4,640 research outputs found

    Relating Noncommutative SO(2,3) Gravity to the Lorentz-Violating Standard-Model Extension

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    We consider a model of noncommutative gravity that is based on a spacetime with broken local SO(2,3) symmetry. We show that the torsion-free version of this model is contained within the framework of the Lorentz-violating Standard-Model Extension. We analyze in detail the relation between the torsion-free, quadratic limits of the broken SO(2,3) model and the Standard-Model Extension. As part of the analysis,we construct the relevant geometric quantities to quadratic order in the metric perturbation around a flat background.Comment: 10 pages, accepted in Symmetr

    Hartree-Fock-Bogoliubov Calculations of the Rotational Band of the Very Heavy 254^{254}No Nucleus

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    We report on Hartree-Fock-Bogoliubov (HFB) calculations of the ground-state rotationnal band of the heavy nucleus 254^{254}No recently observed experimentally. The calculated quadrupole deformation is consistent with the experimental value of β=0.27\beta=0.27 and is almost constant over the whole band. We also reproduce fairly well the excitation spectra and moments of inertia of this isotope up to the maximal experimentally observed state of spin 20. The rather high stability of this nucleus against fission is illustrated by the deformation energy curve providing very high fission barriers at zero spin within the HFB and HFB plus Lipkin-Nogami formalisms. The variation of these barriers with increased angular velocities is also studied.Comment: 4 pages (LaTeX), submitted to Eur. Phys. J A, dedicated to the memory of J. Piperov

    Are Big Gods a big deal in the emergence of big groups?

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    In Big Gods, Norenzayan (2013) presents the most comprehensive treatment yet of the Big Gods question. The book is a commendable attempt to synthesize the rapidly growing body of survey and experimental research on prosocial effects of religious primes together with cross-cultural data on the distribution of Big Gods. There are, however, a number of problems with the current cross-cultural evidence that weaken support for a causal link between big societies and certain types of Big Gods. Here we attempt to clarify these problems and, in so doing, correct any potential misinterpretation of the cross-cultural findings, provide new insight into the processes generating the patterns observed, and flag directions for future research

    A simple model for the quenching of pairing correlations effects in rigidly deformed rotational bands

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    Using Chandrasekhar's S-type coupling between rotational and intrinsic vortical modes one may simply reproduce the HFB dynamical properties of rotating nuclei within Routhian HF calculations free of pairing correlations yet constrained on the relevant so-called Kelvin circulation operator. From the analogy between magnetic and rotating systems, one derives a model for the quenching of pairing correlations with rotation, introducing a critical angular velocity -- analogous to the critical field in supraconductors -- above which pairing vanishes. Taking stock of this usual model, it is then shown that the characteristic behavior of the vortical mode angular velocity as a function of the global rotation angular velocity can be modelised by a simple two parameter formula, both parameters being completely determined from properties of the band-head (zero-spin) HFB solution. From calculation in five nuclei, the validity of this modelised Routhian approach is assessed. It is clearly shown to be very good in cases where the evolution of rotational properties is only governed by the coupling between the global rotation and the pairing-induced intrinsic vortical currents. It therefore provides a sound ground base for evaluating the importance of coupling of rotation with other modes (shape distortions, quasiparticle degrees of freedom).Comment: 10 pages, 8 figures. Submited to PR

    Limits on violations of Lorentz Symmetry from Gravity Probe B

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    Generic violations of Lorentz symmetry can be described by an effective field theory framework that contains both general relativity and the standard model of particle physics called the Standard-Model Extension (SME). We obtain new constraints on the gravitational sector of the SME using recently published final results from Gravity Probe B. These include for the first time an upper limit at the 10^(-3) level on the time-time component of the new tensor field responsible for inducing local Lorentz violation in the theory, and an independent limit at the 10^(-7) level on a combination of components of this tensor field.Comment: 8 pages, 1 figur

    Results of the Austrian-Ceylonese hydrobiological mission 1970 of the 1st Zoological Institute of the University of Vienna (Austria) and the Department of Zoology of the University of Ceylon Vidyalankara Campus, Kelaniya. Pt. 12. Contributions to the ecology of the larvae of some Odonata from Ceylon

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    The Austrian-Ceylonese hydrobiological mission studied 38 biotopes; 28 of which contain Odonata. From the Zygoptera the Calopterydoidea seem to be the dominant form (22 habitats), while the Coenagrionoidea are scarcer (11 habitats). The most frequent species was Euphaea splendens (Epallagidae - 16 habitats) followed by Vestolis apicalis nigrescens (Calopterygidae, 8 habitats) and Neurobasis chinensis (Calopterygidae, 6 habitats). From the Anisoptera Zygonyx ceylanica (Libellulidae: Zygonictinae) was the dominant form (8 habitats), but some Libellulinae remain undescribed. The number of species varied greatly between different biotopes. The biotopes containing Odonata are small brooks, in which the pH was mostly on the limit between acid and alkaline reaction. They are fast running waters, situated in most cases on lower or middle elevations, only three species being found in higher elevations (1800-2000 m). Adaptations to fast currents and other factors are described

    Generation of pulsed bipartite entanglement using four-wave mixing

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    Using four-wave mixing in a hot atomic vapor, we generate a pair of entangled twin beams in the microsecond pulsed regime near the D1 line of 85^{85}Rb, making it compatible with commonly used quantum memory techniques. The beams are generated in the bright and vacuum-squeezed regimes, requiring two separate methods of analysis, without and with local oscillators, respectively. We report a noise reduction of up to 3.8±0.23.8\pm 0.2 dB below the standard quantum limit in the pulsed regime and a level of entanglement that violates an Einstein--Podolsky--Rosen inequality.Comment: 10 pages, 5 figures, accepted for publication in New Journal Of Physici

    Ciliate Codon Translator Program Manual

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    Understanding the evolutionary history of organisms allows us to better comprehend selective pressures and their effects on larger populations. In our study, we focused on analyzing the DNA of ciliate groups, which are single celled protozoans characterized by the presence of cilia on their outer membrane. We utilized the DNA of the organisms to analyze the changes in population genotype over time. We tested existing evolutionary models (designed to represent natural genetic variation over time in populations) against our data to identify the model with the best fit and likelihood. From the DNA and the evolutionary model with the highest likelihood, we can generate phylogenies for the organisms, which allow us to visualize the evolutionary history of the organisms, and additionally can be used to test for selection. To test for selection, we used the dN/dS ratio (dN representing non-synonymous substitutions and changes in the resulting amino-acid; and dS representing synonymous substitutions or silent substitutions). This ratio can then be used to measure positive, negative, or neutral selective pressure on the population, as values greater than one indicate high alterations in proteins which is indicative of selection. These results allow us to better understand the presence of selective pressures on these populations, and allows us to comprehend how the proteins produced by the DNA of these organisms changed over time. We also hope to be able to use this information to make inferences regarding the future of these organisms and their genotypes based off of modern selective pressures

    A PHYLOGENETIC REEVALUATION OF THE GENUS GAVIA (AVES: GAVIIFORMES) USING NEXT-GENERATION SEQUENCING

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    Avian phylogenetic analysis based on DNA sequences, rather than morphological characters, has been used in recent decades to resolve systematic relationships. Advancements in molecular techniques have improved avian phylogenetics and have led to new insights on the relationships between and within taxa. Loons (Aves: Gaviiformes) are one of the oldest living lineages of birds, and the order includes five extant species. The morphological cladogram of Gavia placed G. arctica as a sister species to G. pacifica. However, a more recent study based on mtDNA resulted in a discordant tree splitting the G. arctica/G. pacifica clade, and placed G. pacifica as sister to the (G. immer, G. adamsii) clade. These hypotheses were tested using next-generation sequencing (NGS) data in the form of a RAD-tag dataset comprising 232,094 bps from 2502 variable loci. Bayesian inference, Maximum Likelihood, and Maximum Parsimony phylogenetic analyses of a concatenated dataset strongly supported the traditional phylogeny (G. stellata, ((G. arctica, G. pacifica), (G. adamsii, G. immer))), and differed from the largely mitochondrially-based hypothesis that placed G. pacifica sister to the (G. immer, G. adamsii) clade. Both internally- and externally-calibrated molecular clock based estimates of divergence dates placed the most recent common ancestor of modern loons in the early Miocene, which is earlier than previously thought, ~21.4 mya (20-22.8 mya) provides a more parsimonious explanation for body size evolution in loons
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