51,303 research outputs found

    Conceptual Explanation for the Algebra in the Noncommutative Approach to the Standard Model

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    The purpose of this letter is to remove the arbitrariness of the ad hoc choice of the algebra and its representation in the noncommutative approach to the Standard Model, which was begging for a conceptual explanation. We assume as before that space-time is the product of a four-dimensional manifold by a finite noncommmutative space F. The spectral action is the pure gravitational action for the product space. To remove the above arbitrariness, we classify the irreducibe geometries F consistent with imposing reality and chiral conditions on spinors, to avoid the fermion doubling problem, which amounts to have total dimension 10 (in the K-theoretic sense). It gives, almost uniquely, the Standard Model with all its details, predicting the number of fermions per generation to be 16, their representations and the Higgs breaking mechanism, with very little input. The geometrical model is valid at the unification scale, and has relations connecting the gauge couplings to each other and to the Higgs coupling. This gives a prediction of the Higgs mass of around 170 GeV and a mass relation connecting the sum of the square of the masses of the fermions to the W mass square, which enables us to predict the top quark mass compatible with the measured experimental value. We thus manage to have the advantages of both SO(10) and Kaluza-Klein unification, without paying the price of plethora of Higgs fields or the infinite tower of states.Comment: Title change only. The title "A Dress for SM the Beggar" was changed by the Editor of Physical Review Letter

    Distributed Coupled Multi-Agent Stochastic Optimization

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    This work develops effective distributed strategies for the solution of constrained multi-agent stochastic optimization problems with coupled parameters across the agents. In this formulation, each agent is influenced by only a subset of the entries of a global parameter vector or model, and is subject to convex constraints that are only known locally. Problems of this type arise in several applications, most notably in disease propagation models, minimum-cost flow problems, distributed control formulations, and distributed power system monitoring. This work focuses on stochastic settings, where a stochastic risk function is associated with each agent and the objective is to seek the minimizer of the aggregate sum of all risks subject to a set of constraints. Agents are not aware of the statistical distribution of the data and, therefore, can only rely on stochastic approximations in their learning strategies. We derive an effective distributed learning strategy that is able to track drifts in the underlying parameter model. A detailed performance and stability analysis is carried out showing that the resulting coupled diffusion strategy converges at a linear rate to an O(μ)O(\mu)-neighborhood of the true penalized optimizer

    Linear Convergence of Primal-Dual Gradient Methods and their Performance in Distributed Optimization

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    In this work, we revisit a classical incremental implementation of the primal-descent dual-ascent gradient method used for the solution of equality constrained optimization problems. We provide a short proof that establishes the linear (exponential) convergence of the algorithm for smooth strongly-convex cost functions and study its relation to the non-incremental implementation. We also study the effect of the augmented Lagrangian penalty term on the performance of distributed optimization algorithms for the minimization of aggregate cost functions over multi-agent networks

    Inclusive Decay Rate for BXd+γB \to X_d + \gamma in Next-to-Leading Logarithmic Order and CP Asymmetry in the Standard Model

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    We compute the decay rate for the CKM-suppressed electromagnetic penguin decay BXd+γB \to X_d + \gamma (and its charge conjugate) in NLO QCD, including leading power corrections in 1/mb21/m_b^2 and 1/mc21/m_c^2 in the standard model. The average branching ratio of the decay BXdγB \to X_d\gamma and its charge conjugate is estimated to be in the range 6.0×1062.6×1056.0 \times 10^{-6} \leq \leq 2.6 \times 10^{-5}, obtained by varying the CKM-Wolfenstein parameters ρ\rho and η\eta in the range 0.1ρ0.4-0.1 \leq \rho \leq 0.4 and 0.2η0.460.2 \leq \eta \leq 0.46 and taking into account other parametric dependence. In the stated range of the CKM parameters, we find the ratio R(dγ/sγ)=<BR(BXdγ)>/R(d\gamma/s\gamma) = <BR(B \to X_d\gamma)>/ to lie in the range between 0.017 and 0.074. Theoretical uncertainties in this ratio are found to be small. Hence, this ratio is well suited to provide independent constraints on the CKM parameters. The CP-asymmetry in the BXdγB \to X_d \gamma decay rates is found to be in the range (735)(7 - 35)%. Both the decay rates and CP asymmetry are measurable in forthcoming experiments at BB factories and possibly at HERA-B.Comment: 17 pages including 7 postscript figures; uses epsfig; The changes w.r.t the previous version are: A comment about the Bremsstrahlung corrections is added as well as a note on the feasibility of the measurement $B -> X_d gamma

    Evolution of the spectral index after inflation

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    In this article we investigate the time evolution of the adiabatic(curvature) and isocurvature (entropy) spectral indices after end of inflation for all cosmological scales and two different initial conditions. For this purpose,we first extract an explicit equation for the time evolution of the comoving curvature perturbation (which may be known as the generalized Mukhanov-Sasaki equation). It shall be manifested that the evolution of adibatic spectral index severely depends on the intial conditions and just for the super-Hubble scales and adiabatic initial conditions is constat as be expected.Moreover,it shall be clear that the adiabatic spectral index after recombination approach to a constant value for the isocurvature perturbations.Finally,we re-investgate the Sachs-Wolfe effect and show that the fudge factor 1/3 in the adiabatic ordinary Sachs-Wolfe formula must be replaced by 0.4.Comment: 18 pages,4figure

    Molecular aspects of MERS-CoV

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    This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Middle East respiratory syndrome coronavirus (MERS-CoV) is a betacoronavirus which can cause acute respiratory distress in humans and is associated with a relatively high mortality rate. Since it was first identified in a patient who died in a Jeddah hospital in 2012, the World Health Organization has been notified of 1735 laboratory-confirmed cases from 27 countries, including 628 deaths. Most cases have occurred in Saudi Arabia. MERS-CoVancestors may be found in OldWorld bats of the Vespertilionidae family. After a proposed bat to camel switching event, transmission of MERS-CoV to humans is likely to have been the result of multiple zoonotic transfers from dromedary camels. Human-to-human transmission appears to require close contact with infected persons, with outbreaks mainly occurring in hospital environments. Outbreaks have been associated with inadequate infection prevention and control implementation, resulting in recommendations on basic and more advanced infection prevention and control measures by the World Health Organization, and issuing of government guidelines based on these recommendations in affected countries including Saudi Arabia. Evolutionary changes in the virus, particularly in the viral spike protein which mediates virus-host cell contact may potentially increase transmission of this virus. Efforts are on-going to identify specific evidence-based therapies or vaccines. The broad-spectrum antiviral nitazoxanide has been shown to have in vitro activity against MERS-CoV. Synthetic peptides and candidate vaccines based on regions of the spike protein have shown promise in rodent and non-human primate models. GLS-5300, a prophylactic DNA-plasmid vaccine encoding S protein, is the first MERS-CoV vaccine to be tested in humans, while monoclonal antibody, m336 has given promising results in animal models and has potential for use in outbreak situations

    Band-edge Bilayer Plasmonic Nanostructure for Surface Enhanced Raman Spectroscopy

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    Spectroscopic analysis of large biomolecules is critical in a number of applications, including medical diagnostics and label-free biosensing. Recently, it has been shown that Raman spectroscopy of proteins can be used to diagnose some diseases, including a few types of cancer. These experiments have however been performed using traditional Raman spectroscopy and the development of the Surface enhanced Raman spectroscopy (SERS) assays suitable for large biomolecules could lead to a substantial decrease in the amount of specimen necessary for these experiments. We present a new method to achieve high local field enhancement in surface enhanced Raman spectroscopy through the simultaneous adjustment of the lattice plasmons and localized surface plasmon polaritons, in a periodic bilayer nanoantenna array resulting in a high enhancement factor over the sensing area, with relatively high uniformity. The proposed plasmonic nanostructure is comprised of two interacting nanoantenna layers, providing a sharp band-edge lattice plasmon mode and a wide-band localized surface plasmon for the separate enhancement of the pump and emitted Raman signals. We demonstrate the application of the proposed nanostructure for the spectral analysis of large biomolecules by binding a protein (streptavidin) selectively on the hot-spots between the two stacked layers, using a low concentration solution (100 nM) and we successfully acquire its SERS spectrum
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