923 research outputs found

    Universal deformation rings for the symmetric group S_5 and one of its double covers

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    Let S5S_5 denote the symmetric group on 5 letters, and let S^5\hat{S}_5 denote a non-trivial double cover of S5S_5 whose Sylow 2-subgroups are generalized quaternion. We determine the universal deformation rings R(S5,V)R(S_5,V) and R(S^5,V)R(\hat{S}_5,V) for each mod 2 representation VV of S5S_5 that belongs to the principal 2-modular block of S5S_5 and whose stable endomorphism ring is given by scalars when it is inflated to S^5\hat{S}_5. We show that for these VV, a question raised by the first author and Chinburg concerning the relation of the universal deformation ring of VV to the Sylow 2-subgroups of S5S_5 and S^5\hat{S}_5, respectively, has an affirmative answer.Comment: 10 pages, 5 figures; the proof of Theorem 1.1(a) has been shortene

    Octonionic representations of Clifford algebras and triality

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    The theory of representations of Clifford algebras is extended to employ the division algebra of the octonions or Cayley numbers. In particular, questions that arise from the non-associativity and non-commutativity of this division algebra are answered. Octonionic representations for Clifford algebras lead to a notion of octonionic spinors and are used to give octonionic representations of the respective orthogonal groups. Finally, the triality automorphisms are shown to exhibit a manifest \perm_3 \times SO(8) structure in this framework.Comment: 33 page

    Scalable Multispecies Ion Transport in a Grid Based Surface-Electrode Trap

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    We present a scalable method for the control of ion crystals in a grid-based surface electrode Paul trap and characterize it in the context of transport operations that sort and reorder multispecies crystals. By combining co-wiring of control electrodes at translationally symmetric locations in each grid site with the site-wise ability to exchange the voltages applied to two special electrodes gated by a binary input, site-dependent operations are achieved using only a fixed number of analog voltage signals and a single digital input per site. In two separate experimental systems containing nominally identical grid traps, one using 171Yb+^{171}\mathrm{Yb}^{+}-138Ba+^{138}\mathrm{Ba}^{+} crystals and the other 137Ba+^{137}\mathrm{Ba}^{+}-88Sr+^{88}\mathrm{Sr}^{+}, we demonstrate this method by characterizing the conditional intra-site crystal reorder and the conditional exchange of ions between adjacent sites on the grid. Averaged across a multi-site region of interest, we measure sub-quanta motional excitation in the axial in-phase and out-of-phase modes of the crystals following these operations at exchange rates of 2.5 kHz. These conditional transport operations display all necessary components for sorting qubits, and could be extended to implement other conditional operations involving control fields such as gates, initialization, and measurement.Comment: 11 pages, 7 figure

    Guidance on the Selection of Appropriate Indicators for Quantification of Antimicrobial Usage in Humans and Animals

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    An increasing variety of indicators of antimicrobial usage has become available in human and veterinary medicine, with no consensus on the most appropriate indicators to be used. The objective of this review is therefore to provide guidance on the selection of indicators, intended for those aiming to quantify antimicrobial usage based on sales, deliveries or reimbursement data. Depending on the study objective, different requirements apply to antimicrobial usage quantification in terms of resolution, comprehensiveness, stability over time, ability to assess exposure and comparability. If the aim is to monitor antimicrobial usage trends, it is crucial to use a robust quantification system that allows stability over time in terms of required data and provided output; to compare usage between different species or countries, comparability must be ensured between the different populations. If data are used for benchmarking, the system comprehensiveness is particularly crucial, while data collected to study the association between usage and resistance should express the exposure level and duration as a measurement of the exerted selection pressure. Antimicrobial usage is generally described as the number of technical units consumed normalized by the population at risk of being treated in a defined period. The technical units vary from number of packages to number of individuals treated daily by adding different levels of complexity such as daily dose or weight at treatment. These technical units are then related to a description of the population at risk, based either on biomass or number of individuals. Conventions and assumptions are needed for all of these calculation steps. However, there is a clear lack of standardization, resulting in poor transparency and comparability. By combining study requirements with available approaches to quantify antimicrobial usage, we provide suggestions on the most appropriate indicators and data sources to be used for a given study objective

    Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

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    The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal
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