22,200 research outputs found

    Quartification On An Orbifold

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    We investigate quartification models in five dimensions, with the fifth dimension forming an S1/Z2×Z2′S^1/Z_2\times Z_2' orbifold. The orbifold construction is combined with a boundary Higgs sector to break the quartified gauge group directly to a group H⊂SU(3)4H\subset SU(3)^4 which is operative at the electroweak scale. We consider H=GSM⊗SU(2)ℓH=G_{SM}\otimes SU(2)_\ell and H=GSMH=G_{SM}, where GSMG_{SM} is the standard model gauge group, and find that unification occurs only when the remnant leptonic colour symmetry SU(2)ℓSU(2)_\ell remains unbroken. Furthermore, the demands of a realistic low energy fermion spectrum specify a unique symmetry breaking route for the unifying case of H=GSM⊗SU(2)ℓH=G_{SM}\otimes SU(2)_\ell. We contrast this with four dimensional quartification models where unification may be achieved via a number of different symmetry breaking routes both with and without the remnant SU(2)ℓSU(2)_\ell symmetry. The boundary Higgs sector of our model may be decoupled to achieve a Higgsless limit and we show that the electroweak Higgs doublet may be identified as the fifth component of a higher dimensional gauge field.Comment: 14 pages, misprint corrected, matches PRD versio

    Evaluation of Continuous Monitoring as a Tool for Municipal Stormwater Management Programs

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    The purpose of this study is to evaluate the uncertainty attributable to inadequate temporal sampling of stormwater discharge and water quality, and understand its implications for meeting monitoring objectives relevant to municipal separate storm sewer systems (MS4s). A methodology is presented to evaluate uncertainty attributable to inadequate temporal sampling of continuous stormflow and water quality, and a case study demonstrates the application of the methodology to six small urban watersheds (0.8-6.8 km2) and six large rural watersheds (30-16,192 km2) in Virginia. Results indicate the necessity of high-frequency continuous monitoring for accurately capturing multiple monitoring objectives, including illicit discharges, acute toxicity events, and stormflow pollutant concentrations and loads, as compared to traditional methods of sampling. For example, 1-h sampling in small urban watersheds and daily sampling in large rural watersheds would introduce uncertainty in capturing pollutant loads of 3–46% and 10–28%, respectively. Overall, the outcomes from this study highlight how MS4s can leverage continuous monitoring to meet multiple objectives under current and future regulatory environments

    Orbifold Reduction Of The Quark-Lepton Symmetric Model

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    We investigate the quark-lepton symmetric gauge group in five dimensions, with the gauge symmetry broken by a combination of orbifold compactification of the extra dimension and the Higgs mechanism. The gauge sector of the model is investigated and contrasted with the four dimensional case. We obtain lower bounds on the mass of the exotic gauge bosons, the inverse compactification scale and the exotic leptons. Light neutrinos are obtained without requiring any scale larger than a TeV. However an ultra-violet cut-off of order 101110^{11} GeV is required to suppress proton decay inducing non-renormalizable operators.Comment: References added to match PRD versio

    Suppressing Proton Decay By Separating Quarks And Leptons

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    Arkani-Hamed and Schmaltz (AS) have shown that proton stability need not originate from symmetries in a high energy theory. Instead the proton decay rate is suppressed if quarks and leptons are spatially separated in a compact extra dimension. This separation may be achieved by coupling five dimensional fermions to a bulk scalar field with a non-trivial vacuum profile and requires relationships between the associated quark and lepton Yukawa couplings. We hypothesise that these relationships are the manifestation of an underlying symmetry. We further show that the AS proposal may suggest that proton stability \emph{is} the result of an underlying symmetry, though not necessarily the traditional baryon number symmetry.Comment: 4 pages, references added to match published versio

    Thurstonian Scaling of Compositional Questionnaire Data

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    To prevent response biases, personality questionnaires may use comparative response formats. These include forced choice, where respondents choose among a number of items, and quantitative comparisons, where respondents indicate the extent to which items are preferred to each other. The present article extends Thurstonian modeling of binary choice data (Brown & Maydeu-Olivares, 2011a) to “proportion-of-total” (compositional) formats. Following Aitchison (1982), compositional item data are transformed into log-ratios, conceptualized as differences of latent item utilities. The mean and covariance structure of the log-ratios is modelled using Confirmatory Factor Analysis (CFA), where the item utilities are first-order factors, and personal attributes measured by a questionnaire are second-order factors. A simulation study with two sample sizes, N=300 and N=1000, shows that the method provides very good recovery of true parameters and near-nominal rejection rates. The approach is illustrated with empirical data from N=317 students, comparing model parameters obtained with compositional and Likert scale versions of a Big Five measure. The results show that the proposed model successfully captures the latent structures and person scores on the measured traits
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