1,307 research outputs found

    N=1* model superpotential revisited (IR behaviour of N=4 limit)

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    The one-loop contribution to the superpotential, in particular the Veneziano-Yankielowicz potential in N=1 supersymmetric Yang-Mills model is discussed from an elementary field theory method and the matrix model point of view. Both approaches are based on the Renormalization Group variation of the superconformal N=4 supersymmetric Yang-Mills model.Comment: 31 page

    Exact renormalization group equation in presence of rescaling anomaly II - The local potential approximation

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    Exact renormalization group techniques are applied to mass deformed N=4 supersymmetric Yang-Mills theory, viewed as a regularised N=2 model. The solution of the flow equation, in the local potential approximation, reproduces the one-loop (perturbatively exact) expression for the effective action of N=2 supersymmetric Yang-Mills theory, when the regularising mass, M, reaches the value of the dynamical cutoff. One speculates about the way in which further non-perturbative contributions (instanton effects) may be accounted for.Comment: 13 pages, no figures, uses JHEP3.cl

    Prognostic role of aldosterone in patients with acute coronary syndrome: short and medium term follow-up.

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    AIMS: Different studies have shown a correlation between aldosterone, atherosclerosis and ischemia in the past decade. Evidence exists for the relationship between high levels of aldosterone and augmented risk of cardiovascular diseases, such as hypertension, cardiac failure, coronary artery disease and stroke. The objective of this study was to determine the prognostic role of aldosterone in patients with myocardial infarction. METHODS:The study population included 96 consecutive patients admitted to our department for ST-elevated and non-ST-elevated myocardial infarction from June 2009 to March 2012. Plasma aldosterone levels were measured at admission to hospital in all patients. A 2-year prospective follow-up was performed, and fatal events and non-fatal events, such as reinfarction, congestive heart failure and arrhythmias, were recorded. RESULTS:Aldosterone levels at admission were associated with incidence of congestive heart failure (P\u200a=\u200a0.02), ventricular arrhythmias (P\u200a=\u200a0.01) and all complications (P\u200a=\u200a0.003) after 1-month follow-up. Moreover, high aldosterone levels gave important information in the medium term (24\u200a\ub1\u200a6 months). Specifically, aldosterone was a predictive variable of reinfarction (P\u200a<\u200a0.0001), congestive heart failure (P\u200a<\u200a0.0001) and adverse events (P\u200a=\u200a0.0002). The logistic regression analysis confirmed these results and showed that aldosterone may be predictive of adverse events at medium-term follow-up (odds ratio 1.1, 95% confidence interval 1.03-1.15, P\u200a=\u200a0.02). CONCLUSION:These data show a strong and significant correlation between plasma aldosterone levels at admission for myocardial infarction and fatal and nonfatal adverse events. Aldosterone appears to be a main marker of adverse clinical outcome, in accordance with the literature. These data suggest the need to identify whether antialdosteronic drug treatment, applied acutely in patients with aldosterone elevation, can influence favorably the prognosis of patients with myocardial infarction

    Influence of temperature on extreme rainfall intensity in Sicily (Italy)

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    Some climate model experiments suggest an intensification of short-duration extreme precipitation in many parts of the world associated with a warming climate. This behavior could have a physical motivation due to the fact that warmer air has the potential to hold more atmospheric moisture and, then, to provide more water to rainfall events. The theoretical basis of the relationship that links air temperature and atmospheric humidity is provided by the Clausius-Clapeyron relation, according to which, if the relative humidity remains constant, then atmospheric humidity will increase with temperature at a rate (often referred to as CC-rate) in the order of 6-7% C-1, following the saturation vapour pressure curve as a function of temperature. The study of the relationship between extreme rainfall events and surface temperature could be of capital importance for evaluating the effects of global warming on future precipitation, since it may have important impacts on society with relevant fallouts on several aspects (e.g. flooding, risk protection, etc.). Different approaches have been proposed for the study at different locations of the scaling relationship between extreme rainfall intensity and surface temperature. In some cases, it has been observed a rate consistent with the thermodynamic Clausius-Clapeyron relation (CC-rate). Nevertheless, in many cases, the existence of scaling rate between temperature and extreme precipitation has been demonstrated with significantly different values with respect to the theoretical CC-rate, being in some cases sensibly higher (super-CC) and in other relevantly lower (sub-CC). In this work, an analysis of the scaling relationship between sub-daily extreme rainfall and surface temperature in a semi-arid region (Sicily, Italy) is carried out, also investigating the role of different factors, such as the duration of maximum rainfall depths for fixed duration (i.e. 10, 30 and 60 minutes), the type of adopted regression models (exponential regression, two-segments piecewise regression and LOESS - Locally-weighted scatterplot smoothing - regression), and the climate seasonality (unique season for the entire hydrological year; dry season from April to September and wet season for the remaining part of the year). The original dataset is constituted by hourly temperature and 10-minutes rainfall data collected from 2003 to 2015 by the regional agency SIAS (Servizio Informativo Agrometeorologico Siciliano) through 107 weather stations spread over the region. The results demonstrate that in Sicily the scaling rates are generally lower than the CC-rate; however, the observed tendency towards sub-CC rates is smoothed by the consideration of shorter duration for rainfall maximum depths (higher rates for 10-minutes durations) and under wetter periods (higher rates considering only wet season values), demonstrating how such factors play a fundamental role

    Sensitivity of Nonrenormalizable Trajectories to the Bare Scale

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    Working in scalar field theory, we consider RG trajectories which correspond to nonrenormalizable theories, in the Wilsonian sense. An interesting question to ask of such trajectories is, given some fixed starting point in parameter space, how the effective action at the effective scale, Lambda, changes as the bare scale (and hence the duration of the flow down to Lambda) is changed. When the effective action satisfies Polchinski's version of the Exact Renormalization Group equation, we prove, directly from the path integral, that the dependence of the effective action on the bare scale, keeping the interaction part of the bare action fixed, is given by an equation of the same form as the Polchinski equation but with a kernel of the opposite sign. We then investigate whether similar equations exist for various generalizations of the Polchinski equation. Using nonperturbative, diagrammatic arguments we find that an action can always be constructed which satisfies the Polchinski-like equation under variation of the bare scale. For the family of flow equations in which the field is renormalized, but the blocking functional is the simplest allowed, this action is essentially identified with the effective action at Lambda = 0. This does not seem to hold for more elaborate generalizations.Comment: v1: 23 pages, 5 figures, v2: intro extended, refs added, published in jphy

    Field programmable gate arrays implementations of low complexity soft-input soft-output low-density parity-check decoders

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    Low-density parity-check (LDPC) codes are very efficient error control codes that are being considered for use in many next-generation communication systems. In this study low complexity soft-input, soft-output (SISO) field programmable gate arrays (FPGA) implementations of a novel logarithmic sum-product (LogSP) iterative LDPC decoder and a recently proposed simplified soft Euclidean distance (SSD) iterative LDPC decoder are presented, and their complexities and performance are compared. These implementations operate over any choice of parity check matrix (including those randomly generated, structurally generated and either systematic or non-systematic) and can be parametrically adapted for any code rate. The proposed implementations are both of very low complexity, because they operate using only sums, subtractions, comparisons and look-up tables, which makes them particularly suitable for FPGA realisation. The SSD decoder has a lower implementation complexity than the LogSP LDPC decoder and it also offers the advantage of not requiring knowledge of the channel signal-to-noise ratio, unlike most other LDPC decoders.Fil: Arnone, Leonardo Jose. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Ingeniería Eléctrica; ArgentinaFil: Castiñeira Moreira, Jorge. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Ingeniería Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Farrell, P. G.. Lancaster University; Reino Unid
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