6,248 research outputs found

    Vertex Operators in 4D Quantum Gravity Formulated as CFT

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    We study vertex operators in 4D conformal field theory derived from quantized gravity, whose dynamics is governed by the Wess-Zumino action by Riegert and the Weyl action. Conformal symmetry is equal to diffeomorphism symmetry in the ultraviolet limit, which mixes positive-metric and negative-metric modes of the gravitational field and thus these modes cannot be treated separately in physical operators. In this paper, we construct gravitational vertex operators such as the Ricci scalar, defined as space-time volume integrals of them are invariant under conformal transformations. Short distance singularities of these operator products are computed and it is shown that their coefficients have physically correct sign. Furthermore, we show that conformal algebra holds even in the system perturbed by the cosmological constant vertex operator as in the case of the Liouville theory shown by Curtright and Thorn.Comment: 26 pages, rewrote review part concisely, added explanation

    Making a Universe

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    For understanding the origin of anisotropies in the cosmic microwave background, rules to construct a quantized universe is proposed based on the dynamical triangulation method of the simplicial quantum gravity. A dd-dimensional universe having the topology Dd D^d is created numerically in terms of a simplicial manifold with dd-simplices as the building blocks. The space coordinates of a universe are identified on the boundary surface Sd1 S^{d-1} , and the time coordinate is defined along the direction perpendicular to Sd1 S^{d-1} . Numerical simulations are made mainly for 2-dimensional universes, and analyzed to examine appropriateness of the construction rules by comparing to analytic results of the matrix model and the Liouville theory. Furthermore, a simulation in 4-dimension is made, and the result suggests an ability to analyze the observations on anisotropies by comparing to the scalar curvature correlation of a S2 S^2 -surface formed as the last scattering surface in the S3 S^3 universe.Comment: 27pages,18figures,using jpsj.st

    Recursion Relations in Liouville Gravity coupled to Ising Model satisfying Fusion Rules

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    The recursion relations of 2D quantum gravity coupled to the Ising model discussed by the author previously are reexamined. We study the case in which the matter sector satisfies the fusion rules and only the primary operators inside the Kac table contribute. The theory involves unregularized divergences in some of correlators. We obtain the recursion relations which form a closed set among well-defined correlators on sphere, but they do not have a beautiful structure that the bosonized theory has and also give an inconsistent result when they include an ill-defined correlator with the divergence. We solve them and compute the several normalization independent ratios of the well-defined correlators, which agree with the matrix model results.Comment: Latex, 22 page

    Role of covalency in the ground state properties of perovskite ruthenates: A first principle study using local spin density approximations

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    We investigate the electronic structure of SrRuO3 and CaRuO3 using full potential linearized augmented plane wave method within the local spin density approximations. The ferromagnetic ground state in SrRuO3 could exactly be described in these calculations and the calculated spin magnetic moment is found to be close to the experimentally observed values. Interestingly, the spin polarized calculations for CaRuO3 exhibit large spin moment as observed in the experiments but the magnetic ground state has higher energy than that in the non-magnetic solution. Various calculations for different structural configurations indicate that Ca-O covalency plays the key role in determining the electronic structure and thereby the magnetic ground state in this system.Comment: 8 figure

    Teleportation and entanglement distillation in the presence of correlation among bipartite mixed states

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    The teleportation channel associated with an arbitrary bipartite state denotes the map that represents the change suffered by a teleported state when the bipartite state is used instead of the ideal maximally entangled state for teleportation. This work presents and proves an explicit expression of the teleportation channel for the teleportation using Weyl's projective unitary representation of the space of 2n-tuples of numbers from Z/dZ for integers d>1, n>0, which has been known for n=1. This formula allows any correlation among the n bipartite mixed states, and an application shows the existence of reliable schemes for distillation of entanglement from a sequence of mixed states with correlation.Comment: 12 pages, 1 figur

    Avaliação das projeções de precipitação dos modelos climáticos globais do quarto relatório do IPCC para o Brasil.

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    Este trabalho tem como objetivo avaliar a similaridade das projeções de precipitação dos modelos climáticos globais para o Brasil e suas regiões. Quinze modelos globais do Quarto Relatório do IPCC foram avaliados, considerando suas projeções do período de 2071-2100, cenário A2 de emissão de gases de efeito estufa, e a precipitação observada no período de 1961-1990. Os resultados mostraram que os modelos globais climáticos se comportam de forma diferente para cada região brasileira, indicando tendência de aumento de precipitação em certas áreas geográficas e diminuição em outras. Nos meses de inverno, verifica-se uma tendência de diminuição das precipitações, enquanto no verão a tendência é de aumento das precipitações

    Entanglement-assisted quantum low-density parity-check codes

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    This paper develops a general method for constructing entanglement-assisted quantum low-density parity-check (LDPC) codes, which is based on combinatorial design theory. Explicit constructions are given for entanglement-assisted quantum error-correcting codes (EAQECCs) with many desirable properties. These properties include the requirement of only one initial entanglement bit, high error correction performance, high rates, and low decoding complexity. The proposed method produces infinitely many new codes with a wide variety of parameters and entanglement requirements. Our framework encompasses various codes including the previously known entanglement-assisted quantum LDPC codes having the best error correction performance and many new codes with better block error rates in simulations over the depolarizing channel. We also determine important parameters of several well-known classes of quantum and classical LDPC codes for previously unsettled cases.Comment: 20 pages, 5 figures. Final version appearing in Physical Review

    Insecta, Coleoptera, Elmidae, Amazon region

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    A list of Elmidae species from Amazon is presented. The list was prepared based on a literature surveyand examination of the entomological collection of Instituto Nacional de Pesquisas da Amazônia (INPA). The listincludes 102 species, with ten new occurrences recorded, being one for the Amazon (which includes areas ofBrazil, Bolivia, Colombia, Guyana, French Guyana, Peru, Suriname and Venezuela) three for the Amazonas state,and six for other localities in Brazil. Reports about species bibliography contents were also included, as well asavailable species municipalities distributional data

    RNA secondary structure prediction from multi-aligned sequences

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    It has been well accepted that the RNA secondary structures of most functional non-coding RNAs (ncRNAs) are closely related to their functions and are conserved during evolution. Hence, prediction of conserved secondary structures from evolutionarily related sequences is one important task in RNA bioinformatics; the methods are useful not only to further functional analyses of ncRNAs but also to improve the accuracy of secondary structure predictions and to find novel functional RNAs from the genome. In this review, I focus on common secondary structure prediction from a given aligned RNA sequence, in which one secondary structure whose length is equal to that of the input alignment is predicted. I systematically review and classify existing tools and algorithms for the problem, by utilizing the information employed in the tools and by adopting a unified viewpoint based on maximum expected gain (MEG) estimators. I believe that this classification will allow a deeper understanding of each tool and provide users with useful information for selecting tools for common secondary structure predictions.Comment: A preprint of an invited review manuscript that will be published in a chapter of the book `Methods in Molecular Biology'. Note that this version of the manuscript may differ from the published versio
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