Four-Point One-Loop Amplitude Computation in the Pure Spinor Formalism

The massless 4-point one-loop amplitude computation in the pure spinor formalism is shown to agree with the computation in the RNS formalism.Comment: 10 pages harvmac te

Noncommutative Effects in the Black Hole Evaporation in Two Dimensions

We discuss some possible implications of a two-dimensional toy model for black hole evaporation in noncommutative field theory. While the noncommutativity we consider does not affect gravity, it can play an important role in the dynamics of massless and Hermitian scalar fields in the event horizon of a Schwarzschild black hole. We find that noncommutativity will affect the flux of outgoing particles and the nature of its UV/IR divergences. Moreover, we show that the noncommutative interaction does not affect Leahy's and Unruh's interpretation of thermal ingoing and outgoing fluxes in the black hole evaporation process. Thus, the noncommutative interaction still destroys the thermal nature of fluxes. In the process, some nonlocal implications of the noncommutativity are discussed.Comment: 33+1 pages, 3 eps figures, typos corrected, references added, figure 3 corrected, modifications in sections 4 and 6, version published in Phys. Rev.

The permutation group S_N and large Nc excited baryons

We study the excited baryon states for an arbitrary number of colors Nc from the perspective of the permutation group S_N of N objects. Classifying the transformation properties of states and quark-quark interaction operators under S_N allows a general analysis of the spin-flavor structure of the mass operator of these states, in terms of a few unknown constants parameterizing the unknown spatial structure. We explain how to perform the matching calculation of a general two-body quark-quark interaction onto the operators of the 1/Nc expansion. The inclusion of core and excited quark operators is shown to be necessary. Considering the case of the negative parity L=1 states transforming in the MS of S_N, we discuss the matching of the one-gluon and the Goldstone-boson exchange interactions.Comment: 38 pages. Final version to be published in Physical Review

Late Palaeozoic lithostratigraphy of the Andean Precordillera revisited (San Juan Province, Argentina)

New data on some neopalaeozoic lithostratigraphic units of the central sector of the Argentinean Precordillera are presented. The western Precordillera displays occasional outcrops of siliciclastic rocks of the Late Palaeozoic. These rocks are separated by two main unconformi­ties related to the development of the Chanic (Upper Devonian-early Carboniferous) and Gondwanan (late Carboniferous-early Permian) orogens. A major unconformity marks the beginning of the Andean cycle in middle Permian times. The Del Ratón Formation (800 m) in the studied area is made up of conglomerates and can be divided into two units. The basal part (Lower Member) was deposited in a fjord environment. The Upper Member was generated by an alluvial system that was mainly dominated by upper flow-regime plane beds, whereas its uppermost part accumulated in a fan delta setting. The clast provenance and the main palaeocurrents suggest the existence of a significant topographic high to the W and NW of the present outcrops. The El Planchón Formation (1400 m) is mainly composed of shales and sandstones as a result of sedimentation in a deep-sea fan environment. These lutite-dominated materials graded laterally north­wards into conglomerates in a glacial setting. The Del Ratón and El Planchón formations of the Lower Carboniferous correspond to the synorogenic Chanic sedimentation (Chanic foreland basin). Thereafter, the stratigraphic succession underwent deformation which led to its prolonged subaerial exposure and rubefaction. In Permian times, a marine transgression gave rise to the Del Salto Formation (600 m), which is constituted by beach deposits with some aeolian reworking and which lies unconformably over the Lower Carboniferous rocks. Conglomerates (Quebrada del Alumbre Formation, 100 m) produced by an alluvial system prograded episodically into coastal areas. The Escombrera Formation (350 m) is composed of beach deposits prograding seawards. This formation probably represents the end of the Palaeozoic sedimentary record. Thereafter, a playa-lake and an alluvial fan system were generated (Quebrada de la Arena Formation). This unit (750 m) was the last infill of the Gondwanan retroarc foreland, the total thickness of which was about 4000 m.Se presentan nuevos datos sobre las unidades neopaleozoicas aflorantes en la parte occidental de la Precordillera andina. Esas unidades litoestratigráficas estan separadas por dos discordancias angulares principales asociadas al desarrollo de las orogenias Chánica (Devónico tardío-Carbonífero temprano) y Gondwánica (Carbonífero tardío-Pérmico temprano) respectivamente. Otra nueva discordancia sugiere el inicio del ciclo andino durante el Pérmico medio. La Formación Del Ratón (800 m) está constituida principalmente por conglomerados y puede dividirse en dos unidades de rango menor: la parte basal y la parte superior respectivamente. La parte basal (Miembro inferior) fue acumulada en un fiordo. La parte superior (Miembro superior) fue generada en un sistema alluvial dominado predominantemente por la acumulación de capas planas de alto régimen de flujo, mientras que la parte más alta fue depositada en un entorno de abanico deltaico (fandelta). La procedencia de los clastos y las paleocorrientes principales indican la presencia de un relieve topográfico alto y significativo, situado al O y NO de los afloramientos actuales.La Formación El Planchón (1400 m) constituida principalmente por lutitas y areniscas fue acumulada en un contexto de abanico submarino (deep-sea fan). Estos materiales predominantemente lutíticos pasan lateralmente hacia el norte a conglomerados acumulados en un ambiente sedimentario glacial. Las Formaciones Del Ratón y El Planchón corresponden a la sedimentación sinorogénica Chánica (cuenca de antepaís chánica). Posteriormente, la sucesión estratigráfica sufrió una deformación que dió lugar a una prolongada exposición subaérea y su consiguiente rubefacción. Durante el Pérmico, una transgresión marina produjo la acumulación de la Formación Del Salto (600 m), que está constituída por depósitos de playa con algún retrabajamiento eólico y que recubre discordantemente los materiales del Carbonífero inferior. Un sistema aluvial conglomerático (Formación Quebrada del Alumbre 100 m) pogradó episódicamente sobre las zonas costeras. La Formación Escombrera (350 m), que está constituída por materiales arenosos coste-ros progradantes hacia el mar, representa, muy probablemente, el final del registro sedimentario paleozoico en esta zona. Posteriormente se generó otra discordancia sobre la que se acumularon materiales arenosos en un contexto de cursos fluviales trenzados sobre los que se disponen materiales lutíticos acumulados en una ciénaga (playa-lake) que gradan, primero a cursos trenzados, luego a cursos sinousos y finalmente a abanicos aluviales (Formación Quebrada de la Arena). Esta unidad (750 m) corresponde al último relleno sedimentario de la cuenca Gondwánica de retroarco, cuya potencia es del orden de unos 4000 m.Fil: Colombo, F.. Universidad de Barcelona; EspañaFil: Limarino, Carlos Oscar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; ArgentinaFil: Spalletti, Luis Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Busquets, P. Universidad de Barcelona; EspañaFil: Cardo, R.. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; ArgentinaFil: Mendez Bedia, I. Universidad de Oviedo; EspañaFil: Heredia, N.. Instituto Geológico y Minero de España; Españ

Pure Spinor Superspace Identities for Massless Four-point Kinematic Factors

Using the pure spinor formalism we prove identities which relate the tree-level, one-loop and two-loop kinematic factors for massless four-point amplitudes. From these identities it follows that the complete supersymmetric one- and two-loop amplitudes are immediately known once the tree-level kinematic factor is evaluated. In particular, the two-loop equivalence with the RNS formalism (up to an overall coefficient) is obtained as a corollary.Comment: 10 pages, harvmac TeX. v2: Updated affiliation and Report-no

On the large N limit, W_\infty Strings, Star products, AdS/CFT Duality, Nonlinear Sigma Models on AdS spaces and Chern-Simons p-branes

It is shown that the large $N$ limit of SU(N) YM in $curved$ $m$-dim backgrounds can be subsumed by a higher $m+n$ dimensional gravitational theory which can be identified to an $m$-dim generally invariant gauge theory of diffs $N$, where $N$ is an $n$-dim internal space (Cho, Sho, Park, Yoon). Based on these findings, a very plausible geometrical interpretation of the $AdS/CFT$ correspondence could be given. Conformally invariant sigma models in $D=2n$ dimensions with target non-compact SO(2n,1) groups are reviewed. Despite the non-compact nature of the SO(2n,1), the classical action and Hamiltonian are positive definite. Instanton field configurations are found to correspond geometrically to conformal ``stereographic'' mappings of $R^{2n}$ into the Euclidean signature $AdS_{2n}$ spaces. The relation between Self Dual branes and Chern-Simons branes, High Dimensional Knots, follows. A detailed discussion on $W_\infty$ symmetry is given and we outline the Vasiliev procedure to construct an action involving higher spin massless fields in $AdS_4$. This $AdS_4$ spacetime higher spin theory should have a one-to-one correspondence to noncritical $W_\infty$ strings propagating on $AdS_4 \times S^7$.Comment: 43 pages, Tex fil

Some Superstring Amplitude Computations with the Non-Minimal Pure Spinor Formalism

We use the non-minimal pure spinor formalism to compute in a super-Poincare covariant manner the four-point massless one and two-loop open superstring amplitudes, and the gauge anomaly of the six-point one-loop amplitude. All of these amplitudes are expressed as integrals of ten-dimensional superfields in a "pure spinor superspace" which involves five $\theta$ coordinates covariantly contracted with three pure spinors. The bosonic contribution to these amplitudes agrees with the standard results, and we demonstrate identities which show how the $t_8$ and $\epsilon_{10}$ tensors naturally emerge from integrals over pure spinor superspace.Comment: 20 pages, harvmac te

Using Biotic Interaction Networks for Prediction in Biodiversity and Emerging Diseases

Networks offer a powerful tool for understanding and visualizing inter-species interactions within an ecology. Previously considered examples, such as trophic networks, are just representations of experimentally observed direct interactions. However, species interactions are so rich and complex it is not feasible to directly observe more than a small fraction. In this paper, using data mining techniques, we show how potential interactions can be inferred from geographic data, rather than by direct observation. An important application area for such a methodology is that of emerging diseases, where, often, little is known about inter-species interactions, such as between vectors and reservoirs. Here, we show how using geographic data, biotic interaction networks that model statistical dependencies between species distributions can be used to infer and understand inter-species interactions. Furthermore, we show how such networks can be used to build prediction models. For example, for predicting the most important reservoirs of a disease, or the degree of disease risk associated with a geographical area. We illustrate the general methodology by considering an important emerging disease - Leishmaniasis. This data mining approach allows for the use of geographic data to construct inferential biotic interaction networks which can then be used to build prediction models with a wide range of applications in ecology, biodiversity and emerging diseases

Relating high-energy lepton-hadron, proton-nucleus and nucleus-nucleus collisions through geometric scaling

A characteristic feature of small-x lepton-proton data from HERA is geometric scaling -- the fact that over a wide range of x and Q^2 all data can be described by a single variable $Q^2/Q_{sat}^2(x)$, with all x-dependence encoded in the so-called saturation momentum $Q_{sat}(x)$. Here, we observe that the same scaling ansatz accounts for nuclear photoabsorption cross sections and favors the nuclear dependence $Q_{sat,A}^2\propto A^{\alpha}Q_{sat}^2$, $\alpha \simeq 4/9$. We then make the empirical finding that the same A-dependence accounts for the centrality evolution of the multiplicities measured in Au+Au collisions at RHIC. It also allows to parametrize the high-p_t particle suppression in d+Au collisions at forward rapidities. If these geometric scaling properties have a common dynamical origin, then this A-dependence of $Q_{sat,A}^2$ should emerge as a consequence of the underlying dynamical model.Comment: 4 pages, 3 postscript figure