3,258 research outputs found
Extended 2d generalized dilaton gravity theories
We show that an anomaly-free description of matter in (1+1) dimensions
requires a deformation of the 2d relativity principle, which introduces a
non-trivial center in the 2d Poincare algebra. Then we work out the reduced
phase-space of the anomaly-free 2d relativistic particle, in order to show that
it lives in a noncommutative 2d Minkowski space. Moreover, we build a Gaussian
wave packet to show that a Planck length is well-defined in two dimensions. In
order to provide a gravitational interpretation for this noncommutativity, we
propose to extend the usual 2d generalized dilaton gravity models by a specific
Maxwell component, which gauges the extra symmetry associated with the center
of the 2d Poincare algebra. In addition, we show that this extension is a high
energy correction to the unextended dilaton theories that can affect the
topology of space-time. Further, we couple a test particle to the general
extended dilaton models with the purpose of showing that they predict a
noncommutativity in curved space-time, which is locally described by a Moyal
star product in the low energy limit. We also conjecture a probable
generalization of this result, which provides a strong evidence that the
noncommutativity is described by a certain star product which is not of the
Moyal type at high energies. Finally, we prove that the extended dilaton
theories can be formulated as Poisson-Sigma models based on a nonlinear
deformation of the extended Poincare algebra.Comment: 21 pages, IOP LaTeX2e preprint classfile, Improved discussions, Minor
corrections, More didactic, More self-contained, New results concerning
noncommutativity in curved space-time, Accepted for publication in Classical
and Quantum Gravity on 02 Jul 200
Nonplanar integrability at two loops
In this article we compute the action of the two loop dilatation operator on
restricted Schur polynomials that belong to the su(2) sector, in the displaced
corners approximation. In this non-planar large N limit, operators that
diagonalize the one loop dilatation operator are not corrected at two loops.
The resulting spectrum of anomalous dimensions is related to a set of decoupled
harmonic oscillators, indicating integrability in this sector of the theory at
two loops. The anomalous dimensions are a non-trivial function of the 't Hooft
coupling, with a spectrum that is continuous and starting at zero at large N,
but discrete at finite N.Comment: version to appear in JHE
A double coset ansatz for integrability in AdS/CFT
We give a proof that the expected counting of strings attached to giant
graviton branes in AdS_5 x S^5, as constrained by the Gauss Law, matches the
dimension spanned by the expected dual operators in the gauge theory. The
counting of string-brane configurations is formulated as a graph counting
problem, which can be expressed as the number of points on a double coset
involving permutation groups. Fourier transformation on the double coset
suggests an ansatz for the diagonalization of the one-loop dilatation operator
in this sector of strings attached to giant graviton branes. The ansatz agrees
with and extends recent results which have found the dynamics of open string
excitations of giants to be given by harmonic oscillators. We prove that it
provides the conjectured diagonalization leading to harmonic oscillators.Comment: 33 pages, 3 figures; v2: references adde
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Chiral String in a Curved Space: Gravitational Self-Action
We analyze the effective action describing the linearised gravitational
self-action for a classical superconducting string in a curved spacetime. It is
shown that the divergent part of the effective action is equal to zero for the
both Nambu-Goto and chiral superconducting string.Comment: 5 pages, LaTe
Differential Interests of Agricultural College Students as Measured by the Kuder Preference Record
The Kuder Preference Record has enjoyed wide usage as a counselor\u27s aid in determining categorical interests of individuals. Many studies have been made in an attempt to discover differential interests of occupational groups and of those engaged in the pursuit of various college curricula. Such significant differences in interests as are found have been deemed to be of valuable assistance to the vocational and educational counselor. So far as the writer has been able to discover, little use has been made of the Kuder Preference Record in the measurement of interests of college students pursuing an agricultural curriculum. This may be due to the fact that, until the recent publication of Form C, there was no section of the Kuder Record which, by title at least, was suggestive of interests of those engaged in or preparing for agricultural work. While the outdoor section of Form C is pertinent for agricultural activities in general, it is reasonable to assume that the differential· interests which might occur in the other nine sections have important implications for guidance
Correlators of Giant Gravitons from dual ABJ(M) Theory
We generalize the operators of ABJM theory, given by Schur polynomials, in
ABJ theory by computing the two point functions in the free field and at finite
limits. These polynomials are then identified with the states of
the dual gravity theory. Further, we compute correlators among giant gravitons
as well as between giant gravitons and ordinary gravitons through the
corresponding correlators of ABJ(M) theory. Finally, we consider a particular
non-trivial background produced by an operator with an -charge of
and find, in presence of this background, due to the contribution of
the non-planar corrections, the large expansion is replaced by
and respectively.Comment: Latex, 32+1 pages, 2 figures, journal versio
Prevalence of Salmonella on tomatoes from organic and conventional production in Rio de Janeiro (Brazil).
Outbreaks of salmonellosis associated with tomatoes have been related over the past fifteen years. Tomatoes may become surface contaminated with Salmonella spp. from production of consumption. Purpose: The purpose of this study was to evaluate the prevalence of Salmonella spp. on tomatoes surface from organic and conventional production. Samples were collected in the street cendors and supermarkets, and analzed by two methods; the mini-VIDAS SLM assay a specific enzyme-linked fluorescent immonoassay (ELFA) rapid method and the conventional FDA-BAM. Methods: A total of 263 tomatoes were collected during a two-year (2010-2012) survey. A hundred twenty-seven were from organic production, 61 from supermarkets and 66 from street vendors. From conventional production 136 samples were collected, being 84 from supermarkets and 52 from street vendors. All samples were simultaneously surface analyzed by mini-VIDAS SLM and FDA BAM. Results: Salmonella spp. was not detected by the conventional method and two false positives were found by mini-VIDAS SLM. Significance: Surface tomatoes from organic and conventional production analyzed in the city of Rio de Janeiro showed no potential Salmonella risk to their consumption
Protectionism under R&D policy: innovation rate and welfare
Purpose – The purpose of this paper is to explain how eventual pressures from national lobbies may lead governments to shift from an optimal into a non‐optimal innovation policy. Design/methodology/approach – A theoretical model is developed in order to examine and explain the growth and welfare effects of optimal and non‐optimal innovation policies. The non‐optimal policy corresponds to a subsidy for national innovators that is equivalent to an optimal policy of incentives (tax cuts) to foreign investors. Since we are assessing what can nationals do with the support that could be oriented to foreign firms, we are measuring what the economy loses for not supporting foreign firms. Findings – The authors find welfare loss when supporting national R&D instead of foreign R&D and conclude that the same support given to innovation can produce strikingly different outcomes depending on who receives the support. Practical implications – The analysis allows the impact of the inefficiency caused by policies that are not sound, from a strictly economic point of view, to be measured. Originality/value – The originality of the paper is related to the assessment of the implications and to the measurement of the effects of non‐optimal R&D policies
Pelidnota filippiniae Soula, 2009 (Coleoptera: Melolonthidae: Rutelinae): um novo desfolhador de acácia-australiana, Racosperma mangium (Willd.) Pedley (Fabaceae), na Amazônia Oriental, Brasil.
Plantios de acácia-australiana, Racosperma mangium (Willd.) Pedley (Fabaceae), são opção para reflorestamentos comerciais na Amazônia. O trabalho objetiva, pela primeira vez, reportar e descrever injúrias causadas por Pelidnota filippiniae Soula, 2009 (Coleoptera: Melolonthidae: Rutelinae) em plantio experimental em Dom Eliseu, Pará. Observações mensais foram feitas de 2006 a 2009. A maior incidência ocorreu no início do período chuvoso, em outubro e novembro, nos primeiros anos do plantio, quando diferentes intensidades de desfolha foram observadas. Embora danos significativos não tenham sido constatados, P. filippiniae tem potencial para causar prejuízos à cultura. Recomendam-se monitoramentos mensais nesse período e a catação manual do inseto para evitar maiores danos
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