented. It is valid in the approximation that the additional fermionic variables, used to incorporate the non-abelian degrees of freedom, are treated classically. The action is written as a Bernstein-Leites integral on the supermanifold obtained from the bosonic worldvolume by adjoining the extra fermions. The integrand is a very simple extension of the usual Green-Schwarz action for a single brane; all symmetries, except for kappa, are manifest, and the proof of kappa-symmetry is very similar to the abelian case., Comment: 18 pages. References added

A covariant version of the non-abelian Dirac-Born-Infeld-Myers action is presented. The non-abelian degrees of freedom are incorporated by adjoining to the (bosonic) worldvolume of the brane a number of anticommuting fermionic directions corresponding to boundary fermions in the string picture. The proposed action treats these variables as classical but can be given a matrix interpretation if a suitable quantisation prescription is adopted. After gauge-fixing and quantisation of the fermions, the action is shown to be in agreement with the Myers action derived from T-duality. It is also shown that the requirement of covariance in the above sense leads to a modified WZ term which also agrees with the one proposed by Myers., Comment: 18 pages. Minor alterations to the text; references added

A study of (1,1) supersymmetric two-dimensional non-linear sigma models with boundary on special holonomy target spaces is presented. In particular, the consistency of the boundary conditions under the various symmetries is studied. Models both with and without torsion are discussed., Comment: 20 pages. Minor errors corrected, some new results on the symmetry algebra added, and a connection for the bi-G_2 structure derived

The Green-Schwarz action for an open superstring with additional boundary fermions, representing Chan-Paton factors, is studied at the classical level. The boundary geometry is described by a bundle, with fermionic fibres, over the super worldvolume of a D-brane together with a map from the total space into the type II target superspace. This geometry is constrained by the requirement of kappa-symmetry on the boundary together with the use of the equations of motion for the fermions. There are two constraints which are formally similar to those that arise in the abelian case but which differ because of the dependence on the additional coordinates. The model, when quantised, would be a candidate for a fully kappa-symmetric theory of a stack of coincident D-branes including a non-abelian Born-Infeld sector. The example of the D9-brane in a flat background is studied. The constraints on the non-abelian field strength are shown to be in agreement with those derived from the pure spinor approach to the superstring. A covariant formalism is developed and the problem of quantisation is discussed., Comment: 26 pages. Typographical errors corrected. References added

The superembedding formalism is used to study correction terms to the dynamics of the M2 brane in a flat background. This is done by deforming the standard embedding constraint. It is shown rigorously that the first such correction occurs at dimension four. Cohomological techniques are used to determine this correction explicitly. The action is derived to quadratic order in fermions, and the modified $\k$-symmetry transformations are given., Comment: 38 pages, 3 figures

A superembedding construction of general non-abelian Born-Infeld actions in three dimensions is described. These actions have rigid target space and local worldvolume supersymmetry(i.e. kappa symmetry). The standard abelian Born-Infeld gauge multiplet is augmented with an additional worldvolume SU(N) gauge supermultiplet. It is shown how to construct single-trace actions and in particular a kappa-supersymmetric extension of the symmetrised trace action., Comment: 14 pages

We find the N-soliton solution at infinite theta, as well as the metric on the moduli space corresponding to spatial displacements of the solitons. We use a perturbative expansion to incorporate the leading 1/theta corrections, and find an effective short range attraction between solitons. We study the stability of various solutions. We discuss the finite theta corrections to scattering, and find metastable orbits. Upon quantization of the two-soliton moduli space, for any finite theta, we find an s-wave bound state., Comment: Second revision: Discussions of translation zero-modes in section 4 and scales in section 5 improved; web addresses of movies changed. First revision: Section 6 is rewritten (thanks to M. Headrick for pointing out a mistake in the original version); some references and acknowledgements added. 21 pages, JHEP style, Hypertex, 1 figure, 3 MPEG's at: http://www.physto.se/~unge/traj1.mpg http://www.physto.se/~unge/traj2.mpg http://www.physto.se/~unge/traj3.mpg

We show that the Higgs branch of a four-dimensional Yang-Mills theory, with gauge and matter content summarised by an ADE quiver diagram, is identical to the generalised Coulomb branch of a four-dimensional superconformal strongly coupled gauge theory with ADE global symmetry. This equivalence suggests the existence of a mirror symmetry between the quiver theories and the strongly coupled theories., Comment: 8 pages, 4 figures. Talk delivered by UL at D.V. Volkov Memorial Conference, July 25-29, 2000, Kharkov, to be published in the proceedings

We present a general method to derive the classical mechanics of a system of identical particles in a way that retains information about quantum statistics. The resulting statistical mechanics can be interpreted as a classical version of Haldane's exclusion statistics., Comment: Latex, 4 pages

Starting from the quantum theory of identical particles, we show how to define a classical mechanics that retains information about the quantum statistics. We consider two examples of relevance for the quantum Hall effect: identical particles in the lowest Landau level, and vortices in the Chern-Simons Ginzburg-Landau model. In both cases the resulting {\em classical} statistical mechanics is shown to be a nontrivial classical limit of Haldane's exclusion statistics., Comment: 40 pages, Latex

We describe new $N$-extended 2D supergravities on a $(p+1)$-dimensional (bosonic) space. The fundamental objects are moving frame densities that equip each $(p+1)$-dimensional point with a 2D ``tangent space''. The theory is presented in a $[p+1, 2]$ superspace. For the special case of $p=1$ we recover the 2D supergravities in an unusual form. The formalism has been developed with applications to the string-parton picture of $D$-branes at strong coupling in mind., Comment: 16 pages, Latex

We study the Born-Infeld D-brane action in the limit when the string coupling goes to infinity. The resulting actions is presented in an arbitrary background and shown to describe a foliation of the world-volume by strings. Using a recently developed ``degenerate'' supergravity the parton picture is shown to be applicable also to supersymmetric D-branes., Comment: 14 pages, Latex

Starting from certain 3D non-abelian dual systems, we discuss a number of related dual systems in 2D, some of which are obtained by dimensional reduction. The dualities relate massive scalar and vector fields, and may be relevant for string theory in the context of massive type IIA supergravity. Supersymmetric extensions of the models are also presented., Comment: 16 pages, Latex

Manifestly N=2 supersymmetric Feynman rules are found for different off-shell realizations of the massless hypermultiplet in projective superspace. When we reduce the Feynman rules to an N=1 superspace we obtain the correct component propagators. The Feynman rules are shown to be compatible with a ``duality'' that acts only on the auxiliary fields, as well as with the usual duality relating the hypermultiplet to the tensor multiplet., Comment: Replaced with revised version to be published in Nuc. Phys. B

We consider theories with degenerate kinetic terms such as those that arise at strong coupling in $N=2$ super Yang-Mills theory. We compute the components of generalized $N=1,2$ supersymmetric sigma model actions in two dimensions. The target space coordinates may be matter and/or Yang-Mills superfield strengths., Comment: 11 pages, LateX. This updates the faulty TeX file which has prevented reading the article on the archive for more than 20 years

We propose a Wilsonian action compatible with special geometry and higher dimension N=2 corrections, and show that the holomorphic contribution F to the low energy effective action is independent of the infrared cutoff. We further show that for asymptotically free SU(2) super Yang-Mills theories, the infrared cutoff can be tuned to cancel leading corrections to F. We also classify all local higher-dimensional contributions to the N=2 superspace effective action that produce corrections to the Kahler potential when reduced to N=1 superspace., Comment: 9 pages, Latex

In this note, we construct new representations of D=2, N=4 supersymmetry which do not involve chiral or twisted chiral multiplets. These multiplets may make it possible to circumvent no-go theorems about N=4 superspace formulations of WZWN-models., Comment: 11 pages, latex

Requiring that the path integral has the global symmetries of the classical action and obeys the natural composition property of path integrals, and also that the discretized action has the correct naive continuum limit, we find a viable discretization of the (D=3,N=2) superparticle action., Comment: 10 pages