548,066 research outputs found

    Cube or hypercube of natural units

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    Max Planck introduced four natural units: h, c, G, k. Only the first three of them retained their status, representing the so called cube of theories, after the theory of relativity and quantum mechanics were created and became the pillars of physics. This short note is a little pebble on the tombstone of Michael Samuilovich Marinov.Comment: 7 pages, to be published in ``Multiple facets of quantization and supersymmetry'', Michael Marinov Memorial Volume, Eds. M. Olshanetsky and A. Vainshtein, World Scientific, 200

    SV-map between Type I and Heterotic Sigma Models

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    The scattering amplitudes of gauge bosons in heterotic and open superstring theories are related by the single-valued projection which yields heterotic amplitudes by selecting a subset of multiple zeta value coefficients in the α′\alpha' (string tension parameter) expansion of open string amplitudes. In the present work, we argue that this relation holds also at the level of low-energy expansions (or individual Feynman diagrams) of the respective effective actions, by investigating the beta functions of two-dimensional sigma models describing world-sheets of open and heterotic strings. We analyze the sigma model Feynman diagrams generating identical effective action terms in both theories and show that the heterotic coefficients are given by the single-valued projection of the open ones. The single-valued projection appears as a result of summing over all radial orderings of heterotic vertices on the complex plane representing string world-sheet.Comment: 28 page

    Spanish Customer Satisfaction Indices by Cumulative Panel Data

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    In this paper, we present a new theoretical representation of the Consumer Satisfaction Index (CSI) based on Structural Equation Modelling (SEM). We use panel data collected by an automotive magazine to apply our approach and assess the applicability in the field of marketing by formulating a competitive strategy in the Spanish automobile industry. The basic structure of the CSI is based upon well established theories and approaches to customer satisfaction (see Fornell 1992; Fornell et al., 1996). The structure based upon these theories consists of a number of latent factors, each of which is operationalised by multiple measures. The purpose of this paper is to propose a new way of representing the structure of Spanish Consumer Satisfaction (CS) in the automobile industry to study and compare the implications of its representations. We will discuss that CSI is a global evaluation constructed on the basis of its particular component evaluations. Apart from building a new way of representing the structure of CS, this work tries to correct for the bias produced by the particular method of calculus employed by the magazine.Structural Equation Modeling (SEM), factor analysis, cumulative panel data

    Holographic Aspects of Fermi Liquids in a Background Magnetic Field

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    We study the effects of an external magnetic field on the properties of the quasiparticle spectrum of the class of 2+1 dimensional strongly coupled theories holographically dual to charged AdS4_4 black holes at zero temperature. We uncover several interesting features. At certain values of the magnetic field, there are multiple quasiparticle peaks representing a novel level structure of the associated Fermi surfaces. Furthermore, increasing magnetic field deforms the dispersion characteristics of the quasiparticle peaks from non-Landau toward Landau behaviour. At a certain value of the magnetic field, just at the onset of Landau-like behaviour of the Fermi liquid, the quasiparticles and Fermi surface disappear.Comment: 18 pages, 10 figures. Revised some of the terminology: changed non-separable solutions to infinite-sum solution

    Assessing Multiple Prior Models of Behaviour under Ambiguity

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    The recent spate of theoretical models of behaviour under ambiguity can be partitioned into two sets: those involving multiple priors (in which the probabilities of the various events are not known but probabilities can be attached to the various possible values for the probabilities) and those not involving multiple priors. This paper concentrates on the first set and provides an experimental investigation into recently proposed theories. Using an appropriate experimental interface, in which the probabilities on the various possibilities are explicitly stated, we examine the fitted and predictive power of the various theories. We first estimate subject-by-subject, and then we estimateand predict using a mixture model over the contending theories. The individual estimates suggest that 25% of our 149 subjects have behaviour consistent with Expected Utility, 54% with the Smooth Model (of Klibanoff et al, 2005), 12% with Rank Dependent Expected Utility and 9% with the Alpha Model (of Ghirardato et al 2004); these figures are very close to the mixing proportions obtained from the mixture estimates. However, if we classify our subjects through the posterior probabilities (given all the evidence) of each of them being of the various types: using the estimates we get 38%, 19%, 28% and 16% (for EU, Smooth, Rank Dependent and Alpha); while using the predictions 36%, 19%, 33% and 11%. Interestingly the older models (EU and RD) seem to fare relatively better, suggesting that representing ambiguity through multiple priors is perceived by subjects as risk, rather than ambiguityAlpha Model, Ambiguity, Expected Utility, Mixture Models, Rank Dependent Expected Utility, Smooth Model.

    Employees’ Financial Insecurity and Health: The Underlying Role of Stress and Work–Family Conflict Appraisals

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    Data from two longitudinal samples were utilized to elucidate underlying mechanisms of the well‐established relationship between financial insecurity and health outcomes, stemming from the theoretical rationale of conservation of resources and cognitive appraisal theories. Study 1 (n = 80) consisted of low‐wage food manufacturing employees working full time, while Study 2 (n = 331) was consisted of a larger, heterogeneous sample of full‐time workers representing multiple occupations. Respondents were surveyed on financial insecurity, work‐to‐family conflict (WFC), stress, and health outcomes at two time periods, 3 months apart. Results across our studies provided support for the direct effects of financial insecurity on WFC and stress. In addition, appraisals of WFC and stress serve as significant mediators of the relationship between financial insecurity and health outcomes, including a significant overall lagged effect across time, and perceived stress accounting for the largest proportion of variance in the lagged relationship among Time 1 financial insecurity and Time 2 health outcomes. Besides support for conservation of resources and cognitive appraisal theories, practically, our studies suggest that workplace initiatives to reduce financial insecurity could positively influence employees’ work–family, stress, and health experiences

    Polyploid lineages in the genus Porphyra

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    Whole genome duplication is now accepted as an important evolutionary force, but the genetic factors and the life history implications affecting the existence and abundance of polyploid lineages within species are still poorly known. Polyploidy has been mainly studied in plant model species in which the sporophyte is the dominant phase in their life history. In this study, we address such questions in a novel system (Porphyra, red algae) where the gametophyte is the dominant phase in the life history. Three Porphyra species (P. dioica, P. umbilicalis, and P. linearis) were used in comparisons of ploidy levels, genome sizes and genetic differentiation using flow cytometry and 11 microsatellite markers among putative polyploid lineages. Multiple ploidy levels and genome sizes were found in Porphyra species, representing different cell lines and comprising several cytotype combinations among the same and different individuals. In P. linearis, genetic differentiation was found among three polyploid lineages: triploid, tetraploid and mixoploids, representing different evolutionary units. We conclude that the gametophytic phase (n) in Porphyra species is not haploid, contradicting previous theories. New hypotheses for the life histories of Porphyra species are discussed.FCT (Fundacao para a Ciencia e a Tecnologia, Portugal) [SFRH/BPD/109452/2015, NORIGENOMICS - PTDC/MAR/099698/2008, UID/Multi/04326/2013, BIODIVERSA/004/2015-MARFOR

    Dielectric Fundamental Strings in Matrix String Theory

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    Matrix string theory is equivalent to type IIA superstring theory in the light-cone gauge, together with extra degrees of freedom representing D-brane states. It is therefore the appropriate framework in which to study systems of multiple fundamental strings expanding into higher-dimensional D-branes. Starting from Matrix theory in a weakly curved background, we construct the linear couplings of closed string fields to type IIA Matrix strings. As a check, we show that at weak coupling the resulting action reproduces light-cone gauge string theory in a weakly curved background. Further dualities give a type IIB Matrix string theory and a type IIA theory of Matrix strings with winding. We comment on the dielectric effect in each of these theories, giving some explicit solutions describing fundamental strings expanding into various Dp-branes.Comment: Plain LaTeX, 25 pages. Reference added. Version to appear to NP

    An integrative, multiscale view on neural theories of consciousness.

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    How is conscious experience related to material brain processes? A variety of theories aiming to answer this age-old question have emerged from the recent surge in consciousness research, and some are now hotly debated. Although most researchers have so far focused on the development and validation of their preferred theory in relative isolation, this article, written by a group of scientists representing different theories, takes an alternative approach. Noting that various theories often try to explain different aspects or mechanistic levels of consciousness, we argue that the theories do not necessarily contradict each other. Instead, several of them may converge on fundamental neuronal mechanisms and be partly compatible and complementary, so that multiple theories can simultaneously contribute to our understanding. Here, we consider unifying, integration-oriented approaches that have so far been largely neglected, seeking to combine valuable elements from various theories

    The State of Theoretical Diversity

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    Theory provides the medium for organizing and communicating knowledge that enables scientific collaboration. Review of five years of published work in two major IS journals, Management Information Systems Quarterly and Journal of Management Information Systems, describes the nature of this theoretical diversity in IS research. Two-hundred-seventy-three articles were evaluated for theoretical citations to identify the range of theories in Information Systems. Approximately half of the papers explicitly cited one of the 111 theories identified. Thirty of the theories were cited multiple times, representing 55% of the citations. The large number of theories used and the small number used more than once indicate that theoretical diversity clearly exists in information systems research. Based on the results, no theory emerged as a potential candidate for the role of grand/unified theory of information systems
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